• Laser Solutions
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• v.5 no.1
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• pp.23-31
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• 2002

The uniform metal droplet generation using Nd-YAG laser was studied and experiment was carried out. The shape and volume of developed droplet was measured and the Young-Laplace equation and equilibrium condition of force were applied this model. The differential equation predicting shape of droplet using equilibrium condition of force instead of Navier-stokes equation was induced and numerical solution of differential equation compared with experimentation data. The differential equation was solved by Runge-Kutta method. Surface tension coefficient of droplet was determined with numerical solution relate to experimental result under the statical condition. In case of dynamic vibration, metal droplet shape and detaching critical volume are predicted by recalculating proposed model. The result revealed that this model could reasonably describe the behavior of molten metal droplet on vibration.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.825-828
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• 2004

The objective of this study is to examine mechanical properties of ductile fiber-reinforced mortar designed based on micromechanics. This mortar was produced by employing raw materials commercially available in Korea. To verify property level of this material in uniaxial tension, a series of direct tensile tests were performed with varying water cement ratio. In addition to this, flexural tests as well as compressive tests were carried out. Experiments revealed that the fiber reinforced mortar exhibited high ductility represented by strain hardening behavior in uniaxial tension. Significant enhancements of ductility, in terms of strain at peak stress and post-peak behavior, were also observed during the tests in compression and in bending.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.255-266
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• 2012

Main cable of a suspension bridge is the important member which shows the overall structure integrity at bridge completion. Configuration of main cable is a free hanging state at cable erection completion and is different from that at bridge completion supporting the dead loads such as hanger, girder, and so on. Accordingly, the configuration control under cable erection is considerably significant because the configuration at cable erection completion has direct influence on that at bridge completion. That is performed by sag adjustments at center, side span and tension adjustments at anchor span. The former needs the sag sensitivity which represents the control quantity of strand length corresponding to that of sag. The latter requires the tension sensitivity which shows the change of strand tension according to that of strand temperature. In this study, the fundamental equations of cable were derived with the assumption of either catenary or parabola shape, the differential-related equations using chain rule on horizontal tension were drawn from those and finally the estimation methods of the sag / tension sensitivity were proposed from both those. The nonlinear numerical analysis flow charts of sag sensitivity based on the catenary equations were proposed and the sag sensitivities grounded on the differential-related equations were compared with the results using them for various parameters of sag change. Also, considering the combinations of sag change parameters, the calculation method of the final variation for the cable sag was suggested. For the real suspension bridge under construction with PPWS method, the sag/tension sensitivity were estimated considering the construction conditions like the change of PPWS length, PPWS temperature, bridge span, etc.. We hope that this study will be a systematic guideline for the configuration control under main cable erection and improved highly by field verification in the real bridge site.

• The Research Journal of the Costume Culture
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• v.26 no.3
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• pp.327-345
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• 2018

This study analyzes characteristics related to Kineticism found in different kinds of displays and arts in order to contemplate modern window displays. The standard of analysis is based on kinetic arts pioneer George Rickey's six display factors. Projection features and movements were categorized into "Direct movements," "Indirect movements," and "Relative movements." Results were obtained through analysis of different examples of each category. First, the most observed form of Kineticism was direct movements on the window display. Along with the development of science and techniques, a variety of divergent motional methods has arisen. After that followed indirect movement, which uses visual media and lights for presentation. The third was relative movements, which provides communication in practical experience; users' motion is used to provide modification in vision. Fourth, we observed that direct movements and indirect movements can express fluidity depending on materials, inducing a sense of tension within the window display through visual stimuli together with dynamism from mechanical exposure. Fifth, when direct movements pair with relative movements, it triggers customer participation; though it does not deliberately induce participation, the effects are beyond expectation. Sixth, if indirect movements meet relative movements, the motion of lights offers a major stimulation to the customers along with various expressions, thus achieving an interactive domain.

• Archives of Plastic Surgery
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• v.33 no.6
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• pp.748-752
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• 2006

Purpose:Circular skin lesions between 10 and 35 mm in diameter generate problems often. Direct closure of the lesion risks excessive wound tension or wound dehiscence. Skin grafts heal slowly and often remain unsightly. Traditional skin flaps have a limited role. We treated this circular medium-sized skin lesion(10 - 35 mm sized) by reducing opposed multilobed(ROM) flap. Methods: ROM flap involves a series of semicircular lobes extending both cephalic and caudal from the defect. Direction of the semicircular multilobed flap is set parallel to relaxed skin tension line(RSTL) to minimize scar formation. First semicircle is drawn 60% in diameter of the defect. Second semicircles are drawn at the cephalic and caudal aspects of the original semicircles. These semicircles are 60% in diameter of the first semicircle. Additional semicircles are repeatedly drawn until the tension of skin flaps becomes free. ROM flap has a length-to-base ratio of 0.5 resulting in lower theoretical risk of end flap necrosis than a random pattern flap with a large ratio. The technique involves lobes most distant from the primary defect being transposed in turn closer to the defect. Results: The ROM flap reduces skin tension concerns, lowers the risk of flap necrosis and allows for quicker and more aesthetic healing. Results were generally good and major complications, such as dehiscence, infection, or delayed healing, did not occur. Conclusion: ROM flap repair allows the plastic surgeon an additional option when faced with a circular medium-sized skin lesion.

• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.129-138
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• 1996

Localization of concrete is a phenomenon such that the deformation of concrete is localized in finite region with softening behavior and it governs ultimate load of concrete. In this Paper, concrete under strain localization was modeled with localization region and non-localization region and lc~calization behavior was formulated based on averaging concept of heterogeneous material. By using the formulation, the localization phenomena of concrete under uniaxial loadings were well predicted. The analytical results show that size of localization region of concrete under uniaxial compression is three times of maximum aggregate size and the size effect of concrete is well predicted. The use of tension-softening curve obtained from direct tension test is suitable for well prediction of localization of concrete under uniaxial tension.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.115-123
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• 2018

In a long-span bridge, the cables are important elements that support the load of the bridge. Accordingly, the cable tension is a very important variable in evaluating the health and safety of the bridge. The most popular methods of estimating the cable tensions are the direct method, which directly measures the cable stresses using load cells, hydraulic jacking devices, etc., and the vibration method, which inverses the tensions using the cable shapes and the measured dynamic characteristics. Studies on the use of the electromagnetic (EM) sensor, which detects the magnetic field variations caused by the change in the stress of the steel in the cable, are increasing. In this study, the lift-off test, the EM sensor, and the vibration method (Vision-based System and Accelerometer) were used to measure cable tension, and their results were compared and analyzed.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.3
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• pp.38-44
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• 1988

It is important to control the axial forces of high tension bolts such as the automobile, construction machine, aircraft, marine engine bolts. However, the direct method to measure the axial forces of bolts practically have not been found out. The ultrasonic techniques is based on the principles that the bolt tensile elongation and ultrasonic velocity changes are proportional to the axial force below the yield point of the materials. From the result of the experiment, the coefficient of acoustoelasticity k could be measured as - 11.18*10$_{-5}$m $m^{2}$k $g_{f}$./.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2011.09a
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• pp.3-21
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• 2011

Laboratory experiments and numerical simulations using Particle Flow Code (PFC2D) were performed to study the effects of joint separation and joint overlapping on the full failure behavior of rock bridges under direct shear loading. Through numerical direct shear tests, the failure process is visually observed and the failure patterns are achieved with reasonable conformity with the experimental results. The simulation results clearly showed that cracks developed during the test were predominantly tension cracks. It was deduced that the failure pattern was mostly influenced by both of the joint separation and joint overlapping while the shear strength is closely related to the failure pattern and its failure mechanism. The studies revealed that shear strength of rock bridges are increased with increasing in the joint separation. Also, it was observed that for a fixed cross sectional area of rock bridges, shear strength of overlapped joints are less than the shear strength of non-overlapped joints.

• Journal of computational fluids engineering
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• v.12 no.3
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• pp.41-46
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• 2007

Dynamic behavior of immiscible gas bubble attached to the wall in channel flow plays very important role in many engineering applications. Special attention has been paid to micro direct methanol fuel cell(${\mu}$DMFC) where surface tension becomes dominant factor with minor gravitational effect due to its reduced size. Therefore, displacement of $CO_2$ bubble generating on a cathode side in ${\mu}$DMFC can be very difficult and efficient removal of $CO_2$ bubbles will affect the overall machine performance considerably. We have focused our efforts on studying the dynamic behavior of immiscible bubble attached to the one side of the wall on 2D rectangular channel subject to external shear flow. We used Level Contour Reconstruction Method(LCRM) which is the simplified version of front tracking method to track the bubble interface motion. Effects of Reynolds number, Weber number, advancing/receding contact angle and property ratio on bubble detachment characteristic has been numerically identified.