• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.461-467
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• 2021

Among the defect factors that can occur when a wafer-level lens is molded using a thermosetting material, the mold sticking problem of a molded lens during the release process can damage the molded substrate and deform the substrate at the wafer level. An experiment was conducted to examine the factors affecting the demolding force in the lens forming process. The demolding force was examined according to the coating material of the molds. The mold was surface-treated with ITO and Ti, followed by plasma treatment in an O2 atmosphere. A DLC coating was then performed, and the curing and releasability were examined. A coating method for the pull-off experiment was selected based on the results. To measure the demolding force according to the curing process conditions, a method of curing at a constant pressure and a method of curing at a constant position were applied. As a result, the TiO2 surface treatment reduced the release force. When cured by controlling the location, curing shrinkage can reduce the adhesion energy of the interface during curing, resulting in better demolding.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.80-85
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• 2008

The prediction of the separation trajectories of external stores released from a military aircraft is an important task in the aircraft design area having the objective to define the operational and release envelopes. This paper presents the results obtained for store separation by employing commercial softwares, FLUENT and CFD-FASTRAN. FLUENT treats the rigid body motion by employing a remeshing scheme. CFD-FASTRAN uses Chimera(overset) grid and interpolations. It was found that, for the prediction of the trajectories and behavior of the stores separated from the wing, both codes show the good agreement with the experimental results.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.127-132
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• 2014

Micro/nano-injection molding is one of the main processing techniques for polymer micro-fabrication. Most of the difficulties encountered in polymer micro-molding are caused by the demolding, rather than the filling of molds. Therefore, studying the demolding process is vitally important for manufacturing polymer replicas. The most important parameters are the thermal stress, friction and adhesion forces, and mechanical strength of the resist. In this research, we determinedthe effects of the processing conditions on the ejection force for cases involving two common thermoplastic polymers. The results showed that the processing conditions noticeably influenced the ejection force.

• Korean Journal of Applied Biomechanics
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• v.21 no.5
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• pp.661-667
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• 2011

The purpose of the study was to compare selected kinematic variables between the female medalists and a Korean female javelin thrower at the IAAF World Championships, Daegu 2011. Three medalists and one Korean javelin thrower that participated in the Championships were videotaped using three high-speed cameras (300 frames/s, EX-F1 Exilim, Casio, Japan). This study identified the performance differences between the two groups. The results showed that the Korean female javelin thrower (KFJT) clearly had a greater delivery phase time than the female medalists. In order to throw farther, a thrower must exert a greater force to accelerate their body in a short time. This study also found that the release velocity of the KFJT was lower than that of the female medalists. The KFJT showed evidence of using her extremities differently to achieve the maximum release velocity. When comparing the inclination angle of the trunk across javelin throwers, the lowest value was recorded in the KFJT. Because the trunk position at release plays a significant role in determining the release height and release velocity, the KFJT should not rely on her upper extremities to achieve as high a release velocity as possible.

• Korean Journal of Applied Biomechanics
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• v.21 no.5
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• pp.645-652
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• 2011

The purpose of this study was to analyze, in real time, the glide motion and release motion of domestic athletes and gold and bronze medalists employing the glide technique for the men's shot put at the Daegu World Athletic Championship in 2011. In the glide motion, the Korean athletes had a relatively high body center and shot put heights and lager stretching angles for their hips and knees. In the delivery phase, which shifts to the release phase, the Korean athletes showed slower vertical body center and shot put speeds, and they changed the phase, to the release phase by using a small body angle. In the release phase, the Korean athletes showed differences in their projection speeds and vertical body center speeds. The world-famous players showed high angle speeds, which refer to the composition of the rotation force at the moment of release (body, hip, and shoulder line). In the release phase, the Korean athletes did not have fully stretched hip and knee angles, which might have negatively influenced the vertical speed. Because the Korean athletes showed relatively low projection heights and projection angles. it was found that they need to enhance the muscular power of their, throwing arms and lower limbs.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.471-475
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• 2001

ln this paper, a micromachined micromechanical switch is presented. The presented switch is operated in the vertical direction to the substrate by an electrostatic force between two parallel plates. The moving plate is pulled down to connect the bumps of the bias node$(V_{DD}/ or GND)$ to the bumps of the output node when a oltage difference exists between the moving plate and the input plate. The switch was designed to operate at a low switching voltage$(\risingdotseq5V)$ by including a large-area, narrow-gap, parallel plate capacitor A theoretical analysis of the designed switch was performed in order to determine its geometry fitting the desired pull-in voltage and release voltage. The designed switch was fabricated by surface micromachining combined with Ni electroplating. From the experimental results of the fabricated switch, its pull-in voltage came Out to be less than 5V and the measured maximum allowable current was 150mA. The measured average ON-state resistance was about 8$\Omega$, and the OFF-state resistance was too high to be measured with digital multimeter.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.395_396
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• 2009

This paper handles with effect of electromagnetic force on the cables by fault current accompanied by accident of underground transmission cable. Even though underground transmission cable is an essential transmission method to supply stable power for downtown and population center, interaction of electromagnetic force from fault current is very large comparing to overhead transmission line due to restricted installation space such as tunnel, etc. and close consideration is required for it. This paper describes the effect of electromagnetic force through results of three phase short-circuit test and electromagnetic force analysis using theoretical calculations and electrical evaluation test after three phase short-circuit test, which will be utilized as basic materials for improvement and development of cleat, hanger, etc. to reduce and release effect of electromagnetic force in the future.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2159-2167
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• 2006

In order to find out a physical quantity which controls the fatigue life of a structure and to predict the fatigue life of tires, a finite element simulation methodology to use the cracking energy density (CED) and the virtual crack closure technique (VCCT) was proposed and applied to three different tires of a similar size. CED was calculated to predict the location of a crack initiation, and VCCT was used to obtain the strain energy release rate (SERR) at the tip of an initiated crack. Finite element simulations showed that SERR oscillated in the circumferential direction with its minimum occurring just before the contact zone and its maximum occurring just after the center of the contact zone, and SERR was affected significantly by the frictional force acting on the crack surface. In addition, a durability test was conducted to measure the fatigue life of the three tires. The comparison of SERR values with the test data revealed that the fatigue life increased as the amplitude of SERR decreased or as the R-ratio of SERR increased.

• Korean Journal of Applied Biomechanics
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• v.20 no.1
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• pp.49-55
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• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.1
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• pp.22-29
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• 2008

A sequence of visually experimental observations was conducted to investigate the flow boiling and two-phase flow in a coiled tube. Different boiling modes and bubble dynamical evolutions were identified for better recognizing the phenomena and understanding the two-phase flow evolution and heat transfer mechanisms. The dissolved gases and remained vapor would serve as foreign nucleation sites, and together with the effect of buoyancy, centrifugal force and liquid flow, these also induce very different flow boiling nucleation, boiling modes, bubble dynamical behavior, and further the boiling heat transfer performance. Bubbly flow, plug flow, slug flow, stratified/wavy flow and annular flow were observed during the boiling process in the coiled tube. Particularly the effects of flow reconstructing and thermal non-equilibrium release in the bends were noted and discussed with the physical understanding. Coupled with the effects of the buoyancy, centrifugal force and inertia or momentum ratio of the two fluids, the flow reconstructing and thermal non-equilibrium release effects have critical importance for flow pattern in the bends and flow evolution in next straight sections.