• Tribology and Lubricants
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• v.32 no.3
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• pp.101-105
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• 2016

Trap effect of groove is evaluated in a lubricating system using computational fluid dynamics (CFD) analysis. The simulation is based on the standard k-ε turbulence model and the discrete phase model (DPM) using a commercial CFD code FLUENT. The simulation results are also capable of showing the particle trajectories in flow field. Computational domain is meshed using the GAMBIT pre-processor. The various grooves are applied in order to improve lubrication characteristics such as reduction of friction loss, increase in load carrying capacity, and trapping of the wear particles. Trap effect of groove is investigated with variations in cross-sectional shape and Reynolds number in this research. Various cross-sectional shapes of groove (rectangular, triangle, U shaped, trapezoid, elliptical shapes) are considered to evaluate the trap effect in simplified two-dimensional sliding bearing. The particles are assumed to steel, and defined a single particle injection condition in various positions. The “reflect” boundary condition for discrete phase is applied to the wall boundary, and the “escape” boundary condition to “pressure inlet” and “pressure outlet” conditions. The streamlines are compared with particles trajectories in the groove. From the results of numerical analysis in the study, it is found that the cross-sectional shapes favorable to the creation of vortex and small eddy current are effective in terms of particle trapping effect. Moreover, it is found that the Reynolds number has a strong influence on the pattern of vortex or small eddy current in the groove, and that the pattern of the vortex or small eddy current affects the trap effect of the groove.

• Journal of the Korean Chemical Society
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• v.67 no.6
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• pp.407-414
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• 2023

The present study uses quasi-classical trajectory procedures to examine the vibrational relaxation and dissociation of the methyl and ring C-H bonds in excited methylpyrazine (MP) during collision with either N₂ or O₂. The energy-loss (-ΔE) of the excited MP is calculated as the total vibrational energy (E_T) of MP is increased in the range of 5,000 to 40,000cm^-1. The results indicate that the collision-induced vibrational relaxation of MP is not large, increasing gradually with increasing E_T between 5,000 and 30,000 cm^-1, but then decreasing with the further increase in E_T. In both N₂ and O₂ collisions, the vibrational relaxation of MP occurs mainly via the vibration-to-translation (V→T) and vibration-to-vibration (V→V) energy transfer pathways, while the vibration-to-rotation (V→R) energy transfer pathway is negligible. In both collision systems, the V→T transfer shows a similar pattern and amount of energy loss in the ET range of 5,000 to 40,000cm^-1, whereas the pattern and amount of energy transfer via the V→V pathway differs significantly between two collision systems. The collision-induced dissociation of the C-H_methyl or C-H_ring bond occurs when highly excited MP (65,000-72,000 cm^-1) interacts with the ground-state N₂ or O₂. Here, the dissociation probability is low (10^-4-10^-1), but increases exponentially with increasing vibrational excitation. This can be interpreted as the intermolecular interaction below E_T = 71,000 cm^-1. By contrast, the bond dissociation above E_T = 71,000 cm^-1 is due to the intramolecular energy flow between the excited C-H bonds. The probability of C-H_methyl dissociation is higher than that of C-H_ring dissociation.

• Journal of The Korean Astronomical Society
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• v.35 no.1
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• pp.35-40
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• 2002

Gaudi, Naber & Sackett pointed out that if an event is caused by a lens system containing more than two planets, all planets will affect the central region of the magnification pattern, and thus the existence of the multiple planets can be inferred by detecting additionally deformed anomalies from intensive monitoring of high magnification microlensing events. Unfortunately, this method has important limitations in identifying the existence of multiple planets and determining their parameters (the mass ratio and the instantaneous projected separation) due to the degeneracy of the resulting light curve anomalies from those induced by a single planet and the complexity of multiple planet lensing models. In this paper, we propose a new channel to search for multiple planets via microlensing. The method is based on the fact that the lensing light curve anomalies induced by multiple planets are well approximated by the superposition of those of the single planet systems where the individual planet-primary pairs act as independent lens systems. Then, if the source trajectory passes both of the outer deviation regions induced by the individual planets, one can unambiguously identify the existence of the multiple planets. We illustrate that the probability of successively detecting light curve anomalies induced by two Jovian-mass planets located in the lensing zone through this channel will be substantial. Since the individual anomalies can be well described by much simpler single planet lensing models, the proposed method has an important advantage of allowing one to accurately determine the parameters of the individual planets.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.2
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• pp.109-117
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• 2018

The experimental results are presented of an autonomous flight algorithm of a foldable quadcopter with airdrop launching functions. A foldable wing structure enabled the quadcopter to be inserted into a rocket container with limited space. The foldable quadcopter was then separated from the rocket in the air. The flight pattern was tracked using a global positioning system (GPS) with various sensors, including an inertial measurement unit (IMU) module until a designated target position was reached. Extensive field tests were conducted through an international rocket competition, ARLISS 2017, which was held in Black Rock Desert, Nevada, USA. The flight trajectory record of the experiments is stored in electrically erasable programmable read-only memory (EEPROM) embedded in the main control unit. The flight record confirmed that the quadcopter successfully separated from the rocket, executed flight toward the target for a certain length of time, and stably landed on the ground.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.285-286
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• 2016

We aim to propose the prediction modeling method of ship's position with extracting ship's trajectory model through pattern recognition based on the data that are being collected in VTS centers at real time. Support Vector Machine algorithm was used for data modeling. The optimal parameters are calculated with k-fold cross validation and grid search. We expect that the proposed modeling method could support VTS operators' decision making in case of complex encountering traffic situations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.317-321
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• 2003

A conventional typewriter types letters by hammering a carbon ribbon which is attached at a paper. The laser typing process which write a micro pattern of Chrome on a silicon wafer has been developed. A glass that is coated with 100 nm Chrome (Carbon ribbon) is attached on a silicon wafer (paper). An Nd-Yag laser (hammer) is irradiated on the glass, and the Chrome is transferred on the silicon wafer. Micro patterns are made by controlling laser beam trajectory. The suggested micro pattering can be used at the high density data storage of TeraBit/in$^2$ or at the improvement of productivity of semiconductor manufacturing procedure.

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.362-367
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• 2011

Organic ($Alq_3$) film, which was coated on a donor plate, was transferred to an organic light emitting diode (OLED) substrate with help of heat generated by a dithering laser beam. The laser beam was diffracted in an acousto-optic modulator (AOM), then focused on the laser-to-heat converting layer of the donor plate; the focused spot followed trajectories guided by rotation of a Galvano-mirror. Three different functional waveforms, sine wave, square wave, and saw tooth wave were applied to the AOM as modulation signal to generate the dithering beam. The fluorescence microscope images of the donor plate showed that the patterns of removed $Alq_3$ film were affected considerably by the modulation waveforms and the phase difference between adjacent dithering beams. Further, the printed images of Alq3 film on the OLED substrate were different from the patterns of removed Alq3 film. Atomic force microscope images indicated that not only direct transfer but also deposition by sublimated vapor of Alq3 contributed to the pattern formation. Printed patterns affected considerably the electricity-to-light conversion characteristics of OLEDs. For uniform transfer, not only the phase relation of dithering beam lines but also adequate waveform were important.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.3
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• pp.196-201
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• 2016

This paper analyses the characteristics of a stiffness-based rehabilitation mechanism for improving the function of the elbow joint of a human. We consider an elastic string as a tool for the elbow joint rehabilitation, where the string has been modeled as a linear spring with a stiffness. For effective rehabilitation training by using such a mechanism, we need to analyse the available torque characteristics of the elbow joint according to the stiffness of the string. Through various simulations, the torque pattern and its range of the elbow joint by assigning the stiffness of the string have been identified for a pre-defined trajectory of motion of the elbow joint. Finally, we show that the specified stiffness-based rehabilitation scheme can be used for effective rehabilitation of the elbow joint.

• Journal of Environmental Science International
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• v.19 no.2
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• pp.157-170
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• 2010

Air mass recirculation is a common characteristic in the coastal area as a result of the land-sea breeze circulation. This study simulates the recirculation of air mass over the Gwangyang Bay using WRF-FLEXPART and offers a basic information about the effective domain size that can reflect recirculation. For this purpose, WRF is set up four nested domains and three cases are selected. Subsequently FLEXPART is operated on the basis of WRF output. During the clear summer days with weak wind speed, particles that emitted from Yeosu national industrial complex and Gwangyang iron works flow into emission sources because of the land-sea breeze. When land-sea breeze is strengthen, the recirculation phenomena appears clearly. However particles aren't recirculated under weak synoptic condition. Also plume trajectory is analyzed and as a consequence, the smallest domain area have to be multiplied by 1.3 to understand recirculated dispersion pattern of particles.

• The Journal of Korean Physical Therapy
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• v.22 no.3
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• pp.49-53
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• 2010

Purpose: The purpose of this study was to investigate the plantar pressure distribution between the affected and unaffected side in adult hemiplegia during gait with the use of a quad-cane. Methods: Thirty-four stroke patients from 34 to 83 years of age were enrolled in this study, and in random order, all patients were asked to walk at their most comfortable speed three times along a walkway with the use of quad-cane over a period of three days. Plantar pressure distribution was measured with regard to foot contact pattern and center of pressure (CoP) trajectories during the stance phase, progressing from heel-strike to toe-off. The F-scan system was used to compare the foot pressure of the affected and unaffected sides. Results: A significant reduction in the total contact area, the width of fore foot (FF) and hind foot (HF), and anterior/posterior (AP) CoP trajectory of the affected side was found. However, contact pressure of the hind foot on the affected side during walking increased when compared to that on the unaffected side. Conclusion: We demonstrated that plantar pressure distribution on the affected side of adult hemiplegia patients was generally poorer than that on the unaffected side when these patients walked with cane assistance. However, the use of a quad-cane was shown to increase contact pressure of the hind foot on the affected side because weight can be borne on the affected side during heel-strike with use of the cane.