• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2003년도 추계학술발표대회 논문집
• /
• pp.55-58
• /
• 2003

This paper presents a study on the permittivities of the carbon nano fiber/epoxy composite at microwave frequency. The permittivities of composite materials depend on the concentrations and the dispersion methods of the carbon nano fibers. The experimental values of complex permittivities were obtained for the specimen made by dispersion method using ethyl alcohol as dispersion media and compared with the results by simple mechanical mixing method.

• Journal of applied mathematics & informatics
• /
• 제13권1_2호
• /
• pp.233-245
• /
• 2003

A time fractional advection-dispersion equation is Obtained from the standard advection-dispersion equation by replacing the firstorder derivative in time by a fractional derivative in time of order ${\alpha}$(0 < ${\alpha}$ $\leq$ 1). Using variable transformation, Mellin and Laplace transforms, and properties of H-functions, we derive the complete solution of this time fractional advection-dispersion equation.

• Journal of Mechanical Science and Technology
• /
• 제15권12호
• /
• pp.1683-1690
• /
• 2001

A Lagrangian stochastic model is adopted for the calculations of turbulent dispersion in turbulent channel flows. Dispersion of a fluid particle and relative dispersion between two particles released at the sane location are investigated and compared with the classical seating relations for homogeneous turbulence. The viscous effect is realized by adding a Browinian random walk to the calculation of the position of a particle. The near-wall accumulation of particles is examined.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
• /
• pp.778-781
• /
• 2007

The dispersion of carbon nanotubes in composite and their field emission superiority have been discussed. Four synthesis methods have been studied. The CNT-composite, synthesized by the combination of the chemical and mechanical dispersion routes shows superior dispersion as well as field emission characteristics as compared to other syntheses methods.

• Current Optics and Photonics
• /
• 제3권3호
• /
• pp.193-198
• /
• 2019

We propose a novel method to design a dispersion map for a WDM (Wavelength Division Multiplexing) ring network with the capability of wavelength reconfiguration. The method is simple, but gives us an optimum set of DCMs (Dispersion Compensation Modules) which satisfies a given value of the tolerable residual dispersion. The proposed method does not depend on compensation method, fiber type, or modulation format. We also demonstrate numerically how it works with an example 10-node ring network.

• 한국염색가공학회지
• /
• 제22권4호
• /
• pp.362-372
• /
• 2010

This paper surveys the physical properties of the multiwall carbon nanotube (MWNT) and polyurethane composite film for improvement of mechanical properties and electrical characteristics. The modification of MWNT was carried out by acid treatment with nitric and sulphuric acid mixed solution, and then followed by thermal treatment for enhancing MWNT dispersion with polyurethane. This modified MWNT was mixed with polyurethane by changing the loading content of MWNT and dispersion time under the dimethylformamide solution in the ultrasonic wave apparatus. Various physical characteristics of the modified PU/MWNT films were measured and analyzed in terms of the loading content and dispersion time. The maximum absorbance of the PU/MWNT films were observed with the 2wt% loading at dispersion times of 2 and 24 hour, respectively. The minimum electrical volume resistivity of PU/MWNT film was shown at the loading content of 0.5wt% or more irrespective of dispersion treating time. However the optimum condition was assumed to 2wt% loading at dispersion time of 2 hours by assessing the surface profile of the film using video microscope. The breaking stress and strain of the PU/MWNT film decreased with increasing loading content, but no change of physical properties was shown with increasing in dispersion time.

• 한국항행학회논문지
• /
• 제19권6호
• /
• pp.595-600
• /
• 2015

전통적인 midway 광 위상 공액기 (OPC; optical phase conjugator)가 아닌 non-midway OPC를 분산 제어 (DM; dispersion-managed) 광전송 링크에 적용하여 파장 분할 다중 전송 (WDM; wavelength division multiplexed)을 위한 융통적인 네트워크의 구성 가능성을 분석하였다. 중계 구간의 수가 많을수록, 또한 중계 구간 당 잉여 분산 (RDPS; residual dispersion per span)이 클수록 non-midway OPC를 통한 유연한 링크의 구성 가능성이 커지는 것을 확인하였다. 아울러 OPC 이후의 후반 전송 구획을 구성하는 각 중계 구간의 RDPS를 OPC 이전의 전반 구획의 RDPS의 평균값으로 설정하는 링크 구조가 융통적 링크 구성에 더욱 유리하다는 것을 확인하였다.

• 한국해안해양공학회지
• /
• 제16권2호
• /
• pp.57-63
• /
• 2004

지진해일파는 조석에 비하면 파장이 짧아 상대적으로 분산성이 장하므로, 먼 거리를 전파하는 경우에는 분산성을 고려하여 해석하여야 한다. 본 연구에서는 파동방정식에 기초한 일차원 유한요소모형을 이용하여 지진해일 전파를 수치모의할 때 시간단계를 2단계로 나누어 양해법을 사용하면서도 분산효과를 고려할 수 있는 능동적인 분산보정기법을 개발하였다. 제안된 기법을 이용하여 계산한 수치해와 파의 분산효과를 고려한 해석해의 비교를 통해 본 연구에서 제안한 분산보정기법의 타당성을 확인하였다.

• 대한기계학회논문집B
• /
• 제23권2호
• /
• pp.218-225
• /
• 1999

Flow visualization study has been conducted to simulate the turbulent dispersion behavior of a crossflow jet physically under the conditions of various thermal stratification in a wind tunnel. A smoke jet with the constant ratio of the jet to freestream velocity is injected normally to the cross flow of the thermally stratified wind tunnel(TSWT) for flow visualization. The typical natures of the smoke dispersion under different thermal stratifications such as neutral, weakly stable, strongly stable, weakly unstable, strongly unstable and inversion layer are successfully reproduced in the TSWT. The Instantaneous velocity and temperature fluctuations are measured by using a cold and hot-wire combination probe. The time averaged dispersion behaviors, the centerline trajectories, the spreading angles and the virtual origins of the cross jet are deduced from the edge detected images with respect to the stability parameter. All the general characteristics of the turbulent dispersion behavior reveal that the definitely different dispersion mechanisms are inherent in both stable and unstable conditions. It is conjectured that the turbulent statistics obtained in the various stability conditions quantitatively demonstrate the vertical scalar flux plays a key role in the turbulent dispersion behavior.

• 콘크리트학회논문집
• /
• 제29권3호
• /
• pp.283-290
• /
• 2017

시멘트계 재료의 성능을 개선시키기 위하여 다양한 섬유가 사용되고 있다. 이때, 섬유 사용 목적에 관계없이 섬유의 분산성은 목표로 하는 성능 개선에 매우 중요한 지표이다. 본 연구에서는 모르타르 내의 섬유활성탄의 분산을 전기저항 방법으로 평가하였다. 특히, 믹싱 방법과 섬유의 표면 처리에 따른 섬유 분산성의 차이가 다루어졌다. 연구 결과 표면전기저항 방법은 섬유활성탄의 분산성을 평가하는데 적합하였고, 초음파 방식의 분산 방법이 몰탈믹서와 핸드믹서 방법에 비하여 우월한 것으로 나타났다. 고성능 감수제는 섬유의 분산성을 향상하는 효과가 있었으나 산 처리는 전기저항성을 높이는 결과를 가져왔다.