• 약학회지
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• 제48권1호
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• pp.6-12
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• 2004

Near-infrared spectra of methanol-water mixtures and acetonitrile-water mixtures were acquired to find interactions between solvents widely used for reverse-phase liquid chromatography. Mixtures were prepared to give a series of increasing mole fractions of methanol or acetonitrile in water. Data matrices of acquired spectra were analyzed to determine the proper number of principal components of each mixture system using Malinowski's factor indicator function. Initial guess of score matrix and loading matrix were calculated by nonlinear iterative partial least squares (NIPALS) algorithm for faster computation. Iterative target transform factor analysis (ITTFA) was applied to convert the initial estimation of score matrix to true concentration profile and loading matrix to pure spectra of pure components of the mixtures. In case of methanol-water the number of principal components was found to be 4 and those initial guess of factors were converted to the pure spectra of water methanol and two kinds of complexes. In case of acetonitrile-water the number of pure components of the mixtures was found to be 3 and the pure spectrum of acetonitrile-water complex was found. The nonlinear characteristics of concentration profiles of complexes in the solvent mixtures may give a good criteria in understanding their elution characteristics in reverse-phase liquid chromatogrsphy.

• Journal of Ginseng Research
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• 제12권2호
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• pp.164-172
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• 1988

인삼사포닌 정량분석의 상법 purification과정을 역상소형 $C_18$ 컬럼 전처리로 대체할 수 있었으며, 분석시간은 1/4로 단축되었다. 이 방법을 사용하면 total ginsenoside의 회수율은 높으나 protopanaxatriol계 ginsenoside들의 회수율은 약간 낮았으며, 근중 농도 정도의 당류는 ginsenoside 회수율에 영향을 미치지 않았다. Ginsenoside 회수율의 변이계수는 상법의 경우보다 작았으며 이 방법에 사용되는 ginsenoside의 적정량은 10~15mg이었다. 역상소형컬럼방법은 건삼과 홍삼시료처리시에도 상법과 고도의 유의성을 나타냈다. 신속 역상소형컬럼 방법을 실제로 이용하기 위하여 8점의 시료를 동시에 처리하는 소형아크릴 장치를 사용하였다.

• 한국공간구조학회논문집
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• 제17권3호
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• pp.45-55
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• 2017

The objective of this study is to estimate the mechanical characteristics and nonlinear behaviors on the geometric nonlinear analysis of curved cable-membrane roof systems for long span lightweight roof structures. The weight of a cable-membrane roof dramatically can reduce, but the single layer cable-membrane roof systems are too flexible and difficult to achieve the required structural stiffness. A curved cable roof system with reverse curvature works more effectively as a load bearing system, the pretension of cables can easily increase the structural stiffness. The curved cable roof system can transmit vertical loads in up and downward direction, and work effectively as a load bearing structure to resists self-weights, snow and wind loads. The nonlinear behavior and mechanical characteristics of a cable roof system has greatly an affect by the sag and pretension. This paper is carried out analyzing and comparing the tensile forces and deflection of curved roof systems by vertical loads. The elements for analysis uses a tension only cable element and a triangular membrane element with 3 degree of freedom in each node. The authors will show that the curved cable-membrane roof system with reverse curvature is a very lightweight and small deformation roof for external loads.

• Journal of Power Electronics
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• 제15권1호
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• pp.86-95
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• 2015

An active clamp high step-up boost converter with a coupled inductor is proposed in this paper. In the proposed strategy, a coupled inductor is adopted to achieve a high voltage gain. The clamp circuit is included to achieve the zero-voltage-switching (ZVS) condition for both the main and clamp switches. A rectifier composed of a capacitor and a diode is added to reduce the voltage stress of the output rectifier diode. As a result, diodes with a low reverse-recovery time and forward voltage-drop can be utilized. Since the voltage stresses of the main and clamp switches are far below the output voltage, low-voltage-rated MOSFETs can be adopted to reduce conduction losses. Moreover, the reverse-recovery losses of the diodes are reduced due to the inherent leakage inductance of the coupled inductor. Therefore, high efficiency can be expected. Firstly, the derivation of the proposed converter is given and the operation analysis is described. Then, a steady-state performance analysis of the proposed converter is analyzed in detail. Finally, a 250 W prototype is built to verify the analysis. The measured maximum efficiency of the prototype is 95%.

• Journal of Power Electronics
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• 제19권3호
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• pp.645-654
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• 2019

In this paper, a new high step up DC/DC converter with a modified super-lift technique is presented. The coupled inductor technique is combined with the super-lift technique to provide a tenfold or more voltage gain with a proper duty cycle and a low turn ratio. Due to a high conversion ratio, the voltage stress on the semiconductor devices is reduced. As a result, low voltage ultra-fast recovery diodes and low on resistance MOSFET can be used, which improves the reverse recovery problems and conduction losses. This converter employs a passive clamp circuit to recycle the energy stored in the leakage inductance. The proposed convertor features a high conversion ratio with a low turn ratio, low voltage stress, low reverse recovery losses, omission of the inrush currents of the switch capacitor loops, high efficiency, small volume and reduced cost. This converter is suitable for renewable energy applications. The operational principle and a steady-state analysis of the proposed converter are presented in details. A 200W, 30V input, 380V output laboratory prototype circuit is implemented to confirm the theoretical analysis.

• 한국산업융합학회 논문집
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• 제26권5호
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• pp.937-943
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• 2023

In this study, the mast cover of submarine was reverse engineered and structural analysis was performed. In order to print with the 3D printer, the modeling was reduced to 1/5 size by applying geometric similarity. From the structural analysis results, it was found that the maximum value of equivalent stress generated in the mast cover was 180.9 MPa. This stress value occurs on the inner surface in the major axis. As a result of applying the load condition at a diving depth of 600 m, the mast cover is in a completely elastic state. The 1/5 size model printed on FDM 3D printer with PLA filament was the same as the reverse engineered modeling and it was printed in a perfect shape with no apparent defects. The 1/5 size model printed on PBF 3D printer with SUS316L powder was perfectly manufactured with no apparent defects.

• 대한기계학회논문집B
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• 제38권8호
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• pp.709-714
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• 2014

리버스 옵셋 인쇄는 인쇄전자를 위한 미세 패터닝기술 중 하나로서 수 ${\mu}m$ 이하의 선폭을 구현할 수 있다. 옵셋 인쇄의 특성상 잉크는 PDMS 재질의 블랑켓에 전사된 후 음각으로 패턴된 클리쉐에 접촉하여 불필요한 패턴을 제거하게 되는데, 이 때 블랑켓은 압력에 의하여 음각 패턴 내부로 침투하는 변형이 발생한다. 이러한 변형은 인쇄 압력에 비례하며, 과도한 인쇄 압력은 넓은 면적의 패턴을 인쇄할 때 클리쉐 패턴의 바닥에 블랑켓이 닿는 불량을 일으키게 된다. 이 논문에서는 리버스 옵셋 인쇄에서 가압변위에 따른 PDMS 블랑켓의 변형을 유한요소기법을 이용하여 모델링하고 접촉압력 대비 변형량을 예측함으로써 실제 인쇄 장비의 실험 결과와 비교하여 인쇄결함이 발생하지 않도록 하는 클리쉐의 제작조건을 제시하고자 한다.

• 상하수도학회지
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• 제32권1호
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• pp.55-65
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• 2018

It is necessary to develop a mobile water production system in order to provide stable water supply in case of disasters such as floods or earthquakes. In this study, we developed a modular mobile water production system capable of producing water for various uses such as domestic water and drinking water while improving applicability in various raw water sources. The water production system consists of three stages of filtration (sand filtration - activated carbon filtration - pressure filtration) to produce domestic water and an additional reverse osmosis process to produce drinking water. In laboratory and field experiments, the domestic water production system showed excellent treatment efficiency for particulate matter, but showed limitations in the treatment of dissolved substances such as dissolved organic matter. In addition, ultraviolet irradiation was considered as additional disinfection step, because it does not form precipitates of manganese oxides after disinfection. Reverse osmosis process was added to increase the removal efficiency of dissolved substances and the treated water satisfied drinking water quality standards. Fluorescence analysis of dissolved organic matter showed that the fulvic acid-like substances in raw water was successfully removed in the reverse osmosis process. The mobile water production system developed in this study is expected to be used not only in water supply in case of disaster, but also widely used in islands and rural area.

• 공업화학
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• 제28권3호
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• pp.351-354
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• 2017

역미셀법을 이용하여 열적 안정성이 우수한 감마-알루미나의 합성 공정을 최적화하기 위하여 실험계획법을 사용하였다. 먼저 합성공정에 주 요소인 계면활성제, 물 및 오일의 비에 대한 최적의 실험조건을 설계하기 위하여 혼합물 실험법을 이용하여 12가지 실험조건을 도출하였다. 설계된 조건에서 역미셀법을 이용하여 합성한 입자를 $900^{\circ}C$에서 소성한 결과 입자의 크기에 차이는 있었지만 모두 감마-알루미나 결정구조를 가졌다. 도출된 실험결과를 이용하여 계산된 2차 회귀모델의 결정계수는 93.68%이었으며, P- 값이 0.002로서 유의하다고 할 수 있다. 다양한 입자크기를 가지는 감마-알루미나의 합성조건을 모든 범위에서 대하여 표면도와 등고선도를 이용하여 제시하였다. 그 결과 Surfactant/Water/Oil의 질량비가 0.3450/0.0729/0.5821인 조건에서 합성할 때 약 2.8 nm의 가장 작은 입자가 합성되는 것으로 계산되었다.

• 한국재료학회지
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• 제25권2호
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• pp.95-99
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• 2015

$NiAl_2O_4$ nanoparticle was synthesized by a reverse micelle processing for inorganic pigment. $Ni(NO_3)_2{\cdot}6H_2O$ and $Al(NO_3)_3{\cdot}9H_2O$ were used for the precursor in order to synthesize $NiAl_2O_4$ nanoparticles. The aqueous solution, which consisted of a mixing molar ratio of Ni/Al, was 1:2 and heat treated at $800{\sim}1100^{\circ}C$ for 2h. The average size and distribution of synthesized $NiAl_2O_4$ powders are in the range of 10-20 nm and narrow, respectively. The average size of the synthesized $NiAl_2O_4$ powders increased with an increasing water-to-surfactant molar ratio and heating temperature. The crystallinity of synthesized $NiAl_2O_4$ powder increased with an increasing heating temperature. The synthesized $NiAl_2O_4$ powders were characterized by X-ray diffraction analysis(XRD), a field emission scanning electron microscopy(FE-SEM), and a color spectrophotometer. The properties of synthesized powders were affected as a function such as a molar ratio and heating temperature. Results indicate that synthesis using a reverse miclle processing is a favorable process to obtain $NiAl_2O_4$ spinels at low temperatures. The procedure performed suggests that this new synthesis route for producing these oxides has the advantage of being fast and simple. Colorimetric coordinates indicate that the pigments obtained exhibit blue colors.