• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.6
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• pp.1-11
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• 1998

This paper presents performance analyses of three types of the cylindrical-type ER(electro-rheo-logical) valves, which have different electrode length and width but same electrode area. Following the composition of silicone oil-based ER fluid, the field-dependent yield stresses are obtained from experimental investigation on the Bingham property of the ER fluid. The ER valve which is dependent on the applied electric field is devised and its theoretical model is derived. On the basis of the pressure-drop analysis, three types of the ER valves are designed and manufactured. After experimentally evaluation field-dependent pressure drops, PI controller is formulated to achieve tracking control on desired pressure drop. The controller is then experimentally implemented and tracking control performance is presented in order to demonstrate superior controllability of the ER valve. In addition, the response characteristic of the ER valve with respect to the excitation frequency of the electric fiedls is provided to show the feasibility of practical application.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1044-1047
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• 1996

This paper presents durability characteristics of electrorheological(ER) fluids which undergo a reversible phase change depending upon the imposition of electric fields. The field-dependent Bingham properties are subjected to be altered from long time use of the ER fluid. The level of the changed properties depends upon employed device and test conditions. A piston-rod system which has same mechanism as ER dampers is adopted in this study and tested by increasing operation cycle up to 1 million. Bingham properties of initial and us ER fluids are tested and compared. In addition, these ER fluids are applied to ER damper in order to evaluate damping force performance.

• The Korean Journal of Rheology
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• v.10 no.1
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• pp.31-37
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• 1998

전기장이 인가되고 있는 유로를 유동하는 전기유변유체의 기본성질을 파악하기 위 한 실험 및 해석적 연구를 수행하여 빙햄유체로서의 유효성에 대해 알아보고 전기장과 유로 면 형상 및 진동유동으로 인한 영향에 대해 조사함으로써 ER밸브 및 ER대퍼로의 응용과 관련한 감쇄력 제어에 대해 검토하였다. 첫 번째 실험은 ER밸브의 높이가 2mm인 적극면이 평탄한것과 요철로 된 것을 사용하여 압력손실을 압력변환기로 측정함으로써 전기장 및 유 로형상에 대한 영향을 알아보았다. 압력손실 및 전단응력이 전기자세기와 함수관계를 가짐 을 알수 있었고 전기장세기와 유속의 변화시 손실계수에 의한 ER효과의 상이함이 확인되었 으며 레이놀즈수가 커지면 항복전단응력의 영향은 나타나지 않았다. 두 번째 실험은 실린더 를 정현파로 진동시켜 ER밸브에서 감쇠력제어가 가능한가를 알아보고 빙햄유체모델로 설계 된 ER댐퍼의 모델과 비교하였다. ER배르와 ER댐퍼의 수학적 모델을 시뮬레이션한 결과는 약간 벗어남이 보이기는 하나 실험결과와 일치하요 있다. 이것은 ER유체를 단순히 빙행유 체로 취급할수없으나 거시적으로는 빙햄유체로 취급할수 있음을 시사한다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.56-62
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• 2006

An experimental investigation was performed to study the characteristics of ER(Electro-Rheological) fluid flow in a horizontal rectangular tube with or without D.C voltage. To determine some characteristics of the ER flow, 2D PIV(Particle Image Velocimetry) technique is employed for velocity measurement. This research found the mean velocity distribution with 0kV/mm, 1.0kV/mm and 1.5kV/mm for Re = 0, 0.62, 1.29 and 2.26. When the strength of the electric field increased, the cluster of ERF are clearly strong along the test tube and the flow rate decreased. In this study, the rheology of ER fluid stagnating or flowing through a dispersion meter will be investigated by PIV method. And then the ER effect, which appears at the ER valves and their appliance will be visualized.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1256-1260
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• 2007

Two β-diketone derivatives bearing triphenylene (1-naphthalene-2-yl-3-triphenylen-2-yl-propane-1,3-dione (NTPD)) and naphthalene (1,3-di-naphthalene-2-yl-propane-1,3-dione (DNPD)) and their Ln(III) complexes (Ln = Er or Gd) were synthesized and their photophysical properties were investigated. The sensitized emission of Er3+ ion in Er3+-[NTPD]3(terpy) and Er3+-[DNPD]3(terpy) was observed upon excitation at absorption maximum of ligands. Their photophysical studies indicate the sensitization of Er3+ luminescence by energy transfer through the excited triplet state of β-diketone ligand. The energy transfer rate through the excited triplet state of β-diketone ligand to Er3+ ion occurs faster than that of the oxygen quenching rate.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.120-128
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• 1996

We studied the red, green and blue upconverted emission in 1 at.% $Er^{3+}: LaF_3$ and 1 at.% $Er^{3+}:YAlO_3$ crystals y pumping in 780~820 nm range at 14 K and 295 K. A cw titanium-sapphire laser was used to pump the $^4I_{9/2}$ level in two materials. The spectral analysis of the emission from $^4F_{9/2},\;^4S_{3/2}$ and $^2P_{3/2}$ levels allowed to reveal the upconversion process with multi-step absorption and cross-relaxation energy transfer.

• Analytical Science and Technology
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• v.27 no.6
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• pp.314-320
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• 2014

$La_{2-x}(MoO_4)_3:Er^{3+}/Yb^{3+}$ particles with 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) were successfully prepared by the microwave-modified sol-gel method, and the upconversion photoluminescence properties were investigated. Well-crystallized particles, formed after heat-treatment at $900^{\circ}C$ for 16 h, showed a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, $La_{1.7}(MoO_4)_3:Er_{0.1}Yb_{0.2}$ and $La_{1.5}(MoO_4)_3:Er_{0.05}Yb_{0.45}$ particles exhibited 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 indicated the presence of strong peaks at higher frequencies of 752, 846, 922, 1358 and $1435cm^{-1}$ and lower frequency of $314cm^{-1}$ induced by the disorder of the $[MoO_4]^{2-}$ groups with the incorporation of the $Er^{3+}$ and $Yb^{3+}$ elements into the crystal lattice or by a new phase formation.

• Biomedical Science Letters
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• v.23 no.4
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• pp.416-420
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• 2017

Endoplasmic reticulum (ER) stress induces unfolded protein response (UPR) via inositol-requiring enzyme 1 (IRE1) activation, which sends a molecular signal for X box-binding protein 1 (XBP1) mRNA splicing in the cytosol. IRE1 endoribonuclease activity induces cleavage of XBP1 mRNA. The XBP1 mRNA is then ligated by an uncharacterized RNA ligase and translated to produce spliced XBP1 by 23 nt removed in which contains the PstI restriction enzyme site. The splicing of XBP1 mRNA can be detected by semiquantitative RT-PCR, and then splicing of XBP1 is a useful tool to measure the genetic variability in ER stress. In this study, we have estimated IRE1-dependent splicing of XBP1 mRNA under conditions of various hypothermia. The results indicated that hypothermia regulated ER stress. This study demonstrated that hypothermia is closely related to ER stress and may be useful for early diagnosis of ER-associated disease.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.140-142
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• 1989

1.54um 파장에서 최대 형광을 나타내는 ZrF4-BaF2-LaF3-AlF3-NaF : ErF3 유리를 built-in-casting 법에 의해 제조하였다. Er+3 이온을 0.2몰부터 4몰까지 첨가하였으며, Er+3 이온의 4I13/2 준위의 lifetime 은 Er+3 이온 0.2몰부터 2몰까지 28msec로 최대값을 갖으며 4몰일때는 급격히 감소하였다.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.71-78
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• 1999

This paper presents a new type of energy generative ER suspension system which does not require external power sources. This is accomplished by converting vibration energy(kinetic energy) into electrical energy. In order to undertake this, an appropriate size of the ER damper is manufactured by incorporation a mechanism which changes the linear motion of the ER damper to the rotary motion. This rotary motion is amplified by gears and activates a generator to produce the electrical energy. The efficiency of energy generation is evaluated and the level of damping force with generated power is also investigated. Then, the ER suspension system is applied to the quarter car model, and its vibration isolation is experimentally evaluated with respect to the piston speed.