• International Journal of Aeronautical and Space Sciences
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• 제5권2호
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• pp.1-8
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• 2004

Real-Time Kinematic GPS positioning is widely used for many applications.Resolving ambiguities is the key to precise positioning. Integer ambiguity resolution isthe process of resolving the unknown cycle ambiguities of double difference carrierphase data as integers. Two important issues of resolving are efficiency andreliability. In the conventional search techniques, we generally used chi-squarerandom variables for decision variables. Mathematically, a chi-square random variableis the sum of mutually independent, squared zero-mean unit-variance normal(Gaussian) random variables. With this base knowledge, we can separate decisionvariables to several normal random variables. We showed it with related equationsand conceptual diagrams. With this separation, we can improve the computationalefficiency of the process without losing the needed performance. If we averageseparated normal random variables sequentially, averaged values are also normalrandom variables. So we can use them as decision variables, which prevent from asudden increase of some decision variable. With the method using averaged decisionvalues, we can get the solution more quicklv and more reliably.To verify the performance of our proposed algorithm, we conducted simulations.We used some visual diagrams that are useful for intuitional approach. We analyzedthe performance of the proposed algorithm and compared it to the conventionalmethods.

• 한국응용과학기술학회지
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• 제14권2호
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• pp.41-48
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• 1997

Separation of EPA and DHA from fish oil fatty acid ethyl ester (FAFE) by urea adductive crystallization method was carried out in the supercritical carbon dioxide (SC $CO_2$) as a solvent. Our results showed that SC $CO_2$ is a good candidate as a solvent in the urea adductive crystallization to separate FAFE by the number of unsaturated bonds. Compared to the separation process using methanol. SC $CO_2$ yielded better performance in the overall selectivity of EPA and DHA. The effect of process variables on separation of EPA and DHA was discussed in detailed. A hybrid technology of SC $CO_2$ fractionation and urea adductive crystallization with SC $CO_2$ was conformed as a viable process to separate and concentrate EPA and DHA from fish oil.

• 한국해안·해양공학회논문집
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• 제25권5호
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• pp.285-290
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• 2013

선형과 천해 edge wave로 구분되는 이들의 거동을 더 잘 이해하기 위해 비교하였다. 본 연구에서는 변수분리법을 사용하여, Ursell (1952)이 해의 유도과정 없이 제시한, 선형 edge wave의 해를 얻었다. 천해 edge wave는 비록 천해방정식으로부터 유도되지만 분산특성을 갖는다. 완만한 해저경사의 경우, 천해 파형은 선형 파형과 거의 같게 되고 천해 파형은 다루기가 쉬운 장점이 있다. Gaussian 분포형태의 이동체에 의해 생성되는 edge wave를 계산하기 위해 천해 고유파형으로 전개한 해를 구성하였고, 이에 대한 결과를 제시하고 특성을 기술하였다.

• 한국전산유체공학회지
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• 제19권2호
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• pp.86-92
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• 2014

In this paper, prediction of separation trajectory for Two-stage-To-Orbit space launch vehicle has been numerically simulated by using an aerodynamic database based on steady state analysis. Aerodynamic database were obtained for matrix of longitudinal and vertical positions. The steady flow simulations around the launch vehicle have been made by using a 3-D RANS flow solver based on unstructured meshes. For this purpose, a vertex-centered finite-volume method was adopted to discretize inviscid and viscous fluxes. Roe's finite difference splitting was utilized to discretize the inviscid fluxes, and the viscous fluxes were computed based on central differencing. To validate this flow solver, calculations were made for the wind-tunnel experiment model of the LGBB TSTO vehicle configuration on steady state conditions. Aerodynamic database was constructed by using flow simulations based on test matrix from the wind-tunnel experiment. ANN(Artificial Neural Network) was applied to construct interpolation function among aerodynamic variables. Separation trajectory for TSTO launch vehicle was predicted from 6-DOF equation of motion based on the interpolated function. The result of present separation trajectory calculation was compared with the trajectory using experimental database. The predicted results for the separation trajectory shows fair agreement with reference[4] solution.

• 멤브레인
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• 제10권3호
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• pp.130-138
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• 2000

건/습식 상전환법을 이용하여 비대칭 polyethersulfone (PES) 기체분리막을 제조하였으며, $CO_2$, $N_2$등의 기체에 대한 투과특성을 조사하였다. 분리막 제조에 있어서 주요 변수인 캐스팅 용액과 증발시간 등이 분리막의 구조에 미치는 영향을 파악하고 투과특성을 조사하여 최적의 제조조건을 확립하였다. 또한 제조된 분리막의 표피층에 존재하는 pin-hole과 같은 결점을 보완하기 위하여 실리콘 수지를 코팅하여 그 투과특성의 변화를 조사하였다. 실리콘 수지 코팅이 결점을 보완하는데 효과적임을 확인하였다. 본 연구에서 분리막 제조에 주로 사용한 캐스팅 용액은 PES, 14-methyl-2-pyrrolidone, 아세톤, 에탄올로 구성되었으며, 응고제로는 증류수를 사용하였다. 캐스팅 용액 중의 PES 함량이 높아질수록, 휘발성 유기용매의 비율이 높아질수록, 증발시간이 길수록, 에탄을 첨가제의 농도가 낮을수록 $CO_2$/$N_2$의 선택도는 높아지고 투과도는 낮아지는 결과를 보였다. 최적의 분리막 제조조건 하에서 얻어진 분리막의 분리성능은 $CO_2$/$N_2$의 선택도가 61이고 $CO_2$의 투과도는 21 GPU인 우수한 결과를 보였다.

• 대한기계학회논문집B
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• 제30권7호
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• pp.622-629
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• 2006

The shape optimization of blade sweep in a transonic axial compressor rotor of NASA Rotor 37 has been performed using response surface method and the three-dimensional Wavier-Stokes analysis. Two shape variables of the rotor blade, which are used to define the rotor sweep, are introduced to increase the adiabatic efficiency of the compressor. Throughout the optimization, optimal shape having a backward sweep is obtained. Adiabatic efficiency, which is the objective function of the present optimization, is successfully increased. Separation line due to the interference between a shock and surface boundary layer on the blade suction surface is moved downstream for the optimized blade compared to the reference one. The increase in adiabatic efficiency for the optimized blade is caused by suppression of the separation due to a shock on the blade suction surface.

• 한국전산유체공학회지
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• 제4권1호
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• pp.34-40
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• 1999

Drag reduction on vehicles are the main concern for the body shape designers in order to lower the fuel consumption rate and to aid the driving stability. The drag of bluff bodies like transportation vehicles is mostly pressure drag due to the flow separation, which can be minimized by controlling the location and size of the separation bubble. In the present study, the TURBO-3D code is incorporated with optimal algorithm based on analytical approximation method to obtain an optimal afterbody shape of the MIRA Model corresponding to the lowest drag coefficient. For this purpose three mutually independent afterbody angles are chosen as design variables, while the drag coefficient is chosen as an objective function. It is demonstrated in the present study that an optimal body shape having the lowest drag coefficient which is about 6% lower than that of the original shape has been successfully obtained within number of iterations of tile optimal design loop.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.67-74
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• 1998

Reducing drag of vehicles are the main concern for the body shape designers in order to lower fuel consumption rate and to aid the driving stability. The drag of bluff bodies like transportation vehicles is mostly pressure drag due to the flow separation, which can minimized by controlling the location and size of the separation bubble. In the present study, the TURBO-3D code is incorporated with optimal algorithm based on analytical approximation method to obtain optimal afterbody shape of the MIRA Model corresponding to the lowest drag coefficient. For this purpose three mutually independent afterbody angles are chosen as design variables, while the drag coefficient is chosen as an objective function. It is demonstrated in the present study that an optimal body shape having lowest drag coefficient which is about $6\%$ lower than that of the original shape has been successfully obtained within number of iterations of the optimal design loop.

• 대한화학회지
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• 제65권4호
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• pp.254-259
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• 2021

The purpose of this work is the development of a method for an effective, less expensive, rapid, and simultaneous determination of three phenolic compounds (caffeic acid, gallic acid, and quercetin) widely present in food resources and known for their antioxidant powers. The method relies on partial least squares (PLS) calibration of UV-visible spectroscopic data. This model was applied to simultaneously determine, the concentrations of caffeic acid (CA), gallic acid (GA), and quercetin (Q) in six herb infusion extracts: basil, chive, laurel, mint, parsley, and thyme. A wavelength range (250-400) nm, and an experimental calibration matrix with 21 samples of ternary mixtures composed of CA (6.0-21.0 mg/L), GA (10.0-35.2 mg/L), and Q (6.4-17.5 mg/L) were chosen. Spectroscopic data were mean-centered before calibration. Two latent variables were determined using the contiguous block cross-validation procedure after calculating the root mean square error cross-validation RMSECV. Other statistic parameters: RMSEP, R², and Recovery (%) were used to determine the predictive ability of the model. The results obtained demonstrated that UV-visible spectrometry and PLS regression were successfully applied to simultaneously quantify the three phenolic compounds in synthetic ternary mixtures. Moreover, the concentrations of CA, GA and Q in herb infusion extracts were easily predicted and found to be 3.918-18.055, 9.014-23.825, and 9.040-13.350 mg/g of dry sample, respectively.

• 한국정보과학회논문지:정보통신
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• 제30권1호
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• pp.24-29
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• 2003

이 논문에서는, 독립성분해석기법과 EM기법을 이용한 새로운 혼합영상분리 방법을 제안한다. 독립성분해석기법은 통계적으로 독립된 랜덤변수들의 선형조합으로 측정대상 랜덤신호를 표기하는 여러 통계신호처리 기법 중의 하나로, 정보의 분리, 특징 추출 통의 응용분야에 적용되고 있다. 기술적으로는, 독립성분기법은 주성분 분리기법의 확장이라 볼 수 있고, 근래에 혼합정보의 분리에 관련하여 많이 연구되고 있다. 현재까지의 연구 결과로는 혼합영상의 분리에 있어 독립성분해석기법만으로는 혼합영상분리의 해를 얻지 못하고 있다. 이러한 독립성분해석기법의 약점을 보완하는 방범으로, 최근에 이노베이션 프로세서를 전처리로 하는 독립성분해석기법을 혼합한 시스템을 이용한 혼합영상 분리가 시도되었다. 이노베이션 프로세서를 전처리로 첨가한 혼합영상분리의 과정도 독립성분해석기법만을 사용한 경우보다는 향상된 혼합영상분리를 하지만, 분류된 영상들이 원래의 혼합 전의 영상과 많이 다른 결과를 내고 있다. 기존의 방법들인 독립성분해석기법이나 이노베이션이 전처리로 적용된 경우에도 혼합이전의 영상간의 상관관계가 클 경우, 혼합영상의 분류가 잔 이루어지지 않는다. 본 논문에서는 이 약점을 보완하기 위하여. EM이론을 기존의 시스템에 전처리로 첨가하여 혼합 영상의 분리를 향상시키고자 하였다. 실험 결과에서는 최근에 연구된 이노베이션의 방법보다 EM을 적용시킨 경우가 향상된 혼합영상의 분리의 결과를 보여 주고 있다.