• Journal of Korean Dental Science
• /
• v.4 no.1
• /
• pp.26-32
• /
• 2011

Purpose: The quality of implant surface is one of the factors that influence wound healing of implant site and subsequently affect osseointegration. The objective of modification of the surface properties of an implant is to affect the biological consequence. The purpose of this study is to evaluate the biologic response of osseous tissue to anodized implants. Materials and Methods: Two machined titanium implants for control group were installed in a tibia of each rabbit and two anodized implants for test group were installed in the other tibia of each rabbit. At the moment the implants were installed, resonance frequency analysis (RFA) values were measured. After healing periods of 1, 2, 3, and 7 weeks, the implants were uncovered and RFA values were measured again. Removal torque was measured for one implant in the test group and one implant in the control group. Histological evaluation was executed in the other implants. Results: Both of test group and control group have the tendency of greater RFA change rate and removal torque value as healing periods became longer, but were statistically insignificant (P>0.05). However, in the case of the same healing period, the test group tended to have greater RFA change rate and removal torque than the control group (P<0.05). More active new bone formation from endosteal surface was noted on the anodized surface than machined surface in specimen after 1 week. There were no significant differences between the test group and control group in histological evaluations. Conclusion: In summary, the anodized surface showed slightly favorable results and it is postulated that it may facilitate improved stability in bone.

• Journal of Periodontal and Implant Science
• /
• v.40 no.1
• /
• pp.19-24
• /
• 2010

Purpose: It has been suggested that primary implant stability plays an essential role in successful osseointegration. Resonance frequency analysis (RFA) is widely used to measure the initial stability of implants because it provides superior reproducibility and non-invasiveness. The purpose of this study is to investigate whether the fractal dimension from the panoramic radiograph is related to the primary stability of the implant as represented by RFA. Methods: This study included 22 patients who underwent dental implant installation at the Department of Periodontology of Seoul National University Dental Hospital. Morphometric analysis and fractal analysis of the bone trabecular pattern were performed using panoramic radiographs, and the implant stability quotient (ISQ) values were measured after implant installation using RFA. The radiographs of 52 implant sites were analyzed, and the ISQ values were compared with the results from the morphometric analysis and fractal analysis. Results: The Pearson correlation showed a linear correlation between the ISQ values of RFA and the parameters of morphometric analysis but not of statistical significance. The fractal dimension had a linear correlation that was statistically significant. The correlation was more pronounced in the mandible. Conclusions: In conclusion, we suggest that the fractal dimension acquired from the panoramic radiograph may be a useful predictor of the initial stability of dental implants.

• International Journal of Highway Engineering
• /
• v.12 no.4
• /
• pp.203-209
• /
• 2010

The base asphalt mixtures that used the waste recycle asphalt correcting from the four different overlay construction sites in Seoul city were made using the foamed asphalt method. The sample mixtures were made in different ratio of the recycle asphalt and new asphalt material and the performance of the mixtures of the different ratio was investigated in the laboratory. The laboratory tests includes the Marshall test, the indirect tensile test, the resilient modulus test, the creep test and the wheel tracking test. The test of the recycle foamed asphalt mixtures(RFA) were compared with the those of the recycle hot mix asphalt(RHA) mixtures. The performance of the RFA is comparable to that of the RHA. On the other hand, the indirect tensile strength of the RFA in dry condition is lower than that of RHA and the indirect tensile strength of the RFA in wet condition is much lower than that of the RHA.

• Journal of Wetlands Research
• /
• v.21 no.spc
• /
• pp.51-60
• /
• 2019

In this study, we performed At-site Frequency Analysis(AFA) and Regional Frequency Analysis(RFA) using the observed and climate change scenario data, and the relative root mean squared error(RMMSE) was compared and analyzed for both approaches through Monte Carlo simulation. To evaluate the rainfall quantile, the daily rainfall data were extracted for 615 points in Korea from HadGEM3-RA(12.5km) climate model data, one of the RCM(Regional Climate Model) data provided by the Korea Meteorological Administration(KMA). Quantile mapping(QM) and inverse distance squared methods(IDSM) were applied for bias correction and spatial disaggregation. As a result, it is shown that the RFA estimates more accurate rainfall quantile than AFA, and it is expected that the RFA could be reasonable when estimating the rainfall quantile based on climate change scenarios.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.2 no.2
• /
• pp.107-114
• /
• 2014

The objective of this study is to evaluate the strength development of blast furnace slag concrete in response to the use of recycled aggregate as alkali activator. The influence of the amount of recycled aggregate was evaluated depending on different ratios of replacement for each RFA and RCA to NFA and NCA, respectively. The results indicated that as replacement of RFA and RCA increased, their strength exhibited to be increased. This was due to the fact that the latent hydraulic properties of blast furnace slag was activated by the alkali in recycled aggregates. However, in case of 365-days, it showed lower compressive strength than using NA(natural aggregates) which could be explained as the exhaustively use of alkali containing in RA. The specimens using RA showed about 90% of compressive strength comparing with specimens using NA.

• International Journal of Computer Science & Network Security
• /
• v.23 no.2
• /
• pp.183-192
• /
• 2023

Radiofrequency ablation (RFA) is an alternative treatment for liver cancer to the surgical intervention preferred by surgeons. However, the main challenge remains the use of RF for the ablation of large tumours (i.e., tumours with a diameter of >3 cm). For large tumours, RFA takes a large duration in the ablation process compared with surgery, which increases patient pain. Therefore, RFA for large tumours is not preferred by surgeons. The currently materials used in RF electrodes, such as the nickeltitanium alloy (nitinol), are characterized by low thermal and electrical conductivities. On the other hand, the use of materials that have high thermal and electrical conductivities, such as titanium aluminide alloy (gamma titanium), produces more thermal energy for tumours. In this paper, we developed a cool-tip RF electrode model that uses nickel-titanium alloy and replaced it with titanium aluminide alloy by using the finite element model (FEM). The aim of this paper is to study the effect of the thermal and electrical conductivities of gamma titanium on the ablation volume. Results showed that the proposed design of the electrode increased the ablation rate by 1 cm³ /minute and 6.3 cm³/10 minutes, with a decrease in the required time ablation. Finally, the proposed model reduces the ablation time and damages healthy tissue while increasing the ablation volume from 22.5% cm³ to 62.5% cm³ in ten minutes compared to recent studies.

• Advances in concrete construction
• /
• v.5 no.3
• /
• pp.201-219
• /
• 2017

With the rapid growth in construction sector, it becomes all the more important to assess the amount of Construction and Demolition (C&D) waste being generated and analyze the practices needed to handle and use this waste before final disposal. This serves waste management and disposal issues, paving way to waste utilization in construction industry from the sustainability point of view. C&D waste constitutes a major bulk of total solid waste produced in the world. In this work, an attempt is made to study the performance of concrete using water soaked Recycled Coarse Aggregates (RCA) in replacement levels of 0%, 25%, 50%, 75% and 100% to Natural Coarse Aggregates (NCA). Experiments were designed and conducted to study the performance of RCA based concrete. Further suitable performance enhancement techniques to RCA based concrete were attempted, to achieve compressive strength at least equal to or more than that for no RCA based concrete (control concrete). Performance enhancement study is reported here for 50% and 100% RCA based concretes. All four techniques attempted have given favorable results encouraging use of RCA based concretes with full replacement levels, to adopt RCA based concrete in structural applications, without any kind of concern to the stake holder. Further attempts have also been made to use Recycled Fine Aggregates (RFA) with appropriate modifications to serve as fine aggregates in mortar and concrete. Using RFA blended with river sand fractions as well as RFA with Iron Ore Tailings (IOT) fractions, have given good results to serve as fine aggregates to the extent of 100% replacement levels in mortars and concretes.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.05a
• /
• pp.287-288
• /
• 2012

In this study, Analyzed the effect of the change in RFA and RCA substitution rate on the concrete containing BS bonding materials but no cement. The findings are as follows. First, the fresh concrete has less slump value and air contents as more RFA and RCA is used. In case of hardened concrete, as more RFA and RCA are used, the higher the compressive strength of concrete becomes. Especially, the compressive strength of concrete which used recycled aggregates only is found to be 2.2 times as high as that of concrete using natural fine and coarse aggregates only. But if the concrete is to be used as the structural concrete having the compressive strength of 13.8 MPa, the alkaline materials and some cement are required to be added.

• Journal of Oral Medicine and Pain
• /
• v.45 no.2
• /
• pp.44-47
• /
• 2020

The case of pseudo-aneurysm of internal maxillary artery (IMA) in oral and maxillofacial region is known to be very rare. The etiology of this case was regarded as IMA injury by radiofrequency ablation (RFA) and such incidence was not reported previously. One case of false aneurysm in the IMA was referred from local dental clinic to our department. Left facial swelling was observed with severe trismus immediately after radiofrequency procedure for masseteric nerve block in local dental clinic. Despite of medication and surgical intervention, the swelling did not subside and there was massive bleeding and pulsation on one of the follow ups. The traumatic vascular disorder was suspected and finally diagnosed with angiography and treated by embolization procedure. RFA targeting masseteric nerve or trigeminal ganglion may cause traumatic injury to adjacent anatomic structures such as IMA, resulting in pseudo-aneurysm. Clinicians must be aware of potential damages of RFA. Angiography enables the solid diagnosis for pseudo-aneurysm, and selective embolization can be optimum treatment method.

• Advances in concrete construction
• /
• v.10 no.3
• /
• pp.237-245
• /
• 2020

Past research efforts already established geopolymer as an environment-friendly alternative binder system for ordinary Portland cement (OPC) and recycled aggregate is also one of the promising alternative for natural aggregates. In this study, an effort was made to produce eco-friendly mortar mixes using geopolymer as binder and recycled fine aggregate (RFA) partially and study the resistance ability of these mortar mixes against the aggressive environments. To form the geopolymer binder, 70% fly ash, 30% ground granulated blast furnace slag (GGBS) and alkaline solution comprising of sodium silicate solution and 14M sodium hydroxide solution with a ratio of 1.5 were used. The ratio of alkaline liquid to binder (AL/B) was also considered as 0.4 and 0.6. In order to determine the resistance ability against aggressive environmental conditions, acid attack test, sulphate attack test and rapid chloride permeability test were conducted. Change in mass, change in compressive strength of the specimens after the immersion in acid/sulphate solution for a period of 28, 56, 90 and 120 days has been presented and discussed in this study. Results indicated that the incorporation of RFA leads to the reduction in compressive strength. Even though strength reduction was observed, eco-friendly mortar mixes containing geopolymer as binder and RFA as fine aggregate performed better when it was produced with AL/B ratio of 0.6.