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High-pressure behavior and tribological properties of wind turbine gear oil
Sobahan Mia,Shota Mizukami,Ryusei Fukuda,Shigeki Morita,Nobuyoshi Ohno 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
Different types of synthetic polyalphaolefin (PAO) oils and a mineral oil are considered in this study. High-pressure viscosity test was done and pressure-viscosity coefficient was measured for all sample oils. Results showed the better performance of PAO oils than the mineral oil. Authors also tested some other tribological properties such as low-temperature behavior, bulk property, frictional coefficient,and wear behavior, which are important for wind turbine gear oil. Low-temperature behavior and frictional property of PAO oils exhibited the better results. Study also showed that the prediction of low-temperature fluidity is possible using the sound velocity in the oil. Finally, the presence of polymethakrylate (PMA) absorbent in PAO oil exposed comparatively better results among all PAO oils.
K. M. A. Sobahan,Yong Jun Park,Chang Kwon Hwangbo 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
In this paper, the effect of deposition angle on the optical and the structural properties of Ta2O5 thin films fabricated by using electron beam evaporation with a glancing angle deposition (GLAD) technique is reported. The refractive index and the porosity at various deposition angles are studied. We see that the refractive index decreases and the porosity increases with increasing deposition angle. The calculated in-plane birefringence of GLAD Ta2O5 films shows a maximum value of 0.04 at a deposition angle of 70. The microstructure and the morphology are also investigated by using scanning electron microscope (SEM). The cross-sectional SEM images illustrate a highly oriented microstructure composed of slanted columns and voids due to the shadowing effect and limited adatom diffusion. Therefore, the glancing angle deposition technique is an original way to control the columnar microstructure with an enhanced birefringence. In this paper, the effect of deposition angle on the optical and the structural properties of Ta2O5 thin films fabricated by using electron beam evaporation with a glancing angle deposition (GLAD) technique is reported. The refractive index and the porosity at various deposition angles are studied. We see that the refractive index decreases and the porosity increases with increasing deposition angle. The calculated in-plane birefringence of GLAD Ta2O5 films shows a maximum value of 0.04 at a deposition angle of 70. The microstructure and the morphology are also investigated by using scanning electron microscope (SEM). The cross-sectional SEM images illustrate a highly oriented microstructure composed of slanted columns and voids due to the shadowing effect and limited adatom diffusion. Therefore, the glancing angle deposition technique is an original way to control the columnar microstructure with an enhanced birefringence.
Optical and Structural Properties of ZnO Thin Films Fabricated by Using Oblique Angle Deposition
박용준,K. M. A. Sobahan,남현정,김진주,황보창권 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61
In this paper, we report the optical and the structural properties of ZnO thin films deposited by using radio-frequency magnetron sputtering with an oblique angle deposition (OAD) technique. The effect of deposition angle on the refractive index and the in-plane birefringence were studied. With increasing deposition angle, the refractive index decreases, and the in-plane birefringence increases. The in-plane birefringence reaches its maximum value of 0.061 at a deposition angle of 60˚ and then decreases with further increase of the deposition angle. The microstructure and the morphology were also investigated by using a scanning electron microscope (SEM).
Linear polarization-discriminatory state inverter fabricated by oblique angle deposition
Park, Yong Jun,Sobahan, K. M.,Kim, Jin Joo,Hwangbo, Chang Kwon The Optical Society 2009 Optics express Vol.17 No.13
<P>In this paper, we report a linear polarization-discriminatory state inverter made of three-layer sculpture thin film fabricated by oblique angle deposition technique. The first and third layers are quarter-wave plates of zigzag structure and the middle of them is a circular Bragg reflector of left-handed helical structure. It is found that the normal incidence of P-polarized light on this polarization-discriminatory state inverter becomes the S-polarized light at output, while the incident S-polarized light of wavelength lying in the Bragg regime is reflected. The microstructure of the linear polarization-discriminatory state inverter is also investigated by using a scanning electron microscope.</P>
Yong Jun Park,K. M. A. Sobahan,Chang Kwon Hwangbo 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
In this paper, we report the optical and the structural properties of a circular polarization handedness inverter consisting of a half-wave plate and a Bragg reflector. The half-wave plate with a zigzag structure and the Bragg reflector with a helical structure were fabricated by using a glancing angle deposition (GLAD) technique. The thin-film half-wave plate with a zigzag structure was found to have the same properties as those of a conventional half-wave plate. The circular polarization handedness inverter was observed to change the circular polarized state of the incident light into the opposite state at the output The structure and the surface morphology of these devices were also investigated by using a scanning electron microscope (SEM). In this paper, we report the optical and the structural properties of a circular polarization handedness inverter consisting of a half-wave plate and a Bragg reflector. The half-wave plate with a zigzag structure and the Bragg reflector with a helical structure were fabricated by using a glancing angle deposition (GLAD) technique. The thin-film half-wave plate with a zigzag structure was found to have the same properties as those of a conventional half-wave plate. The circular polarization handedness inverter was observed to change the circular polarized state of the incident light into the opposite state at the output The structure and the surface morphology of these devices were also investigated by using a scanning electron microscope (SEM).
Optical Properties of TiO2 Zigzag Films Prepared by Using Oblique Angle Deposition
황보창권,Yong Jun Park,K. M. A. Sobahan 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4
We present the optical properties of TiO2 films with a zigzag structure fabricated by using an oblique angle deposition (OAD) technique. Two fixed orientations of the substrate, 90 different from each other, were used during the deposition. At each orientation, the zigzag structure of the TiO2 film was fabricated at an oblique angle of 60。 for the first half of the deposition and –60 for the second half. The in-plane birefringence of the TiO2 zigzag films deposited on glass substrate at the two different orientations was determined. For both orientations, the in-plane birefringence was found to be almost the same in magnitude, but opposite in sign. As an application, quarter-wave plates of zigzag structures were fabricated by using the OAD technique for both orientations of the substrate.
Optical and Structural Properties of Bilayer Circular Filter Prepared by Glancing Angle Deposition
Yong Jun Park,KM Abdus Sobahan,Jin Joo Kim,Chang Kwon Hwangbo 한국광학회 2009 Current Optics and Photonics Vol.13 No.2
In this paper, we report the optical and structural properties of a bilayer circular filter fabricated by a glancing angle deposition technique. The bilayer circular filter is realized by a two-layer TiO2 helical film with layers of opposite structural handedness. It is found that the bilayer circular filter reflects both right and left circularly polarized light with wavelength lying in the Bragg regime. The microstructure of the bilayer circular filter is also investigated using a scanning electron microscope.
Optical and Structural Properties of ZrO2 Thin Films Fabricated by Using Glancing Angle Deposition
황보창권,박용준,K. M. A. Sobahan 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
In this paper, the optical and the structural properties of ZrO2 thin lms deposited by using electron beam evaporation with a glancing angle deposition (GLAD) technique are presented. The films prepared by using the glancing angle deposition technique were highly oriented structures composed of slanted columns and voids due to the shadow effect and limited adatom diffusion. The relationships among the refractive index, the porosity and the deposition angle were studied. The results show that the refractive index decreases and the porosity increases with increasing deposition angle. The in-plane birefringence of the ZrO2 thin lms was measured and it reached a maximum value of 0.038 at a deposition angle of 70˚. The microstructure and the morphology were also investigated by using a scanning electron microscope (SEM). We found that the optical anisotropy and the microstructure of the ZrO2 thin lms could be controlled by the GLAD technique.