• Nuclear Engineering and Technology
• /
• v.54 no.3
• /
• pp.1098-1108
• /
• 2022

The effect of the material hardening model of the canister on a finite element vertical cask drop simulation is investigated for the strain-based acceptance evaluation. Three different hardening models are considered in this paper: the isotropic hardening model, the strain rate-dependent Johnson-Cook (J-C) hardening model, and the modified J-C model which are believed to be the most accurate. By comparing the results using the modified J-C model, it is found that the use of the J-C model provides similar or larger stresses and strains depending on the magnitudes of the strain and strain rate. The use of the isotropic hardening model always yields larger stresses and strains. For the strain-based acceptance evaluation, the use of the isotropic hardening model can produce highly conservative assessment results. The use of the J-C model, however, produces satisfactory results.

• Journal of Korea Multimedia Society
• /
• v.25 no.2
• /
• pp.311-324
• /
• 2022

In this paper, we adjusted the feedback and learning materials for each learning based on ARCS motivation which applied DEVS methodology. We designed the ARCS professor-student model that expresses the continuous change in the student's attitude toward the class according to the student's attention, relevance, confidence, and satisfaction. It was applied to computational thinking and data analysis classes Based on the designed model. Before and after class, the students were asked the same question and then analyzed for each part of the ARCS. It was observed that students' perceptions of Attention, Relevance, and Satisfaction were improved except for Confidence. we observed that the students themselves felt that they lacked a lot of confidence compared to other ARS through the analysis. Although, Confidence showed a 13.5% improvement after class but it was about 33% lower than the average of other ARS. However, when it was observed that students' self-confidence was 30% lower than other motivational factors it was confirmed that the part that leads C to a similar level in other ARS is necessary.

• The Journal of Advanced Prosthodontics
• /
• v.13 no.2
• /
• pp.117-125
• /
• 2021

PURPSE. The aim of this study was to evaluate the labio-lingual alterations of the alveolar bone where the implant was placed immediately after tooth extraction. MATERIALS AND METHODS. Implants were placed immediately after tooth extraction on anterior alveolar ridges in the maxilla and mandible. The pinguide system was used to help determine the location and path of implants during the surgical process. The horizontal distance from implants to the outer border of alveolar bone was measured at the rim and middle of the implants in the cone beam computed tomography images. The alteration of alveolar bone was evaluated comparing the horizontal distances measured immediately after surgery and 3 months after surgery. RESULTS. The results show that more resorption occurred towards the labial bone than the lingual bone in the maxilla. A similar amount of labial and lingual bone resorption was observed in the mandible. CONCLUSION. Considering the horizontal alteration of alveolar bone, labio-lingual positioning of the implant towards the lingual bone in the maxilla and at the center of the alveolar ridge in the mandible is recommended when it is placed immediately after tooth extraction.

• Current Optics and Photonics
• /
• v.5 no.4
• /
• pp.370-374
• /
• 2021

Corals are the remains of animals that grow on warm beaches. They have been used as decorative jewels because of their variety of colors, and as medicinal materials for treating cancers, AIDS, and other therapeutic uses because of their chemical elements. Corals are mainly composed of calcium carbonate (CaCO₃) and have many air pores, tens to hundreds of micrometers in size. The refractive indices and absorption coefficients of dried sliced staghorn corals are investigated using terahertz time-domain spectroscopy. The measured values are similar to those for CaCO₃, as expected. It is observed that a sample with a microstructure formed by air pores can guide terahertz waves. The dispersion, effective index, and loss of the guiding modes of coral core surrounded by five triangular air pores are numerically calculated. The simulated spatial distribution of the electric field of the guide mode at 1.25 THz shows the mode to be tightly confined to the core.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.42
• /
• pp.34.1-34.7
• /
• 2020

Purpose: The purpose of this study was to evaluate the influence of biodegradable polycaprolactone membrane on new bone formation and the biodegradation of biphasic alloplastic bone substitutes using animal models. Materials and methods: In this study, bony defect was formed at the canine mandible of 8 mm in diameter, and the defects were filled with Osteon II. The experimental groups were covered with Osteoguide as barrier membrane, and the control groups were closed without membrane coverage. The proportion of new bone and residual bone graft material was measured histologically and histomorphometrically at postoperative 4 and 8 weeks. Results: At 4 weeks, the new bone proportion was similar between the groups. The proportion of remaining graft volume was 27.58 ± 6.26 and 20.01 ± 4.68% on control and experimental groups, respectively (P < 0.05). There was no significant difference between the two groups in new bone formation and the amount of residual bone graft material at 8 weeks. Conclusion: The biopolymer membrane contributes to early biodegradation of biphasic bone substitutes in the jaw defect but it does not affect the bone formation capacity of the bone graft.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.2
• /
• pp.101-108
• /
• 2022

Centrifugal pumps are typically used in many slurry industries to transport solid materials. Solid particles in the slurry frequently shock the walls inside the pump, significantly abrading the flow path. Wear damage causes replacement of the pump components, which wastes manpower and time. Therefore, previous studies have been conducted on factors to improve efficiency and life time. This study identifies trends in pumps supplying lime to desulfurized devices from thermal power plants. The shear stress transport(SST) model is used to determine the erosion trend of the centrifugal pump that transfers lime slurry. The purpose of this study is to identify efficiency and erosion trends by selecting three of the various impeller design elements. The three impeller blade design variables mentioned above represent the inlet draft angle and blade angle of leading edge(L.E) and trailing edge(T.E). The maximum value of the erosion density rate tends to be similar to the Input power.

• Progress in Superconductivity and Cryogenics
• /
• v.24 no.4
• /
• pp.36-39
• /
• 2022

Since the MgB₂ superconductor is simply composed of two constituents of Mg and B, its performance can be monitored easily with the change of one ingredient compared to the other. With the powder size of B less than 100 nm, two different sizes of Mg powders are used to investigate the reaction temperature dependence of MgB₂ bulk samples. In the range of 630-700℃ for the duration of 30 min., the un-reacted Mg is seen only at 630℃ with Mg powder size of <5 ㎛, whereas Mg traces are detected at all the temperature range with Mg powder size of <45 ㎛. The reaction temperature dependence of MgB₂ superconducting transition temperature, T_c, shows little difference whether Mg powder size is large or small in this range except for the 630℃. It is worthy of notice that the critical current densities of MgB₂ show higher performance with the small size of Mg compared to the large one at all field ranges. With the Mg powder size of <45 ㎛, flux pinning is enhanced with decreasing the reaction temperature, whereas flux pinning properties is quite similar in the Mg powder size of <5 ㎛ except for the 630℃, where Mg is left behind after the reaction.

• Journal of the Korean Society for Heat Treatment
• /
• v.35 no.6
• /
• pp.295-302
• /
• 2022

The present study aims to investigate the effect of Al content on microstructure and hardness of discontinuous precipitates (DPs) formed by continuous cooling (CC) in Mg-8%Al and Mg-9.5%Al alloys. The DPs had a wide range of (α+β) interlamellar spacings, which may well be attributed to the different transformation temperatures during CC. The higher Al content gave rise to the higher level of interlamellar spacings of the DPs, and thicker and larger amount of β phase layer in the DPs. It is noticeable that the Mg-9.5%Al alloy exhibited higher hardness of the DPs than the Mg-8%Al alloy, but the ratio of increase in hardness of the DPs compared to that of the as-cast state was similar regardless of the Al content. The reason was discussed based on the differences in microstructures of the DPs for the Mg-8%Al and Mg-9.5%Al alloys.

• Steel and Composite Structures
• /
• v.43 no.3
• /
• pp.389-401
• /
• 2022

This study investigated the flowability and mechanical properties of cost-effective steel fiber reinforced ultra-high performance concrete (UHPC) by using locally available materials for field-cast application. To examine the effect of mixture constituents, five mixtures with different fractions of silica fume, silica powder, ground granulated blast furnace slag (GGBS), silica sand, and crushed natural sand were proportionally prepared. Comprehensive experiments for different mixture designs were conducted to evaluate the fresh- and hardened-state properties of self-consolidating UHPC. The results showed that the proposed UHPC had similar mechanical properties compared with conventional UHPC while the flow retention over time was enhanced so that the field-cast application seemed appropriately cost-effective. The self-consolidating UHPC with high flowability and low viscosity takes less total mixing time than conventional UHPC up to 6.7 times. The X-ray computed tomographic imaging was performed to investigate the steel fiber distribution inside the UHPC by visualizing the spatial distribution of steel fibers well. Finally, the tensile stress-strain curve for the proposed UHPC was proposed for the implementation to the structural analysis and design.

• Advances in materials Research
• /
• v.11 no.3
• /
• pp.237-250
• /
• 2022

The cone bolts with expanded front ends supply improved anchoring performances and increase energy absorbing capacities due to ploughing in the grouted drills. Within this study, use of a novel energy absorber for the cone bolt heads were investigated to assess its design in terms of supplying high support performances. Additionally, different grout material designs were tested to investigate whether the energy absorption capacities of the rock bolts can be improved using a silicone based thermoset polymer (STP) additive. To determine load bearing and energy absorption capacities, a series of deformation controlled pull-out tests were carried out by using bolt samples grouted in rock blocks. According to the results obtained from this study, maximum load bearing capacities of cone bolts are similar and mostly depend on the steel material strength, whereas the energy absorption capacity was determined to significantly vary in accordance with the displacement limits of the shanks. As a result of using STP additive and new polyamide absorber rings, displacement limits without the steel failure increase. The STP additive was found to improve the energy absorption capacities of grouted cone bolts. The absorber rings designed within this study were also assessed to be highly effective and able to double up the energy absorption capacities of the cone bolts.