• The Journal of the Acoustical Society of Korea
• /
• 제15권2E호
• /
• pp.45-49
• /
• 1996

From the reverberation signals received in the shallower water, the surface scattered signals are identified by using the multipath eigneray model that provides launch angles, grazing angles and transmission loss from the high frequency directional source to and from the rough surface. For small scale surface waves, the perturbation method is used to compute the backscattering strength for various grazing angles and wind speeds. A scheme to inversely estimate the wind speed, by which the observed surface reverberation levels are produced, has been tested. In result, for low grazing angles the perturbation method can be used to predict the backscattering stregth, thereby the surface wind can be indirectly estimated.

• Tribology and Lubricants
• /
• 제26권6호
• /
• pp.329-335
• /
• 2010

Recently, the End-milling processing is needed the high-precise technique to get a good surface roughness and rapid time in manufacturing of precision machine parts and electronic parts. The optimum surface roughness has an effect on end-milling working condition such as, cutting direction, spindle speed, feed rate and depth of cut, and so on. It needs to form the correlation of working conditions and surface roughness. Therefore this study was carried out to presume of surface roughness on end-milling working condition of Al7075 by regression analysis. The results was shown that the coefficient of determination($R^2$) of regression equation had a fine reliability of 87.5% and nonlinear regression equation of surface rough was made by multiple regression analysis.

• 한국표면공학회지
• /
• 제47권1호
• /
• pp.25-32
• /
• 2014

The effects of shot peening pressure on electrochemical and surface morphological characteristics of ALBC3 alloy were investigated in this work. The surface hardness of ALBC3 alloy was improved by shot peening process under all shot peening pressures between 2 and 5 bar, and the hight value of surface hardness was observed to be about 420 Hv at 4 bar of the shot peening pressure. The shot peened surface presented very rough surface due to shot ball collision. The result of anodic potentiodynamic polarization in seawater revealed that there is no significant difference between the shot peened and non-shot peened specimen in terms of corrosion characteristics. Therefore, the optimum projection pressure is determined to be 4 bar.

• 대한기계학회논문집A
• /
• 제28권11호
• /
• pp.1692-1696
• /
• 2004

This paper presents the thermally induced hot spot characteristics of rubbing surface in the friction pad disk brake. During the braking period, the rubbing surface with irregular asperities that are strongly engaged in rough surface, wear, and deformed surface due to a friction heating may produce an irregular distorted geometry of the disk surface. The tribological interactions between the disk and the pads are unstable if the contact stress is severe, in which the irregularity develops the contact pressure distribution, leading eventually to localized contact, high temperature and formation of hot spots. The computed results of contact spots that are simulated using a coupled thermal-mechanical analysis present sinusoidal distortions and localized extrusions of the disk surface, which are strongly related to a hot spot in the practical disk brake.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2021년도 가을 학술논문 발표대회
• /
• pp.168-169
• /
• 2021

A hydrophobic surface increases the contact angle between water and cement paste. There are two methods to increase water contact angle, i.e. lowering the surface energy and adjusting the surface roughness of concrete. The hydrophobicity of concrete can be quantitatively evaluated according to the chemical and physical properties of the solid surface. So far, researches have shown the chemical properties of hydrophobic concrete, however it has not covered how to control surface. This study demonstrated the hydrophobic cement paste prepared by low-resolution molds printed with a 3D printer that exhibit rough surface. Thus, we presented the most hydrophobic characteristics of mold.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.915-918
• /
• 2005

Advances in Information Technology and in Biomedicine have created new uses for CAD technology with many novel and important biomedical applications. Such applications can be found, for example, in the design and modeling of orthopedics, medical implants, and tissue modeling in which CAD can be used to describe the morphology, heterogeneity, and organizational structure of tissue and anatomy. CAD has also played an important role in computer-aided tissue engineering for biomimetic design, analysis, simulation and freeform fabrication of tissue scaffolds and substitutes. And all the applications require precision geometry of the organs or bones of each patient. But the geometry information currently used is polygon model with none solid geometry and is so rough that it cannot be utilized for accurate analysis, simulation and fabrication. Therefore a case study is performed to deduce a transformation method to build free form surface from a rough polygon data or medical images currently used in the application. This paper describes the transformation procedure in detail and the considerations for accurate organ modeling are discussed.

• 한국전자통신학회논문지
• /
• 제5권4호
• /
• pp.345-351
• /
• 2010

FVTD법을 이용한 전자파전파의 해석은 정확한 결과를 내고 있으나 컴퓨터 자원의 많은 메모리와 소요 시간을 필요로 하고 있다. 논문에서는 시간 세분화에 의해 수정된 FVTD기법인 TS-FVTD기법을 제안한다. TS-FVTD 기법은 기존의 방법과는 달리 전체 계산영역을 스텝 사이즈가 크고 거친 격자로 분할하여, 유전체 영역을 비유전율의 평방근에 의존하는 국부 시간 세분화 방법을 제시한다. 이 기법은 계산 소요시간 및 메모리 소비량을 절약하면서도 정확한 수치 결과를 구할 수 있다. 또한 굴곡 표면의 유전체 도파관의 전자계 계산에 적용하여 제안하는 기법의 유효성을 검토하였다.

• 한국의류학회지
• /
• 제29권8호
• /
• pp.1158-1167
• /
• 2005

The purpose of this study is to examine the effect of structural properties of plain knit fabrics on the subjective textures and sensibilities of consumers. We investigated the relationship of subjective textures and sensibilities according to fiber contents of wool/rayon and stitch loop length. We made 20 plain knit fabrics, as specimens, with a combination of 5 kinds of fiber contents and 4 kinds of stitch loop length. A factor analysis showed that subjective textures are classified into 3 categories with $R^2=70.32\%$: 'surface-rough', 'drapable', 'bulky' and 'elastic' and subjective sensibilities into 3 categories with $R^2=68.12\%$: 'stable/neat', 'feminine/elegant' and 'natural/comfortable'. The fiber contents of wool/rayon had a positive and linear relation with 'surface-rough', but had a relatively non-linear one with 'bulky' and 'elastic' categories of textures, and 'feminine/elegant' of sensibilities. The stitch loop length had a linear influence on 'drapable' and 'stable/neat', but had a non-linear influence on other subjective textures and sensibilities.

• 한국기계가공학회지
• /
• 제6권3호
• /
• pp.77-84
• /
• 2007

As a life cycle of product bas shortend, Rapid prototypiug has come into the spotlight to shortened the time of producint a prototype. But It followed in laminated directivity and of the prototype production which is decided the interference which Beccuase of invisible rough surface, some inferences have occured during an assembly hour. Consequently, This study on rapid prototyping has parameter to determine surface roughness and surface form precision of total shape. In order to improve Surface form precision, it can control parameters which are Laminate Height, Layer Hatch Overcue, Fill Cure Depth. In addition, we found the parameter which have a deep effect on surface roughness among various parameters, and then, tried to reduce the interference that can be occurred by surface roughness during assembly.

• Tribology and Lubricants
• /
• 제29권4호
• /
• pp.228-234
• /
• 2013

This paper presents analysis of elastohydrodynamic lubrication (EHL) of ball bearings, in which surface roughness is considered. A lot of time is required to obtain a solution in the case of EHL analysis where surface roughness is considered, because the analysis requires a variety of analytic nodes. To save time, we use the full approximation scheme (FAS) among multilevel methods. We analyze the results of EHL and contact analyses in terms of pressure. We also compare the results for smooth and rough surfaces with respect to film thickness. We confirm that the film pressure decreases as compared to contact pressure because of the presence of lubricants between the ball and the raceway. Furthermore, in the case when surface roughness is considered, the film pressure increases because of contact asperities. Therefore, surface roughness should be considered when designing ball bearings.