• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4573-4584
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• 2015

The traditional feature extraction algorithms for recognition of communication signals can hardly realize the balance between computational complexity and signals' interclass gathered degrees. They can hardly achieve high recognition rate at low SNR conditions. To solve this problem, a novel feature extraction algorithm based on Holder coefficient was proposed, which has the advantages of low computational complexity and good interclass gathered degree even at low SNR conditions. In this research, the selection methods of parameters and distribution properties of the extracted features regarding Holder coefficient theory were firstly explored, and then interval gray relation algorithm with improved adaptive weight was adopted to verify the effectiveness of the extracted features. Compared with traditional algorithms, the proposed algorithm can more accurately recognize signals at low SNR conditions. Simulation results show that Holder coefficient based features are stable and have good interclass gathered degree, and interval gray relation classifier with adaptive weight can achieve the recognition rate up to 87% even at the SNR of -5dB.

• 한국환경과학회지
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• 제10권6호
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• pp.451-459
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• 2001

Adsorption characteristics of triadimefon and diniconazole(pesticide) by natural zeolite($CLI_N$) and several synthetic zeolites were Investigated. The synthetic zeolites used En this study were as follows: Faujasite synthesized from coal fly ash($FAU_F$); Zeolite synthesized from the mixture of FAU and Na-Pl synthesized from the ratio of Cheju scoria 6 to coal fly ash 4 by weight($(FAU + Na-Pl)_{SF}$); waste fluid catalytic cracking catalyst($FCC_W$). The distribution coefficient, $K_D$ and Freundlich constant, $K_F$ decreased in the fellowing sequence : $FCC_W ＞ FAU_F ＞ (FAU + Na-Pl)_{SF} ＞CLI_N$ among the zeolites. The distribution coefficient and the adsorption capacity of $(FAU + Na-Pl)_{SF}$ for pesticides were 4.4 and 2.6 times higher for triamefon, and 2.0 and 2.4 times higher for diniconazole than those of $CLI_N$, respectively.

• 방사성폐기물학회지
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• 제20권2호
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• pp.151-160
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• 2022

The sorption of Eu on MX-80 bentonite in Na-Ca-Cl solutions is investigated at a molal proton concentration (pH_m) range of 3 to 10 and an ionic strength (I) range of 0.1 to 6 m (mol·kgw^-1). The sorption equilibrium of Eu on MX-80 is achieved within 14 to 21 d at I = 0.1 and 6 m. The sorption distribution coefficient (K_d) values of Eu for MX-80 increase as pH_m increases from 3 to 6 for all I values, and they are independent of pH_m between 8 and 10 at I ≥ 0.5 m. Meanwhile, at I = 0.1 m, the K_d value at pH_m = 10 is slightly lower than those at pH_m = 8 and 9. The K_d values are not affected by the I values between 0.5 m and 6 m, whereas the K_d value at I = 0.1 m is greater than those at I ≥ 0.5 m, except at pH_m = 10. A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model is applied to the Eu sorption data for I ≤ 4 m, and the equilibrium constants of the sorption reactions are estimated.

• 융합신호처리학회논문지
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• 제24권2호
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• pp.97-102
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• 2023

방향타는 조선 분야에서 중요한 역할을 하기 때문에 방향타의 유체역학적 특성을 조사하기 위해 수치 시뮬레이션이 수행되었다. 유체역학적 힘과 같은 일부 값은 예인 탱크에서 쉽게 측정할 수 있지만, 실험을 통해 압력 분포, 속도 분포, 와류 발생과 같은 유동장에 대한 자세한 정보를 얻기는 어렵다. 본 연구에서는 전산유체역학(CFD)을 이용하여 방향타에 작용하는 유체역학 계수와 레이놀즈수가 미치는 영향을 연구하였다. 상용 전산유체역학 프로그램 Ansys Fluent를 이용하여 방향타 주위의 유동 특성을 연구하였고, 이때 k-epsilon 난류 모델이 사용되었다. 먼저 CFD 상용코드를 이용하여 KCS 방향타의 받음각에 따른 항력계수와 양력계수를 구하였다. 둘째, 동일한 조건에서 2차원 양력계수와 항력계수를 3차원 계수와 비교되었다. 셋째, 레이놀즈수가 유체역학적 힘에 미치는 영향이 연구되었다.

• 한국가시화정보학회지
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• 제11권1호
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• pp.16-21
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• 2013

In this study, diffusion coefficients of 20 kDa FITC-dextran in 2% agarose gel with different cell concentrations were measured using fiberoptic-based fluorescence recovery after photobleaching technique. As increasing cell concentration suspended in agarose gel, the diffusion coefficients were decreased. The diffusion coefficient of agarose gel which contains $10{\times}10^6$ cells/ml was decreased to 11% that of in agarose gel without cells. The distribution of fluorescence dye in 3D scaffold was also simulated. The simulation result shows that the diffusion coefficient is more significant factor than the scaffold structure.

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.445-454
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• 2002

The sorption of U(Vl) on a domestic granite is studied as a function of experimental conditions such as contact time, solution-solid ratio, ionic strength, and pH using a batch procedure. The distribution coefficients, $K_{d}$＇s, of U(VI) are about 1-100mL/g depending on the experimental conditions. The sorption of U(VI) onto granite particles is greatly dependent upon the contact time, solution-solid ratio, and pH, but very little is dependent on the ionic strength. It is noticed that an U(VI)-carbonate ternary surface complex can be formed in the neutral range of pH. In the alkaline range of pH above 7, U(VI) sorption onto granite particles is greatly decreased due to the formation of anionic U(VI)-carbonate aqueous complexes.s.

• 소성∙가공
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• 제19권1호
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• pp.25-31
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• 2010

To achieve desired microstructure and mechanical property of a manufacturing product, heat treatment process is applied as a secondary process after forging. Especially, quenching process is used for improving strength, hardness, and wear resistance since phase transformation occurs owing to rapid heat transfer from the surface of the specimen. In the present paper, a study on surface temperature measurement for water quenching of eutectoid steel was investigated. In order to determine the temperature history in experiments, three different measuring schemes were used by varying installation techniques of K-type thermocouples. Depending on the measured temperature distribution at the surface of the specimen, convective heat transfer coefficients were numerically determined as a function of temperature by the inverse finite element analysis considering the latent heat generation due to phase transformation. Based on the inversely determined convective heat transfer coefficient, temperature, phase, and hardness distributions in the specimen after water quenching were numerically predicted. By comparing the experimental and computational hardness distribution at three different locations in the specimen, the best temperature measuring scheme was determined. This work clearly demonstrates the effect of temperature measurement on the final mechanical property in terms of hardness distribution.

• 대한기계학회논문집B
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• 제20권1호
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• pp.369-376
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• 1996

Variations of the drag and lift forces of a circular cylinder in a planar turbulent jet were experimentally investigated. The force was directly measured using the load cell and estimated by integrating the pressure distribution on the cylinder. As the cylinder moves outward from the center of the jet, the direction of lift force changes and the drag force decreases. Reynolds number, the ratio of cylinder's diameter to half width of jet had effect on maximum drag coefficient and the location where the direction of lift changes.

• 한국산학기술학회논문지
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• 제21권4호
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• pp.317-323
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• 2020

본 연구에서는 수막설비에 사용되는 워터커튼 노즐의 형상 인자 변화에 따른 분사압력과 방사유량 그리고 액적의 평균크기의 상관관계를 분석하였다. 이를 위해서 노즐의 내부 직경과 폭을 변화한 총 5개(D5W3, D5W6, D5W8, D4W6 그리고 D7W6) 각각의 노즐을 제작하였으며, 액적 측정 실험 장치를 구성하여 노즐의 수력직경 변화에 따른 유량 계수와 액적의 분포 상수를 반복실험을 통하여 산출하였다. 그 결과 유량계수는 노즐의 직경과 폭이 증가함에 따라 수력직경의 0.79 지수승과 62.8의 상수값에 비례하여 증가하는 것으로 나타났으며, 평균 액적의 크기는 분사 압력의 -0.235 지수승의 크기로 감소하였다. 특히, 본 연구에서 정의한 액적의 분포상수는 수력 직경의 0.258 지수승과 244.21의 크기에 비례하여 증가하는 것으로 나타났으며, 동일 워터커튼 노즐에 대해서 분사압력의 크기가 증가할수록 평균 액적의 크기가 감소하는 것을 검증하였다. 본 연구 결과는 수막설비용 노즐의 형상 설계에 따른 유동 특성을 예측하기 위한 노즐의 분사압력, 방사유량 그리고 평균 액적크기의 설계 자료로 활용이 유용할 것으로 판단된다.

• Tribology and Lubricants
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• 제24권4호
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• pp.196-204
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• 2008

In this study, the pressure distributions on the oil film of piston pin bearings are found by two-dimensional lubrication analysis in order to help the optimum design of the bearings of piston pin. The lubrication analysis is carried out together with an equation related with the oil pressure-viscosity index. The oil film pressure distribution is used as an input data for pressure boundary conditions at the piston pin-boss surface. Finally, the piston pin-boss stress distribution coupled with the thermal stress is calculated, and then compared with the results of the stress analysis which is not counted with the oil film pressure boundary condition.