• Journal of Korea Game Society
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• v.8 no.3
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• pp.61-68
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• 2008

Quadtree-based terrain visualization methods have been used in a lot of applications. However, because most procedures are performed on the CPU, the rendering speed is slow in comparison to methods using GPU. In this paper, we present a quadtree-based terrain visualization method working on the GPU with specially designed data structure, error-texture and LOD-texture, and block-based acceleration method. In preprocessing step, we calculate errors in world space and store them to error-texture. In rendering step, we examine projected errors of error-texture and choose the detail level, then store the projected errors to LOD-texture. View frustum culling is performed as block unit using the values of error-texture and LOD-texture. This method reduces CPU load and performs time consuming jobs such as LOD selection and view frustum culling.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.401-407
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• 2011

The conventional method of magnetic abrasive polishing is not suitable for non-magnetic materials because such polishing is basically possible when magnetic force exists and the magnetic force in non-magnetic materials is very low. The installation of an electromagnet under the working area of a non-magnetic material, which is called second-generation magnetic abrasive polishing in this study, can enhance the magnetic force. Experimental evaluation and optimization of process parameters for polishing magnesium alloy steel was performed by adopting the design of experiments and the response surface method. The results indicated that the intensity of the magnetic force and spindle speed are significant parameters that affect the improvement of surface roughness. A prediction model for the surface roughness of the magnesium alloy steel is developed using the second-order response surface method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.887-892
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• 2014

In a conventional magnetic abrasive polishing process, the polishing abrasives are mixed with ferrous particles and slight cutting oil to form a cluster of abrasives. However, when a tool rotates at a high revolution speed, most of the polishing abrasives are scattered away from it due to the increase in centrifugal force. This phenomenon directly reduces the polishing efficiency. The use of a highly viscous matter such as silicone gel instead of cutting oil for mixing is one method to solve this problem and increase abrasive adhesion. Another method to avoid high abrasive scattering is the application of wet magnetic abrasive polishing (WMAP). In WMAP, abundant mineral oil is preliminarily applied to the workpiece surface. This study experimentally evaluated the effect of WMAP on abrasive adhesion. The relationship between the amount of working abrasives and polishing conditions was characterized. Despite the lower adhesion ratio of polishing abrasives, the surface roughness was found to be significantly improved as the result of WMAP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.801-804
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• 2003

The autopilot system of vessel is proposed to take service safety sorority, to elevate service efficiency, to decrease labor and to improve working environment. Ultimate purpose of it is to minimize the number of crew by guaranteeing economical efficiency of shipping service. Recently, the research is being achieving to compensate various nonlinear parameters of vessel and apply it is course keeping control, track keeping control, roll-rudder stabilization, dynamic ship positioning and automatic mooring control etc. using optimizing control technique. Relation between rudder angle controlled by steering machine of vessel and ship-heading angle, and load condition of ship are nonlinear, which affect various parameters of shipping service. The speed and direction of waves, velocity and quantity of wind, which also cause the non-linearity of it. Therefore the autopilot system of ship requires the robust control algorithm can overcome various non-linearity. On this paper, we design the autopilot system of ship, which overcome nonlinear parameters and disturbance of it using Fuzzy Algorithm, evaluate the proposed algorithm and its excellence through simulation

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.471-479
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• 2010

The adiabatic two-phase flow in single rectangular microchannels was studied for different aspect ratios. The working fluids were liquid water and nitrogen gas. The hydraulic diameters of the rectangular microchannels were 490, 322, and $143\;{\mu}m$, and the widths of the microchannels were around $500\;{\mu}m$. The two-phase flow pattern was visualized using a high-speed camera and a long-distance microscope. This study was focused on bubble flow regimes. From the visualized images, the bubble velocity, bubble length, number of bubbles, and void fraction were evaluated. Further, the pressure drop in a single bubble was evaluated by using a unit cell model. The bubble velocity is proportional to the superficial velocity. Further, the relationship between the void fraction and the volumetric quality is linear. The pressure drop in a single elongated bubble is strongly related to the aspect ratio. Finally, the new correlation about the pressure drop of a single elongated bubble in the rectangular microchannel was proposed.

• Journal of Digital Convergence
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• v.18 no.2
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• pp.103-110
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• 2020

The fire incident of KT's Ahyun branch occurred last year indicates that hyper-connected society led by 5G technology would be a dystopia instead of a utopia unless seamless connection of 5G service is well secured. Looking backward on 1999, we could peacefully and happily greet the new millennium by making a great effort to prevent the millennium bugs(Y2K) from causing the catastrophe such as a shut-down of banking system. Likewise, we should make a great effort to keep 5G networks and 5G service continuously working without the disruption of even just a second, which would enable us to avoid facing any catastrophes caused by the disruption of 5G service. As a way to do so, it can be considered that 5G service is designated as universal service because it has the key features of public goods like telephone and high-speed internet services.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.3
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• pp.166-175
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• 2005

Health effects associated with metal working fluid (MWF) exposures include dermatitis, respiratory disease, hypersensitive pneumonitis, and asthma. Frequently, occupational exposures to MWFs are controlled by ventilating an enclosure with an air cleaning unit that includes a fan preceded by various kinds of filtration. There are several kinds of air cleaning units used in machining centers. But the associated troubles have hindered from efficiently using these devices. The main problem is the relatively short period of filter replacement. The reason is that the air cleaning units usually do not have the de-oiling systems, thus leading the earlier clogging of filters and reducing the flow rate of hood. Thus, the first stage of study was conducted to overcome this problem by developing the new oil mist collector equipped with the easy de-oiling system. The principle of de-oiling is that the centrifugal force generated by spinning the drum covered by filter fabric separates oils from the filter fabric. It would be very similar to the spin-dry laundry. By adopting this de-oiling technique, the problems associated with the conventional oil mist collectors could be solved. Several tests/analyses were performed to make the lab-scale oil mist collector. The collection efficiencies and the de-oiling efficiencies of commercially available filter fabrics were tested. Subsequently, the endurance test were conducted by observing SEM photos of filter fabrics and measuring tensile strength/expansion coefficient after spinning the filter drum for 20 minutes at the different rotation speeds. By doing these experiments, the most appropriate filter fabric and rotation speed/duration were selected. Finally, the new oil mist collector was designed. In the near future, this device must be tested in the real machining center.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1593-1598
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• 2011

The purpose of this study is to perform parameter selection and develop a method for the condition monitoring of an LCD conveyance robot. To determine the vibration characteristics of the driving part of the robot, the gear mesh frequency (GMF) of the speed-reducing gearbox is calculated and confirmed by frequency analysis. In order to ensure reproducibility of the measured data, an appropriate working pattern is selected and experiments are carried out. For condition monitoring of the robot, a wireless measurement system is constructed and used in parameter selection, with the GMF as the center. A method involving the use of the standard deviation of the measured data and another method involving the use of multiple value of amplitude are proposed.

• Journal of Biosystems Engineering
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• v.30 no.2 s.109
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• pp.81-88
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• 2005

Manual transplanting Chinese cabbage needs 184 hours per ha in Korea. Mechanization of Chinese cabbage transplanting operation has been highly required because it needs highly intensive labor during peak season. This study was conducted to developed walking-type Chinese cabbage transplanter. In order to find out design factor of the transplanter, a kinematic analysis software, RecurDyn, was used. The prototype was tested in the circular soil bin and its operating motion was captured and analyzed using high speed camera system. Prototype was one row type which utilized original parts of engine, transmission and etc. from walking-type rice transplanter in order to save the manufacturing cost. Success ratio of pick-up device of hole-pin type and latch type were $96.0\%$ and $99.2\%$, respectively. which was highly affected by feeding accuracy of feeding device of seedling. Transplanting device of the prototype produced a elliptic loci which were coincident with those produced by the computer simulation. Prototype proved good performance in transplanting with mulching and without mulching operation, either. Working performance of prototype was 22 hours per ha and operation cost of the prototype was 961,757 won per ha. So, it would reduce $88\%$ of the labor and $29\%$ of operation cost.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.685-690
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• 2006

The rail clamp is the device to prevent that a crane slips along rails due to the wind blast as well as to locate the crane in the set position for loading and unloading containers. The wedge typed rail clamp should be designed to consider the structural stability and the durability because it compresses both rail side with large clamping force by the wedge working as the wind speed increases. In this research, the design of experiments(DOE) and the variation technology(VT) built in ANSYS WORKBENCH are utilized to determine the optimum shape of a jaw. The optimum results obtained by two methods are compared and examined.