• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.323-329
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• 2004

The electrical and rheological properties pertaining to the electrorheological (ER) behavior of chitosan derivatives, chitosan, chitosan ammonium salt and chitosan phosphate suspensions in silicone oil were investigated. Chitosan derivative suspensions showed a typical ER response (Bingham flow behavior) upon application of an electric field. However, chitosan phosphate suspension exhibited an excellent shear yield stress compared with chitosan and chitosan ammonium salt suspensions. The difference in behavior results from the difference in the conductivity of the disperse phases due to the difference of their polarizability. The shear stress for the chitosan, chitosan ammonium salt and chitosan phosphate suspensions exhibited a linear dependence on the volume fraction of particles and 1.18 ,1.41 and 1.67 powers of the electric field. On the basis of the experimental results, the newly synthesized chitosan derivative suspensions found to be an ER fluid.

• KSTLE International Journal
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• 제5권2호
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• pp.49-51
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• 2004

The electrical and rheological properties pertaining to the electrorheological (ER) behavior of chitosan derivatives, chitosan, chitosan ammonium salt and chitosan phosphated suspensions in silicone oil were investigated. Chitosan derivative suspensions showed a typical ER response (Bingham flow behavior) upon application of an electric field. However, chitosan phosphate suspension exhibited an excellent shear yield stress compared with chitosan and chitosan ammonium salt suspensions. The difference in behavior results from the difference in the conductivity of the disperse phases due to the difference of their polarizability. The shear stress for the chitosan, chitosan ammonium salt and chitosan phosphate suspensions exhibited a linear dependence on the volume fraction of particles and 1.18, 1.41 and 1.67 powers of the electric field. On athe basis of the experimental results, the newly synthesized chitosan dervative suspensions found to be an ER fluid.

• 한국재료학회지
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• 제25권9호
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• pp.480-486
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• 2015

$Pb_{1-x}MoO_4:Er^{3+}/Yb^{3+}$ phosphors with various doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}=0.05$, 0.1, 0.2, and $Yb^{3+}=0.2$, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at $900^{\circ}C$ for 16 h, exhibit a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, the $Pb_{0.7}MoO_4:Er_{0.1}Yb_{0.2}$ and $Pb_{0.5}MoO_4:Er_{0.05}Yb_{0.45}$ particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of $Pb_{1-x}MoO_4$ through the incorporation of the $Er^{3+}$ and $Yb^{3+}$ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the $MoO_{4-x}$ group.

• 한국전기전자재료학회논문지
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• 제18권12호
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• pp.1101-1105
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• 2005

We have investigated the optical properties of Erbium (Er)-implanted GaN by photoluminescence (PL). Various doses of Er ion were implanted on GaN epilayers by ion implantation. Visible green emission lines due to inner 4f shell transitions for $Er^{3+}$ were observed from the PL spectrum of Er-implanted GaN. The emission spectrum consists of two narrow green lines at 537 and 558 nm. The green emission lines are identified as $Er^{3+}$ transitions from the $^{5}H_{11/2}$ and $^{4}S_{3/2}$ levels to the $^{4}I_{15/2}$ ground state. The stronger peaks in the case with the dose of $5{\times}10^{14}cm^{-2}$, together with the relatively higher intensity of the $Er^{3+}$ luminescence in the lower doped sample. It implies that some damage remains in the case with the dose of $1{\times}10^{16}cm^{-2}$. The peak positions of emission lines due to inner 4f shell transitions for $Er^{3+}$ do not change with increasing temperature. It indicates that $Er^{3+}$ related emission depends very little on the ambient temperature.

• 공업화학
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• 제26권3호
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• pp.319-325
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• 2015

분무열분해법을 이용하여 서브 미크론 크기의 $CeO_2:Er^{3+}/Yb^{3+}$ 상향 변환 형광체 입자를 합성하고 $Er^{3+}$ 및 $Yb^{3+}$ 농도 변화에 따른 발광특성을 조사하였다. 합성한 $CeO_2:Er^{3+}/Yb^{3+}$는 $Er^{3+}$ 활성이온의 $^4S_{3/2}/^2H_{11/2}{\rightarrow}^4I_{15/2}$ 및 $^4F_{9/2}{\rightarrow}^4I_{15/2}$ 전이에 기인한 강한 녹색 및 적색 발광을 보였다. 가장 높은 발광을 보이는 활성제 농도는 Er = 1.0% 그리고 Yb = 2.0%이며, 농도소광 현상은 쌍극자-쌍극자 상호작용을 통해 일어남이 확인되었다. 레이저 다이오드 여기 광 세기에 대한 발광강도 의존성을 활성이온 농도에 따라 조사하였고, 발광 중간 에너지 레벨의 주 소멸과정을 고려하여 발광 메커니즘을 조사하였다. $Yb^{3+}$에서 $Er^{3+}$으로 에너지 전달은 바닥 상태 흡수(ground state absorption, GSA)에 기여하고, $Yb^{3+}$ 도핑은 $^4I_{11/2}{\rightarrow}^4I_{13/2}$ 전이를 가속화시켜 적색/녹색 발광세기 비를 상승시킨다. 최종적으로 분무열분해법으로 제조된 $CeO_2:Er^{3+}/Yb^{3+}$ 형광체의 발광은 선형 감쇠가 중간 에너지 레벨의 고갈을 지배하는 2 광자 프로세스에 의해 일어남을 확인하였다.

• Biomolecules & Therapeutics
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• 제13권4호
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• pp.227-231
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• 2005

The estrogen receptor (ER) is activated and degraded by estrogen. We have examined ER downregulation and activation under hypoxia mimetic conditions. Cobalt chloride induced ER downregulation at 24 h of treatment. This degradation involved hypoxia-inducible factor-1$\alpha$ (HIF-1$\alpha$) as examined by using a constitutively active form of HIF-1$\alpha$, HIF-1$\alpha$/VP16, constructed by replacing the transactivation domain of HIF-1$\alpha$ with that of VP16. Western blot analysis revealed that E2-induced ER downregulation was observed within ${\~}6h$, whereas HIF-1$\alpha$/VP16-induced ER degradation was observed within 12${\~}$20h. HIF-1$\alpha$/VP16 activated the transcription of estrogen-responsive reporter gene in the absence of estrogen. These results suggest that ER downregulation and activation under hypoxia maybe mediated in part by a HIP-1$\alpha$ expression.

• 대한의생명과학회지
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• 제13권2호
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• pp.157-160
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• 2007

Endoplasmic reticulum (ER) plays formation of disulfide bonds and proper folding of secretory proteins. Cellular responses to ER stress enhances the stress-activated kinase pathway and the induces a lot of immediate-early genes. Among of them, the early growth response-1 (Egr-1), a transcription factor, which plays an important role in cell growth, development, differentiation, apoptosis and various types of injury. For that reason, we have tested the expression of Egr-1 against ER stress inducible drugs (tunicamycin, DTT, A23187 and BFA) to understand what kind of aspect occurred by ER stresses.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1082-1086
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• 2007

Optical characteristics of $YCOB(YCa_4B_3O_{10})$, known as a crystal of self frequency doubling, was investigated when Yb and Er ions were co-doped 20 % and 2 %, respectively. The absorption cross section of Er,Yb:YCOB crystal at $1.0\;{\mu}m$ was larger than that of Yb:YCOB, which means that the former was profitable for more energy absorption than the latter. The fluorescent lifetime at $1.5\;{\mu}m$ was measured to be 1.27 ms at room temperature, and lengthened to 1.54 ms and 1.62 ms at low temperatures of 77 K and 6 K, respectively. The line widths of fluorescent spectrum at $1.5\;{\mu}m$ were getting narrower as lowering temperature. However, we didn't observe a temperature dependent peak wavelength shift.

• Asian-Australasian Journal of Animal Sciences
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• 제27권12호
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• pp.1684-1690
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• 2014

Estrogen and its receptors are essential hormones for normal reproductive function in males and females during developmental stage. To better understand the effect of estrogen receptor (ER) gene in yak (Bos grunniens), reverse transcription-polymerase chain reaction (PCR) was carried out to clone $ER{\alpha}$ and $ER{\beta}$ genes. Bioinformatics methods were used to analyze the evolutionary relationship between yaks and other species, and real-time PCR was performed to identify the mRNA expression of $ER{\alpha}$ and $ER{\beta}$. Sequence analysis showed that the ER open reading frames (ORFs) encoded 596 and 527 amino acid proteins. The yak $ER{\alpha}$ and $ER{\beta}$ shared 45.3% to 99.5% and 53.9% to 99.1% protein sequence identities with other species homologs, respectively. Real-time PCR analysis revealed that $ER{\alpha}$ and $ER{\beta}$ were expressed in a variety of tissues, but the expression level of $ER{\alpha}$ was higher than that of $ER{\beta}$ in all tissues, except testis. The mRNA expression of $ER{\alpha}$ was highest in the mammary gland, followed by uterus, oviduct, and ovary, and lowest in the liver, kidney, lung, testis, spleen, and heart. The $ER{\beta}$ mRNA level was highest in the ovary; intermediary in the uterus and oviduct; and lowest in the heart, liver, spleen, lung, kidney, mammary gland, and testis. The identification and tissue distribution of ER genes in yaks provides a foundation for the further study on their biological functions.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.393-398
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• 1999

The temperature dependence of the viscosity was determined for an electrorheological(ER) fluid consisting of 35 weight% zeolite particles in hydraulic oil 46cSt. Thermal activation analysis were performed by changing the ER fluid's temperature from -1$0^{\circ}C$ to 5$0^{\circ}C$ at fixed electric field. According to the analysis, the activation energy for flow was about 79.64kJ/mole at E=0kV/mm. Generally, the hydraulic oil 46cSt will be operated at the temperature of about 4$0^{\circ}C$, the ER fluid's electric field dependence of viscosities were investigated at this temperature. also, the influence of adding the dispersant(Carbopl 940) on electrorheological effect of the ER fluid was discussed.