• Journal of the Korean Geosynthetics Society
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• v.3 no.4
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• pp.41-48
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• 2004

Recently a method for increasing the bearing capacity by laying the reinforcing materials with three or four layers as a method reinforcing the ground was studied recently. The purpose of this study is to examine the method for increasing shear-strength factor of the ground by reinforcing the ground under the foundation. According a method of wrapping ground with bakk-shape or semicircle-shape by geotextile was developed in this study and it looks likes anaspect that spreading footing exits under spread footing. A simulation loading-test using Aluminum sticks was carried out in order to examine the mechanism about bearing capacity of spread footing reinforced by geotextile. Increase of ultimate bearing capacity was verified in this simulation loading-test when charging loads to spread footing, which is propose from this study, reinforced by geotextile. And moving directions of points of the ground were also checked by grid-type indication method, and the areas where plastic failure appeared were checked by B-shutter photographing.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.380-387
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• 2004

Recently the geosynthetics reinforced retaining wall has been widely used instead of the steel reinforced retaining wall. The geosynthetics reinforced retaining wall is a very dangerous structure if the geosynthetics lose their strength about tension or if it lose their pullout resistence, but it was known that the geosynthetics reinforced wall had a great resistence and was a very safe structure against a earthquake or a dynamic load. It can be said that most important factors in the stability of the geosynthetics reinforced wall are the horizontal length of reinforcement and the vertical distance between two reinforcements. That is to say, as the length of reinforcement is longer, the structure is more stable and as the vertical distance between two reinforcements is shorter, it is more stable. In this study, in order to get the critical condition with a safety rate of 1, various kinds of model tests about geosynthetics reinforced wall has been performed. Photos by B-shutter method has been taken during tests and from photos, which show us the failure state, the critical condition about failure has been conformed. Accordingly the equation, which says the limit of stability in geosynthetics reinforced wall., has been proposed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.659-664
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• 2002

New design method about the spread footing was developed using only soil and geosynthetics. This footing will be able to replace the concrete footing at constructing the foundation of small structures. As shown in Fig-3(b), after excavating the ground in semicircular shape, geosynthetics is layed on the semicircular shape of ground and let the soil filled. Geosynthetics of upper side are fixed tightly each other It can be thought to be a kind of great bag with semicircular shape. We performed two kinds of experiments to investigate the deformation and the failure shape of spread footing reinforced by geosynthetics. First, after making model ground with aluminium rods, the lattice point of 1cm ${\times}$ 1cm size of the side of aluminium rods have been painted with various kinds of colors. We have observed the movement of painted rods during loading. Second, we have taken pictures about failure process using B-shutter method. Analysing the behavior of model ground reinforced in a semicircular shape, we could know the reinforced one has much greater and wider plastic area than unreinforced one at failure. Based on the experimental results, new design method was proposed, which has a possibility to apply at the field works.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.7 s.262
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• pp.644-652
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• 2007

In this paper, a technique of simultaneously measuring the velocity and the temperature in micro-scale flow is proposed. This method uses particle tracking velocimetry (PTV) for measuring the velocity and laser induced fluorescence (LIE) for measuring the temperature. To measure the accurate velocity and temperature, images for PTV and for LIE are separated by using two light sources and a shutter which is synchronized with a camera. By using only one camera, measurement system can be simplified and the error from complicate optical system can be minimized. Error analyses regarding the concentrations of fluorescent dye and particle and the light source fluctuation are also conducted. It is found that the error of the temperature and the velocity highly depends on the concentration of fluorescent particles which are used for PTV. This technique is applied to the simultaneous measurement of the velocity and the temperature in the electrokinetic flow. It is found that the velocity and temperature vary with the electric field strength and the concentration of electrolyte.

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.341-351
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• 2008

This study investigated the effect of intermittent polymerization on the rate of polymerization shrinkage and cuspal deflection in composite resins. The linear polymerization shrinkage of each composite was measured using the custom-made linometer along with the light shutter specially devised to block the light at the previously determined interval. Samples were divided into 4 groups by light curing method; Group 1) continuous light (60s with light on); Group 2) intermittent light (cycles of 3s with 2s light on & 1s with light off for 90s): Group 3) intermittent light (cycles of 2s with 1s light on & 1s with light off for 120s); Group 4) intermittent light (cycles of 3s with 1s light on & 2s with light off for 180s). The amount of linear polymerization shrinkage was measured and its maximum rate (Rmax) and peak time (PT) in the first 15 seconds were calculated. For the measurement of cuspal deflection of teeth, MOD cavities were prepared in 10 extracted maxillary premolars. Reduction in the intercuspal distance was measured by the custom-made cuspal deflection measuring machine. ANOVA analysis was used for the comparison of the light curing groups and t-test was used to determine significant difference between the composite resins. Pyramid showed the greater amount of polymerization shrinkage than Heliomolar (p < 0.05). There was no significant difference in the linear polymerization shrinkage among the groups. The Rmax was group 4 < 3, 2 < 1 in Heliomolar and group 3 < 4 < 2, 1 in Pyramid (p < 0.05). Pyramid demonstrated greater cuspal deflection than Heliomolar. The cuspal deflection in Heliomolar was group 4 < 3 < 2, 1 and group 4, 3 < 2, 1 in Pyramid (p < 0.05). It was concluded that the reduced rate of polymerization shrinkage by intermittent polymerization can help to decrease the cuspal deflection.