• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.318-321
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• 2009

Transformation plasticity is that when a phase transformation of ferrous or non-ferrous alloys progresses even under an extremely small applied stress compared with a yield stress of the material, a permanent deformation occurs. One of widely accepted description for the transformation was proposed by Greenwood and Johnson [1]. Their description is based on an assumption that a weaker phase of an ideal plastic material could deform plastically to accommodate the externally applied stress and the internal stress caused by the volumetric change accompanying the phase transformation. In this study, an implicit finite element model was developed to simulate the deformation behavior of a low carbon steel during phase transformation. The finite element model was coupled with a phase field model, which could simulate the kinetics for ferrite to austenite transformation of the steel. The thermo-elasto-plastic constitutive equation for each phase was adopted to confirm the weaker phase yielding, which was proposed by Greenwood and Johnson [1]. From the simulation, the origin of the transformation plasticity was quantitatively discussed comparing with the other descriptions of it.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1187-1194
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• 2017

In this paper, a high step-up DC-DC PWM converter with continuous input current and low voltage stress is presented for renewable energy application. The proposed converter is composed of a boost converter integrated with an auxiliary step-up circuit. The auxiliary circuit uses an additional coupled inductor and a balancing capacitor with voltage doubler and switching capacitor technique to achieve high step-up voltage gain with an appropriate switch duty cycle. The switched capacitors are charged in parallel and discharged in series by the coupled inductor, stacking on the output capacitor. In the proposed converter, the voltage stress on the main switch is clamped, so a low voltage switch with low ON resistance can be used to reduce the conduction loss which results in the efficiency improvement. A detailed discussion on the operating principle and steady-state analyses are presented in the paper. To justify the theoretical analysis, experimental results of a 200W 40/400V prototype is presented. In addition, the conducted electromagnetic emissions are measured which shows a good EMC performance.

• 분석과학
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• 제20권3호
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• pp.251-254
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• 2007

수용액 내에서 환원제인 sulfurous acid와 휘발성이 강한 Os(III)을 반응시킨 후 생성된 비휘발성 Os(IV)을 inductively coupled plasma atomic emission spectrometry (ICP-AES)로 분석하였다. pH 2-10의 수용액에서 sulfurous acid와 Os(VIII)의 정량적 반응에 의하여 생성된 Os(VI)을 ICP-AES로 분석하였다. 동축형 분무기(concentric type nebulizer)에 의한 시료 도입 방법에서 sulfurous acid와 osmium은 반응 직후부터 안정한 신호를 나타내었으며 다양한 ICP-AES 조건에서 3회 반복 측정했을 때 재현성은 0.5-4.5%였으며, 검출 한계는 2.5-57.7 ng/g이었다.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.980-992
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• 2024

Steam line break accident (SLB) in the nuclear reactor is one of the representative Non-LOCA accidents in which thermal-hydraulics and neutron kinetics are strongly coupled each other. Thus, the multi-scale and multi-physics approach is applied in this study in order to examine a realistic safety margin. An entire reactor coolant system is modelled by system scale node, whereas sub-channel scale resolution is applied for the region of interest such as the reactor core. Fuel performance code is extended to consider full core pin-wise fuel behaviour. The MARU platform is developed for easy integration of the codes to be coupled. An initial stage of the steam line break accident is simulated on the MARU platform. As cold coolant is injected from the cold leg into the reactor pressure vessel, the power increases due to the moderator feedback. Three-dimensional coolant and fuel behaviour are qualitatively visualized for easy comprehension. Moreover, quantitative investigation is added by focusing on the enhancement of safety margin by means of comparing the minimum departure from nucleate boiling ratio (MDNBR). Three factors contributing to the increase of the MDNBR are proposed: Various geometric parameters, realistic power distribution by neutron kinetics code, Radial coolant mixing including sub-channel physics model.

• Steel and Composite Structures
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• 제52권5호
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• pp.501-513
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• 2024

Two-directional functionally graded materials (2D-FGMs) show extraordinary physical properties which makes them ideal candidates for designing smart micro-switches. Pull-in instability is one of the most critical challenges in the design of electrostatically-actuated microswitches. The present research aims to bridge the gap in the static pull-in instability analysis of microswitches composed of 2D-FGM. Euler-Bernoulli beam theory with geometrical nonlinearity effect (i.e. von-Karman nonlinearity) in conjunction with the modified couple stress theory (MCST) are employed for mathematical formulation. The micro-switch is subjected to electrostatic actuation with fringing field effect and Casimir force. Hamilton's principle is utilized to derive the governing equations of the system and corresponding boundary conditions. Due to the extreme nonlinear coupling of the governing equations and boundary conditions as well as the existence of terms with variable coefficients, it was difficult to solve the obtained equations analytically. Therefore, differential quadrature method (DQM) is hired to discretize the obtained nonlinear coupled equations and non-classical boundary conditions. The result is a system of nonlinear coupled algebraic equations, which are solved via Newton-Raphson method. A parametric study is then implemented for clamped-clamped and cantilever switches to explore the static pull-in response of the system. The influences of the FG indexes in two directions, length scale parameter, and initial gap are discussed in detail.

• 생약학회지
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• 제46권4호
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• pp.342-351
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• 2015

In this study, we performed quantitative determination of the three marker compounds such as gallic acid, ellagic acid, and quercetin in the 70% ethanol extracts of non-processed Sanguisorbae Radix and processed Sanguisorbae Radix using a high-performance liquid chromatography coupled with photodiode array detector. The analytical column for separation of the three compounds was used a Gemini $C_{18}$ column ($5{\mu}m$, $4.6{\times}250mm$) by the gradient elution with distilled water and acetonitrile containing 1.0% (v/v) acetic acid as mobile phase. The flow rate and injection volume were $1.0{\mu}L/min$ and $10{\mu}L$. The concentrations of gallic acid, ellagic acid, and quercetin in non-processed Sanguisorbae Radix were 0.25, 0.26, and 0.007%, respectively, while the concentrations of gallic acid, ellagic acid, and quercetin in non-processed Sanguisorbae Radix 0.14-0.55, 0.27-2.03, and 0.001-0.007%, respectively. Among the three components, the amount of the ellagic acid was increased after processing in Sanguisorbae Radix.

• 한국전기전자재료학회논문지
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• 제24권6호
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• pp.504-509
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• 2011

The conducting current of non-uniform plasma immersed electrode consists of ion current and secondary electron emission current caused by the impinging ion current. The ion current is determined by the ion dose passing through the sheath in front of electrode and the ion distribution in front of the electrode plays an important role in the secondary electron emission. The investigation of the distributed plasma and secondary electron effect on electrode ion current was carried out as the stainless steel electrode plugged with quartz tube was immersed in the inductively coupled Ar plasma using the antenna powered by 1 kw and the density profile was measured. After that, the negative voltage was applied by 1 kV~6 kV to measure the conduction current for the analysis of ion current.

• 생약학회지
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• 제46권2호
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• pp.123-132
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• 2015

In this study, we carried out quantification analysis of the six marker components, geniposidic acid, chlorogenic acid, geniposide, pinoresinol diglucoside, liriodendrin, and genipin in the 70% ethanol extracts of non-processed Eucommiae Cortex and processed Eucommiae Cortex using a high-performance liquid chromatography coupled with photodiode array detector. The six components were separated on Gemini C₁₈ column (5 μm, 4.6×250 mm) by the gradient elution with 1.0% (v/v) acetic acid in water and 1.0% (v/v) acetic acid in acetonitrile as mobile phase. The flow rate was 1.0 mL/min and the injection volume was 10 mL. The amount of geniposidic acid, chlorogenic acid, geniposide, pinoresinol diglucoside, liriodendrin, and genipin in non-processed Eucommiae Cortex were 1.31, 0.31, 0.66, 0.46, 0.46, and 0.03%, respectively, while the amount of the six compounds in non-processed Eucommiae Cortex were 0.04-0.78, 0.01-0.14%, 0.05-0.63%, 0.01-0.37%, 0.15-0.42%, and not detected, respectively. After processing treatment, the contents of three iridoids, two lingnan, and one phenylpropanoid decreased in Eucommiae Cortex.

• Journal of Plant Biotechnology
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• 제41권1호
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• pp.1-9
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• 2014

So far it has been generally considered that proteomic approaches are very useful for studying plant-microbes interaction. In this review, recent studies based on papers published from 2010 to 2013 have investigated proteomics analysis in various interaction during plant-fungal pathogen infection by means of gel-based proteomics coupled with mass spectrometry (MS)-based analysis. In rice, three papers focused on rice-Magnaporthe oryzae interaction were mainly reviewed in this study. Interestingly, another study showed proteomic changes in rice inoculated with Puccinia triticina, which is not only an fungal pathogen in wheat and but also results to the disease resistance with non-host defense manner in rice. Additionally, proteomics analysis has been widely subjected to understand defense mechanism during other crops (wheat, tomato, strawberry and mint) and their fungal pathogen interaction. Crops inoculated are analyzed to identify differentially regulated proteins at various tissues such as leaf and apoplast using 2-DE analysis coupled with various MS approaches such as MALDI-TOF MS, nESI-LC-MS/MS and MudPIT, respectively. Taken together, this review article shows that proteomics is applicable to various organisms to understand plant-fungal pathogen interaction and will contribute to provide important information for crop disease diagnosis and crop protection.

• 혜화의학회지
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• 제23권1호
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• pp.93-104
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• 2014

Glycyrrhizae Radix et Rhizoma has been extensively used by human beings as a medicinal herb as well as natural sweetener. In this study, we performed quantification analysis of three major constituents including liquiritin, glycyrrhizin, and glycyrrhetinic acid in the 70% ethanol extracts of non-processed Glycyrrhizae Radix et Rhizoma and processed Glycyrrhizae Radix et Rhizoma using a high-performance liquid chromatography coupled with photodiode array detector. The analytical column for separation of the 3 constituents used a Gemini C18 column kept at $40^{\circ}C$ by the gradient elution of two mobile phase. The amounts of liquiritin, glycyrrhizin, and glycyrrhetinic acid in non-processed Glycyrrhizae Radix et Rhizoma were 2.57%, 3.52%, and not detected. After processing by roasting, the best roasting temperature and time of iquiritin, glycyrrhizin, and glycyrrhetinic acid were $160^{\circ}C$-15 min (2.46%), $160^{\circ}C$-15 min (3.67%), and $240^{\circ}C$-15 min (0.76%), respectively.