• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.87-88
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• 2010

A permeability of concrete is a very important factors evaluating durability. So, we are carrying out a lot of relational data bases and experiment regarding a permeability. In order to evaluate a permeability of concrete, we are proceeding study on the water penetration and diffusion in concrete by water pressure. Because a way to evaluate a permeability of concrete has a limit. We will present a good method of evaluating durability of concrete using the water penetration depth of concrete by water pressure. To carry this out, we executed experiment with penetration depth of concrete by water pressure and verified it though FEM analysis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.197-207
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• 1992

Fatigue life and penetration behavior were examined analytically by variety of initial front face crack length and initial crack depth. The fatigue crack shape before penetration is almost semielliptical, and the aspect ratio by calculation using the Newman-Raju's formula is smaller than the value obtained by the experiment. It is found that the crack growth behavior on the back surface after penetration is unique and can be divided into three stage a, b and c. By using the K value proposed by the authors, particular crack growth behavior and the change in crack shape can be evaluated quantitatively. It is found that fatigue life and penetration behavior were more dependent on initial front face crack length than initial crack depth.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.2
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• pp.321-325
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• 2011

After investigating the analytic model to predict penetration depth, we propose an analytical model which can be used in estimating the normal penetration characteristics of small projectiles, when they are impacted to the concrete targets with ordnance velocities. The major parameters of this model are nose factor of penetrator, compressive strength and density of targets, and impact velocity. We can predict accelerations, velocities, displacements of projectiles and applied forces by this proposed model. Estimated penetration depths were shown 5% error. We also verified the usefulness of the new method with laboratory impact test data.

• Journal of the Korean Society of Costume
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• v.11
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• pp.51-60
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• 1987

The penetration force of needle and penetration energy kave been investigated, in order to research into the sewing factors that influence the weft knitted fabric with high elastic property. The results of the studies are a follows: (1) As the results have showed a high correlativity between the needle penetration energy and force, it proves that the dynamic energy produced by the friction of the needle as it penetrates and withdraws from the knitted fabric contributes to the heat growth of the needle. (2) To reduce frictional force the use of thin needles, medium ball point needle and super needle are effective. (3) The reduction in number of plies of fabric or also in the case of a decrease in penetration speed have been effective in lowering the penetration energy and force.

• Restorative Dentistry and Endodontics
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• v.2 no.1
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• pp.32-37
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• 1976

The author has studied comparatively the sealing quality of polycarboxylate cement, one of the newest dental cement systems, and zinc oxide eugenol cement by means of penetration of 2% methylene blue solution through the root apex of human teeth in 72 cases as time elapsed. Followings are the results obtained from this study. 1) In all groups, there was no increase in penetration related to increased time of immersion in the dye. 2) In polycarboxylate cement groups, there was a significant difference in depth of dye penetration of each tooth, but in zinc oxide eugenol cement group, there was a slight difference. 3) The depth of dye penetration of zinc oxide eugenol cement group is slightly lower than that of poly carboxylate cement groups. 4) In polycarboxylate cement groups, Carbolit cement group showed comparatively lower grade of dye penetration than Carbo cement group.

• Laser Solutions
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• v.4 no.2
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• pp.13-19
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• 2001

When a high-power laser beam is irradiated on the surface of material, it is well known that a cavity, called a keyhole induced by the pressure action of the vapor plume, is generated in the molten material. This paper describes the interaction between a pulsed CO$_2$ laser beam and water. The laser-beam is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. Experimental results show that the depth of laser-beam penetration is limited by hydrodynamic instability. The instability of the surface cavity can be understood by the capillary instability of a hollow jet. Theoretical computation of the steady keyhole shape has been performed. modifying the model suggested by Andrews et al. (1976). The model predicts the qualitative behavior of the keyhole but significantly underestimates the average diameter.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.25-26
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• 2018

In this study, the device was developed for evaluating the effect of pressure on chloride ion penetration of concrete. And chloride-ion penetration depth and water soluble chloride contents was evaluated concrete using ordinary portland cement and blast-furnace slag cement using developed device. As a result, chloride ion penetration of concrete was promoted according to the action of pressure and the exposure period. and the incorporation of blast-furnace slag was effective for chloride attack resistibility under pressure.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.169-174
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• 2017

The objective of this study was to verify the experimental and numerical results of spray evolution injected from different types of the nozzle-hole geometries. Spray visualization was taken by high speed camera under the different conditions. For the simulations of spray tip penetration, turbulence, evaporation and break-up model were applied K-zeta-f, Dukowicz and Wave model, respectively. Also, the prediction accuracy of spray tip penetration was increased by varying the spray cone angle. At the same time, the results of this work were compared in terms of spray tip penetration, and SMD characteristics. The numerical results of spray evolution process and spray tip penetration showed good agreement with experimental one.

• Bulletin of the Society of Naval Architects of Korea
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• v.7 no.1
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• pp.45-56
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• 1970

The penetration of domestic high-titania potassium type arc welding rod has been investigated experimentally. The penetration of this type arc welding rod is influenced much more by changing welding current than welding speed and thickness of base metal in range of $6{\sim}9mm$. Values of penetrations were $1.00{\sim}1.75mm$ for $3.2mm{\phi}$ rod, and $1.10{\sim}1.86mm$ for $4mm{\phi}$ rod in adequate welding current range. The domestic rod's penetration is deeper than same type rod of the United State's product.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.705-711
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• 2012

The purpose of this study is to develop the model to estimate the penetration rate of metal under a high power continuous wave laser irradiation. To estimate it, an empirical modeling is more practical when the penetration phenomena of metal by laser irradiation is too complex to be analyzed by the numerical simulation. When several methods published earlier were applied to our results, we found out that their methods were not appropriate as the model. Therefore, we suggested the new empirical method considering effective intensity as a key variable. As a result, we confirmed that the new method was effective to model the penetration rate of SUS304 metal and expected that it could be available to other metals.