• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.553-565
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• 2001

One-bottle adhesive system was recently developed in order to simplify the clinical skills and save chair time after continuous improvements on dentin bonding agents. To test the shear bond strength of a new "one-bottle adhesive" system to bovine dentin various commercially available one-bottle adhesives(Prime & Bond $2.1^{(R)}$, One Coat $Bond^{(R)}$, Syntac $Sprint^{(R)}$, Single $Bond^{(R)}$) were included for comparison. And we observe the interfacial morphology by scanning electron microscope. The results were as follows; 1. Group II (One Coat $Bond^{(R)}$) showed higher shear bond strength than group I (Prime & Bond $2.1^{(R)}$), group III(Syntac $Sprint^{(R)}$), and group IV(Single $Bond^{(R)}$), but no statistically significant difference was founded between groups(p>.05). 2. Relating reverse-cone shape resin tags were observed in samples of all groups under SEM. We could observed hybrid layer, resin tag and many lateral branches in every group. But, we observed in group III rare lateral branched than other three groups, and discontinuous hybrid layer.

• Journal of Korea Water Resources Association
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• v.47 no.11
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• pp.1077-1086
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• 2014

The flood wave generated due to dam break is affected by initial depth upstream since it is related with hydraulic characteristics propagating downstream, and flow resistance stress has influence on the celerity, travel distance, and approaching depth of shock wave in implementing numerical simulation. In this study, a shallow water flow model employing SU/PG scheme was developed and verified by analytic solutions; propagation characteristics of dam break according to flow resistance and initial depth were analyzed. When bottom frictional stress was applied, the flow depth was relatively higher while the travel distance of shock wave was shorter. In the case of Coulomb stress, the flow velocity behind the location of dam break became lower compared with other cases, and showed values between no stress and turbulent stress at the reach of shock wave. The value of Froude number obtained by no frictional stress at the discontinuous boundary was the closest to 1.0 regardless of initial depth. The adaption of Coulomb stress gave more appropriate results compared with turbulent stress at low initial depth. However, as the initial depth became increased, the dominance of flow resistance terms was weakened and the opposite result was observed.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.802-810
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• 2006

For a thorough train control, the precise train position detection is necessarily required. The widely used current way for train position detection is the one of using track circuits. The track circuit has a simple structure, and has a high level of reliability. However trains can be detected only on track circuits, which have to be installed on all ground sections, and much amount of cost for its installation and maintenance is needed. In addition, for the track circuit, only discontinuous position detection is possible because of the features of the closed circuit loop configuration. As the recent advances in telecommunication technologies and high-tech vehicle-based control equipments, for the train position detection, the method to detect positions directly from on trains is being studied. Vehicle-based position detection method is to estimate train positions, speed, timing data continuously, and to use them as the control information. In this paper, the features of GPS navigation and DR navigation are analyzed, and the navigation filters are designed by constructing vehicle-based train position detection method by combining GPS navigation and DR navigation for their complementary cooperation, and by using kalman filter. The position estimation performance of the proposed method is also confirmed by simulations.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.100-109
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• 2002

Significant damage to concrete results from the intrusion of corrosive solutions, for example, dissolved chlorides corrode reinforcing steel and cause spatting. Effectively blocks the penetration of these solutions will eliminate or greatly reduce this damage and lead to increased durability. This study is to investigate the effects of pozzolanic admixtures, fly ash and silica fume, and a blast furnace slag on the chloride ion penetration of concretes. The main experimental variables wore the water-cementitious material ratios, the types and amount of admixtures, and the curing time. And it is tested for the porosity and pore size distributions of cement paste, chloride ion permeability based on electrical conductance, and 180-day ponding test for chloride intrusion. The results show that the resistance of concrete to the penetration of chloride ions increases as the w/c was decreased, and the increasing of curing time. Also, concrete with pozzolans exhibited higher resistance to chloride ion penetration than the plain concrete. The significant reduction in chloride ion permeability(charge passed) of concrete with pozzolans due to formation of a discontinuous macro-pore system which inhibits flow. It is shown that there is a relationship between chloride ion permeability and depth of chloride ion penetration of concrete, based on the pore structure (porosity and pore size distributions) of cement paste.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.3
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• pp.133-147
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• 2005

Various types of ray-tracing methods are used to predict the quantity measures of radiation illumination, the uniformity of illumination, radiation performance of LCD BLU(Hack-Light Unit). The uniformity of radiation illumination is one of the most important design factor of BLU and is usually controlled by the diffusive-ink pattern printed on the bottom of light-guide panel of BLU. Therefore it is desirable to produce an improved (ideally, the optimal) ink pattern to achieve the best uniformity of radiation illumination. In this paper, we applied the Welder-Mead simplex-search method among various direct search method to compute the optimal ink pattern. Direct search methods are widely used to optimize the functions which are often highly nonlinear, unpredictably discontinuous, and nondifferentiable, The ink-pattern controlling the uniformity of radiation illumination is one type of these functions. In this paper, we found that simplex search methods are well suited to computing the optimal diffusive-ink pattern. In extensive numerical testing, we have found the simplex search method to be reasonably efficient and reliable at computing the optimal diffusive-ink pattern. The result also suggests that optimization can improve the functionality of simulation tools which are used to design LCD BLU.

• Explosives and Blasting
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• v.24 no.2
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• pp.41-50
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• 2006

Excavation by explosives blasting necessarily involves noise and vibration, which is highly prone to face claims on the environmental and structural aspects from the neighbors. When the blasting carried out in the vicinity of a structure, the effect of blasting vibration on the stability of the structure should be carefully evaluated. In the conventional method of evaluation, an equation for blast vibration is obtained from test blasting which is later used to determine the amount of charge. This method, however, has limitations in use since it does not consider topography and change in ground conditions. In order to overcome the limitations, dynamic numerical analysis is recently used in continuum or discontinuous models, where the topography and the ground conditions can be exactly implemented. In the numerical analysis for tunnels and rock slopes, it is very uncommon to simulate multi-hole blasting. A single-hole blasting pressure is estimated and the equivalent overall pressure at the excavation face is used. This approach based on an ideal case usually does not consider the ground conditions. And this consequently results in errors in calculation. In this presentation of a case study, a new approach of using blast waves obtained in the test blast is proposed. The approach was carried out in order to improve the accuracy in calculating blasting pressure. The stability of a structure in the vicinity of a slope blasting was examined using the newly proposed method.

• Journal of Korean Society of Transportation
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• v.28 no.2
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• pp.99-108
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• 2010

In this paper I tried to find out changed and improved streetscape through the simulation using components of streetscape abstracted by factor analysis after analyzing present situation and problems of the streetscape for housing developments prepared on publis water surface. An analysis object is located in Haeundae Marine City in Busan. As a result of analysing the streetscape of marine city at present, I could see that main problems were discontinuous street space that did not reflect the characteristic of seashore, uncomfortable and insecure passage owing to coexistence street at seashore, insufficient street facilities for pedestrians, and disordered outdoor signboards. Therefore, I put the causal problems of marine city's streetscape in the insufficient street components, disharmony, and discontinuity so analysed the simulation elements applying selected street components and evaluated them to deduce demand factors having common meaning. As the result, the common demand factors were 'street furniture', 'harmonious streetscape with surrounding', 'landscape with natural openness', and 'landscape with dynamic symbol' in the order. So it needs to stress on a plan for proper arrangement of 'street facilities' and symbolic streetscape having continuity and harmony with surrounding so that the plan can proceed more properly for marine city's identity.

• The Journal of Internal Korean Medicine
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• v.22 no.2
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• pp.145-160
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• 2001

Objectives : The purpose of this investigation is to evaluate the effect of Geupoongjibo-dan Extracts on Reversible Forebrain Ischemia in Mongolian Gerbils. Methods : The change rate of water content in cerebral tissues, the numercal change of the CA1 pyramidal neuron in the hippocampus, the change of delayed neuronal death(necrosis apoptosis) through light microscopy, the reactivity change of glycoprotein in neuronal membrane and the ultrastructural change of pyramidal neuron through electron microscopy caused by dalayed neuronal death were investigated. Results : 1. The change rate of water content in the normal group showed 78.90% on the third day, and 79.12% on the seventh day after an attack of ischemia. The rate in the control group showed 82.25% and 85.13%, respectively. The rate in the sample group showed a significant decrease: 81.72% and 83.66%. 2. Light microscopy revealed that the cells, continuous and systematic forms in the pyramidal cells of hippocampus, changed into discontinuous and unsystematic forms in the normal group when compared with the control group. The cells were less damaged in the sample group. 3. The mean of the numerical change of the CA1 pyramidal neurons in the hippocampus was 104 in the normal group. The mean of the control group was decreased to 27. The mean of the sample group was 44. 4. TUNEL staining examination reveals that the whole part of the hippocampus of the normal group had negative reactivity. As far as CA1 pyramidal neurons in the hippocampus, the control group had positive reactivity. The sample group was more positive than the control group. 5. Electron microscopy reveals that the ischemic injury of the control group had both necrotic and apoptotic morphology. The sample group was less necrotic, and more apoptotic morphology than the control group. 6. Lectin histochemisrical examination reveals that the normal group had positive reactivity to PNA and SBA in interneuron, and weak positive reactivity to WGA Con A LCA in intercelluar space. The reactivity to PNA and WGA decreased in the control group. The reactivity to PNA and WGA tended to increase in the sample group. Conclusions : The data shows that the effect of Geupoongjibo-dan Extracts on Reversible Forebrain Ischemia in MG is a significant result.

• Journal of Life Science
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• v.17 no.5 s.85
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• pp.658-663
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• 2007

Bacillus thuringiensis is a well-known species of entomophathogenic bacteria that is widely used as a biopesticide against many insect pests. It produces parasporal crystals ($\delta$-endotoxin) and endospores during sporulation. In this report, the $\delta$-endotoxin produced by Bacillus thuringiensis BT-1 and BT-2 were characterized by Scanning Electron Microscope(SEM), Transmission Electron Microscope(TEM), SDS-PACE, and solubilization activity by alkaline solution. BT-1, BT-2 were cultured in the GBY medium, and the $\delta$-endotoxin of them was purified with discontinuous sucrose density gradient centrifugation. Their $\delta$-endotoxin was observed by SEM and TEM. Morphologically, the $\delta$-endotoxin of BT-1 was a square and flat type, whose size was $1.73{\mu}m{\times}0.7{\mu}m$, and the $\delta$-endotoxin of the BT-2 was spherical form whose size was $1.1{\mu}m{\times}0.9{\mu}m$ determined by SEM and TEM. The $\delta$-endotoxin of the BT-1 was composed of 28 kDa and 21 kDa, however, it of the BT-2 was composed of 50 kDa, 35 kDa, and 22 kDa bands determined by SDS-PACE. The purified crystals of BT-1 and BT-2 were dissolved gradually in alkaline solution as time goes by, and it was perfectly dissolved after 3 hours. It is supposed that the $\delta$-endotoxin of crystal was converted to a state of activation in the course of time in the intestines of insect.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.6
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• pp.318-326
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• 2011

This study has been performed to investigate the effect of Al addition on High Temperature Gas Nitriding (HTGN) in 13%Cr-0.16%C stainless steel with different Al contents of 0.54%, 1.76% and 2.36%, respectively. HTGN treatment was carried out at $1100^{\circ}C$ for 1 hr, 5 hrs and 10 hrs. Nitrogen-permeated surface layers showed round type carbides of $Cr_{23}C_6$ and needle type nitrides of AlN in the matrix of martensite, representing 600~700 Hv. And the thickness of the surface layer increased with increasing Al content and HTGN treatment time. The inner region that was not permeated nitrogen showed chromium carbides in the mixed phase of martensite and ferrite for the 0.53% Al alloyed steel, however chromium carbides in the matrix of ferrite single phase were shown for the steels with the addition of 1.76%Al and 2.36%Al, representing the hardness of ~200 Hv. During nitrogen permeation from surface to the interior, substitutional elements of Cr, Al and Si moved toward the surface and interstitial element of carbon also moved from interior to the surface. This movement of alloying elements leads high concentration of these elements at the outmost surface, subsequently the lowest peak of substitutional elements were shown in the vicinity of near surface. After showing the lowest peak, the high concentration region of Al and C were formed due to the continuous movement of Al toward the surface. The long discontinuous precipitates of $Cr_{23}C_6$ and AlN were formed along the outmost surface owing to the high concentration of these alloying elements.