• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.83-87
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• 1995

Impact-bouncing height of steel balls dropped from 1m height on various floor materials were measured to evaluate impact-bouncing characteristics depending on floor materials and the effect of these properties on walkability and fatigue of humanbody. Stone and tile finished concrete floor showed the highest bouncing height of around 70%, and soil showed the lowest bouncing height of around 3%. The second highest bouncing height was about 40% which corresponded to terazo finished concrete floor and about twice as high as the bouncing height on concrete floor without finishing. The impact-bouncing height could be lowered to 15~20% by using gum tile on concrete floor. Steel showed similar bouncing height to concrete floor, and wood-based materials showed the second lowest bouncing height next to soil. Among wood-based materials, hardwood species having higher specific gravities showed relatively high bouncing height of 8~24%, softwood species having low specific gravities showed relatively lower bouncing height of 5~18%, and wood composites showed bouncing height of 8~18%. Among all the materials used in this study, wood-based floor materials corresponded to the bouncing height of 10~15% which is considered to be best for humanbody. Surface painting on wood-based materials increased the bouncing height, and the number of bouncing of steel balls after dropping from 1m height increased as the bouncing height increased.

• Proceedings of the KSRS Conference
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• v.1
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• pp.520-523
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• 2006

Whereas it is well known that the surface roughness parameters, the RMS height and the correlation length, of a natural soil surface are underestimated with a short surface profile, it is not clear how much the underestimated surface parameters affect the backscattering coefficients of the surface for various incidence angles and polarizations. The backscattering coefficients of simulated and measured surface profiles are computed using the integral equation method (IEM) and analyzed in this paper to answer this question. It is shown that the RMS error of the backscattering coefficients between 5-m- and 1-m-long measured surface profiles is 1.7 dB for vv-polarization and 0.5 dB for hh-polarization at a medium range of incidence angle ($15^{\circ}{\leq}{\theta}{\leq}70^{\circ}$), while the surface roughness parameters are significantly reduced; from 2.4 cm to 1.5 cm for the RMS height s and from 35.1 cm to 10.0 cm for the autocorrelation length l. This result is verified with numerous simulations with various roughness conditions and various wavelengths.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.355-360
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• 2010

Purpose: Analysis performance for spectacle lens which sales in domestic market and optimization design a spectacle lens which is corrected aberration. Methods: Measured center thickness, radius and aspherical surface coefficient for spherical and aspherical lenses which were ${\pm}$5.00D. Refractive index for every lens was 1.6 and they came from 4 different companies. I used 3 types of equipment to measure lenses. ID-F150 (Mitutoyo) : Center Thickness, FOCOVISION (SR-2, Automation Robotics) : Radius, PGI 1240S (Taylor Hobson) : Aspherical surface coefficient. Designed a lens which had 27 mm of distance from lens rear surface to center of eye, 4 mm of pupil diameter and small aberration on center vision $30^{\circ}C$. To shorten axial distance compared with the measured lens rise merits for cosmetic. Lens Design tool was CODE V (Optical Research Associates). Results: -5.00D aspherical lens had somewhat high astigmatism and distortion compared with the spherical lens. But it had a merit for cosmetic because of short axial height and decrease edge thickness. Improved a performance of distortion and ascertain merits for cosmetic due to short axial height and decrease edge thickness same as (-) lens in case of +5.00 aspherical lens. Though an optimization process front surface aspherical lens had a good performance for astigmatism and distortion and the merit for beauty compared with measured spherical lens. Conclusions: Design trend for domestic aspherical lens is decrease axial height and thickness to increase a merit for cosmetic not but increase performance of aberration. From design theory for optimization design front surface aspherical spectacle lens which has improved performance of aberration and merit for cosmetic at the same time compared with the measured lens. Expect an improved performance from design back aspherical lens compared with front aspherical lens.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.4
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• pp.165-175
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• 1997

This study qualitatively reviewed effect of the height of loading and the ratio of penetration on. the characteristics of deformation of cellular bulkhead by performing a model test of embedded steel plate cellular bulkhead which had different loading height and penetration ratio. And we also examined the effect of the loading height upon the shear behavior by performing two-dimensional model test making use of aluminum rods for a filler. Besides, test results and theoretical values based on Hansen's earth pressure theory were compared and reviewed. In consequence, it was ascertained that the yield moment of cells depended on the height of loading and the ratio of penetration, and the slip surface was located on the lower area of a cell interior according as the height of loading becomes lower. The theoretical consideration which was based on the theory of earth pressure proposed by Hansen revealed that the test results accorded with the theoretical values to some degree, and the same results were derived about the location change of the slip surface.

• Journal of radiological science and technology
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• v.45 no.4
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• pp.313-320
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• 2022

Both angiography and interventional procedures accompanied by angiography provide many diagnostic and therapeutic benefits to patients and are rapidly increasing. However, unlike general radiography or computed tomography using the same X-ray, the amount of radiation is quite high, but the dose range can vary considerably for each patient and operator. The high sensitivity of the lens to radiation during cerebral angiography and neurointervention is already well known, and although there are many related studies, it is insufficient to easily reduce radiation in diagnosis and treatment. In this situation, in particular, by adding three-dimensional rotational angiography (3D-RA) to the existing two-dimensional (2D) angiography, it is now possible to make an accurate diagnosis. However, since this 3D-RA acquires images through projection of more radiation than before, the exposure dose of the lens may be higher. Therefore, we tried to analyze whether the radiation dose of the lens can be reduced by moving the lens out of the field range by adjusting the table height and magnification ratio during the examination using 3D-RA. The surface dose was measured using a rando phantom and a radiophotoluminescent glass dosimeter (PLD) and the radiation dose was compared by adjusting the table height and magnification ratio based on the central point. As a result, it was found that the radiation dose of the lens decreased as the table height increased from the central point, that is, as the lens was out of the field of view. In conclusion, in 3D-RA, moving the table position of about 2 cm in height will make a significant contribution to the dose reduction of the lens, and it was confirmed that adjusting the magnification ratio can also reduce the surface dose of the lens.

• Composites Research
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• v.24 no.6
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• pp.31-36
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• 2011

According to the evaluation on GMT-sheet by molding conditions, fiber projection on the moldings surface was investigated. Fiber projection is one of the major defects on moldings surface due to matrix shrinkage. That is, fiber projection happens from different shrinkage of matrix and glass fiber. Height of fiber projection from moldings surface becomes smaller when molding pressure is higher during holding pressure and cooling process. Height of fiber projection is dominantly affected by molding pressure. With consideration of molding pressure, the formation of surface unevenness and change in fiber projection height was elucidated. In addition, coating layer is effective to suppress surface defects, and there is no fiber projection or crack in case that coating is applied. Coating layer improves surface roughness up to the level of the polypropylene which is a single material.

• Journal of Wetlands Research
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• v.24 no.3
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• pp.196-203
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• 2022

This paper contributed to the understanding of the effect of the blade relative position on performance of micro gravitational vortex turbine in free water surface. In a constant vortex flow, the rotation, voltage and current of micro vortex water turbine were measured according to the position change of the blade installed at the relative vortex height (y/h_v) ranging from 0 to 0.778 below the free water surface. The flow rate ranged from 0.0063 to 0.00662 m³/s. The results of the experiments showed that relative positions of the blade affected the performance of vortex water turbine because the distributions of incoming flow velocity and turbulence intensity were changed. The highest amount of the energy generated by the vortex water turbine occurred in the relative vortex height ranging from 0.111 to 0.222. The output power at the relative vortex height of 0.111 was about 2.4 times larger than the relative vortex height of 0.588 below the free water surface.

• Journal of KIBIM
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• v.13 no.2
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• pp.1-15
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• 2023

Since the 1960s, the Korean Peninsula, which consists of 77.4 of the country's land and mountains, has seen a surge in demand for buildings due to population concentration due to urbanization and industrialization. Since then, the development of slopes has been inevitable due to the concentration and expansion of the city's population. When building a building on a slope, it is important to set the height of the surface. In this case, the means of regulating buildings in construction-related laws, such as the building closure ratio, floor area ratio, number of floors and total floor area of buildings, have an overall effect on buildings through the height of the surface. In the Korean Building Act, the setting of the height of the ground affects the calculation of the building height limit standard and the calculation of the underground floor, and it takes a long time to calculate. Therefore, the time required for attempts to change various design plans of buildings increases. The purpose of this study is to speed up the time required to calculate the weighted average of the surface when constructing buildings on slopes. In addition, the existing calculation process allows various design attempts compared to the same time given.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.409-414
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• 2010

This paper describes the surface form measurement of a spherical smooth surface by using single shot off-axis Fizeau interferometry. The demodulated phase map is obtained and unwrapped to remove the $2\pi$ ambiguity. The unwrapped phase map is converted to height and the 3D surface height of the surface object is reconstructed. The results extracted from the single shot off-axis geometry are compared with the results extracted from four-frame phase shifting in-line interferometry, and the results are in excellent agreement.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.53-60
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• 2001

Surface roughness plays a significant role in friction, wear, and lubrication in machine components. Most engineering surfaces have the nongaussian height distribution. So, in this study, contact simulations are conducted for not only gaussian surfaces but also nongaussian surfaces. Nongaussian rough surface considering the kurtosis is generated numerically And the effects of kurtosis on real contact area fraction, average gap, and mean asperity contact pressure are studied. It will be shown that the real contact area fraction and the mean asperity contact pressure are sensitive to the characteristics of surface geometry according to kurtosis.