• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.73-79
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• 2011

Purpose of this experiment is to evaluate the effect of titanium on the castability when the titanium is added to the Co-Cr alloy. Raw materials Cobalt, Chrome, Molybdenum, Silicon, Manganase, Carbon, Nitrogen, Titanium were weighted and prepared. $Biosil^F$ (Degudent, Germany) was the control group. To the experimental group, different weight percent of titanium was added from 1 wt% to 4 wt%. The wax pattern is $30{\times}40$ cm in size, rectangular in shape and has total of 160 grids. Centrifugal machine (Neutrodyne Easy Ti: Manfredy) was used for casting. For evaluation of the castability, the number of complete grids was counted by visual inspection and X-ray inspection. The test showed similar castability with the control group in the titanium addition of 1 wt% to 3 wt%. The titanium addition of 4 wt% showed poor result. With titanium lower than 4 wt%, the experiment metals showed proper castability with high expectation of successful clinical use.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.60-69
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• 2016

Purpose: The objective of this study was to compare the accuracy of digital models from 3 dimentional (3D) optical scanner and cone beam computed tomography (CBCT). Materials and Methods: We obtained digital models from 11 pairs of stone casts using a 3D optical scanner and a CBCT, and compared the accuracy of the models. Results: The error range of average positive distance was 0.059 - 0.117 mm and negative distance was 0.066 - 0.146 mm. Statistically (P < 0.05), average positive distance was larger than $70{\mu}m$ and shorter than $100{\mu}m$, and that of negative distance was larger than $100{\mu}m$ and shorter than $120{\mu}m$. Conclusion: We concluded that the accuracy of digital models generated from CBCT is not appropriate to make final prostheses. However, it may be acceptable for provisional restorations and orthodontic diagnoses with respect to the accuracy of the digitalization.

• Membrane Journal
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• v.23 no.6
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• pp.425-431
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• 2013

This paper has studied the hydrophilizing effect of support on the performance of pressure retarded osmosis (PRO). The hydrophilicity of polyester support has been controlled with cellulose solutions. In order to investigate the effect of hydrophilizing of support, the performance test has been conducted with membrane which compose of active layer and support in absence of support layer. The active layer has been made by casting of cellulose tri-acetate (CTA) 1,4-dioxane solution (13 wt%) and combined with the hydrophilized support. The results show that water fluxes of PRO membranes with hydrophobic or hydrophilized support were measured $0.8L/m^2hr$ and $1.2L/m^2hr$ under $5kgf/cm^2$ pressure, respectively. However, water flux increase did not accord with hydrophilicity of supports treated by cellulose solutions. It is because the porosity and pore size of supports decrease as the cellulose concentration increases. This result confirms that both the hydrophilization of support and the maintenance of membrane porosity are important to enhance the performance of PRO membrane.

• Polymer(Korea)
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• v.36 no.6
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• pp.789-794
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• 2012

Poly(lactic-co-glycolic acid) (PLGA) has been most widely used due to its advantages such as good biodegradability, controllable rate of degradation and metabolizable degradation products. We manufactured composite scaffolds of PLGA scaffold penetrated DBP gel (PLGA/DBP gel) by a simple method, solvent casting/salt leaching prep of PLGA scaffolds and subsequent soaking in DBP gel. Chondrocytes were seeded on the PLGA/DBP gel. The mechanical strength of scaffold, histology (H&E, Safranin-O, Alcian-blue) and immunohistochemistry (collagen type I, collagen type II) were performed to elucidate in vitro and in vivo cartilage-specific extracellular matrices. It was better to keep the characteristic of chondrocytes in the PLGA/DBP gel scaffolds than that PLGA scaffolds. This study suggests that PLGA/DBP gel scaffold may serve as a potential cell delivery vehicle and a structural basis for in vivo tissue engineered cartilage.

• Journal of the Korean Society for information Management
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• v.29 no.4
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• pp.143-163
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• 2012

The dominant model of acquiring scholarly contents at academic libraries is so called big deal where libraries subscribe to a bundle of hundreds, if not thousands of journals in a multi-year contract with fixed annual rate increase. The bid deal, started in the mid-1990s, offered a number of advantages for academic libraries and their users. However, escalating prices for these packages have become a serious issue casting doubts about the sustainability of the subscription-based model. At the moment, it appears there is no viable alternative other than pay-per-view method that is being tested at some libraries. Libraries' budget situation will remain a key factor that might change the situation. Open access started in the 2000s as a vehicle to eliminate barriers to publishing and distributing peer-reviewed scholarly journal articles. Open access publishing is witnessing two-digit growth annually. Open access articles now occupy close to 20% of two major citation databases: Scopus and Web of Science. Google Scholar service, debuted in late 2004, is now a popular tool for discovering and accessing scholarly articles from a vast selection of journals around the world. There is a call for taking Google Scholar seriously as a potential replacement of library databases amid concerns regarding the quality of journals indexed, limited search capabilities vis-$\grave{a}$-vis library databases, and monopoly of public goods. Escalating budget problems, rapid growth of open access publishing and the emergence of powerful free tool, such as Google Scholar, need to be taken seriously as these forces might bring disruptive changes to the existing subscription-based model of scholarly contents at academic libraries.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.1-9
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• 2020

The manufacturing processes of high-precision parts for PGM (Precision Guided Missiles) have not been improved for decades; they still depend on machining or high-precision casting. These processes have an advantage when making small amounts of high-reliability parts in the usual case of a PGM system. In the case of a PGM system, however, which has been made for striking an extensive area, requires hundreds of bomblet units that require mass productivity. In addition, in the case of a part that is very difficult to machine, mass productivity and quality cannot be satisfied at the same time. In particular, cost reduction is an essential precondition to strengthening the export competitiveness of Korean defense articles. This study examined whether the MIM process is appropriate for manufacturing high-precision parts that require mass productivity. The optimized MIM process condition was determined after carrying out fundamental research. Comparisons of the quality of prototype parts with original parts and a functional test of a fuse that had been made with MIM parts highlighted the application possibility of the MIM process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.251-255
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• 2007

We made $(1-x)BCB-xBNT(BaNd_2Ti_4O_{12})$ (x=20, 30, 40, 50 vol%) composite thick film with a high dielectric constant and low loss by the hand casting method. Dielectric constant and dielectric loss of prepared thick film are measured at 1MHz and curing behavior of the film are observed through thermal analysis such as DSC. We investigated the effect of contents of BNT filler and curing behavior of film on dielectric properties of BCB-BNT composite. Dielectric constant increased with increasing BNT filler from 20 to 50 vol% and dielectric loss ($tan{\delta}$) decreased with increasing BNT filler. Dielectric constant and loss ($tan{\delta}$) of composite material was not nearly dependent on the curing behavior. But as a result of TCC (Temperature Characteristics of Coefficient) decreased with increasing the curing temperature, we confirmed that the curing of these composite system is most stable above $250^{\circ}C$.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.3
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• pp.257-265
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• 1999

To investigate the sequential changes in microvascular architecture and osseous regeneration during the bony healing after an application of the guided tissue regeneration method, we made artificial defects measuring $0.7cm{\times}0.3cm$ in size on femoral bones of rats measuring about 200gm and applied non-absorbable TEFE membrane at experimental sites but not at control sites. Then we observed the sequential changes and correlations between new vacuolation and bony regeneration using microvascular corrosion cast method and routine light microscopic observation at 1, 2 and 3 weeks after operation, respectively. The results showed that there were close relationships between regeneration of microvasculature and bone. In early phase, the invasion of granulation tissue at control sites delayed bony regeneration, however, in later phase, there was no remarkable differences in bony regeneration between control and experimental sites. The placement of barrier also affected in revascularization of regenerating bony defects. This is, the experimental sites showed parallel arranged nutritional vessels along long axis with well developed retiform plexus whereas the control revealed vertical invasion of microvasculature from outside of marrow space through bony defects which was also rearrange with time into parallel pattern with a vertical plexus but lesser organized than that of experimental sites. These findings suggest that the reconstruction of regenerating vasculature within the marrow cavity only may be sufficient and/or more be efficient in regeneration of bony defects.

• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.176-181
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• 2017

PURPOSE. The purpose of this study was to evaluate the marginal and internal gaps of Ni-Cr and Co-Cr copings, fabricated using the dental ${\mu}-SLA$ system. MATERIALS AND METHODS. Ten study dies were made using a two-step silicone impression with a dental stone (type IV) from the master die of a tooth. Ni-Cr (NC group) and Co-Cr (CC group) alloy copings were designed using a dental scanner, CAD software, resin coping, and casting process. In addition, 10 Ni-Cr alloy copings were manufactured using the lost-wax technique (LW group). The marginal and internal gaps in the 3 groups were measured using a digital microscope ($160{\times}$) with the silicone replica technique, and the obtained data were analyzed using the non-parametric Kruskal-Wallis H test. Post-hoc comparisons were performed using Bonferroni-corrected Mann-Whitney U tests (${\alpha}=.05$). RESULTS. The mean (${\pm}$ standard deviation) values of the marginal, chamfer, axial wall, and occlusal gaps in the 3 groups were as follows: $81.5{\pm}73.8$, $98.1{\pm}76.1$, $87.1{\pm}44.8$, and $146.8{\pm}78.7{\mu}m$ in the LW group; $76.8{\pm}48.0$, $141.7{\pm}57.1$, $80.7{\pm}47.5$, and $194.69{\pm}63.8{\mu}m$ in the NC group; and $124.2{\pm}52.0$, $199.5{\pm}71.0$, $67.1{\pm}37.6$, and $244.5{\pm}58.9{\mu}m$ in the CC group. CONCLUSION. The marginal gap in the LW and NC groups were clinically acceptable. Further improvement is needed for CC group to be used clinical practice.

• Journal of Korea Technology Innovation Society
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• v.19 no.1
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• pp.191-229
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• 2016

As Korean national R&D projects have steadily grown in size, the needs of enhancing the efficiency and effectiveness of the national R&D budge spending has been also discussed. Therefore, many efforts have been made to establish performance assessment system to improve the efficiency and effectiveness of the national R&D project. One example of such efforts is the stipulation of connecting the results of performance evaluation ranking of the national R&D projects with the budge allocation of for the coming fiscal year. Unlike the stipulated article in the law/regulation that 'more budge shall be allocated to a project rated over excellent grade and vice versa', however, precedent studies have been casting mixed opinions over to the effectiveness of the connection between assessment results and budge allocation. In this respect, the present study attempted to empirically examine if the laws and institutions related to the results of performance evaluation ranking of the national R&D projects with the budge allocation work properly, using panel regression analysis and quantitative data. In addition, this study investigated into the deterrent factors to the connectivity between the performance results of the national R&D projects and budge allocation and sought for a way to improve the system of performance assessment and enhance the reliability of the results by minimizing the hindrance factors.