• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.249-267
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• 1994

The purpose of this study was to compare the fatigue, physical properties, flexibility and surface roughness of titanium used in removable partial dentures with those of a type IV and alloy and a cobalt- chromium alloy. Fatigue testing subjected the test specimen to rapid cycling at a given stress until failure occurred by using a small-sized, electrodynamic type bending fatigue testing machine. The S-N curves for the framework materials were generated. For tensile testing, a tensile bar as described in the ADA Specification No.14 was subjected to tensile loading until failure occurred. Load-displacement curves were generated for 18 gauge round specimen and tapered half round specimen. Then the flexibilities were calculated. The surface roughnesses were compared by analyzer. Through analyses of the data, the following conclusions were obtained. 1. The fatigue property of titanium was higher than that of a type IV gold alloy$(p\leq0.05)$, but there was no significant difference between titanium and a cobalt-chromium alloy $(p\geq0.05)$. 2. The yield strength, the ultimate tensile strength and Victors hardness of titanium were higher than those of a type IV gold alloy but lower than those of a coalt-chromium alloy$(p\leq0.05)$. 3. The percentage of elongation and reduction of area of titanium were the highest $(p\leq0.05)$. 4. The surface roughness of titanium was the greatest$(p\leq0.05)$. 5. The flexibility of titanium was lower than that of a type IV gold alloy but higher than that of a cobalt-chromium alloy$(p\leq0.05)$.

• Journal of Korean Society of Steel Construction
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• v.26 no.5
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• pp.463-471
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• 2014

As building height and span is getting taller and longer, the researches to increase material's strength and serviceability are continuously performed. This study evaluated mechanical and chemical properties of newly developed high-strength steel (HSS) for building structures, namely HSA800 and verified cost-effectiveness and applicability of HSS for a tall building by comparing the analysis results of normal strength steel (SM490) model. HSA800 was manufactured by TMCP to have a good weldability in spite of HSS and satisfied Korean Industrial Standards (KS). The analysis results for evaluating cost-effectiveness show that total steel quantity could be saved approximately 30% when using HSS compared to SM490. It is expected that HSA800 will contribute to enhance constructability of building.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.432-438
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• 2009

In this paper, we synthesized LSG powder by Modified-GNP method. Lanthanum, strontium and gallium (LSG) were selected in the preparation of an oxygen-electrode (anode) for High Temperature Steam Electrolysis system (HTSE). The used amount and concentration of nitric acid were varied to find out an appropriate composition for oxygen-electrode (anode). In order to optimize the molar ratio of La and Sr, ratio of La to Sr was varied that 2:8, 5:5 and 8:2. The combined LSGs were calcined for 2 hours at $700^{\circ}C$ and were sintered in a furnace for 4 hours at $1200^{\circ}C$. The phase and crystallinity of LSG powder were determined by XRD. The surface morphology was observed through SEM photograph, and the specific surface area was investigated with BET. The thermochemical property was determined by TG/DTA. The synthesized preparation was obtained of $La_{0.8}Sr_{0.2}GaO_{3}$ formula for 3M nitric acid, which was the best perovskite phase.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.179-183
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• 2016

Background: As an important detecting device, TLD is a widely used in the radiation monitoring. It is essential for us to study the property of detecting element. The aim of this study is to calculate the thermo-luminescence efficiency of TL elements. Materials and Methods: A batch of thermo-luminescence elements were irradiated by the filtered X-ray beams of average energies in the range 40-200 kVp, 662 keV $^{137}Cs$ gamma rays and then the amounts of lights were measured by the TL reader. The deposition energies in elements were calculated by theory formula and Monte Carlo simulation. The unit absorbed dose in elements by photons with different energies corresponding to the amounts of lights was calculated, which is called the thermo luminescent efficiency (${\eta}^{(E)}$). Because of the amounts of lights can be calculated by the absorbed dose in elements multiply ${\eta}^{(E)}$, the ${\eta}^{(E)}$ can be calculated by the experimental data (the amounts of lights) divided by absorbed dose. Results and Discussion: The deviation of simulation results compared with theoretical calculation results were less than 5%, so the absorbed dose in elements was calculated by simulation results in here. The change range of ${\eta}^{(E)}$ value, relative to 662 keV $^{137}Cs$ gamma rays, is about 30% in the energy range of 33 keV to 662 keV, is in accordance by the comparison with relevant foreign literatures. Conclusion: The ${\eta}^{(E)}$ values can be used for updating the amounts of lights that are got by the direct ratio assumed relations with deposition energy in TL elements, which can largely reduce the error of calculation results of the amounts of lights. These data can be used for the design of individual dosimeter which used TLD-2000 thermo-luminescence elements, also have a certain reference value for manufacturer to improve the energy-response performance of TL elements by formulation adjustment.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.703-708
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• 2006

The slurry infiltrated fiber concrete(SIFCON) is recognized as one of the most promising new construction materials. Compressive and direct tensile tests are performed to investigate the mechanical property of SIFCON. Hooked-end steel fibers are used in the mix with fiber volume fraction varied from 4% to 10%. The water/cement ratio is kept constant at 0.4. The amount of silica fume added is 10% by weight of cement and 0.5% of water reducing agent is added to improve the workability of the slurry. The test results in this study show that the compressive strength of SIFCON is about 1.59 to 2.68 times in comparison with the cement paste. Tensile strength is showed the enhancement of about 2.51 to 8.77 times. It is also observed that the toughness and ductility of SIFCON are increased significantly with the increasing in fiber volume fraction.

• Journal of Korean Association for Spatial Structures
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• v.5 no.4 s.18
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• pp.71-77
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• 2005

Bonded CFRP Plate method used murk in reinforcement method is very efficient for stress increment of reinforced members. But CFRP plate dosen't display enough its capacity and have the destruction characteristic of premature failure that reach failure by debond plate, because near-surface-bond using epoxy. Such destruction character of reinforced specimens take the influence at variables as steel reinforcement ratio, concrete strength, kind of reinforcement materials, reinforced length, property of epoxy used in binder and so on. In this study, performed experiment results are compared and considered on flexural performance of Near Surface Mounted Reinforcement used CFRP-Rod, as complement about structural behavior of RC beam reinforced flexural capacity in CFRP plate and premature failure of reinforcement material. Main variables of RC beam applied CFRP Plate external bond method are experimental variables as reinforcement length, reinforcement position (tension face and side face of beam) and existence of ironware in end parts. In case of CFRP-Rod, variable is reinforcement length.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.153-158
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• 2002

$Al_2O_3$ composites powders with 1∼11 wt% $TiO_2$ were prepared by wet method and sintered at 1350$^{\circ}C$, 1450$^{\circ}C$ for 2h. Mechanical properties and microstructural evolution were investigated in this study. $Al_2O_3$-3 wt% $TiO_2$ composite were high bulk density of 2.37 g/$cm^3$ and low apparent porosity of 6.3%. The composites containing of 3 wt% $TiO_2$ showed moderately high bending strength of 68.9 MPa and the young's modulus of 35.5 MPa. The composites with increasing $TiO_2$ contents exhibit reduced thermal expansion coefficient due to the formation of $Al_2TiO_5$ phase.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.128-132
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• 2007

[ $B_4C$ ] ceramics were fabricated by spark plasma sintering process and their sintering behavior, microstructure and mechanical properties were evaluated. Relative density of $B_4C$ ceramics were obtained by spark plasma sintering method reached as high as 99% at lower temperature than conventional sintering method, in addition, without any sintering additives. The mechanical properties of $B_4C$ ceramics was improved by a methanol washing process which can be removed $B_2O_3$ phase from a $B_4C$ powder surface. This improvement results ken the formation of homogeneous microstructure because the grain coarsening was suppressed by the elimination of $B_2O_3$ phase. Particularly, fracture toughness of the sintered specimen using a methanol washed powder improved over 30% compared with the specimen using an as-received commercial powder.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.603-606
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• 2000

The cost needed for the construction and management of highways in the whole nation is rapidly growing so the research that can decrease the cost is required. However, most of the highway specs have simply converted from those of other countries, including USA. Therefore, some of our design and construction specs were not the optimum ones based on our own situation, requiring a research under the actual traffic and environment of our nation. The use of test road develops many aspects of highway engineering. Those are evaluation of construction materials, a general overview of korea pavement design and serviceability under the actual traffic and environmental condition of the nation. It is also economical and efficient compared to the trial construction of each item in spreaded form. A test road, 7.7km long with two lanes, is being constructed on the Inner Central Expressway. In this test road, 2.7km is planned for asphalt pavement and 3.4km is planned for concrete pavement. Three test bridges and five earth retaining structures will be included in the test road. Based on the master plan, the major performance was progressing such as detailed research modules of each area, preliminary research for the future research, sensor surveys for the behavior analyses of pavements and structures with installation methods and data acquisition systems, the foundation research of Integrated Instrumentation System and the Management Plan for automated measurement. Some area(structure research division, geotechnical research division) was designed the instrumentation plan because some instrument sensors must be installed during the construction of the test road. And then the instrumentation plan of each area was enforcing because a large majority of the instrument sensors must be installed after the construction of the test road. The field surveys with material property tests and pilot instrumentation test with sensor tests was also performing in accordance with the construction in the field.

• Progress in Superconductivity and Cryogenics
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• v.19 no.2
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• pp.25-28
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• 2017

In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses that could affect its electromechanical transport property. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with the delamination problem of multi-layered REBCO CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal and mechanical cycling. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in the multi-layered REBCO CC tapes becomes a critical issue. Various trials to increase the delamination strength by improving interface characteristics at interlayers have been performed. In this study, in order to investigate the influences of laser cleaning and Ag annealing treated at the substrate side surface, transverse tensile tests were conducted under different sample configurations using $4.5mm{\times}8mm$ upper anvil. The mechanical delamination strength of differently processed CC samples was examined at room temperature (RT). As a result, the Sample 1 with the additional laser cleaning and Ag annealing processes and the Sample 2 with additional Ag annealing process only showed higher mechanical delamination strength as compared to the Sample 3 without such additional treatments. Sample 3 showed quite different behavior when the loading direction is to the substrate side where the delamination strength much lower as compared to other cases.