• 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 Visualization
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• v.9 no.3
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• pp.38-43
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• 2011

When draining takes place through an axially located drain port in a cylindrical tank without any prevent, a vortex with an air core occurs. In this study, semi spherical concave and convex meshes with different size inner hole are used to find the air core can suppress. The study is carried out with different values of inner hole of mesh and different install direction of semi spherical mesh using PIV and measured velocity distribution. By providing a mesh, the air core can be prevented, even if the ratio of inner hole of mesh and diameter of cylinder is around 0.66. The experimental results show that a convex mesh type is more effective to suppress the air core generation than a concave mesh type.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.419-424
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• 2016

In this paper, we studied a light distribution for the LED chips arrangement using an optical design software. The structures of the edge type LED luminaires are reflector plane, LGP(lighting guide plane) and diffuse plane. The reflector plane is on the middle of the overall structure. We had simulation that placing LED chips on the reflector center of the reflector edge by changing the position of LED chips above the reflector center at 1mm, 2mm, and 3mm respectively. In the case, when LED chips are on the center of the reflector, it shows the light distribution of the general diffuse illumination, the semi-direct distribution with 0.56 efficiency and the direct distribution with 0.31 efficiency. And the wedge type LGP shows more efficiency than the flat type. Gradually increasing shape of semi-spherical type by 0.015mm has power of 1.02W, efficiency of 0.25, and maximum luminous intensity of 0.104W/sr, it also and shows the better optical characteristics than the reflector plane that have no patterns. This semi-spherical type shows the better optical characteristics than the reflector plane that have no patterns.

• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.712-716
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• 2003

The semi-diabatic potential energy surfaces (PESs) of the excited states of polyatomic molecules can be constructed for use in ab initio molecular dynamics (AIMD) studies by relying on the continuity of the electronic energy, oscillator strength, and spherical extent of an excited state along with first derivatives of these quantities as computed by using the equation-of-motion coupled-cluster (EOM-CC) method. The semidiabatic PESs of both the π → $π^*$ valence excited state and the 3s-type Rydberg state of ethylene are presented and discussed in this paper, in conjunction with some of the AIMD results we obtained for these states.

• Transactions of Materials Processing
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• v.9 no.4
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• pp.389-394
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• 2000

The studies on gram size refinement for rheocast processing of hypereutectic Al-18%Si alloys have been investigated in the present study. To increase the efficiency of mechanical stirring, sieve type stirrer are newly designed and implemented for rheocasting of hypereutectic Al-18%Si alloy. Mechanical stirring of semi-solid slurry by using sieve type mechanical stirrer results in morphological changes of the primary Si particles, from angular rod shape to near spherical shape and uniform distribution of proeutectic Si. The remarkable spheroidization of Primary Si Particles and distributional uniformity of proeutectic Si show well the efficiency of sieve type mechanical stirring method which can accelerate the coalescence-fracture-wear of the individual particles by strong turbulent flow between lattices during rotation of sieve type stirrer.

• Polymer(Korea)
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• v.36 no.5
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• pp.628-636
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• 2012

The polymer concentration dependence of depletion layer was investigated by means of dynamic light scattering after the very small amount of polystyrene spherical latex particles was added into the matrix solution of poly(vinyl alcohol)(PVA)/dimethyl sulfoxide. At the dilute regime, the magnitude of depletion layer kept constant at the level of $63{\pm}3%$ of the radius of gyration of the corresponding PVA chain. Next, at the early semi-dilute regime of $1.5{\leq}C[{\eta}]{\leq}3$, polymer concentration dependence of the layer thickness ${\delta}$ was obtained as ${\delta}{\sim}C^{-0.8}$, and this experimental value was very close to theoretical one of -0.75. However it was observed above $C[{\eta}]$ >3 that its thickness decreased abruptly, and this was ascribed to aggregation effect of latex particles which was driven by Oosawa type attractive interaction.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.446-454
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• 2016

In this paper, we present experimental results of the soil discharge characteristics as a function of moisture content when a 1.2/50-㎲ lightning impulse voltage is applied. For this study, laboratory experiments were carried out based on factors affecting the transient behavior in soils. The electrical breakdown voltages in soils were measured for a 0-6% range of moisture content for sand and a 0 - 4% range of moisture content for gravel. A test cell with semi-spherical electrodes buried face-to-face in the middle of a cylindrical container was used. The distance separating the electrodes is 100 mm. As a result, the time-lag to breakdown in soils decreases as the amplitude of applied voltage increases. The time-lag to initiation of ionization streamer is decreased, with an increase in the moisture content. However, the formative time-lag is rarely changed. The behavior of soil discharges depend not only on the type of soil and its moisture content but also on the amplitude of the impulse voltage. When the test voltage is applied repeatedly, electrical breakdown occurs along different discrete paths, leading radially away from the injected electrode. i.e., the fact that the ionization streamers propagate in different paths from shot to shot was observed.

• Structural Engineering and Mechanics
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• v.6 no.6
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• pp.693-710
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• 1998

This paper concerns studies on the shape formation of post-tensioned and shaped steel domes. The post-tensioned and shaped steel domes, assembled initially at ground level in an essentially flat condition, are shaped to a curved space form and erected into the final position by means of a post-tensioning technique. Based on previous studies on this shape formation principle, three post-tensioned and shaped steel domes have been constructed. The results of the shape formation tests and finite element analyses are reported in this paper. It is found that the first two test domes did not furnish a part-spherical shape as predicted by finite element analyses, because the movements of some mechanisms were not controlled sufficiently. With a revised post-tensioning method, the third dome obtained the theoretical prediction. The test results of the three post-tensioned and shaped domes have shown that a necessary condition to form a desired space shape from a planar layout with low joint stiffnesses is that the movements of all the existing mechanisms must be effectively controlled as indicated by the finite element analysis. The extent of the maximum elastic deformation of a post-tensioned and shaped steel structure is determined by the strength of the top chords and their joints. However, due to the semi-rigid characteristic of the top chord joints, the finite element analyses cannot give a close prediction for the maximum elastic deformations of the post-tensioned and shaped steel domes. The results of the current studies can be helpful for the design and construction of this type of structure.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.3
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• pp.147-152
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• 2007

Spermiogenesis and mature spermatozoa of the Korean false minnow Pseudogobio esocinus (Cyprinidae) are described by means of scanning and transmission electron microscopy. Spermiogenesis is characterized by lateral development of the flagellum, absence of nuclear rotation, and eccentric nuclear fossa formation. The spermatozoa have a spherical head containing a nucleus with highly condensed chromatin and no acrosome. The nuclear fossa contains the proximal centriole and anterior part of the distal centriole. The midpiece is type A II and contains semi-fused mitochondria around the axoneme. However, the symmetrical distribution of 4 or more the mitochondria does not follow a general pattern of the cyprinid spermatozoa. Cytoplasmic vesicles in the midpiece are common in Cypriniformes and some of Siluriformes and Characiformes spermatozoa.