• Journal of Power Electronics
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• 제18권5호
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• pp.1336-1346
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• 2018

Wide band gap semiconductor devices such as SiC MOSFETs are becoming the preferred devices for high frequency and high power density converters due to their excellent performances. However, the proportion of the switching loss that accounts for the whole inverter loss is growing along with an increase of the switching frequency. In view of the third quadrant working characteristics of a SiC MOSFET, synchronous rectification discontinuous pulse-width modulation is proposed (SRDPWM) to further reduce system losses. The SRDPWM has been analyzed in detail. Based on a frequency domain mathematical model, a quantitative mathematical analysis of the harmonic characteristic is conducted by double Fourier transform. Meanwhile, a switching loss model and a conduction loss model of inverter for SRDPWM have been built. Simulation and experimental results verify the result of the harmonic analysis of the double Fourier analysis and the accuracy of the loss models. The efficiencies of the SRDPWM and the SVPWM are compared. The result indicates that the SRDPWM has fewer losses and a higher efficiency than the SVPWM under high switching frequency and light load conditions as a result of the reduced number of switching transitions. In addition, the SRDPWM is more suitable for SiC MOSFET converters.

• Current Photovoltaic Research
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• 제8권1호
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• pp.33-38
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• 2020

Single-phased SnS thin films have been prepared by RF magnetron sputtering at various deposition pressures. The effect of deposition pressure on the structural and optical properties of polycrystalline SnS thin films was studied using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer. The XRD analysis revealed the orthorhombic structure of the SnS thin films oriented along the (111) plane direction. As the deposition pressure was increased from 5 mTorr to 15 mTorr, the intensity of the peak on the (111) plane increased, and the intensity decreased under the condition of 20 mTorr. The binding energy difference at the Sn 3d_5/2 and S 2p_3/2 core levels was about 324.5 eV, indicating that the SnS thin film was prepared as a pure Sn-S phase. The optical properties of the SnS thin films indicate the presence of direct allowed transitions with corresponding energy band gap in the rang 1.47-1.57 eV.

• Journal of Pharmaceutical Investigation
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• 제41권5호
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• pp.309-315
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• 2011

A sensitive and specific liquid chromatographic method coupled with tandem mass spectrometry (LC-MS/MS) was developed for the analysis of ambroxol (active moiety of acebrophylline). After acetonitrile precipitation of proteins from plasma samples, ambroxol and the domperidone (internal standard, IS) were eluted on a C18 column. The isocratic mobile phase was consisted of 10 mM ammonium acetate and methanol (10 : 90, v/v), with flow rate at 0.2 mL/min. A tandem mass spectrometer, as detector, was used for quantitative analysis in positive mode by a multiple reaction monitoring mode to monitor the m/z 379.2${\rightarrow}$264.0 and the m/z 426.2${\rightarrow}$175.1 transitions for ambroxol and the IS, respectively. Twenty four healthy Korean male subjects received two capsules (100 mg ${\times}$ 2) of either the test or the reference formulation of acebrophylline HCl in a 2 ${\times}$ 2 crossover study, this was followed by a 1week washout period between either formulation. $AUC_{0-t}$ (the area under the plasma concentration-time curve) was calculated by the linear trapezoidal rule. $C_{max}$ (maximum plasma drug concentration) and $T_{max}$ (time to reach $C_{max}$) were compiled from the plasma concentration-time data. The 90% confidence intervals for the log transformed data were acceptable range of log 0.8 to log 1.25 (e.g., log 0.8964 - log 0.9910 for $AUC_{0-t}$ log 0.8690 - log 1.0750 for $C_{max}$). The major parameters, $AUC_{0-t}$ and $C_{max}$ met the criteria of Korea Food and Drug Administration for bioequivalence indicating that Acephyll$^{(R)}$ capsule (test) is bioequivalent to Surfolase$^{(R)}$ capsule (reference).

• 한국응용과학기술학회지
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• 제17권3호
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• pp.158-166
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• 2000

A conductimetric study of foam formed from mixture of the protein, ${\beta}-lactoglobulin$, and the nonioinc surfactant, SML, revealed that their stability was reduced at concentrations of SML in the range $3{\sim}10mM$. The interaction of SML with ${\beta}-lactoglobulin$ was investigated by fluorimetry and a dissociation constant of $0.2{\mu}M$ was calculated for the complex. Surface tension studies confirmed the presence of interaction between the two components and provided evidence for the progressive displacement of ${\beta}-lactogloblin$ from the air/water interface with increasing SML concentration. Experiments using air-suspended microscopic thin liquid films revealed transitions in the chainage characteristics and thickness of the film at SML concentrations below that which resulted in destabilization of the foam. However, measurements of surface mobility of fluorescent-labeled ${\beta}-lactoglobulin$ by a photobleaching method identified that a transition to a mobile system occurred at a SML concentration which correlated with the onset of instability in the disperse phase. The results would indicate that maintenance of the viscoelastic properties of the surface is paramount importance in determining the stability of interfaces comprising mixtures of protein and surfactant.

• 한국광물학회지
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• 제30권3호
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• pp.83-91
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• 2017

천연산 녹주석($Be_3Al_2Si_6O_{18}$, P6/mcc) 중 산출지가 각각 다른 아쿠아마린 시료인 녹주석-A, 녹주석-B를 물을 압력전달 매개체로 사용하여 고압실험 및 고온-고압실험을 실시하였다. 기존 문헌과 다르게 압력전달 매개체로 물을 이용했을 때 고압 및 고온-고압 상태에서 녹주석의 조성과 구조에 어떠한 영향을 주며 탄성 특성이 어떻게 변하는지를 확인하기 위함이다. 그 결과 녹주석-A, B의 체적탄성률은 각각 111(7) GPa, $K{_0}^{\prime}=73(7)$; 110(9) GPa, $K{_0}^{\prime}=65(8)$로 확인되었다. 이는 기존 연구에서 메탄올 에탄올 4 : 1 체적비로 혼합하여 관찰한 것과 다른 값 및 경향성을 보여주는 것으로 확인하였으며 관찰된 녹주석의 치밀화는 ICE VI, ICE VII 상변이 구간인 약 1.0 GPa, 약 2.5 GPa 구간과 일치하였다.

• 대한전자공학회논문지TC
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• 제47권7호
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• pp.128-134
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• 2010

본 논문에서는 저부엽과 저손실 특성을 갖는 고전력 20-출력 스트립라인 전력분배기를 설계, 제작하고 측정하였다. 20-출력전력분배기는 S 대역 선형 배열 안테나의 급전회로를 위해 설계되었으며, 좁은 빔폭과 매우 낮은 저부엽 특성을 위해 Dolph-Chebyshev 전류 분포를 활용하였다. 20-출력 전력분배기는 8-출력 분배기 1개, 4-출력 분배기 3개와 링 하이브리드 전력분배기 3개로 구성되었으며, 전력분배의 기본적인 구조로는 T-접합 분배 구조를 사용하였다. 삽입손실과 반사손실을 개선하기 위해서 노치를 T-접합 분배 구조에 적용하였으며 N형 커넥터와 스트립라인 사이의 천이구조를 수정하였다. 설계, 제작된 전력분배기는 대역 내에서 약 0.3 dB의 삽입손실과 8o 보다 작은 rms 위상 부정합 특성을 보였다. 20-출력 전력분배기 2개를 대칭적으로 구성할 경우 40 dB 이상의 저부엽 특성 결과를 20-출력 전력분배기 측정 결과로부터 합성할 수 있었다.

• 공업화학
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• 제28권6호
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• pp.679-684
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• 2017

베시클 막을 유연하게 만드는 edge activator를 혼합하여 수화 액정형 베시클을 제조하고 niacinamide를 베시클 안에 포집시켰다. 제조 과정 중 액정 상 형성 및 액정의 열적 상전이 현상을 편광현미경과 시차주사 열량계(DSC)를 통해 살펴보았다. Sodium deoxycholate, lysolecithin, polysorbate 80 등의 edge activator를 첨가하면 수화 액정형 베시클 입자가 수십 나노 사이즈로 줄어들었다. 수화 액정형 베시클을 활용하여 niacinamide를 피부 침투시키면 수용액 상태로 도포했을 때보다 피부 침투된 niacinamide의 양이 크게 증가하는데, 10% sodium deoxycholate를 혼합한 베시클에서는 niacinamide 침투량이 4배 가까이 증가하였다. 이러한 결과로부터 edge activator를 베시클에 혼합하면 베시클의 피부 침투력이 향상됨을 알 수 있었다.

• 폴리머
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• 제24권6호
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• pp.837-844
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• 2000

본 연구에서는 반도체 봉지제로 사용되는 상용 EMC중 가속제의 함량이 다른 두 종류의 프리프레그에 대하여 그 경화거동을 등온 및 승온조건에서 시차 주사 역량계, 점도계 및 유전율 측정계를 이용하여 분석하였다. 경화반응 속도변수는 Kamal의 자동촉매 반응식을 이용하여 m+n을 2로 가정한 후 Ryan Dutta의 방법에 따라 계산에 의한 경화반응 속도의 예측 치와 실제 실험 데이터가 10$0^{\circ}C$를 제외한 나머지 온도에서는 잘 일치하는 경향을 나타내었다. 경화과정 중 겔화와 유리화와 같은 상 전이를 관찰하였으며 각각의 등온 경화온도에서 경화시간에 따른 유리전이 온도 ($T_{g}$ )를 측정하여 경화온도와 유리전이 온도가 같아지는 유리화점을 구할 수 있었고 절대온도와의 사이에 Arrhenius관계가 성립함을 확인하였다. 또한 평판형 전극을 이용한 DEA는 EMC의 경화 과정을 동정하는데 효과적으로 이용될 수 있음을 알 수 있었다. 같은 종류의 수지 시스템에서는 TTT diagram상에서 $_{gel}$$T_{g}$ 가속제의 농도에 상관없이 일정한 온도에서 나타남을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.357-364
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• 2014

Size controlled, $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ cathode powders were prepared by co-precipitation method followed by heat treatment at temperatures between 750 and $850^{\circ}C$. The synthesized samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance. The synthesized $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ after calcined at $750^{\circ}C$ has a good electrochemical performance with an initial discharge capacity of $190mAhg^{-1}$ and good capacity retention of 100% after 30 cycles at 0.1C ($17mAg^{-1}$). The capacity retention of $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ after calcined at $750^{\circ}C$ is better than that at 800 and $850^{\circ}C$ without capacity loss at various high C rates. This is ascribed to the minimized cation disorder, a higher conductivity, and higher lithium ion diffusion coefficient ($D_{Li}$) observed in this material. In the differential scanning calorimetry DSC profile of the charged sample, the generation of heat by exothermic reaction was decreased by calcined at high temperature, and this decrease is especially at $850^{\circ}C$. This behavior implies that the high temperature calcinations of $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ prevent phase transitions with the release of oxygen.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.16-16
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• 2002

The presently commercialized lithium-ion batteries use layer structured LiCoO₂ cathodes. Because of the high cost and toxicity of cobalt, an intensive search for new cathode materials has been underway in recent years. Recently, a concept of a one-to-one solid state mixture of LiNO₂ and LiMnO₂, i.e., Li[Ni/sub 0.5/Mn/sub 0.5/]O₂, was adopted by Ohzuku and Makimura to overcome the disadvantage of LiNiO₂ and LiMnO₂. Li[Ni/sub 0.5/Mn/sub 0.5/]O₂ has the -NaFeO₂ structure, which is characteristic of the layered LiCoO₂ and LiNiO₂ structures and shows excellent cycleability with no indication of spinel formation during electrochemical cycling. Layered Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials with high homogeneity and crystallinity were synthesized using a mechanical alloying method. The Li[Ni/sub 0.475/Co/sub 0.05/Mn/sub 0.475/]O₂ electrode delivers a high discharge capacity of 187 mAh/g between 2.8 and 4.6 V at a high current density of 0.3 mA/㎠(30 mA/g) with excellent cycleability. The charge/discharge and differential capacity vs. voltage studies of the Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials showed only one redox peak up to 50 cycles, which indicates that structural phase transitions are not occurred during electrochemical cycling. The magnitude of the diffusion coefficients of lithium ions for Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂(x = 0.5 and 0.475) are around 10/sup -9/ ㎠/s measured by the galvanostatic intermittent titration technique (GITT).