• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.201-207
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• 2006

Soil tests are generally conducted using a membrane to measure a pore water pressure. However, it has also been recognized that the membrane penetrates into the specimen by the change of the confining pressure, and it results in the erroneous measurement in the pore water pressure and the volumetric strain. This study examined the effectiveness of the correction equation of the membrane penetration on the basis of the experimental data acquired during the isotropic unloading and the cyclic shear process using the hollow cylindrical shear test equipment. The results showed that the membrane penetration by the correction equation could be overestimated when the mean effective stress was lower than 20kPa in this study. The limitations originated from the sudden increase near the zero effective stress, and in order to prevent the overestimation in low effective stress condition, the use of the constant a was proposed in this study. Furthermore, the correction equation for the membrane penetration had to be applied carefully when the initial relative density was high and the density changes were occurred by the relocation of the soil particle by the liquefaction.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.11-18
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• 2006

[ $Co_3O_4$ ] particles with non-aggregation characteristics were prepared by various conditions such as preparation temperature, flow rate of carrier gas, and concentration of spray solution using spray pyrolysis. The morphology and crystallinity of the preformed particles obtained by spray pyrolysis at various conditions affected the mean size and morphology of the post-treated $Co_3O_4$ particles. The preformed particles with hollow and porous morphology obtained from spray solution with citric acid and ethylene glycol turned to $Co_3O_4$ particles with nano size, regular morphology and non-aggregation characteristics after post-treatment at $800^{\circ}C$. On the other hand, the preformed particles obtained by the preparation conditions of short residence time of particles inside hot wall reactor and high reactor temperature turned to $Co_3O_4$ particles with aggregated morphology after post-treatment. The mean crystallite size and particle size of the $Co_3O_4$ particles prepared from optimum preparation conditions were 47 nm and 210 nm at post-treatment temperature of $800^{\circ}C$.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.134-142
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• 2011

Although combustion is essential in most energy generation processes, it is one of the major causes of air pollution. Exhaust pipes with circular fin were designed to study the effect of cooling the recirculated exhaust gases (EGR) of Diesel engines on the chemical composition of the exhaust gases and the reduction in the percentages of pollutant emissions. The gases examined in this study were oxides of nitrogen (NOx), carbon dioxide ($CO_2$) and carbon monoxide (CO). In addition, $O_2$ concentration in the exhaust was measured. The designs adopted in this study were about exhaust pipes with solid and hollow fins around them direct surface force measurement in water using a nano size colloidal probe technique. The direct force measurement between colloidal surfaces has been an essential topic in both theories and applications of surface chemistry. As particle size is decreased from micron size down to true Carbon nano Colloid size (<10 nm), surface forces are increasingly important. Nano particles at close proximity or high solids loading are expected to show a different behavior than what can be estimated from continuum and mean field theories. The current tools for directly measuring interaction forces such as a surface force apparatus or atomic force microscopy (AFM) are limited to particles much larger than nano size. This paper use Water and CNC fluid at normal cooling system of EGR. Experimental result showed all good agreement at Re=$2.54{\times}10^4$ by free convection and Re=$3.36{\times}10^4$ by forced air furnace.

• Archives of Craniofacial Surgery
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• v.22 no.5
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• pp.239-246
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• 2021

Background: Bone grafts can provide an optimal environment for permanent tooth to erupt and enhance the stability of the alveolar maxilla. Although autologous bone is an optimal source for osteogenesis, its inevitable donor site morbidity has led to active research on bone substitutes. This study was designed to evaluate the safety and feasibility of using biphasic calcium phosphate (BCP; Osteon) as a bone substitute in dogs. Methods: Bilateral third and fourth premolars of four 15-week-old mongrel dogs were used. All teeth were extracted except the third premolar of the right mandible, which was used as a control. After extraction of the premolars, each dog was administered BCP (Osteon), demineralized bone matrix (DBM; DBX), and no graft in the hollow sockets of the right fourth premolar, left fourth premolar, and left third premolar, respectively. Radiographs were taken at 2-week intervals to check for tooth eruption. After 8 weeks, each dog was sacrificed, and tooth and bone biopsies were performed to check for the presence of tooth and bone substitute particle remnants. Results: Four weeks after the operation, permanent tooth eruptions had started at all the extraction sites in each dog. Eight weeks after the operation, all teeth had normally erupted, and histological examination revealed BCP particles at the right fourth premolar. Conclusion: In all four dogs, no delay in the eruption of the teeth or shape disfigurement of permanent teeth was observed on gross inspection and radiologic evaluation. On histological examination, most of the BCP and DBM were replaced by new bone. Bone substitutes can be used as graft materials in patients with alveolar clefts.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.65-71
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• 2017

To prepare the Cu-based filler material indicating enhanced oxidation resistance property and Ag content, Ag-coated Cu particles was fabricated by Ag plating of 40 wt % on the spherical Cu particles with an average size of $2{\mu}m$ and their oxidation behavior was also evaluated. In the case that ethylenediaminetetraacetic acid was used alone, the fabricated particles frequently showed broken structures such as delamination at Ag shell/core Cu interface and hollow structure that are induced by excessive galvanic displacement reaction. As a result, fraction of defect particles increased up to 19.88% after the Ag plating of 40 wt.%. However, the fraction in the 40 wt.% Ag-coated Cu particles decreased to 9.01% and relatively smooth surface and dense microstructure in the Ag shell were also observed with additional usage of hydroquinone as a complexing agent. Ag-coated Cu particles having the enhanced microstructure did not show any weight increase by oxidation for exposure to air at $160^{\circ}C$ for 2 h, indicating increased oxidation resistance property.

• Journal of the Korean Geotechnical Society
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• v.25 no.11
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• pp.105-115
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• 2009

The Jeju sand was sampled from the beach in Jeju Island and its basic properties were analyzed. The cementation effect of Jeju coastal sediments was evaluated from in-situ tests such as SPT, CPT, and the Suspension-PS test. It was shown from test results that the Jeju sand has high extreme void ratios due to the angularity of grains and the intra-particle voids of hollow particles, similar to typical calcareous sands. From cone penetration test in the calibration chamber, it was found that the cone resistance($q_c$)-relative density($D_R$)-vertical effective stress(${\sigma}_v'$) relation of Jeju sand almost matches that of high compressible quartz sand. However, the $q_C-D_R-{\sigma}_v'$ correlation suggested for uncemented Jeju sand overestimates the relative density of coastal sediments of Jeju Island due to the cementation effect. From the analysis of the relation of cone resistance, N value, and small strain shear modulus measured in-situ, it seems reasonable to assume that the coastal sediment of Jeju Island is a naturally cemented one.