• Applied Chemistry for Engineering
• /
• v.26 no.6
• /
• pp.698-705
• /
• 2015

Two series of symmetric dimesogenic compounds containing a butylene or 1-methylbutylene spacer as a flexible group were synthesized. The mesogenic groups of synthesized compounds consist of an azobenzene group with a terminal substituent. Chemical structures as well as, thermal, mesomorphic, and photochemical properties of the synthesized compounds were investigated using FT-IR, $^1H-NMR$, differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and UV-visible spectrometry. P-H, P-F, and $P-OC_6H_{13}$ showed monotropic liquid crystal phases, whereas the others showed enantiotropic liquid crystal phases. Compounds with butylene group as a flexible spacer exhibited wider mesophase temperature ranges and higher thermal transition temperatures than compounds containing a 1-methylbutylene group. Compounds with a high absolute value of the Hammett substituent constant exhibited high thermal transition temperatures and improved stability in the liquid crystal phase. Furthermore, in the absence or presence of UV light illumination, terminal substituents of the azomesogenic group were important factors in deciding the maximum absorbance wavelength (${\lambda}_{max}$) and the rate of photoisomerization (K).

• Applied Chemistry for Engineering
• /
• v.25 no.6
• /
• pp.624-631
• /
• 2014

In this study, a new series of conjugated polymer 3-(5-(5,6-bis(octyloxy)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-10-(4-(octyloxy)phenyl)-10H-phenothiazine (P1) and 3-(5-(5,6-bis(octyloxy)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-10-(4-((2-ethylhexyl)oxy)phenyl)-10H-phenothiazine (P2) were synthesised and organic photovoltaics (OPVs) properties were characterized. The push-pull structure polymer consisted of phenothiazine derivative as an electron donor and benzothiadiazole derivative as an electron acceptor. The aliphatic chain substituted aromatic ring was substituted at the position of N in phenothiazine for the electron-rich and improved solubility. Excellent thermal stabilities of P1 and P2 were confirmed by measured Td values as 321.9 and $323.7^{\circ}C$, respectively and the degrees of polymerization were 4,911 (P1) and 5,294 (P2). The maximum absorption wavelength of P1 and P2 were 549 and 566 nm, respectively. The device was fabricated and the OPVs property was measured. As a result, the power efficiency of conversion for P1 and P2 were 0.96 and 0.90%, respectively.

• Korean Journal of Materials Research
• /
• v.8 no.8
• /
• pp.737-743
• /
• 1998

The synthesis of $SrAI_2O_4:Eu^{2+}$ phosphor and its properties of both photoluminescence and long-phosphorescent were investigated as a function of sintering condition. Single phase of $SrAl_2O_4$ was obtained by sintering the mixtures of $SrCO_3$, $Eu_2O_3$, $AI_2O_34 and 3wt% $B_2O_3$ powders over 100$0^{\circ}C$ in Ar/H2 atmosphere. The optimum sintering condition for the long-phosphorescent phosphor of $SrAI_2O_4:Eu^{2+}$ was found at 130$0^{\circ}C$ for 3hours. The PL emission spectrum of $SrAI_2O_4:Eu^{2+}$ shows a maximum peak intensity at 520nm(2.384eV) with a broad emission extending from 450 to 650nm which resulted from the $4f^65d^1$$\rightarrow$$4f^7$ transition of $Eu^{+2}$ under 360nm exitation. Monitored at 520nm. the excita¬tion spectrum of $SrAI_2O_4:Eu^{2+}$ exhibits a maximum peak intensity at 360nm (3.44eV) with a broad absorption band extending from 250 to 480nm.

• Journal of the Microelectronics and Packaging Society
• /
• v.28 no.1
• /
• pp.1-12
• /
• 2021

Here, we introduce a laser-induced graphene synthesis technology and its applications for the electric/electronic device manufacturing process. Recently, the micro/nanopatterning technique of graphene has received great attention for the utilization of these new graphene structures, which shows progress developments at present with a variety of uses in electronic devices. Some examples of practical applications suggested a great potential for the tunable graphene synthetic manners through the control of the laser set-up, such as a selection of the wavelength, power adjustment, and optical techniques. This emerging technology has expandability to electric/electronic devices combined together with existed micro-packaging technology and can be integrated with the new processing steps to be applied for the operation in the fields of biosensors, supercapacitors, electrochemical sensors, etc. We believe that the laser-induced graphene technology introduced in this paper can be easily applied to portable small electronic devices and wearable electronics in the near future.

• Applied Chemistry for Engineering
• /
• v.32 no.1
• /
• pp.28-34
• /
• 2021

SiO2/Ag core-shell nanoparticles were synthesized by combining modified Stöber process and reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane reverse micells. The SiO2/Ag core-shells were studied for structure, morphology and size using UV-visible spectroscopy, XRD, SEM and TEM. The size of a SiO2/Ag core-shell could be controlled by changing the [water]/[DDBA] molar ratio (WR) values. The size and the polydispersity of SiO2/Ag core-shells increased with increase of the WR value. The resultant Ag nanoparticles exhibit a strong surface plasmon resonance (SPR) peak at 430 nm over the amorphous SiO2 nanoparticles. The SPR peak shifted to the red side with increase in nanoparticle size. Conductive pastes with 70 wt% SiO2/Ag core-shell were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste film of the SiO2/Ag core-shell showed higher surface resistance than the commercial Ag paste in the range of 460~750 µΩ/sq.

• Applied Chemistry for Engineering
• /
• v.34 no.1
• /
• pp.36-44
• /
• 2023

Core-shell TiO₂/Ag nanoparticles were synthesized by a modified sol-gel process and the reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane. The structure, shape, and size of the TiO₂/Ag nanoparticles were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The size of TiO₂/Ag nanoparticles could be controlled by changing the [water]/[DDBA] molar ratio values. The size and the polydispersity of TiO₂/Ag nanoparticles increased when the [water]/[DDBA] molar ratio rose. The resultant Ag nanoparticles over the anatase crystal TiO₂ nanoparticles exhibited a strong surface plasmon resonance (SPR) peak at about 430 nm. The SPR peak shifted to the red side with the increase in nanoparticle size. Conductive pastes with 70 wt% TiO₂/Ag nanoparticles were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste films of the TiO₂/Ag nanoparticles demonstrated greater surface resistance than conventional Ag paste in the range of 405~630 μΩ/sq.

• Korean Journal of Environmental Agriculture
• /
• v.34 no.1
• /
• pp.38-45
• /
• 2015

BACKGROUND: For commercial production of greenhouse crops under shorter day length condition, supplementary radiation has been usually achieved by the artificial light source with higher electric consumption such as high-pressure sodium, metal halide, or incandescent lamps. Light-Emitting Diodes (LEDs) with several characteristics, however, have been considered as a novel light source for plant production. Effects of supplementary lighting provided by the artificial light sources on growth of Kale seedlings during shorter day length were discussed in this experiment. METHODS AND RESULTS: Kale seedlings were grown under greenhouse under the three wave lamps (3 W), sodium lamps (Na), and red LEDs (peak at 630 nm) during six months, and leaf growth was observed at intervals of about 30 days after light exposure for 6 hours per day at sunrise and sunset. Photosynthetic photon flux (PPF) of supplementary red LEDs on the plant canopy was maintained at 0.1 (RL), 0.6 (RM), and $1.2(RH){\mu}mol/m^2/s$ PPF. PPF in 3 W and Na treatments was measured at $12{\mu}mol/m^2/s$. Natural light (NL) was considered as a control. Leaf fresh weight of the seedlings was more than 100% increased under the 3 W, Na and RH treatment compared to natural light considering as a conventional condition. Sugar synthesis in Kale leaves was significantly promoted by the RM or RH treatment. Leaf yield per $3.3m^2$ exposed by red LEDs of $1.2{\mu}mol/m^2/s$ PPF was 9% and 16% greater than in 3W or Na with a higher PPF, respectively. CONCLUSION: Growth of the leafy Kale seedlings were significantly affected by the supplementary radiation provided by three wave lamp, sodium lamp, and red LEDs with different light intensities during the shorter day length under greenhouse conditions. From this study, it was suggested that the leaf growth and secondary metabolism of Kale seedlings can be controlled by supplementary radiation using red LEDs of $1.2{\mu}mol/m^2/s$ PPF as well as three wave or sodium lamps in the experiment.

• Journal of the Korean Ceramic Society
• /
• v.41 no.8
• /
• pp.573-577
• /
• 2004

We have synthesized a Eu$^{2＋}$-activated Sr$_3$MgSi$_2$ $O_{8}$ blue phosphor and investigated an attempt to develop blue LEDs by combining it with a InGaN blue LED chip (Len=405 nm). The InGaN-based Sr$_3$MgSi$_2$ $O_{8}$：Eu LED Lamp shows two bands at 405 nm and 460 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the Sr$_3$MgSi$_2$ $O_{8}$：Eu phosphor. The 460 m emission band is ascribed to a radiative recombination of Eu$^{2＋}$ impurity ions in the Sr$_3$MgSi$_2$ $O_{8}$ host matrix. As a consequence of a preparation of W blue LED Lamp using the Sr$_3$MgSi$_2$ $O_{8}$：Eu blue phosphor, the highest luminescence efficiency was obtained at the ration of epoxy/blue phosphor(1/0,202). At this time, the CIE chromaticity was x=0.1417 and y=0.0683.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2002.05a
• /
• pp.125-129
• /
• 2002

실시간 운영체제(Real-Time Operating System: 이하 RTOS라 함) 개발환경에서 제공하는 도구 중에 하나인 RTOS 시뮬레이터는 타겟 하드웨어가 호스트에 연결되어 있지 않아도 호스트에서 응용프로그램의 개발과 디버깅을 가능하게 해주는 타겟 시뮬레이션 환경을 제공해 줌으로서, 개발자로 하여금 빠른 시간 내에 응용프로그램을 개발할 수 있도록 지원하며 하드웨어 개발이 완료되기 전에도 응용프로그램을 개발할 수 있게 해 준다. 그러한 이유로 현재 대부분의 상용 RTOS 개발환경에서는 RTOS 시뮬레이터를 제공하고 있다. 그러나 현재 상용 RTOS 시뮬레이터들은 대부분 RTOS의 기능적인 부분들만 호스트에서 동작하도록 구현되어 있어서 RTOS나 RTOS 응용프로그램이 실제 타겟에서 실행될 때의 실질적인 시간 추정이 불가능하다. 이러한 문제점은 실시간 시스템이 정해진 시간 내에 결과를 출력해야 하는 시스템임을 감안한다면 RTOS 시뮬레이터의 가장 큰 결점이 되기 때문에 실행시간 추정 기능을 가지면서 실용화도 가능한 RTOS 시뮬레이터가 필요하다. 본 연구에서는 이러한 문제점을 해결하여 RTOS와 RTOS 응용프로그램이 실제 타겟에서 처리될 때의 실행시간 추정이 가능하고 상용화가 가능한 기계 명령어 기반(machine instruction-based)의 RTOS 시뮬레이터를 연구 개발하였다. 나아가 실행시간의 주요 요소인 파이프라인과 캐쉬의 영향도 고려함으로서 실행시간 추정의 정확도를 향상시켰다 본 연구에서 사용된 RTOS는 한국전자통신연구원(ETRI)에서 2000년에 개발된 Q+이고, Q+가 동작하는 타겟 하드웨어는 ARM 계열의 StrongARM SA-110 마이크로프로세서와 21285 주제어기가 장착된 EBSA-285 보드이다. 측정하면서 수행하였다. 검증 결과 random 상태에서는 문헌자료에 부합되는 예측결과를 보여주었으나, intermediate와 constant 상태에서는 문헌보다 다소 낮은 속도를 보여주었다 이러한 속도차는 추후 현장 데이터를 수집하여 보다 실질적인 검증을 통하여 조정되어야 할 것으로 판단된다.지발광(1.26초)보다 구애발광(1.12초)에서 0.88배 감소하였고, 암컷에서 정지발광(2.99초)보다 구애발광(1.06초)에서 0.35배 감소하였다. 발광양상에서 발광주파수는 수짓의 정지발광에서 0.8 Hz, 수컷 구애발광에서 0.9 Hz, 암컷의 정지발광에서 0.3 Hz, 암컷의 구애발광에서 0.9 Hz로 각각 나타났다. H. papariensis의 발광파장영역은 400 nm에서 700 nm에 이르는 모든 영역에서 확인되었으며 가장 높은 첨두치는 600 nm에 있고 500에서 600 nm 사이의 파장대가 가장 두드러지게 나타났다. 발광양상과 어우러진 교미행동은 Hp system과 같은 결과를 얻었다.하는 방법을 제안한다. 즉 채널 액세스 확률을 각 슬롯에서 예약상태에 있는 음성 단말의 수뿐만 아니라 각 슬롯에서 예약을 하려고 하는 단말의 수에 기초하여 산출하는 방법을 제안하고 이의 성능을 분석하였다. 시뮬레이션에 의해 새로 제안된 채널 허용 확률을 산출하는 방식의 성능을 비교한 결과 기존에 제안된 방법들보다 상당한 성능의 향상을 볼 수 있었다., 인삼이 성장될 때 부분적인 영양상태의 불충분이나 기후 등에 따른 영향을 받을 수 있기 때문에 앞으로 이에 대한 많은 연구가 이루어져야할 것으로 판단된다.태에도 불구하고 [-wh]의미의 겹의문사는 병렬적 관계의 합성어가 아니라 내부구조를 지니지 않은 단순한 단어(minimal $X^{0}$

• Journal of the Korean Society of Radiology
• /
• v.9 no.3
• /
• pp.169-174
• /
• 2015

$LiGd_9(SiO_4)_6O_2:Ce^{3+}$ phosphors were synthesized by solid-state reaction method. The structural characteristic was investigated by X-ray powder diffraction analysis. The emission and excitation spectra of the $Ce^{3+}$ ions doped $LiGd_9(SiO_4)_6O_2$ phosphors were obtained under the UV excitation. The emission spectra of $LiGd_9(SiO_4)_6O_2:Ce^{3+}$ shows the band at 410 nm corresponding to the $^2F_{5/2}$ and $^2F_{7/2}$ states of $Ce^{3+}$. The red shift of $Ce^{3+}$ emission is found as the $Ce^{3+}$ concentration increases, which could be explained by the change in crystal-field symmetry and strength with increasing $Ce^{3+}$ concentration. Fluorescence decay time of $Ce^{3+}$ was about 20 ns. When the concentration of $Ce^{3+}$ increases life time was slightly reduced.