• Journal of Institute of Control, Robotics and Systems
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• v.16 no.11
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• pp.1060-1067
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• 2010

In this paper, we present a new type of spherical robot having two arms. This robot, called KisBot, mechanically consists of three parts, a wheel-shaped body and two rotating semi-spheres. In side of each semi-sphere, there exists an arm which is designed based on slider-crank mechanism for space efficiency. KisBot has hybrid types of driving mode: rolling and wheeling. In the rolling mode, the robot folds its arms through inside of itself and uses them as pendulum, then the robot works like a pendulum-driven robot. In the wheeling mode, two arms are extended from inside of the robot and are contacted to the ground, then the robot works like a one-wheel car. The Robot arms can be used as a brake during rolling mode and add friction to the robot for climbing a slope during wheeling mode. We developed a remote controlled type robot for experiment. It contains two DC motors which are located in the center of each semi-sphere for main propulsion, two RC motors for each arm operation, speed controllers for each semi-sphere, batteries for main power source, and other mechanical components. Experiments for the rolling and wheeling mode verify the hybrid driving ability and efficiency of the our proposed spherical robot.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.1-6
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• 2015

To improve the efficiency of a reverse engineering process, many researches have recently tried to develop efficient, automatic 3D scanning devices. A new automatic 3D scanning device using a spherical coordinate system mechanism is introduced in this study. This device incorporates a guide motion along the spherical coordinate to compound each 3D data point automatically. The experiments correlating the system assembling tolerance with the form accuracy were conducted to verify the efficiency of the system for the scanning of an object, including complex shapes and manifold sections. In addition, the required time and system accuracy, taken during the scanning process of complicated artifact models, were investigated. Further, based on these empirical results, it was ascertained that the superior productivity of this new device offers a more precise and efficient scan when compared to conventional methodologies.

• Korean Journal of Remote Sensing
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• v.27 no.3
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• pp.213-223
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• 2011

The purpose of this study is to estimate the spherical wave parameters that appears in synthetic aperture radar (SAR) image acquired over the coast of Chukk, Micronesia. The retrieval of ocean wave parameters consists of two main stages: the first is to determine the dominant wavelengths by Fast Fourier Transform (FFT) over 16 sub-image areas and the second is to estimate wave slopes and heights using dispersion relationship under various water wave conditions. It is assumed that the spherical waves are linear and progressive. These type of waves have the range and azimuth components traveling in radial directions. The azimuth travelling waves are more affected by the velocity bunching mechanism and it is difficult to estimate the wave parameters for these affected areas in SAR imagery. In order to compensate these effects, the velocity bunching ratio (VBR) based on modulation transfer function (MTF) was compared with the intensity ratio for neighbor area in the radial direction in order to assign the spherical wave properties for azimuthally travelling waves. Dispersion relation provides the good estimates for the wave heights for all the selected sub-image areas in the range of 1m to 2m. VBR based on MTF was found to be 0.78 at wave height of 1.36m, while the intensity-based VBR was 0.69 which corresponds to the height of 1.75m. It can be said that the velocity bunching accounts for azimuthally travelling spherical waves and the difference results from the sea-bottom effects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.871-884
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• 2015

Fluid transport is a key issue in the development of microfluidic systems. Recently, Myong (2014) has proposed a new concept for droplet transport without external power sources, and numerically validated the results for a hypothetical 2D shape, initially having a hemicylindrical droplet shape. Myong and Kwon (2015) have also examined the transport mechanism for an actual water droplet, initially having a 3D hemispherical shape, on a horizontal hydrophilic/hydrophobic surface, based on the numerical results of the time evolution of the droplet shape, as well as the total kinetic, gravitational, pressure and surface free energies inside the droplet. In this study, a 3D numerical analysis of an initially spherical droplet is carried out to establish a new concept for droplet transport. Further, the transport mechanism of an actual water droplet is examined in detail from the viewpoint of the capillarity force imbalance through the numerical results of droplet shape and various energies inside the droplet.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.473-478
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• 2000

The TiO2 powder with the values of the large specific surface area more than 150$m^2$/g has been prepared with the homogeneous precipitation process below 5$0^{\circ}C$ and its formation mechanism was investigated using the SEM, TEM and Raman Spectroscopy. With the spontaneous hydrolysis of aqueous TiOCl2 solutions, all the precipitates were fully and homogeneously crystallized with the rutile TiO2 phase simply by heating, which as transformed to the anatase TiO2 phase as increasing the addition of SO42- ions to the aqueous TiOCl2 solution. The precipitates were formed with spherical secondary particles which consisted of acicular, spherical and mixed primary particles corresponding to the rutile, anatase and mixed phases, respectively. It can be thought that the formation and phase determination of crystalline TiO2 powders even at ambient temperature would be related with the existence of the capillary force. This force might be varied depending on the shape change of the primary particles.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.4
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• pp.484-490
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• 2012

This paper is devoted to investigate the feasibility of using a medium power ground-based laser to produce a torque on LEO satellites of various shapes. The laser intensity delivered to a satellite is calculated using a simple model of laser propagation in which a standard atmospheric condition and linear atmospheric interaction mechanism is assumed. The laser force is formulated using a geocentric equatorial system in which the Earth is an oblate spheroid. The torque is formulated for a cylindrical satellite, spherical satellites and for satellites of complex shape. The torque algorithm is implemented for some sun synchronous low Earth orbit cubesats. Based on satellites perigee height, the results demonstrate that laser torque affecting on a cubesat has a maximum value in the order of $10^{-9}$ which is comparable with that of solar radiation. However, it has a minimum value in the order of $10^{-10}$ which is comparable with that of gravity gradient. Moreover, the results clarify the dependency of the laser torque on the orbital eccentricity. As the orbit becomes more circular it will experience less torque. So, we can conclude that the ground based laser torque has a significant contribution on the low Earth orbit cubesats. It can be adjusted to obtain the required control torque and it can be used as an active attitude control system for cubesats.

• International Journal of Automotive Technology
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• v.4 no.4
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• pp.165-172
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• 2003

This article deals with the spin loss analysis of friction drive CVTs, especially for the cases of S-CVT and SS-CVT. There are two main sources of power loss resulting from slippage in the friction drive CVT, spin and slip loss. Spin loss, which is also a main design issue in traction drives, results from the elastic contact deformation of rotating bodies having different rotational velocities. The structure and operating principles of the S-CVT and SS-CVT are first reviewed briefly. And to analyze the losses resulting from slippage, we reviewed previous analyses of the friction mechanism. A modified classical friction model is proposed, which describes the friction behavior including Stribeck (i.e., pre-sliding) effect. It is also performed an in-depth study for the velocity fields generated at the contact regions along with a Hertzian analysis of deflection. Hertzian results were employed to construct the geometric parameters and normal pressure distributions of the contact surface with respect to elastic and plastic deformations. With analytic formulations of the relative velocity field, deflection, and friction mechanism of the S-CVT and SS-CVT, quantitative analyses of spin loss for each case are carried out. As a result, explicit models of spin loss were developed.

• Tribology and Lubricants
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• v.24 no.6
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• pp.297-301
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• 2008

In many dynamic seals such as lip seal and compression packings, it is well known that wear occur at the surface of heat treated steel shaft as results of the intervened wear particle. It is widely understood that the dominant wear mechanism related in sealing surfaces is abrasive wear. However, little analytical and experimental studies about this problems have been done until now. In this paper, a contact analysis is carried out using MARC to investigate the wear mechanism in contact seal applications considering elastomeric seal, a elastic perfect-plastic micro-spherical particle and steel surface. Deformed seal shapes, contact and von-Mises stress distributions for various particle sizes and interference are showed. The maximum von-Mises stress within steel shaft was exceeded its yield strength and plastic deformation occurred at steel surface. Therefore, the sealing surface can be also worn by sub-surface fatigue due to wear particles together with well known abrasion. The numerical methods and models used in this paper can be applied in design of dynamic sealing systems, and further intensive studies are required.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.06a
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• pp.11-14
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• 2001

Our study have aimed to identify the deformation and breakup mechanism of minor phase in polymer blends under uniaxial enlongational flow. Experimentally, we measured the transient elongational viscosity of PS/HDPE blends using the uniaxial elongational rheometer at two temperatures. And we observed the evolution of blend morphology with elongation time. Morphological change was observed by quenching the specimen after deformation. If the viscosity variation of PS was compared with that of HDPE at each temperature, PS showed larger temperature dependence than HDPE. At 155$^{\circ}C$, the dispersed phase of larger size were easily affected by affine deformation. The initial spherical shape changed to flat ellipsoid at first, then flat ellipsoid to bulbous shape, and bulbous to thin thread and its satellites. But dispersed phase of smaller size showed the change from sphere to ellipsoid. At 175$^{\circ}C$, the dispersed phase were mostly deformed from spherical shape to ellipsoid. As a result, the morphological change of dispersed phase in elongational deformation is affected by chain flexibility and viscosity ratio. We need to further study to make sure the mechanism of elongation of viscoelastic polymer blends.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.420-426
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• 2002

$ZrO_2$, $Y_2O_3$-doped $ZrO_2$ and CaO-doped $ZrO_2$ powders were prepared by hydrothermal crystallizing spherical $ZrO_2$ gel which had been synthesized by thermal hydrolysis reaction. After the hydrothermal crystallization process, the formed crystallized powders sustained its original spherical shape and had the mean particle size of $0.4{\mu}m$. The particles were composed of about 10nm sized primary particles. The agglomeration strength between the primary particles appears very weak considering that the spherical particles were broken into the primary particles during the pressing process. The particle shape, size, phase fraction and dopant content were analyzed and crystallization mechanism of spherical gel was discussed.