• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.128-134
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• 2012

The performance evaluation and fabrication of integrated-optic electric-field sensor utilizing $Ti:LiNbO_3$ asymmetric Mach-Zehnder intensity modulator with a push-pull lumped electrode and a plate-type probe antenna to measure an electric field strength is described. The modulator has a small device size of $46{\times}7{\times}1\;mm$ and operates at a wavelength $1.3{\mu}m$. The devices are simulated based on the BPM software and fabricated utilizing Ti-diffused $LiNbO_3$ channel optical waveguides. The minimum detectable electric field is 1.02 V/m and 6.91 V/m, corresponding to a dynamic range of ~35 dB and ~10 dB at the frequencies of 500 KHz and 5 MHz, respectively.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.1005-1112
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• 1995

The Effects of 0~9% stretching on the microstructure and mechanical properties have been investigated in Al-Li-Cu-Mg alloys. Stretching made T$_1$(Al$_2$CuLi) precipitates finer and more uniform, however, had no effect on the size of $\delta$'. The number of sheared $\delta$'precipitates distributed in the matrix were reduced. The 6% stretching improved the yield strength of the alloys aged at 15$0^{\circ}C$ for 120 hours from 328~342 MPa to 466~488MPa, however, decreased the elongation from 9.7~10.4% to 5.7%.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.507-512
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• 2005

When carbon electrode is used as an anode in Li ion battery, passivation film forms on the electrode surface during the initial charge process due to so called Solid-Electrolyte Interphase (SEI). The passivation film formed by solvent decomposition during the initial charge process affects charge/discharge capacity. In this paper, 1 M $LiPF_6,EC:DEC$ (1 : 1, volume ratio) electrolyte with $Li_2CO_3$, at various temperatures, the electrochemical characteristics of passivation film formed on Kawasaki Mesophase Fine Carbon electrode surface were investigated by using chronopotentiometry, cyclic voltammetry, and impedance spectroscopy. Experimental observations indicated that as solvent decomposition occurred, the decomposition voltage was strongly dependent on ionic conductivity, which was low in the process at low temperature. The impedance of passivation film formed during the initial charge process, were dependent on the temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.389-393
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• 2000

High-quality $Er^{3+}$ doped Mg : $LiNbO_3$single crystal fibers were grown by a micro-pulling down ($\mu$-PD) method. Single crystal fibers were pulled down through the nozzle, at a pulling down rate of 0.5 mm/min and using a Pt crucible with a nozzle 1 mm in diameter in air atmosphere. Defects such as bubbles, cracks and inclusions were not detected in any of the grown crystals. The optical transmission of Er : Mg : $LiNbO_3$crystal was measured and the energy levels of $Er_2O_3$ ion could be calculated. The photoluminescence spectrum of crystal fibers showed an energy band emission with the strongest line corresponding to the $^4I_{3/2}{\to}^4I_{15/2}$transition. The concentration dependence of the entire wavelength region emission intensity upon excitation intensity measured emission intensity for the 3 mol% MgO doped fibers was larger than that for the 1, 5 mol% MgO doped fibers.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.659-662
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• 2012

Yttrium (Y) and niobium (Nb) doped spherical $Li_4Ti_5O_{12}$ were synthesized to improve the energy density and electrochemical properties of anode material. The synthesized crystal was $Li_4Ti_5O_{12}$, the particle size was less than $1{\mu}m$ and the morphology was spherical and well dispersed. The Y and Nb optimal doping amounts were 1 mol% and 0.5 mol%, respectively. The initial capacity of the dopant discharge and charge capacity were respectively 149mAh/g and 143 mAh/g and were significantly improved compared to the undoped condition at 129 mAh/g. Also, the capacity retention of 0.2 C/5 C was 74% for each was improved to 94% and 89%. It was consequently found that Y and Nb doping into the $Li_4Ti_5O_{12}$ matrix reduces the polarization and resistance of the solid electrolyte interface (SEI) layer during the electrochemical reaction.

• Journal of Hydrogen and New Energy
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• v.31 no.6
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• pp.622-629
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• 2020

The performance and cost of electric vehicles (EVs) are much influenced by the performance and service life of the Li-ion battery system. In particular, the cell performance and reliability of Li-ion battery packs are highly dependent on their operating temperature. Therefore, a novel battery thermal management is crucial for Li-ion batteries owing to heat dissipation effects on their performance. Among various types of battery thermal management systems (BTMS'), the phase change material (PCM) based BTMS is considered to be a promising cooling system in terms of guaranteeing the performance and reliability of Li-ion batteries. This work is mainly concerned with the basic research on PCM based BTMS. In this paper, a basic experimental study on PCM based battery cooling system was performed. The main purpose of the present study is to present a comparison of two PCM-based cooling systems (n-Eicosane and n-Docosane) of the unit 18650 battery module. To this end, the simplified PCM-based Li-ion battery module with two 18650 batteries was designed and fabricated. The thermal behavior (such as temperature rise of the battery pack) with various discharge rates (c-rate) was mainly investigated and compared for two types of battery systems employing PCM-based cooling. It is considered that the results obtained from this study provide good fundamental data on screening the appropriate PCMs for future research on PCM based BTMS for EV applications.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.6
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• pp.228-241
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• 2021

This study verified the performance change of a LiDAR when it detects road signs, which are potential cooperation targets for an autonomous vehicle. In particular, road signs of different colors and materials were produced and tested in controlled rainfall on the real road environment. The NPC and intensity were selected as the performance indicators, and a T-Test was used for comparison. The study results show that the performance of LiDAR for the detection of road signs was reduced with the increase of rainfall. The degradation of performance in retroreflective sheets was lesser than painted road signs, but at the amount of 40 mm/h or more, the detection performance of retroreflective sheets deteriorates to an extent that data cannot be collected. The performance level of black paint was lower than that of other colors on a clear day. In addition, the white sheet was most sensitively degraded with the increase in precipitation. These performance verification results are expected to be utilized in the manufacturing of road facilities that improve the visibility of sensors in the future.

• Journal of IKEEE
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• v.26 no.2
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• pp.232-239
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• 2022

We analyzed the effect of post-annealing on lithium phosphate (Li₃PO₄) solid-state thin-film. Li₃PO₄ thin films were deposited by radio frequency (RF) sputtering, with subsequent annealing of the films at 200-400 ℃. SEM imaging of the sample surfaces showed no significant difference in morphology between the annealed and non-annealed samples. XRD analysis indicated that the samples consist of an amorphous-like structure. Post-annealing changes in binding energy were confirmed by XPS analysis, while the leakage current density at -6 V was measured to be about 7.15 times lower in a device that had been annealed at 400 ℃ vs a non-annealed device. It was confirmed that the leakage current decreased with increasing post-annealing temperature.

• Journal of Powder Materials
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• v.30 no.6
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• pp.516-520
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• 2023

Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO₄ is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO₄O has two redox reactions (V⁵⁺/V⁴⁺/V³⁺) but low electrochemical activity. In this study, LiVPO₄O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO₄O_1-xF_x, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

• Journal of Pharmacopuncture
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• v.8 no.2
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• pp.67-82
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• 2005

Effects of Phaseoli Semen rubra Herbal-acupuncture at zusanli(ST-36), Quchi(LI-11) and Sanyinjiao(Sp-6) on lipid composition, liver function, oxidative capacity and molecular biological aspects were investigate in high fat diet induced obese rats. Forty male Sprague-Dawley rats weighing about 400g were divided into 4 groups according to body weight and raised four weeks with control, zusanli(ST-36), Quchi(LI-11) and Sanyinjiao(Sp-6) Herbal-acupuncture groups. 1. Plasma total cholesterol and LDL-cholesterol showed a low values in the (ST-36) and (LI-11) Herbal-acupuncture groups and HDL-cholesterol showed a high values in the (ST-36) Herbal-acupuncture groups. 2. Plasma triglyceride and glucose showed a low values in the (ST-36) and (LI-11) Herbal-acupuncture groups. 3. The contents of plasma free fatty acids showed a tendence to decrease in the Herbal-acupuncture groups, however in the Herbal-acupuncture groups, the values showed no significantly different. 4. The activities of AST and ALT showed no significantly different in all treatment groups. 5. The contents of plasma ${\beta}-lipoprotein$ and free fatty acids showed a tendency to decrease in the Herbal-acupuncture groups compared to those of control group. In the Herbal-acupuncture groups, the values of (ST-36) and (LI-11) Herbal-acupuncture groups showed a low in the acupuncture groups. 6. Liver total cholesterol and triglyceride showed a low values in the (ST-36) and (LI-11) Herbal-acupuncture groups. 7. Contents of plasma TBARS showed a low values in the (ST-36) and (LI-11) Herbal-acupuncture groups, however contents of liver TBARS showed no significantly different among treatment groups. 8. Values of liver glutathione peroxidase and catalase activity showed a tendency to increase in the (ST-36) and (LI-11) Herbal­acupuncture groups. Values of liver super oxide dismutase activity showed a high in the (ST-36) Herbal-acupuncture groups compared to those of other groups. 9. Expression of apo-B mRNA in liver cell showed a low in (ST-36) Herbal-acupuncture groups, however expression of apo-E mRNA showed a high in Herbal-acupuncture groups and $TNF-{\alpha}$ mRNA in adipose cell showed no different among all the treatment groups. Expression of Leptin mRNA showed a tendance to decrease in (ST-36) Herbal-acupuncture group. 10. Histological character of liver, those of (ST-36) Herbal-acupuncture group showed a good, however other treatment groups showed slight vasodilation and slight fat accumulation. These results indicated that Phaseoli Semen rubra Herbal-acupuncture at (ST-36) and (LI-22) suppressed adipose tissue mass and lipid peroxidation and increased antioxidant system.