• Macromolecular Research
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• 제16권4호
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• pp.320-328
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• 2008

We established a thermodynamic framework of group contribution method based on modified double lattice (MDL) model. The proposed model included the long-range interaction contribution caused by the Coulomb electrostatic forces, the middle-range interaction contribution from the indirect effects of the charge interactions and the short-range interaction from modified double lattice model. The group contribution method explained the combinatorial energy contribution responsible for the revised Flory-Huggins entropy of mixing, the van der Waals energy contribution from dispersion, the polar force, and the specific energy contribution from hydrogen bonding. We showed the solvent activities of various polymer solution systems in comparison with theoretical predictions based on experimental data. The proposed model gave a very good agreement with the experimental data.

• 공업화학
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• 제33권5호
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• pp.523-531
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• 2022

A NiCo-metal organic framework (MOF) electrode, prepared using urea as a surfactant, was synthesized using a one-pot hydrothermal method. The addition of urea to the NiCo-MOF creates interstitial voids and an ultra-thin nanostructure in the NiCo-MOF, which improves its charge transfer performance. We obtained the optimal metal to surfactant ratio to achieve the best specific capacitance. The NiCo-MOF was employed as the working electrode material in a three-electrode system. Field emission scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy were employed to characterize the microstructures and morphologies of the composites. Cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy curves were employed to quantify the electrochemical properties of the electrodes in a 6 M KOH electrolyte.

• Transactions on Electrical and Electronic Materials
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• 제14권3호
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• pp.121-124
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• 2013

The incorporation of 90 nm alumina particles into an epoxy matrix to form a composite microstructure is described in present study. It is shown that the use of ultrafine particles results in a substantial change in the behavior of the composite, which can be traced to the mitigation of internal charges when a comparison is made with conventional $Al_2O_3$ fillers. A variety of diagnostic techniques have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that, when the size of the inclusions becomes small enough, they act cooperatively with the host structure and cease to exhibit interfacial properties. It is postulated that the $Al_2O_3$ particles are surrounded by high charge concentrations. Since $Al_2O_3$ particles have very high specific areas, these regions allow limited charge percolation through $Al_2O_3$ filled dielectrics. The practical consequences of this have also been explored in terms of the electric strength exhibited. It would appear that there was a window in which real advantages accumulated from the nano-formulated material. An optimum filler loading of about 0.5 wt.% was indicated.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.335-338
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• 2009

액체로켓에 산화제를 충전하는 과정은 크게 산화제 탱크의 냉각, 고유량 충전, 소유량 충전, 온도 보정을 위한 추가 충전으로 나눌 수 있다. 나로호(KSLV-I) 1단의 산화제는 액체산소를 사용하며, 각 충전모드에 해당하는 유량 및 온도 요구조건이 제시되어 있다. 이러한 유량 및 온도 요구조건을 만족하기 위해서 산화제 공급시스템에는 유량조절용 밸브와 열교환기가 설치되어 있다. 본 연구에서는 발사체 산화제 충전과정에서 정밀한 유량 공급을 위하여 상용 1차원 열-유동 해석 프로그램인 Flowmaster를 이용하여 1차원 유동 시스템 해석을 수행하였다. 아울러 제한된 인증 시험을 통하여 각 모드에서의 유량 조건을 만족시키기 위한 유량제어밸브들의 유량 보정 민감도를 해석적으로 구하였다.

• 전자공학회논문지A
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• 제33A권7호
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• pp.176-184
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• 1996

To overcome the drawbacks of conventional LDMOSFETs, we propose RESURF EDMOSFETs which can be adapted in varous circuit applications, be driven without charge pumping circuity and thowe threshold voltage can be adjusted. The devices have the diffused drift region formed by a high tmperature process before the gate oxidaton. After the polysilicon gate electrode formation, a fraction of the drift region around the gate edge is opened for supplemental self-aligned ion implantation to obtain self-aligned drift region. This leads to a shorter gate length and desirable drift region junction contour under the gate edge for minimum specific-on-resistance. In additon, a and maximize the breakdown voltage. Also, by biasing the metal field plate, we can reduce the specific-on-resistance further. The devices are optimized by using the TSUPREM-4 process simulator and the MEDICI device simulator. The optimized devices have the breakdwon voltage and the specific-on-resistance of 101.5V and 1.14m${\Omega}{\cdot}cm^{2}$, respectively for n-channel RESURF EDMOSFET, and 98V and 2.75m.ohm..cm$^{2}$ respectively for p-channel RESURF EDMOSFET. To check the validity of the simulations, we fabricated n-channel EDMOSFETs and confirmed the measured breakdown voltage of 97V and the specific-on-resistance of 1.28m${\Omega}{\cdot}cm^{2}$. These results are superior to those of any other reported power devices for smart power IC applications.

• Bulletin of the Korean Chemical Society
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• 제16권7호
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• pp.574-577
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• 1995

Solvatochromic effect and hydrogen bonding interaction of NPNOH, NPNO- and NPNOR were investigated. Electronic transition energies of the dyes were plotted against empirical solvent polarity parameters, Taft's π* and Reichardt's ET(30). Good correlations were observed when the excitation energies were plotted against the energy calculated by multiple linear regression method which was developed by Taft. There is an intrinsic difference between betaine for ET(30) polarity scale and the azoderivative, which is derived from the specific hydrogen bond incurred with probe molecules and solvents. The hydrogen bonding plays a very important role for stabilization of an excited state molecule by solvents especially when a solute possesses a negative charge as with NPNO-.

• ETRI Journal
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• 제36권5호
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• pp.829-834
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• 2014

In this paper, a lateral power metal-oxide-semiconductor field-effect transistor with ultra-low specific on-resistance is proposed to be applied to a high-voltage (up to 200 V) integrated chip. The proposed structure has two characteristics. Firstly, a high level of drift doping concentration can be kept because a tilt-implanted p-drift layer assists in the full depletion of the n-drift region. Secondly, charge imbalance is avoided by an extended trench gate, which suppresses the trench corner effect occurring in the n-drift region and helps achieve a high breakdown voltage (BV). Compared to a conventional trench gate, the simulation result shows a 37.5% decrease in $R_{on.sp}$ and a 16% improvement in BV.

• Macromolecular Research
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• 제17권10호
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• pp.746-749
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• 2009

Poly(ethylene terephthalate) (PET) fabric/poly(3,4-ethylenedioxythiophene) (PEDOT) composite with stable and high electrochemical activity was fabricated by chemical and electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on a PET fabric in sequence. Effects of polymerization conditions on the following characteristics of the composite were studied: electrical conductivity and surface morphology. The electrochemical properties were also investigated by cyclic voltammetry and cyclic charge/discharge experiments. The specific volume resistivity, electrical conductivity and specific discharge capacitance of the composite were 0.034 $\Omega-cm$ and 25 S/cm, and 54.5 F/g, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.214.1-214.1
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• 2011

In this work, the electrochemical properties of the surface treated multi-walled carbon nanotubes (MWNTs) are investigated for supercapacitors. Nitrogen- and oxygen functional groups containing MWNTs are prepared by nitrogen precursors and acidic treatment, respectively. The surface properties of the MWNTs are confirmed by X-ray photoelectron spectroscopy (XPS) and Zeta-potential measurements. The electrochemical properties of the MWNTs are investigated by cyclic voltammetry, impedance spectra, and charge-discharge cycling performance in 1 M $H_2SO_4$ at room temperature. As a result, these functionalized MWNTs lead to an increase in the specific capacitance as compared with the pristine MWNTs. It proposes that the pyridinic and pyridinic-N-oxides nitrogen species influence on the specific capacitance due to their positive charges, and thus an improved electron transfer at high current loads, since they are the most important functional groups affecting capacitive behaviors.

• Carbon letters
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• 제12권4호
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• pp.252-255
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• 2011

Carbon-based electric double-layer capacitors are being evaluated as potential energy-storage devices in an expanding number of applications. In this study, samples of carbon black (CB) treated at different temperatures ranging from $650^{\circ}C$ to $1100^{\circ}C$ were used as electrodes to improve the efficiency of a capacitor. The surface properties of the heat-treated CB samples were characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The effect of the heat-treatment temperature on the electrochemical behaviors was investigated by cyclic voltammetry and in galvanostatic charge-discharge experiments. The experimental results showed that the crystallinity of the CBs increased as the heat-treatment temperature increased. In addition, the specific capacitance of the CBs was found to increase with the increase in the heat-treatment temperature. The maximum specific capacitance was 165 $F{\cdot}g-1$ for the CB sample treated at $1000^{\circ}C$.