• Publications of The Korean Astronomical Society
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• v.24 no.1
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• pp.19-34
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• 2009

From the short-period variability survey (SPVS) in Bohyunsan Optical Astronomy Observatory, I obtained time-series BV CCD images in the region of the young open cluster M29 (NGC 6913) for 15 nights from May 30, 2008 to September 17, 2009. I observed 48 variable stars including 45 new ones. They consisted of 5 $\delta$ Scuti, a Cepheid, 16 eclipsing binaries and 24 semi-long periodic and/or slow irregular type variable stars including $\beta$ Cephei and LPB type stars. For the rest two ones, the type of variability was not defined. I also checked the variability of the 26 known variable stars listed in the GCVS. Only three ones among 26 known variable stars confirmed variability.

• Kyungpook Mathematical Journal
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• v.55 no.3
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• pp.705-714
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• 2015

In this paper, we introduce and investigate an interesting subclass $M_{\Sigma}({\gamma},{\lambda},{\delta},{\varphi})$ of analytic and bi-univalent functions of complex order in the open unit disk ${\mathbb{U}}$. For functions belonging to the class $M_{\Sigma}({\gamma},{\lambda},{\delta},{\varphi})$ we investigate the coefficient estimates on the first two Taylor-Maclaurin coefficients ${\mid}{\alpha}_2{\mid}$ and ${\mid}{\alpha}_3{\mid}$. The results presented in this paper would generalize and improve some recent works of [1],[5],[9].

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1250-1252
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• 2003

This Paper presents Sigma-Delta Modulation(SDM) schemes to generate switching waveform for a high-power factor boost-type rectifier. The SDM scheme can be implemented by simple digital algorithm unlike conventional PWM schemes with several hardware, and has the characteristics of spectrum-spreading and noise-shaping effects, which are profitable in harmonic reduction of input current in the boost-type rectifier. The comparison results of their spectrum performances shows that the 1st-order SDM has better harmonic suppression effect than conventional PWM scheme and Dithered SDM scheme.

• Journal of Applied Biological Chemistry
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• v.51 no.6
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• pp.262-271
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• 2008

Natural abundances of stable isotopes of nitrogen and carbon (${\delta}^{15}N$ and ${\delta}^{13}C$) are being widely used to study N and C cycle processes in plant and soil systems. Variations in ${\delta}^{15}N$ of the soil and the plant reflect the potentially variable isotope signature of the external N sources and the isotope fractionation during the N cycle process. $N_2$ fixation and N fertilizer supply the nitrogen, whose ${\delta}^{15}N$ is close to 0%o, whereas the compost as. an organic input generally provides the nitrogen enriched in $^{15}N$ compared to the atmospheric $N_2$. The isotope fractionation during the N cycle process decreases the ${\delta}^{15}N$ of the substrate and increases the ${\delta}^{15}N$ of the product. N transformations such as N mineralization, nitrification, denitrification, assimilation, and the $NH_3$ volatilization have a specific isotope fractionation factor (${\alpha}$) for each N process. Variation in the ${\delta}^{13}C$ of plants reflects the photosynthetic type of plant, which affects the isotope fractionation during photosynthesis. The ${\delta}^{13}C$ of C3 plant is significantly lower than, whereas the ${\delta}^{13}C$ of C4 plant is similar to that of the atmospheric $CO_2$. Variation in the isotope fractionation of carbon and nitrogen can be observed under different environmental conditions. The effect of environmental factors on the stomatal conductance and the carboxylation rate affects the carbon isotope fractionation during photosynthesis. Changes in the environmental factors such as temperature and salt concentration affect the nitrogen isotope fractionation during the N cycle processes; however, the mechanism of variation in the nitrogen isotope fractionation has not been studied as much as that in the carbon isotope fractionation. Isotope fractionation factors of carbon and nitrogen could be the integrated factors for interpreting the effects of the environmental factors on plants and soils.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.61-69
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• 2016

A numerical simulation of the solid/liquid coexistence temperature range, using solidification segregation model linked with the Kurz-Giovanola-Trivedi model, explained the mechanism of the BTR shrinkage (with an increase in welding speed) in type 310 stainless steel welds by reduction of the solid/liquid coexistence temperature range of the weld metal due to the inhibited solidification segregation of solute elements and promoted dendrite tip supercooling attributed to rapid solidification of laser beam welding. The reason why the BTR enlarged in type 316 series stainless welds could be clarified by the enhanced solidification segregation of impurity elements (S and P), corresponding to the decrement in ${\delta}-ferrite$ crystallization amount at the solidification completion stage in the laser welds. Furthermore, the greater increase in BTR with type 316-B steel was determined to be due to a larger decrease in ${\delta}-ferrite$ amount during welding solidification than with type 316-A steel. This, in turn, greatly increases the segregation of impurities, which is responsible for the greater temperature range of solid/liquid coexistence when using type 316-B steel.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.516-521
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• 1989

Reaction between the $N_2O_2-type$ tetradentate ligand, ethylenediamine-N,N'-di-S-${\alpha}$-isobutylacetic acid (SS-emiba) and $RhCl_3{\cdot}3H_2O$ has yielded ${\Delta}-s-cis-\;and\;{\wedge}-uns-cis-[Rh(SS-eniba)Cl_2]-$. ${\Delta}-s-cis-[Rh(SS-eniba)Cl_2]^-$ has been utilized to react with S-methyl-L-cystcine(Smc) to give ${\Delta}-s-cis-[Rh(SS-eniba(Smc)]^+$. The oxidation of ${\Delta}-s-cis-[Rh(SS-eniba(Smc)]^+$ using $H_2O_2$ has produced ${\Delta}-s-cis-[Rh(SS-eniba)(Smc-o)]^+$, in which the coordinated sulfur has been converted into the sulfoxide group. In a separate series of experiments the S-methyl-L-cysteine is oxidized by $H_2O_2$ to give S-methyl-L-cysteine sulfoxide, which is then coordinated to ${\Delta}-s-cis-[Rh(SS-eniba)Cl2]^-$ to make the standard complet of ${\Delta}-s-cis-[Rh(SS-eniba)(Sme-o)]+$ for comparison with the complex obtained from the oxidation of ${\Delta}-s-cis-[Rh(SS-eniba)(Smc)]^+\;by\;H_2O_2.$

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.109-112
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• 2005

Electronic and magnetic properties of $Ti_{1-x}M_xO_{2-\delta}$ (M=Co and Fe) thin films grown by sol-gel method have been investigated. Anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films were successfully grown on $Al_2O_3$ (0001) substrates and exhibited p-type electrical conductivity while the undoped films n-type conductivity. Room temperature vibrating sample magnetometry measurements on the anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films with same x ($=4.8 at.{\%}$) showed quite similar magnetic hysteresis curves with the saturation magnetic moment of $\~4 {\mu}_B$ per Co ion despite their differences in structural and electronic properties. Such giant magnetic moment is attributable to the unquenched orbital moment of the $Co^{2+}$ ions substituting the octahedral $Ti^{4+}$ sites. Similar ferromagnetic behavior was observed for $Ti_{1-x}Fe_xO_{2-\delta}$ films that are highly resistive compared to the Co doped samples. Saturation magnetic moment was found to decrease for higher x, i.e., $\~2$ and $\~1.5 {\mu}_B$ per Fe ion for x=2.4 and 5.8 at. $\%$, respectively. Conversion electron $M\ddot{o}ssbauer$ spectroscopy measurements predicted the coexistence of $Fe^{2+}$ and $Fe^{3+}$ ions at the octahedral sites of $Ti_{1-x}Fe_xO_{2-\delta}$.

• Journal of Korea Foundry Society
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• v.33 no.4
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• pp.162-170
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• 2013

The effects of Mn content and cooling rate on the eutectic reaction of flake graphite cast irons were studied by a combined analysis of macro/micro-structure and cooling curve data. The correlation between the eutectic reaction parameter and macro/microstructure was systematically investigated. Two sets of chemical compositions with different Mn contents were designed to cast. Three types of molds for cylindrical specimens with different diameters were prepared to analyze the cooling rate effect. The difference between undercooling temperature and cementite eutectic temperature (${\Delta}T_1=T_U-T_{E,C}$), which is decreased by increasing the Mn content or increasing the cooling rate, is considered to be a suitable eutectic reaction parameter for predicting graphite morphology. According to the criterion, A-type graphite is mainly suggested to form for ${\Delta}T_1$ over $20^{\circ}C$, and D-type graphite is mainly suggested to form for ${\Delta}T_1$ below $0^{\circ}C$. Eutectic reaction time (${\Delta}T$), which is increased by increasing the Mn content and decreased by increasing the cooling rate, is regarded as a suitable eutectic reaction parameter for predicting eutectic cell size. Eutectic cell size is found to decrease in proportion to the decrease of ${\Delta}T$.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.273-284
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• 2020

This paper proposes a method of designing and controlling delta robots with low-cost DC motors, which are widely used in the automation process. Simulation was performed by interpreting the mechanics and dynamics of the delta robot, and based on this analysis, low-cost DC motor was selected. Experiments were conducted to obtain characteristic values of motors and the current-position cascade control system was designed and implemented. In order to verify the feasibility of the proposed system, the experiment to check that the end-effector of the delta robot follows the target path was progressed. Through the experiment, the limitations of using low-cost motors were overcome by designing compensation algorithms and the performance of the position control was verified.

• BMB Reports
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• v.28 no.6
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• pp.484-489
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• 1995

The product of bacteriophage T7 gene 2.5 is a single-stranded DNA binding protein and plays an important role in T7 DNA replication, recombination, and repair. Genetic analysis of T7 phage defective in gene 2.5 shows that the gene 2.5 protein is essential for T7 DNA replication and growth (Kim and Richardson, 1993). The C-terminal truncated gene 2.5 protein ($GP2.5-{\Delta}21C$) cannot substitute for wild-type gene 2.5 protein in vivo; suggesting that the C-terminal domain of gene 2.5 protein is essential for protein-protein interactions (Kim and Richardson, 1994; J. Biol. Chem. 269, 5070-5078). Truncated gene 2.5 proteins lacking 19 residues ($GP2.5-{\Delta}19N$) and 39 residues ($GP2.5-{\Delta}39N$) from the amino-terminal domain were constructed by in vitro mutagenesis. $GP2.5-{\Delta}19N$ can support the growth of T7 phage lacking gene 2.5 while $GP2.5-{\Delta}39N$ cannot substitute for wild-type gene 2.5 protein in vivo; however, its ability to bind to single-stranded DNA is not affected. These results clearly demonstrate that the 20~39 amino-terminal region of gene 2.5 protein is required for T7 growth in vivo but may not be involved in DNA binding activity.