• 전자공학회논문지A
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• 제32A권1호
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• pp.36-44
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• 1995

For a parabolic reflector antenna, a simple method is presented for computing efficiently the average power pattern degradations caused by the surface roughness of the reflector and misalignments between the reflector and the feed. In this procedure, both nonuniform surface errors and nonuniform illuminations are employed. The assumptions to derive the expressions are that in each annular region of the antenna, the rms value of the surface roughness is known, and in a zone in a annular region, the phase error by misalignments is constant, and can be taken to its value at the center of the zone. Detailed parametric studies are performed with derived expressions to determine the effects of those errors and illumination tapers on parameters such as gain and sidelobe levels.

• 한국자기학회지
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• 제5권5호
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• pp.663-666
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• 1995

The domain wall motion coercivity, $H_{c}$, of magnetic materials arises from the dependence of the wall energy on localized changes in material parameters (magnetization, anisotropy, exchange energy densities). However, in an otherwise perfectly homogeneous material, the domain wall energy might change due to the change in the volume of the wall versus the wall position. Thus, any surface roughness contributes to the coercivity. Assuming different two-dimensional surface profiles, characterized by average wavelengths ${\lambda}_{x}$ and ${\lambda}_{y}$, and relative thickness variations dh/h, the coercivity due to the surface roughness has been calculated. Compared to the one dimensional case, the 2D coercivity is reduced. Depending on the ratio of ${\lambda}$ to the domain wall width, $H_{c}$ has a maximum around 2, and increasing with dh/h. With the decreasing thickness of the thin film and GMR heads, it might be the domain factor in determining the coercivity.

• KSTLE International Journal
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• 제3권1호
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• pp.7-11
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• 2002

The roughness effects are very important due to the presence of interacting asperities in mixed lubrication regime. An average Reynolds equation using flow factors is useful to determine the effects of surface roughness on mixed lubrication. In this study, the effect of kurtosis on flow factors is investigated using random rough surfaces generated numerically, The results show that flow factors are very sensitive to h/$\sigma$ according to the value of kurtosis in the partial lubrication regime.

• Composites Research
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• 제26권6호
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• pp.380-385
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• 2013

본 논문에서는 유리섬유복합재(glass fiber reinforced plastic composites)의 드릴가공조건변화에 따른 박리지수와 표면조도 특성이 분석되었다. 드릴 가공된 홀의 입출구에서 이미지 픽셀을 이용하여 박리지수를 산출할 수 있는 관계식이 유도되었으며, 복합재 시편을 제작하여 진동 및 열 영향을 최소화할 수 있는 가공조건에서 드릴가공을 수행하여 보다 신뢰성 있게 표면조도값을 얻기 위하여 6점평균표면조도측정 방식이 적용되었다. 실험 결과로부터 GFRP 드릴가공에서 박리지수는 이송속도 증가에 감소하고, 절삭속도 증가에도 미세하게 감소함을 볼 수 있었다. 또한 드릴가공된 홀 내부에서 표면조도는 이송속도가 증가할수록 증가하고, 절삭속도 변화에는 영향을 받지 않음이 파악되었다.

• 한국기계가공학회지
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• 제11권5호
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• pp.60-67
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• 2012

In the study, the effect grinding condition on the workpiece arithmetical average roughness(Ra) to 10 steps leading to cutting each section with the spindle rotational speed 8000rpm and feed rate 150mm/min of grinding in GC(green silicon carbide) grinding processing after heat treatment and non heat treatment of SCM415 material. Also the following conclusions were obtained analysis of stress distribution displacement and finite elements method(FEM) on assemble parts with 3+2 axis simultaneous control through grinding and gave a load 11kg on ATC arm both sides gave a load of 11kg. For the centerline average roughness(Ra) in the heat and non-heat treatment work pieces, which were appeared the most favorable in the fifth section were $0.511{\mu}m$ and $0.514{\mu}m$, that were shown in the near the straight line section was the smallest deformation of curve. In addition, the bad surface roughness appeared on the path is too long by changing angle, the more inclined depth of cut, because the chip discharging is not smoothly.

• 한국공작기계학회논문집
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• 제13권5호
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• pp.7-15
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• 2004

The purpose of this study was to present the method to choose the optimum machining condition for the wire EDM. This was completed by examining the ever-changing quality of the material and by improving the function of the wire electric discharge machine. Precision metal mold products and the unmanned wire electric discharge machining system were used and then applied in industrial fields. This experiment uses the wire electric discharge machine with brass wire electrode of 0.25mm. To measure the precision of the machining surface, average values are obtained from 3 samples of measures of center-line average roughness by using a third dimension gauge and a stylus surface roughness gauge.

• 한국정밀공학회지
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• 제26권1호
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• pp.57-62
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• 2009

Recently, with the increasing lightness and miniaturization of high resolution camera phones, the demand for aspheric glass lens has increased because plastic and spherical lens are unable to satisfy the required performance. An aspheric glass lens is fabricated by the high temperature and pressure molding using a tungsten carbide molding core, so precision grinding technology for the molding core surface are required. This paper reports a development of feedrate control grinding method for aspherical molding core using parallel grinding method. A plane molding core was ground using conventional and feedrate control grinding method. The performance of the feedrate control method was evaluated by measurement of surface roughness. The result indicated that the average surface roughness was reduced to 1.5 nm, which is more efficient than the conventional grinding method.

• 한국생산제조학회지
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• 제19권4호
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• pp.462-468
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• 2010

Fatigue crack growth caused by surface defects is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, LPG/LNG fuel tank and other various structures. So, this paper aims to investigate the relationship between the surface roughness of fracture CT specimens and the moments on the specimen when doing fatigue test for the evaluation and the assurance of safety of structures from fatigue crack deconstruction. In this experiment, the CT specimens were loaded by a fatigue testing machine with changing loads until they are broken. The surface roughness of the fracture CT specimens was measured using 3D precise shape measuring equipment and digital holography. As a result of this study, It was identified that the average roughnesses are similar at the positions that has a same moments by comparing the results with the moments on the specimen according to the position.

• 한국표면공학회지
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• 제57권4호
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• pp.296-305
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• 2024

The aim of this in vitro study was to evaluate the changes in the roughness and weight of titanium discs treated with 3 different types of magnetostrictive ultrasonic scaler tip. Eighty identical disks (10 mm in diameter), 50 for surface roughness and 30 for weight change, were investigated in this study. For this study, 3 types of scaler tip were used as follows; Powerline(FSI-PWR-1000), Slimline(FSI-SLI-1000), and Thinsert(-16 00037374). The power was set to high power(HP), medium power(MP), and low power(LP), in the blue zone recommended by the manufacturer. Surface topography analysis was carried out using scanning electron microscopy (SEM). Surface roughness measurements, the average surface roughness (Ra) and mean roughness profile depth (Rz), were compared between treated and non-treated surfaces with a profilometer. A PowerLINE-MP of magnetostrictive ultrasonic scalers for implant patients might be recommended when considering changes in the roughness and weight of titanium discs.

• 한국안전학회지
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• 제17권1호
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• pp.11-17
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• 2002

The purpose of this study was to present the method to choose the optimization machining condition for the wire electric machine. This was completed by examining the ever-changing quality of the material and by improving the function of the wire electric discharge machine. Precision metal mold products and the unmanned wire electric discharge machining system were used and then applied in industrial fields. This experiment uses the wire electric discharge machine with brass wire electrode of 0.25mm. To measure the precision of the machining surface, average values are obtained from 3 samples of measures of center-line average roughness by using a third dimension gauge and a stylus surface roughness gauge. In this experiment, we changed no-node voltage to 7 and 9, pulse-on-time to $6{\mu}s,\;8{\mu}s$ and $10{\mu}s$, pulse-off-time to $8{\mu}s,\;10{\mu}s$ and $13{\mu}s$, and experimented on wire tension at room temperature by 1000gf, 1200gf, and 1400gf, respectively.