• Current Optics and Photonics
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• 제1권4호
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• pp.396-401
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• 2017

In this article, we proposed hybrid polarization singularity configurations, based on the superposition of two orthogonal circularly polarized components, one of which is a light beam with two optical vortices. The topological configurations are the hybridization of lowest-order polarization singularities, but are different from high-order polarization singularities. Our numerical simulation may provide a theoretical basis for expanding the variety of polarization singularity configuration.

• 설비공학논문집
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• 제3권3호
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• pp.186-196
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• 1991

Numerical analysis has been performed to investigate the effects of the turbulence intensity and Prandtl number on the local heat transfer around a circular cylinder in crossflow. The governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. For laminar flow, the calculations were performed for the Reynolds numbers 26 and 200. The results showed good agreement with the experimental results. For turbulent flow of the Reynolds number $1{\times}10^5$ and $2{\times}10^6$, the results showed that with an increase in the turbulent intensity in the main stream, the local Nusselt number increases in the front region of the circular cylinder. But the effect of turbulent intensity on the local Nusselt number diminishes in the wake region. The influence of Prandtl numbers show similar trend to that of turbulent intensity.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2039-2042
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• 2002

In this paper, we propose a technique used to simplify the trellis diagram, thus, reduce the complexity of Viterbi decoder in term of the number of Compare-Select (CS) operations needs in decoding process. It is shown that if the branch metrics are properly decomposed into orthogonal components. The trellis diagram can be modified that each original state with large number branches terminating to it can be broken into a number of sub-states having smaller number of branches terminating to them. Simulation results shown that the newly proposed technique can be used reduced the complexity of 8 and 16 PSK-TCMs without degrading the BER performance.

• 한국기계가공학회지
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• 제7권1호
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• pp.17-21
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• 2008

Recently developed automotive components are of lightweight nature, providing automobiles with a high fuel efficiency and performance. In response to those trends of car developments, this study proposes a structural optimization method for the lower control ann. Lightweight design of lower control am can be achieved through two approaches: design and material technology. In this research, the former includes optimization technology, and the latter the technologies for selecting aluminum as a steel-substitute material. In this research, the design of experiments(DOE) built in ANSYS WORKBENCH are utilized to determine the optimum shape of a Lower Control Arm. And optimum design is compared first model and reduced design variable model that considered sensitivity using orthogonal array.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.94-101
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• 2003

Recently, miniaturization and weight reduction is getting more attention due to various benefits in automotive components design. It is a trend that the design of experiment(DOE) and statical design method are frequently used for optimization. In this research, the safety of lower control arm is evaluated according to its material change form S45C to A16061 for the reduction of arm's weight. The variance analysis on the basis of structure analysis and DOE is applied to the lower control m. We have proposed a statistical design model to evaluate the effect of structural modification by performing the practical multi-objective optimization considering mass, stress and deflection.

• Earthquakes and Structures
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• 제2권4호
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• pp.323-336
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• 2011

The problem of reconstruction of complete building response from a limited number of response measurements is considered. The response at the intermediate degrees of freedom is reconstructed by using piecewise cubic Hermite polynomial interpolation in time domain. The piecewise cubic Hermite polynomial interpolation is preferred over the spline interpolation due to its trend preserving character. It has been shown that factorization of response data in variable separable form via singular value decomposition can be used to derive the complete set of normal modes of the structural system. The time domain principal components can be used to derive empirical transfer functions from which the natural frequencies of the structural system can be identified by peak-picking technique. A reduced-rank approximation for the system flexibility matrix can be readily constructed from the identified mass-orthonormal mode shapes and natural frequencies.

• 반도체디스플레이기술학회지
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• 제17권2호
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• pp.61-66
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• 2018

The objective of this research study is to investigate the optimal process parameters of electrical discharge machining (EDM) on SCM440 steel with copper as a tool electrode. The effect of various process parameters on machining performance is investigated in this study. Modern ED machinery is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, etc. This paper reports the results of an experimental investigation by Taguchi method carried out to study the effects of machining parameters on material surface roughness in electric discharge machining of SCM440 steel. To predict the optimal condition, the experiments are conducted by using Taguchi's L27 orthogonal array. The work material was ED machined with copper electrodes by varying the pulsed current, pulse on-time, voltage, servo speed and spark speed. Investigations indicate that the surface roughness is strongly depend on pulsed current.

• 전력전자학회논문지
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• 제4권1호
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• pp.50-56
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• 1999

본 연구에서는 시간영역에서 전력이 해석되어지므로 이해하기 쉽고, 비교적 계측하기 용이한 상관함수에 의한 순시전력이론에 대해서 고찰하였다. 상관함수에 의한 순시전력이론은 시간영역에서 전압과 전류의 자기상관함수와 상호상관함수에 의해서 전력과의 전압과 상관성에 따라 상관전력과 비상관 전력으로 분해된다. 분해된 두 가지 전력성분으로부터 비선형 부항의 특성에 따라 전력과 전류를 유효성분, 기본파 무효성분 그리고 고조파성분 등 3성분으로 분해한다. 능동전력필터는 그 보상특성상 전력과 전류의 3성분만을 다루며, 실시간 제어를 위해 그외의 여러 복잡한 그리고 구현의 어려움이 있는 전력모델은 경제적이지 못하다. 상관함수적인 순시전력이론에 의해 분석된 전력성분들의 타당성을 입증하기 위해서 전압형 DSP능동전력필터를 제작하였다. 싸이리스터 제어 유도전동기 구동시스템의 전력을 제안된 순시전력이론에 의해 3성분으로 분해한 후, 이들 성분중에서 보상기준전류로 고조파성분과 기본파 무효성분을 각각 제어하여 그 보상결과로부터 타당성을 입증하였다.

• Journal of Ginseng Research
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• 제40권4호
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• pp.344-350
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• 2016

Background: Mountain-cultivated ginseng (MCG) and cultivated ginseng (CG) both belong to Panax ginseng and have similar ingredients. However, their pharmacological activities are different due to their significantly different growth environments. Methods: An ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS)-based approach was developed to distinguish MCG and CG. Multivariate statistical methods, such as principal component analysis and supervised orthogonal partial-least-squares discrimination analysis were used to select the influential components. Results: Under optimized UPLC-QTOF-MS/MS conditions, 40 ginsenosides in both MCG and CG were unambiguously identified and tentatively assigned. The results showed that the characteristic components of CG and MCG included ginsenoside Ra3/isomer, gypenoside XVII, quinquenoside R1, ginsenoside Ra7, notoginsenoside Fe, ginsenoside Ra2, ginsenoside Rs6/Rs7, malonyl ginsenoside Rc, malonyl ginsenoside Rb1, malonyl ginsenoside Rb2, palmitoleic acid, and ethyl linoleate. The malony ginsenosides are abundant in CG, but higher levels of the minor ginsenosides were detected in MCG. Conclusion: This is the first time that the differences between CG and MCG have been observed systematically at the chemical level. Our results suggested that using the identified characteristic components as chemical markers to identify different ginseng products is effective and viable.

• Journal of Ginseng Research
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• 제42권3호
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• pp.277-287
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• 2018

Background: Temperature is an essential condition in red ginseng processing. The pharmacological activities of red ginseng under different steam temperatures are significantly different. Methods: In this study, an ultrahigh-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry was developed to distinguish the red ginseng products that were steamed at high and low temperatures. Multivariate statistical analyses such as principal component analysis and supervised orthogonal partial least squared discrimination analysis were used to determine the influential components of the different samples. Results: The results showed that different steamed red ginseng samples can be identified, and the characteristic components were 20-gluco-ginsenoside Rf, ginsenoside Re, ginsenoside Rg1, and malonyl-ginsenoside Rb1 in red ginseng steamed at low temperature. Meanwhile, the characteristic components in red ginseng steamed at high temperature were 20R-ginsenoside Rs3 and ginsenoside Rs4. Polar ginsenosides were abundant in red ginseng steamed at low temperature, whereas higher levels of less polar ginsenosides were detected in red ginseng steamed at high temperature. Conclusion: This study makes the first time that differences between red ginseng steamed under different temperatures and their ginsenosides transformation have been observed systematically at the chemistry level. The results suggested that the identified chemical markers can be used to illustrate the transformation of ginsenosides in red ginseng processing.