• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1789-1793
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the reactions of 5-nitro-8-quinolyl nicotinate (4) and 5-nitro-8-quinolyl isonicotinate (5) with alkali metal ethoxides (EtOM; M = K, Na and Li) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [EtOM] curve slightly upward for the reactions with EtOK and EtONa but are linear for the reactions with EtOLi and for those with EtOK in the presence of 18-crown-6-ether. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that the reactivity increases in the order $EtO^-{\approx}EtOLi$ < EtOK < EtONa for the reactions of 4 and EtOLi < $EtO^-$ < EtOK < EtONa for the reactions of 5. Comparison of the kinetic results for the reactions of 4 and 5 with those reported previously for the corresponding reactions of 5-nitro-8-quinolyl benzoate (2) and picolinate (3) has revealed that the esters possessing a pyridine ring (i.e., 3-5) are significantly more reactive than the benzoate ester 2 due to the presence of the electronegative N atom (e.g., 2 << 3 < 4 < 5). It has been concluded that $M^+$ ion catalyzes the reactions of 3-5 by increasing the electrophilicity of the reaction center through a five-membered cyclic transition state (TS) for the reaction of 3 and via a four-membered cyclic TS for the reactions of 4 and 5.

• Publications of The Korean Astronomical Society
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• v.13 no.1 s.14
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• pp.149-166
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• 1998

The structure and environments of the molecular clouds near the SNR $HB3(G132.7\pm1.3)$ are studied. The molecular complex which is located at the southern rim of HB3 was proposed by former investigators as the one interacting with HB3. This complex region of $2^{\circ}\times2^{\circ}\;at\;l=133^{\circ}$ has been observed at $^{12}CO,\;^{13}CO,\;J=1-0\;at\;a\;1'$, resolution with the 14-m radio telescope at Taeduk Radio Astronomy Observatory. We have reached to the following four conclusions. The possibility that these molecular complex and HB3 are interacting with each other cannot be supported with any of our data. The morphologies of the two show no similarities. Neither particular features for the interaction are found in the CO lines. The hypothetical 'Molecular wall' which was expected to exist on the northwestern rim of HB3 as a cause for the noncircular morphology of HB3 is turned out to be nonexistent in CO. The molecular complex which resembles a 'bar' at a low resolution is now resolved into a U-shaped shell. It seems that the U-shape is consist of two independent components. No peculiarities, such as unseen masses or bright stars capable of forming HlI regions, are found within the U-shape region. The total mass included in the complex is estimated to be $M_{total}\;=\;2.9\~8.4\times10^5\;M_\bigodot$, which is in good agreement with previous observations within errors. Considering about 12 clumps distinguishable within the complex, the total mass implies that masses of each of clumps are on the order of $10^4\;M_\bigodot$, which makes these good objects for further studies in relation to star-formation. Especially the clumps associated with W3 are worthy for more high resolution observations for better understanding of astrophysical phenomenon ongoing in them.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.145-149
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• 2016

$(Bi_{1/2}Na_{1/2})_{0.94}Ba_{0.06}(Ti_{1-x}Nb_x)O_3$ (BNBTxNb) ceramics were investigated in terms of the crystal structure as well as the ferroelectric, dielectric, and piezoelectric properties. While little change was observed in the microstructure except for a slight decrease in the average grain size, a significant change was noticed in the temperature dependence of dielectric and piezoelectric properties. It was shown that the property changes are closely related to the downward shift in the position of the ferroelectric-to-relaxor transition temperature with increasing amount of Nb doping. A special emphasis is put on the fact that Nb doping is so effective at decreasing the ferroelectric-to-relaxor transition temperature that even at no more than 2 at.% Nb addition, the transition temperature was already brought down slightly below room temperature, resulting in the birth of a large strain at 0.46 %, equivalent to $S_{max}/E_{max}=767pm/V$.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.4
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• pp.409-412
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• 2002

The LNA(Low Noise Amplifier) is designed for use in low cost commercial application covered fully IMT-2000 band(1920~2170MHz, BW=250MHz). It is optimized source inductance for source lead and designed to equivalent etched line. The LNA uses a high pass impedance matching network for noise match and simple structure. The bias circuit designs have been made self-biased with a negative voltage applied to gate. The power supply voltage is 8V, total current is 180mA. The LNA is biased at a Vgs of -0.4, Vds of 4V for first stage and Vds of 5V for second stage. The LNA is designed competitively for commercial product specification. The measured gain and noise figure of the completed amplifier was 20dB and 1dB, respectively. Also, input VSWR, P1dB and gain flatness was measured of 1.14 ~ l.3dB, 22.4dBm and $\pm$0.45dB, respectively. The designed LNA can be used for commercial product.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1178-1183
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• 2004

In this paper, a novel microstrip patch antenna with switchable polarization is proposed. The proposed antenna has a simple structure, consisting of a square radiating patch, a pair of L-type spur-lines, and a microstrip line feed. It can produce either linear polarization or circular polarization by setting the diode on or off From the measured results, low cross polarization levels when operated in the linear polarization, and good axial ratios in the circular state have been observed.

• Asian Oncology Nursing
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• v.3 no.2
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• pp.122-132
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• 2003

Purpose: The purpose of this study was to identify predictive factors of Brest Self-Examination practice of clinical nurses. Method: The subject for this study were 277 nurses in 8 university hospitals in Busan. The data were collected from September 21 to October 20, 2001 by means of a structure questionnaire. The instruments used for this study were Choi's BSE knowledge scale. Kim's BSE attitude scale and Jung's BSE practice scale. The data were analyzed using frequency, percentage, mean, Peason Correlation, t-teat, ANOVA, scheffe's test, and multiple stepwise Regression using SPSS program. Result: 1. The mean score of BSE practice for the total sample was 7. 25${\pm}$4.62. 2. Statistically significant factors influencing the BSE Practice among social demographic characteristics were age(F=2.734, P=0.44), Married status(t=2.598, p=0.010). 3. Statistically significant factors influencing the BSE Practice among BSE relating characteristics were enlisting the help of significant peers(t=3.34, P=0.00), Intention of Practice for BSE(t=10.462, p=0.00), performance of BSE(t=7.800, P=0.00), frequency of performance in BSE(F=13.932, p=0.00), confidence in Knowledge of BSE technique(F=5.350, p=0.00), confidence in finding breast nodule(F=7.204, p=.00), asking client's BSE (t=3.153, P=0.01). 4.The mild correlation between nurse's BSE knowledge and practice was found(r=0.366,p=0.000). 5. There were significant predictors of BSE Practice. Performance of BSE was the best significant predictive factor(R2=.383, p=.000) Another significant predictive factors were knowledge, intension of practice, married status, frequency of performance. Conclusion: Degree of nurses' performance of BSE was average. It is necessary to develope the nurses' educational program for BSE with its focus on above predictive factors of performance of BSE.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2410-2414
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• 2014

A kinetic study is reported on nucleophilic substitution reactions of Y-substituted-phenyl picolinates (7a-7h) with a series of cyclic secondary amines in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. Comparison of the kinetic results with those reported previously for the corresponding reactions of Y-substituted-phenyl benzoates (1a-1f) reveals that 7a-7h are significantly more reactive than 1a-1f. The Br${\o}$nsted-type plot for the aminolysis of 4-nitrophenyl picolinate (7a) is linear with ${\beta}_{nuc}=0.78$, which is typical for reactions proceeding through a stepwise mechanism with expulsion of the leaving group being the rate-determining step. The Br${\o}$nsted-type plots for the piperidinolysis of 7a-7h and 1a-1f are also linear with ${\beta}_{lg}=-1.04$ and -1.39, respectively, indicating that the more reactive 7a-7h are less selective than the less reactive 1a-1f to the leaving-group basicity. One might suggest that the enhanced reactivity of 7a-7h is due to the inductive effect exerted by the electronegative N atom in the picolinyl moiety, while the decreased selectivity of the more reactive substrates is in accord with the reactivity-selectivity principle. However, the nature of intermediate (e.g., a stabilized cyclic intermediate through the intramolecular H-bonding interaction for the reactions of 7a-7h, which is structurally not possible for the reactions of 1a-1f) is also responsible for the enhanced reactivity with a decreased selectivity.

• Journal of the Korean Magnetics Society
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• v.26 no.3
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• pp.86-91
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• 2016

The cogging torque of a brushless dc (BLDC) motor results from the interaction between permanent magnets and iron core, and it causes noise and induce vibrations. During a manufacturing process, assembly tolerances lead to the change of the electromagnetic structure of a BLDC motor where permanent magnets are not properly glued to the surface of rotor core. In this paper, the effect of magnet separation from the surface of rotor core on the cogging torque is investigated due to assembly tolerance. The relationship with key design parameters is considered such as separation between magnets and rotor core, the number of magnets having separation, as well as the several types of arrangements among neighboring magnets. Finite element method (FEM) has been used to analyze a BLDC motor, and the allowable assembly tolerance is proposed to prevent generating noise and vibrations. Within proposed assembly tolerance, it is concluded that the cogging torque of a BLDC motor is decreased, and hence noise and vibrations.

• Korean journal of applied entomology
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• v.32 no.2
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• pp.193-199
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• 1993

The morphological relationship between Drosophila melanogaster and D. simulans, and their hybrids were investigated using comparisons of internal reproductive organs. male sex comb tooth number and male genital discs. InterspecIfic hybrids of all crosses were completely sterile, and had rudImentary gonads. Dysgenic ovaries and testes were morphologically similar to those of gonadal dysgenesis stenlity associated with the PM system in D. melal1ogaster. The mean number of sex comb tooth in D. melrmogaster, D. simulans and their male hybrids were 10.73, 8.35 and 9.97, respectively. The general aspects of the genital disc of the malo hybrid were a mosaic-like structure between D. melanogaster and D. simulans.

• Textile Coloration and Finishing
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• v.30 no.3
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• pp.190-198
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• 2018

We fabricated high transmission and high scattering poly(ethylene-co-vinyl acetate)(EVA) films embedding $SiO_2$ nanoparticles to improve outcoupling efficiency in organic display. The 800nm diameter $SiO_2$ nanoparticles aggregated and formed $1.56{\mu}m$ (with ${\pm}0.853{\mu}m$ standard deviation) diameter microparticles in EVA. The total transmission of scattering film was 83.3% on Polyethylene terephthalate(PET), which was higher than reference 82.8% PET substrate. The diffuse transmission and haze of the $SiO_2$ embedded EVA film were 76.1% and 91.4%, respectively. The optimized condition was 1:1 weight ratio of $SiO_2$ nanoparticles to EVA in Tetrahydrofuran(THF) solution. When the ratio of $SiO_2$ was larger than 1, the total transmission decreased by the increase in backscattering of light due to high scattering. With the optimized condition, we could succeed to fabricate a large scale film(35m in length) with a roll-to-roll process.