• Applied Biological Chemistry
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• v.28 no.2
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• pp.51-55
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• 1985

Dried black soybeans were soaked in water at the temperature range of $4^{\circ}C{\sim}100^{\circ}C$ and in salt or sugar solution at $100^{\circ}C$ in order to investigate their effects on the cooking ratio and diffusion property of color pigments. As the temperature increased, the equilibrated absorbance at 490nm of soaking water after 120min was linearly increased. The activation energy for diffusion of color pigments were found to be 4.23 Kcal/mole at the range of $60^{\circ}C{\sim}100^{\circ}C$ and 8.31 kca1/mo1e at $4^{\circ}C{\sim}60^{\circ}C$. The cooking ratio, % cooked beans after heating, of black soybeans were more affected by the salt concentration that of sugar. Both concentrations reduced the cooking ratio as they increased. The sorption isotherm of Kongjaban showed a quite different curves between the storage at $4^{\circ}C$ and $25^{\circ}C$. The sorption and desorption rates during storage could be represented by the equation of $log({\frac{dw}{dt}}{\times}10^3))=alogt+logb$ with a very high correlation.

• Nuclear Engineering and Technology
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• v.11 no.2
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• pp.119-126
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• 1979

The reaction of 4,4'-dihydroxydiphenl methane (4,4'-DPM) with glycidyl methacrylate (GMA) catalyzed by triethylbenzyl ammonium chloride (TEBAC) has been studied for the purpose of synthesis of electron beam curable prepolymer. The reaction was in good agreement with third-order kinetics. according to -d[GMA]/dt=k[TEBAC][DPM][GMA] and the apparent activation energy was about 33.4kca1/mole. However, the reaction rates were increased if tile reaction proceeded after the mixtures exposed to air for 24 hrs at room temperature. The effects of the catalyst and the difference in the reactivity between 2.2'-DPM to GMA were discussed. The plausible reaction mechanism was proposed on basis of experimental data obtained.

• International journal of advanced smart convergence
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• v.4 no.1
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• pp.64-70
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• 2015

This paper proposes fluorescent electronic ballast with high power factor and low line input current harmonics. The system performance can be improved by a charged pump circuit. Details of design and circuit operation are described. The proposed electronic ballast is modified from single-stage half bridge class D electronic ballast by adding capacitor parallel with each power switch and setting the circuit parameter to operate under class DE inverter condition. By using this proposed method the DC bus voltage can be reduced around by 50% compare with conventional class D inverter circuit. Because the power switches are operated at zero voltage switching condition and low dv/dt of class DE switching. The experimental results show that the proper frequency of the prototype is around 50 kHz with input power factor of 0.982, $THD_i$ 10.2% at full load and efficiency of more than 90%.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.448-456
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• 2012

This paper presents a multilevel inverter configuration which is designed by insertion of a bidirectional switch between capacitive voltage sources and a conventional H-bridge module. The modified inverter can produce a better sinusoidal waveform by increasing the number of output voltage levels. By serial connection of two modified H-bridge modules, it is possible to produce 9 output voltage levels including zero. There are 24 basic switching patterns with the 9 output voltage levels. Among the patterns, we select the 2 most efficient switching patterns to get a lower switching loss and minimum dv/dt stress. We then analyze characteristics of Total Harmonic Distortion (THD) of the output voltage with variation of input voltage by computer-aided simulations and experiments.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.479-487
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• 1988

In this study we studied the function of Glycerol as a DCCA(Drying Control Chemical Additives) in the preparation of silica bulk glas through Sol-Gel method. We used TEOS(Tetra Ethyl Ortho Silicate) and maintained the mixing ratio of TEOS : H2O : EtOH : HCI as 1 : 4 : 4 : 0.0007(mol) and varied glycerol input quantity from 0.1vol% considering the ethnaol input quantity as 100vol%. We investigated the changes from Sol-Gel Synthetic solutions to the glass using DT-TG, FT-IR and other instruments. The results obtained from this experiment showed that the dried gels made from the synthetic solutions containing 0.1-1.0vol% of glycerol were easily heat-treated up to 85$0^{\circ}C$ so that transparant bulk silica glass was prepared.

• Journal of The Korean Astronomical Society
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• v.46 no.4
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• pp.151-159
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• 2013

We discuss the orbital period changes of the Algol semi-detached eclipsing binary DI Peg by constructing the (O-C) residual diagram via using all the available precise minima times. We conclude that the period variation can be explained by a sine-like variation due to the presence of a third body orbiting the binary, together with a long-term orbital period increase (dP/dt=0.17 sec/century) that can be interpreted to be due to mass transfer from the evolved secondary component (of rate $1.52{\times}10^{-8}M_{\odot}/yr$) to the primary one. The detected low-mass third body ($M_{3min.}=0.22{\pm}0.0006M_{\odot}$) is responsible for a periodic variation of about 55 years light time effect. We have determined the orbital parameters of the third component which show a considerable eccentricity $e_3=0.77{\pm}0.07$ together with a longitude of periastron ${\omega}_3=300^{\circ}{\pm}10^{\circ}$.

• Korean Journal of Mathematics
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• v.25 no.4
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• pp.483-494
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• 2017

In the current manuscript, we investigate the pointwise convergence of the singular integral operators involving power nonlinearity given in the following form: $$T_{\lambda}(f;x)={\int_a^b}{\sum^n_{m=1}}f^m(t)K_{{\lambda},m}(x,t)dt,\;{\lambda}{\in}{\Lambda},\;x{\in}(a,b)$$, where ${\Lambda}$ is an index set consisting of the non-negative real numbers, and $n{\geq}1$ is a finite natural number, at ${\mu}$-generalized Lebesgue points of integrable function $f{\in}L_1(a,b)$. Here, $f^m$ denotes m-th power of the function f and (a, b) stands for arbitrary bounded interval in ${\mathbb{R}}$ or ${\mathbb{R}}$ itself. We also handled the indicated problem under the assumption $f{\in}L_1({\mathbb{R}})$.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1298-1305
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• 2016

This paper presents the development of a short-circuit protection mechanism on a high voltage switch (HVS) board which is built by a series connection of semiconductor switches. The HVS board is able to quickly detect and limit the peak fault current before the signal board triggers off a gate signal. Voltage clamping techniques are used to safely turn off the short-circuit current and to prevent overvoltage of the series-connected switches. The selection method of the main devices and the development of the HVS board are described in detail. Experimental results have demonstrated that the HVS board is capable of withstanding a short-circuit current at a rated voltage of 10kV without a di/dt slowing down inductor. The corresponding short-circuit current is restricted to 125 A within 100 ns and can safely turn off within 120 ns.

• Bulletin of the Korean Mathematical Society
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• v.49 no.4
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• pp.787-797
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• 2012

In this paper the authors study the $L^p$ boundedness for parabolic Littlewood-Paley operator $${\mu}{\Phi},{\Omega}(f)(x)=\({\int}_{0}^{\infty}{\mid}F_{\Phi,t}(x){\mid}^2\frac{dt}{t^3}\)^{1/2}$$, where $$F_{\Phi,t}(x)={\int}_{p(y){\leq}t}\frac{\Omega(y)}{\rho(y)^{{\alpha}-1}}f(x-{\Phi}(y))dy$$ and ${\Omega}$ satisfies a condition introduced by Grafakos and Stefanov in [6]. The result in the paper extends some known results.

• JOURNAL OF ELECTRICAL WORLD
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• s.255
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• pp.76-83
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• 1998

대용량 파워일렉트로닉스기기의 보다 대용량화$\cdot$소형경량화 및 저손실화 요구에 응하기 위하여 조지전압 4.5KV, 가제어전류 4KA의 고내압$\cdot$대용량 CGT(gate commutated turn-off : 게이트 전류형 턴오프) 사이리스터를 개발하여 상품화하였다. GCT사이리스터는 대용량 파워일렉트로닉스기기의 키파트로서 폭넓게 사용되고 있는 GTO(Gate turn-off)사이리스터와 Turn-on동작이 같고 gto사이리스터의 이점이 저On전압특성을 그대로 갖는 한편 턴오프동작은 ''턴오프 게인이 1''인 새로운 원리에 기초하고 있으며 턴오프특성에서는 GTO사이리스터에 비해 다음과 같은 특징을 갖고있다. (1)GTO사이리스터응용에서 턴오프시 dv/dt를 억제하기 위하여 필요한 스나버회로가 없어도 턴오프동작이 가능하다. (2)축적시간을 종래 GTO사이리스터의 약 1/10로 저감할 수 있다. (3)게이트축적전하를 종래의 GTO사이리스터의 약 1/2로 저감할 수 있다. 이러한 턴오프특성에 의하여 GCT사이리스터는 대용량 파워 일렉트로니스기기에 스나버회로 손실발생의 억제에 의한 손실의 저감, 고속동작화, 직병렬접속 응용에 의한 대용량화의 용이성, 게이트구동회로의 용량을 반감하는 등 많은 메리트를 가져다 준다.