• Current Photovoltaic Research
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• 제2권2호
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• pp.53-58
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• 2014

$Tb^{3+}$ - or $Ce^{3+}$-doped $LaBO_3$ phosphors were synthesized by a solid-state reaction process with different concentrations of activator ions. The XRD spectra showed the monoclinic $LaBO_3$ pattern with the main peak occurring at (014) plane, irrespective of the kind of activator ions. The crystallite size was determined by using the Scherrer formula, and the maximum was obtained with an activator concentration of 0.05 mol for both phosphors. The emission spectra of $LaBO_3$ phosphors doped with $Tb^{3+}$ ions under excitation at 269 nm exhibited three major emission bands at 488, 544, and 587 nm. The strongest emission was green at 544 nm owing to the $^5D_4-^7F_5$ transition at a $Tb^{3+}$ ion concentration of 0.05 mol. For the $Ce^{3+}$-doped $LaBO_3$ phosphors, one strong blue band centered at 469 nm and weak multipeaks were observed. These results suggest that the optimum green and blue emission can be realized by controlling the concentration and type of activator ions incorporated in the host crystal.

• 한국미생물생명공학회:학술대회논문집
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• 한국미생물생명공학회 2001년도 Proceedings of 2001 International Symposium
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• pp.135-136
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• 2001

The Tk-ptp gene encoding a protein tyrosine phosphatase (PTPase) from the hyperthermophilic archaeon Thermococcus kodakaraensis KODI was cloned and sequenced. Sequence analysis indicated that Tk-ptp encoded a protein consisting 147 amino acid residues (16,953 Da). The wild type and the mutants were expressed in Escherichia coli cells as His-tagged fusion proteins and examined for enzyme characteristics. Tk-PTP possessed two unique features that were not found in eucaryal and bacterial counterparts. First, the recombinant Tk-PTP showed the phosphatase activity not only for the phosphotyrosine but also phosphoserine. Second, the conserved Asp (Asp-63), which was considered to be a critical residue, was not involved in catalysis. In order to know a specific substrate for Tk-PTP, C93S mutant was used to trap substrate protein. Proteins of 120, 60 and 53 kDa were isolated specifically from KODI cell lysates by affinity chromatography with Tk-PTP-C93S. It is suggested that these proteins are tyrosine-phosphorylated substrates of Tk-PTP.

• 한국정밀공학회지
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• 제32권2호
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• pp.149-157
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• 2015

Ball and roller bearings are commonly used machine elements for supporting rotating motion about shafts in simple devices including bicycles, in-line skates, and electric motors, as well as in complex machines. Heat is generated by the friction in the bearings, which causes the temperature inside the bearing to increase. If the heat is not appropriately removed from the bearing, elevated temperatures may give rise to premature failure. It is, therefore, important to be able to calculate the temperature in the bearings due to friction.Here, we describe a method to estimate the frictional torque in bearings using an empirical formula developed using a method based on bearing analysis tool and the measured frictional torque in a spindle system. Thermal analysis of the spindle system including the bearings was achieved using the finite element method (FEM), and the bearing temperature was compared with measured data to verify the empirical formula.

• 한국측량학회지
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• 제32권6호
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• pp.591-597
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• 2014

A wide variety of image application methods, such as aerial image, terrestrial image, terrestrial laser, and stereo image point are currently under investigation to develop three-dimensional 3D geospatial information. In this study, matching points, which are needed to build a 3D model, were examined under diverse weather conditions by analyzing the stereo images recorded by closed circuit television (CCTV) cameras installed in the U-City. The tests on illuminance and precipitation conditions showed that the changes in the number of matching points were very sensitively correlated with the changes in the illuminance levels. Based on the performances of the CCTV cameras used in the test, this study was able to identify the optimal values of the shutter speed and iris. As a result, compared to an automatic control mode, improved matching points may be obtained for images filmed using the data obtained through this test in relation to different weather and illuminance conditions.

• 한국분말재료학회지
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• 제21권3호
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• pp.222-228
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• 2014

Much research into fuel cells operating at a temperature below $800^{\circ}C$. is being performed. There are significant efforts to replace the yttria-stabilized zirconia electrolyte with a doped ceria electrolyte that has high ionic conductivity even at a lower temperature. Even if the doped ceria electrolyte has high ionic conductivity, it also shows high electronic conductivity in a reducing environment, therefore, when used as a solid electrolyte of a fuel cell, the powergeneration efficiency and mechanical properties of the fuel cell may be degraded. In this study, gadolinium-doped ceria nanopowder with $Al_2O_3$ and $Mn_2O_3$ as a reinforcing and electron trapping agents were synthesized by ultrasonic pyrolysis process. After firing, their microstructure and mechanical and electrical properties were investigated and compared with those of pure gadolinium-doped ceria specimen.

• 원예과학기술지
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• 제32권5호
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• pp.694-701
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• 2014

Allium hookeri L. (Alliaceae family) is an important ethnomedicinal plant native to the Himalayan region of Asia. The aim of this research was to establish a high-frequency plant regeneration system for in vitro propagation of A. hookeri. Among the tissue types examined, receptacle explants derived from immature flower buds showed the highest regeneration rate of shoots ($93.33{\pm}4.63%$), roots ($76.67{\pm}7.85%$), and calli ($80.00{\pm}7.43%$) when cultured on Gamborg B5 (B5) medium containing $10{\mu}M$ 6-benzylaminopurine (BA) + $1{\mu}M$ naphthalene acetic acid (NAA), $0.5{\mu}M$ BA + $5{\mu}M$ NAA, and $1{\mu}M$ BA + $10{\mu}M$ NAA, respectively. Shoot multiplication was superior when cultured in liquid rather than on solid medium and relatively high concentrations of BA, ranging from 5 to $10{\mu}M$. Efficient bulblet formation following root induction from shoot clumps was achieved with culture in liquid B5 medium containing 7% (w/v) sucrose. Regenerated bulblets were successfully acclimatized to ex vitro conditions with a greater than 95% survival rate. By this method, a maximum of 62 plantlets per receptacle could be propagated within 9 weeks of initial culture. The in vitro propagation system established in this study will promote A. hookeri biotechnology, including large-scale production of healthy and aseptic clones, preserving parental genotypes with desirable traits, and genetic manipulation to enhance medicinal value.

• Journal of the Optical Society of Korea
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• 제15권2호
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• pp.161-167
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• 2011

In this paper, we propose an in-plane switching (IPS) mode for liquid crystal displays (LCDs) that, in principle, is free of retardation of the LC cell. Basically, the optical configuration of the LC cell consists of an A-plate and an LC layer for switching between the dark and bright states. We could achieve a fast response time compared with the conventional in-plane LC cell because the free retardation condition of the proposed LC cell enables us to reduce the cell gap even by quarter-wave retardation without any change of the optimized LC material in the transmissive mode. Experiments for verification of the proposed in-plane switching LC cells have shown a significant reduction of the rising time and falling time simultaneously due to the small cell gap. Furthermore, we also proposed an optical configuration for wide viewing property of the retardation free IPS LCD by applying the optical films. We proved the wide-view property of the retardation free IPS LCD by comparing its optical luminance with the calculated optical property of the conventional IPS LCD.

• Nuclear Engineering and Technology
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• 제20권4호
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• pp.246-252
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• 1988

KAERIT 토카막 장치의 플라즈마 생성을 위한 수소기차 방전실험에 관해 기술하였다. 이 실험에서는 일주전압, 토로이달 자장, 충전기체 압력, 오차자장 및 예비전리 등이 방전시작에 미치는 영향이 연구되었다. 오차자장은 방전에 가장 큰 영향을 미치는 인자로서 방전전압이 최소가 되는 것은 결국 오차자장 성분을 가장 잘 상쇄시켰을 때였다. 예비전리의 효과는 전반적으로 두드러지지는 않았지만 밀폐 성능이 나쁠수록 상대적으로 크게 나타났다. 실험적으로 구해진 방전시작조건은 이론적인 모델의 계산결과와 비교하였다. 실험에서의 방전영역이 이론적인 계산결과에 비해 줄어드는 경향을 보이고 있는 것은 고려되지 않은 다른 인자에 기인하는 것으로 판단되지만 토카막의 방전시작단계를 다루기에는 이 모델로도 충분하다.

• Elastomers and Composites
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• 제51권4호
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• pp.263-268
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• 2016

In the polymer shaping process that uses molds, the quality of the molded products is determined not only by the flow of the (molten) polymer but also by the air venting in the cavity. Inadequate air venting in the cavity can cause defects in the product, such as voids, short shot, or black streaks. As it is critical to consider the location and size of the vents for proper venting of the air in the cavity, a method that predicts the flow of air and material is required. The venting of air by the flow of rubber inside the cavity was simulated by using a multi-phase computational fluid dynamics method. Through computer simulation, the interface of rubber and air over time was predicted. Then, the velocity and pressure distribution of the venting air were observed. Our research proposes a fundamental method for analyzing the multi-phase flow of polymer materials and air inside the cavity of a mold.

• Journal of Applied Biological Chemistry
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• 제42권4호
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• pp.169-174
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• 1999

Arabidopsis AHL gene contains 4 exons encoding a putative protein highly homologous to the yeast salt-sensitive enzyme HAL2, a 3'(2'),5'-bisphosphate nucleotidase involving in reductive sulfate assimilation. AHL cDNA complemented yeast met22 (hal2) mutant. AHL fusion protein expressed in E. coli exhibited $Mg^{2+}$-dependent, 3'-phosphoadenosine 5'-phosphate (PAP)-specific phosphatase activity. $Li^+,\;Na^+,\;K^+$ and $Ca^{2+}$ ions inhibit the enzyme activity by competing with $Mg^{2+}$ for the active site of the enzyme. The enzyme activity was also sensitive to ${\mu}M$ concentrations of toxic heavy metal ions such as $Cd^{2+},\;Cu^{2+}$ and $Zn^{2+}$, but was not recovered by addition of more $Mg^{2+}$ ions, suggesting that these ions inactivate the enzyme with a mechanism other than competition with $Mg^{2+}$ ions. Inhibition of the AHL enzyme activity may result in accumulation of PAP, which is highly toxic to the cell. Thus, the AHL enzyme could be one of the intial targets of heavy metal toxicity in plants.