• Journal of Sensor Science and Technology
• /
• v.15 no.1
• /
• pp.53-57
• /
• 2006

This paper describes a novel processing technique for fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for super-temperature MEMS applications. PDMS (polydimethylsiloxane) mold is fabricated on SU-8 photoresist using standard UV photolithographic process. Liquid precursor is injected into the PDMS mold. Finally, solid polymer structure is cross-linked using HIP (hot isostatic pressure) at $400^{\circ}C$, 205 bar. Optimum pyrolysis and annealing conditions are determined to form a ceramic microstructure capable of withstanding over $1400^{\circ}C$. The fabricated SiCN ceramic microstructure has excellent characteristics, such as shear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}{\Omega}$) and BDV (min. 1.2 kV) under optimum process condition. These fabricated SiCN ceramic microstructures have greater electric and physical characteristics than bulk Si wafer. The fabricated SiCN microstructures would be applied for supertemperature MEMS applications such as heat exchanger and combustion chamber.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.4
• /
• pp.39-52
• /
• 2000

A design of 2 stage S-DLVA(successive detector log video amplifier) was studied to detect wide dynamic radar pulse ranging from -70 ㏈m to 0㏈m. A basic design idea was focused on the linear detection in logarithmic scale of wide dynamic range radar pulses from nosie-like weak power of -70 ㏈m to relatively high power 0 ㏈m. It is highly formidable, since it requires high speed detection less than 10 nsec over the operating frequency ranges from 6 to 18 ㎓. A limiter diode, a tunnel diode and an L17-C were used as a protecting device, a detector diode and a log video amplifier in companion as a single stage detector to give voltage output proportional to the input power of about 35 ㏈ dynamic range. A protype of 2-stage DLVA having one more single stage detector was fabricated with a 32 ㏈ low noise amplifier and a 3 ㏈ hybrid coupler to provide total 70 ㏈ dynamic range detection. The logging characteristics were measured to have log slope of 25m.V/㏈ against 70 ㏈ logging range from -55 ㏈m to +15 ㏈m, the log linearity of within +/- 1.5 ㏈, and tangential sensitivity was at -63 ㏈m. The pulse dynamics of rise time and recovery time were measured as 50 nsec and 1.2 $\mu$sec, respectively. The reason might be due to the parasitic capacitances of packaged limiter, tunnel diode, and L17-C.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.3
• /
• pp.281-287
• /
• 2012

The internal oxide scale of twelve superheater and reheater tubes were tested which were serviced for 30,000~120,000 hours in thermal power plants. The oxide scale was formed in three layers. The Cr-rich area was observed beneath the original metal surface. The hematite ($Fe_2O_3$) phase was formed on the outer surface. The intermediate layer was magnetite ($Fe_3O_4$). The thickness of Cr-rich layer was about half of the total scale. All layers grew during the operation hour of the plant. The thickness of thickest scale was 0.2mm in superheater tubes. This can increase the tube metal temperature about $7^{\circ}C$ more than initial state. $7^{\circ}C$ tube metal temperature can reduce tube life about 30%, but the boiler tube's design margin is big enough therefore it has been analyzed that it would not effect on the life span.

• The Korean Journal of Zoology
• /
• v.38 no.2
• /
• pp.167-176
• /
• 1995

Glucose-regulated proteins (grp's), srp94 3nd grp78/BiP, are a group of stress proteins which are highly synthesized in cells exposed to a variety of stressful agents including tunicamycin 3nd Ca2+ ionophore. Grp78/BiP is hon to function as a molecular chaperone which regulates the folding and assembly of secretory or membrane proteins, but the biological function of grp941 remains to be elucidated. In this study, we have examined the intracellular distribution of grV's and the function of srp94. Grp's are resident in the endoplasmic reticulum (ERI 3nd a specific sequence (Lys-Asp-Glu-Leu) at their C-terminus is known to be responsible for their retention within the ER. However, it has been unclear whether upon disturbance of cellular Caa+ homeostasis by the Ca2+ ionophore, grp94 is retained within the ER or secreted into the medium. In this study, we showed that in the presence of C3a+ ionophore, grp94 and gif78/BiP are present in the cells, mainly within the ER. We have also investigated whether grp94 might function as a molecular chaperone. Here we showed that in the immunoglobulin (Ig)-secreting hvbridom3 cells, grp94 transientlY interacts with fully glycosylated Is heavy chain, suggesting that grpg94 may be involved in facilitating the folding and assembly of Ig heavy chains.

• Journal of Magnetics
• /
• v.16 no.2
• /
• pp.108-113
• /
• 2011

The electron spin resonance lineshape (ESRLS) function for the electron spin resonance linewidth (ESRLW) of $Cr^{3+}$ (S = 3/2) in ferroelectric lithium niobate single crystals doped with 0.05 wt% of Cr, is obtained by using the projection operator technique (POT), developed by Argyres and Sigel. The ESRLS function is calculated to be axially symmetric about the c - axis and analyzed by using the spin Hamiltonian $H_{SP}={\mu}_B(B{\cdot}{^\leftrightarrow_{g}}{\cdot}S)+S{\cdot}{^\leftrightarrow_{D}}{\cdot}S$ with the parameters g = 1.972 and D = $0.395\;cm^{-1}$. In the ca plane, the linewidths show a strong angular dependence, whereas in the ab plane, they are independent of the angle. This result implies that the resonance center has an axial symmetry along the c - axis. Further, from the temperature dependence of the linewidths that is shown, it can be seen that the linewidths increase as the temperature increases, at a frequency of v = 9.27GHz. This result implies that the scattering effect increases with increasing temperature. Thus, the POT is considered to be more convenient to explain the scattering mechanism as in the case of other optical resonant systems.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.11
• /
• pp.2584-2588
• /
• 2009

The effect of $LaF_3$ coating on the structural and electrochemical properties of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_{2}$ cathodes was investigated using XRD, SEM, TEM, and a cycler. The coating layer consisted of nano-sized particles attached nonuniformly to the surface of pristine powder. Despite the surface coating treatment, phase difference by $LaF_3$ coating was not detected. The discharge capacities of coated electrodes were a little lower than that of pristine sample at a 1 C rate. However, as the C rate increases, the capacity retention of the coated sample becomes obviously superior to that of the pristine sample. The cyclic performances of the electrodes in the voltage range of 4.8 $\sim$ 3.0 V were also improved by the surface coating. Such enhancement is attributed to the presence of the $LaF_3$ coating layer, which effectively suppressd the reaction between electrodes and electrolytes on the surface of the $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_{2}$ electrode.

• Journal of Magnetics
• /
• v.21 no.2
• /
• pp.159-163
• /
• 2016

Antiferromagnet (AFM)/ferromagnet (FM) bilayer structures are widely used in the magnetic devices of sensor and memory applications, as AFM materials can induce unidirectional anisotropy of the FM material via exchange coupling. The strength of the exchange coupling is known to be sensitive to quality of the interface of the AFM/FM bilayers. In this study, we utilize proton irradiation to modify the interface structures and investigate its effect on the magnetic properties of AFM/FM structures, including the exchange bias and magnetic thermoelectric effect. The magnetic properties of IrMn/CoFeB structures with various IrMn thicknesses are characterized after they are exposed to a proton beam of 3 MeV and $1{\sim}5{\times}10^{14}ions/cm^2$. We observe that the magnetic moment is gradually reduced as the amount of the dose is increased. On the other hand, the exchange bias field and thermoelectric voltage are not significantly affected by proton irradiation. This indicates that proton irradiation has more of an influence on the bulk property of the FM CoFeB layer and less of an effect on the IrMn/CoFeB interface.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.11
• /
• pp.627-634
• /
• 2000

In this paper, new micromachined tunble bandpass filters for multi-band millimeter-wave telecommunication systems are proposed. Two types of mm-wave tunable filters are fabricated using micromachning technology and the responses of the filters are measured. One is two-pole lumped elements filter and the other two-pole resonators filter. Frequency tunability of the filter is achieved by changing the gap between a common CPW ground plate and the movable cantilever beam connected to the transmission line with the controllable renge of 2.5${\mu}m$. The deflection of cantilever beam is measured with the applied DC voltage. With the applied bias voltage from 0 to 50 V, the fabricated filters show 0.6 GHz(2.3%) at 26.6 GHz, and 0.8 GHz(2.5%) at 32 GHz center frequency shift for the lumped elements and resonators filter, respectively. The life time of the fabricated gold cantilever structure are tested.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.341-342
• /
• 2006

Gadolinium-substituted bismuth titanate, $Bi_{3.3}Gd_{0.7}Ti_3O_{12}$ (BGT), thin films were successfully fabricated on Pt(111)/Ti/$SiO_2$/Si substrates by a sol-gel method and their structural and ferroelectric properties have been characterized. Fabricated BGT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The remanent polarization ($2P_r$)) of BGT thin film annealed at $720^{\circ}C$ was $25.85\;{\mu}C/cm^2$ at an applied voltage of 5 V. The BGT thin films exhibited a 11 % reduction in their switching charge after no less than $10^{11}$ switching cycles at a frequency of 1 MHz.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.321.1-321.1
• /
• 2013

높은 광흡수 계수를 갖는 Cu(In,Ga)Se2(CIGS) 화합물 박막 소재는 고효율 태양전지 양산을 위해 가장 전도유망한 재료이나 상대적으로 매장량이 적은 In 및 Ga을 사용한다는 소재적 한계가 있다. Cu2ZnSnSe4(CZTSe) 혹은 Cu2ZnSnS4(CZTS)와 같은 Cu-Zn-Sn-Se계 화합물 반도체는 CIGS 내 희소원소인 In과 Ga이 범용원소인 Zn 및 Sn으로 대체된 소재로써 미래형 저가 태양전지 개발을 위해 활발히 연구되고 있는데, 그 화합물 조합에 따라 0.8eV부터 1.5eV까지의 에너지 밴드갭을 갖는 것으로 알려져 있다. 본 연구에서는 열분해법으로 CZTS 나노 입자를 합성하였다. 용매로 Oleylamine을 사용하였는데, $260{\sim}340^{\circ}C$의 온도 범위에서 5시간 30분 동안 CZTS 나노입자를 합성하였고, $300^{\circ}C$에서 5시간 30분~9시간까지 합성하였다. 헥산을 이용하여 원심분리기와 초음파세척기로 용매인 Oleylamine을 제거하였고, 진공오븐에서 건조된 CZTS 분말의 FE-SEM (Field Emission Scanning Electron Microscope), XRD (X-Ray Diffraction), EDS (Energy Dispersive Spectroscopy) 분석 등을 통해 합성온도에 따른 구조적, 화학적 조성 변화를 조사하였다.