• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.91-103
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• 2009

Slope failure depends upon the climatic features related to related rainfall, structural geology and geomorphological features as well as the variation of the mechanical behaviors of soil constituting a slope. In this paper, among many variables, effects of soil layer thickness on the slope failure process, and variations of matric suction and volumetric water content were observed. When the soil layer is relatively thick, the descending wetting front decreases matric suction and the observed matric suction reaches to "0" value. When the wetting front reaches to the impermeable boundary, the bottom surface of steel soil box, ascending wetting front was observed. This observation can be postulated to be the effects of various sizes of pores. When macro size pores exist, the capillary effects can be reduced and infilling of pore will be limited. The partially filled pores would be filled with water during the ascending of the wetting front, which bounces from the impermeable boundary. This assumption has been assured from the observation of variation of the volumetric water contents at different depth. When the soil layer is thick (thickness = 20 cm), for granular material, erosion is a cause triggering the slope failure. It has been found that the initiation of erosion occurs when the top soil is fully saturated. Meanwhile, when the soil layer is shallow (thickness = 10 cm), slope slides as en mass. The slope failure for this condition occurs when the wetting front reaches to the interface between the soil layer and steel soil box. As the wetting front approaches to the bottom of soil layer, reduction of shear resistance along the boundary and increase of the unit weight due to the infiltration occur and these produce complex effects on the slope failure processes.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.981-989
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• 1998

Positions, angulation and mesiodistal dimension of lower incisors are important in esthetics, occlusion and post-treatment stability of tower arch. When lower incisor is congenitally missing, problems such as increased overjet and overbite, closing in of adjacent teeth and size/space discrepancies may occur. When creating treatment plans, incisor position and angulation, lip support, anteroposterior skeletal relationship canine-molar relationship, overjet overbite, remaining growth potential, crowding and anterior tooth ratio have to be considered. For an accurate analysis of incisal size discrepancy, diagnostic model set-up may be helpful. The two patients in this presentation both had two lower incisor missing, but the degree of crowding, skeletal relationship, lip support, molar relationship are different and therefore treatment plan was different as well. Long term follow-up may be necessary for stability and retention.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.441-444
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• 2008

Ultra high performance concrete (UHPC) in this study is composed of sand, cement, silica fume, siliceous powder, superplasticizer and steel fiber. UHPC is composed of fine mineral particles below 0.5mm in diameter. In general, siliceous powder improves the mechanical properties of concrete by physical and chemical effect. Physical effect is related with filling interior voids which weaken the mechanical properties and chemical effect with reaction of $SiO_2$ with cement hydrates in a condition of high temperature and pressure. We evaluated the effect of siliceous powder's particle size on the mechanical properties of ultra high performance concrete in air pressure and $90^{\circ}C$ steam curing condition. siliceous powder's particle size in this study is in the range of $2{\mu}m$ to $26{\mu}m$. Fluidity in a fresh concrete, compressive strength, ultimate strain, elastic modulus and flexural strength in a hardened concrete was evaluated. We could find out that the smaller siliceous powder's particle size is, the better the fluidity and strength properties.

• KSBB Journal
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• v.21 no.5
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• pp.360-365
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• 2006

The objectives of this study were to develop nano-pore silica particles and to modify its surface for use as an enzyme immobilization matrix. Sol-gel reaction was used to produce silica particles of various nano pore sizes with hydroxyl groups on their surfaces. The surface was modified with aldehyde that was confirmed by fluorescence imaging. Trypsin was covalently immobilized by reductive amination. Surface density of the immobilized trypsin was ca. $350{\mu}g/m^2$, which was approximately 17- and 35-fold higher than those from the surfaces with hydroxyl and amine group, respectively. About 90% of the initial enzyme activity was maintained after the 12th use of repeated use. When compared with the commercial matrices, the nano-pore silica particle was superior in terms of immobilization yield and specific activity. This study suggests the nano porous silica particles can be used as enzyme immobilization matrix for industrial applications.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.167-174
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• 2021

Recent investigation into the integrity of nuclear containment buildings has highlighted the importance of developing an elaborate diagnostic method to evaluate the distribution and size of cavities inside concrete walls. As part of developing such a method, this paper presents a finite element approach to modeling elastic waves propagating in the containment building walls of a nuclear power plant. We introduce a perfectly matched layer (PML) wave-absorbing boundary to limit the large-scale nuclear containment wall to the region of interest. The formulation results in a semi-discrete form with symmetric damping and stiffness matrices. The transient elastic wave equations for a mixed unsplit-field PML were solved for displacement and stresses in the time domain. Numerical results show that the sensitivity of displacement, velocity, acceleration, and stresses is large depending on the size and location of the cavity. The dynamic response of the wall slightly differs depending on the existence of the containment liner plate. The results of this study can be applied to a full-waveform inversion approach for characterizing cavities inside a containment wall.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.141-155
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• 2023

Monitoring technology based on electrical resistivity is widely used for non-destructive data collection and health analysis of underground structures and tunnels. Vulnerable sections such as fault zone generates many problems during construction of the tunnel. These problems cause displacement and stress changes of the ground. Therefore, it is necessary to predict the state of the fault zone section to ensure the mechanical stability of the underground structure. Monitoring the size of joints and the porosity of the fillings is essential for rocks. Previous studies have not considered the variety of fillings in rock joints. In this study, electrical resistivity tests were conducted according to the particle mixing state of the sandy fillings. When the size of fillings is decreased at the constant porosity, the electrical resistivity tends to increase. The results of this study are expected to be useful as basic electrical resistivity data for predicting the ground conditions and evaluation of the ground behavior that is containing sandy fillings in the rock joint for tunnels.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.172-180
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• 2019

In this study, the microstructure and gamma-ray shielding efficiency of CRT glass mortar specimen were evaluated with replacement ratio and material properties. The results show that as the replacement ratio of CRT waste glass increases, the volume of pores with diameters below 50 nm and above 400 nm is increased. Also, the half-value layer of CRT glass mortar decreased with the increasing of linear attenuation coefficient. In addition, compressive and flexural strength were reduced when CRT waste glass was replaced as the fine aggregate, but the mechanical performance of CRT mortar specimen could be obtained by substitution of the mineral admixture.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.297-303
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• 2004

Two dimensional cellular automaton (CA) models were developed to investigate growth of biofilms in aquatic ecosystems. Simple local rules on CA were applied to governing growth of bacterial populations in relation to different nutrient concentrations. Initial bacterial distribution played an important role in determining population size and morphology of biofilm at low concentrations of nutrition. With clumped distribution, population size increased slowly compared with uniform and random distributions, while the porosity tented to be higher with uniform distribution compared with other initial distributions.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.513-522
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• 2019

Catalysts based on organic compounds, transition metal and metal-organic frameworks (MOFs) have been applied to degrade or remove organophosphorus toxic compounds (OPs). During the last 20 years, various MOFs were designed and synthesized to suit application purposes. MOFs with $Zr_6$ based metal node and organic linker were widely used as catalysts due to their tunability for the pore size, porosity, surface area, Lewis acidic sites, and thermal stability. In this review, effect on catalytic efficiency between MOFs properties according to the structure, stability, particle size, number of connected-ligand, organic functional group, and so on will be discussed.

• Journal of dental hygiene science
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• v.14 no.3
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• pp.390-396
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• 2014

The purpose of this study was to examine the size, form of dental arch and occlusion type in college students in our country and the relationship of the factors. The subjects in this study were 210 selected dental hygiene students. The collected data were analyzed by a statistical package PASW 18.0. When their size, form and occlusion of dental arch were analyzed, the inter-canine width of the maxillary was 34.38 mm, and the inter-first molar width was 52.05 mm. The canine depth was 8.60 mm, and the first molar depth was 28.69 mm. As for the mandibular, the inter-canine width was 26.42 mm, and the inter-first molar width was 44.83 mm. The canine depth was 5.54 mm, and the first molar depth was 24.38 mm. Concerning the form of dental arch, the percentage of normal dental arch in the maxillary stood at 29.0, and that of crowding stood at 60.5. The percentage of spacing stood at 10.5. In the case of the mandibular, the percentage of normal dental arch stood at 29.0; crowding, 55.7; and spacing, 15.2. In relation to occlusion, the percentage of normal occlusion stood at 16.7. As to malocclusion, class I that accounted for 55.7 was most common, and class II and class III respectively accounted for 20.5 and 7.1. When the size of dental arch was compared according to the form and occlusion of it, dental arch was largest (45.95 mm) in size when the form of dental arch in the inter-first molar width of the mandibular was spacing. The size of dental arch was 44.73 mm when its form in the same region was normal, and that was 44.58 mm when its form in the same region was crowding (p=0.032). Regarding the relationship between the form and occlusion of dental arch, crowding was most common when there were class I, II and III of malocclusion both in the maxillary and mandibular.