• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.631-637
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• 1990

Lithium fluolide single crystals were grown by a floating zone method, with infrared radiation convergence type heater, which is free of contamination from the crucible wall. The crystals grown by this apparatus are 5cm in length and 5-6mm in diameter. The grown cryatal was examined by an optical microscope, XRD, Laue camera, Vickers hardness tester, and FTIR.

• Korean Journal of Acupuncture
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• v.21 no.2
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• pp.29-46
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• 2004

Objectives and Methods : This study was performed to investigate the effect of electro -acupuncture at four gates(bilateral LR3 and LI4) on brain activity in normal subjects using fMRI. Results and Conclusions : 1. fMRI signal increase by electro-acupuncture at Lt. LR3 was observed in Rt. Middle frontal gyrus in group average as well as more than half of the subjects. 2. fMRI signal decreases by electro-acupuncture at Lt. LR3 were observed in Rt. Superior frontal gyrus, Rt. Middle temporal gyrus, Rt. Cingulate gyrus in group average as well as more than half of the subjects. 3. fMRI signal increases by electro-acupuncture at Lt. LI4 were observed in Lt. Superior frontal gyrus, Lt. Middle frontal gyrus, Lt. Inf. Semi-Lunar Lobule(cerebellum), Rt. Middle frontal gyrus, Rt. Cingulate gyrus in group average as well as more than half of the subjects. 4. fMRI signal decreases by electro-acupuncture at Lt. LI4 were observed in Lt. Middle frontal gyrus, Lt. Inferior frontal gyrus, Lt. Precentral gyrus and Rt. Middle frontal gyrus, Rt. Middle temporal gyrus, Rt. Precuneus, Rt. Inferior frontal gyrus, Rt. Postcentral gyrus in group average as well as more than half of the subjects. 5. fMRI signal increase by electro-acupuncture at Lt. LR3 and Lt. LI4 in group average as well as more than half of the subjects was not observed. 6. fMRI signal decreases by electro-acupuncture at Lt. LR3 and Lt. LI4 were observed in Lt. culmen(cerebellum), Lt. Cingulate gyrus와 Rt. Middle frontal gyrus, Rt. Cingulate gyrus, Rt. Inferior frontal gyrus in group average as well as more than half of the subjects. 7. fMRI signal increases by electro-acupuncture at four gates (bilateral LR3 and LI4) were observed in Lt. Middle temporal gyrus and Lt. Postcentral gyrus in group average as well as more than half of the subjects. 8. fMRI signal decrease by electro-acupuncture at four gates (bilateral LR3 and LI4) were observed in Lt. Middle frontal gyrus, Lt. Precentral gyrus, Lt. Inferior frontal gyrus, Lt. Middle temporal gyrus, Lt. Frontal sub-gyral and Rt. Tuber(cerebellum) in group average as well as more than half of the subjects.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.524-530
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• 2006

$xCa(Li_{1/4}Nb_{3/4})O_{3}-(1-x)CaTiO_{3}$ ceramics were sintered under the presence of zinc-borosilicate(ZBS) glass and resultant microwave dielectric properties were investigated with a view to applying the composition to low-temperature co-fired ceramic(LTCC) technology. The addition of $5{\sim}15wt%$ ZBS glass ensured successful sintering below $900\;^{\circ}C$. In general, increased addition of ZBS glass increased sinterability but it decreased the quality factor($Q{\times}f_{0}$) significantly due to the formation of an excessive liquid and second phases. As for the addition of $CaTiO_3$, the dielectric constant(${\epsilon}_r$) and temperature coefficient of resonant frequency(${\tau}_f$) increased, while the quality factor($Q{\times}f_{0}$) did not show an apparent change. The sintered $0.9Ca(Li_{1/4}Nb_{3/4})O_{3}-0.1CaTiO_{3}$ specimen at $900\;^{\circ}C$ with 10 wt% ZBS glass demonstrated 39.6 in dielectric constant(${\epsilon}_r$), 4,400 in quality factor$(Q{\times}f_{0}),\;and\;-11ppm/^{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_f$).

• Transactions on Electrical and Electronic Materials
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• v.9 no.1
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• pp.20-23
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• 2008

Organic light-emitting diodes (OLEDs) are attractive because of possible application in display with low-operating voltage, low-power consumption, self-emission and capability of multicolor emission by the selection of emissive materials. To investigated the optical effects, we studied the electrical and optical characteristics due to thickness variation of electron injection materials LiF on organic light-emitting diodes in the ITO (indium-tin-oxide)/N,N'-diphenyl-N, N'-bis(3-methyphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/tris(8-hydroxyquinoline) aluminum $(Alq_3)/LiF$ layer/Al device. We maintained the thicknesses of TPD and $Alq_3$ layers at 40 nm and 60 nm, respectively. The deposition rates of TPD and $Alq_3$ were in the $1.5{\AA}/s$ under a base pressure of $5{\times}10^{-6}$ Torr. It was found that luminance and luminous efficiency of the device with 0.7 nm LiF layer improve 25 times and 7 times than the device without the LiF layer, respectively.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.430-436
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• 1990

Glasses of different compositions were synthesized by substituting each component of 56ZrF4-14BaF2-6LaF3-4AlF3-20NaF(ZBLAN) with HfH4, SrF2, GdF3, InF3 and LiF3, each of similar size and chemical property with the component being substituted, respectively. The heating rate used in the DSC runs was 10K/min. All ofthe glasses exhibit glass transition temperatures of 510$\pm$10K, while crystallization temperatures vary between 625 and 720K depending upon different glass compositions. For most glasses crystallization temperatures obtained while cooled are lower than those obtained while heated, but InF3 or SrF2 containing glasses showed opposite trend. HBLAN, ZHBLAN and ZHBLANLi glasses, which were made by substituting HfH4, LiF for ZrF4 and NaF of ZBLAN respectively, showed improvement in the glass stability.

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

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.185-190
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• 2016

Background: In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. In this spectrometer, several measurements with different size Bonner spheres are required. Operators should, therefore, place these spheres in several times to a measurement point where radiation dose might be relatively high. In order to reduce this effort, novel neutron energy spectrometer using an onion-like single Bonner sphere was proposed in our group. This Bonner sphere has multiple sensitive spherical shell layers in the single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a LiF-ZnS mixed powder scintillator sheet and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. Amount of LiF neutron converter is reduced near polar region, where the band-shaped detectors are concentrated, in order to uniform the directional sensitivity. The LiF-ZnS mixed powder has an advantage of extremely high light yield. However, since it is opaque, scintillation photons cannot be collect uniformly. This type of detector shows no characteristic shape in the pulse height spectrum. Subsequently, it is difficult to set the pulse height discrimination level. This issue causes sensitivity fluctuation due to gain instability of photodetectors and/or electric modules. Materials and Methods: In order to solve this problem, we propose to replace the LiF-ZnS mixed powder into a flexible and Transparent RUbber SheeT type $LiCaAlF_6$ (TRUST LiCAF) scintillator. TRUST LiCAF scintillator can show a peak shape corresponding to neutron absorption events in the pulse height spectrum. Results and Discussion: We fabricated the prototype detector with five sensitive layers using TRUST LiCAF scintillator and conducted basic experiments to evaluate the directional uniformity of the sensitivity. Conclusion: The fabricated detector shows excellent directional uniformity of the neutron sensitivity.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.1
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• pp.11-19
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• 2015

The production of nuclear fuel cladding tube is expected to increase with the nuclear power plant expansion. Zirconium(Zr) scrap that is generated during manufacturing is also expected to increase. Zr electrorefining experiment was carried out in the fluoride salt of LiF-KF-ZrF₄ using multiple electrode for scale up and improving throughput Zr electrorefiner develop-ment. The Zr reduction peak observed at-0.8 V(vs.Ni). Polarization behavior showed that the amount of applied current increases because of decreasing cell resistance as the number of cathode increases. Experimental results showed the highest recovery rate about 98% at lowest current density of 25.64 mA/cm² using 6 electrodes. XRD and TG analysis result show that pure Zr was recovered 99.92% and ICP analysis shows that lower impurity content than conventional impurity content of the Anode(97.8%). Electrorefining consumes energy about 7.15 kWh/kg less than 39.7% compared to the Kroll process using 6 electrode width of 20 mm and height of 65 mm. Because of increasing cell efficiency and recovery rate, using multiple cathode is determined as an efficient technique for scale up electrorefining Zr scrap.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.614-623
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• 1993

Electrical characteristics of LiF-$Li_{2}O-B_{2}O_{3}-P_{2}O_5$ glasses with fixed $Li_2O$ content have been investigated by using AC impedance spectroscopy. Part of the total lithium ions present in these glasses contributes to conduction, and the changes in electrical conductivity with composition was inconsistent with the weak electrolyte model. The power law could not be used to determine the hopping ion concentration in these glasses. Both mobile carrier density and mobility have been modified as Li were added in the form of LiF. The formation of $(B-O-P)^-,di^-$, and metaborate group gave additional available sites for Li+ diffusion causing the enhancement of conductivity. The observed maximum conductivity was $2.43 \times 10^{-4}$S/cm at $150^{\circ}C$ at the composition containing 8mol% LiF. The decomposion potential amounted to 5.94V. The Li/glass electrolyte/$TiS_2$ solid-state cell showed open circuit voltage of 3.14V and energy density of 22 Wh/Kg at $150^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3738-3742
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• 2013

The reaction mechanism of $SiF_2$ radical with HNCO has been investigated by the B3LYP method of density functional theory(DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/$6-311++G^{**}$ level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)/$6-311++G^{**}$//B3LYP/$6-311++G^{**}$ level. $SiF_2+HNCO{\rightarrow}IM3{\rightarrow}TS5{\rightarrow}IM4{\rightarrow}TS6{\rightarrow}OSiF_2CNH(P3)$ was the main channel with low potential energy, $OSiF_2CNH$ was the main product. The analyses for the combining interaction between $SiF_2$ radical and HNCO with the atom-in-molecules theory (AIM) have been performed.