• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.215-223
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• 2010

Purpose: The present study was aimed to evaluate the level of cortical bone strain during the placement of an implant. The primary concern was to investigate if the extent of overloading area near the marginal bone could be affected by microthread fabricated at the cervical 1/3 of an implant. Materials and methods: Three dimensional finite element analysis was used to simulate the insertion of 3 implants. Control model was $4.1{\times}10$ mm implant (Submerged model, Dentis Co,, Daegu, Korea) equipped with a main thread only. Type I was with main thread and microthread, and Type II had similar thread pattern but was of tapered body. A PC-based finite element software (DEFORM 3D ver 5, SFTC, Columbus, OH, USA) was used to calculate a total of 3,600 steps of analysis, which simulated the whole insertion. Results: Results showed that the strain field in the marginal bone within 1 mm of the implant wall was higher than 4,000 micro-strain in the control model. The size of bone overloading was 1-1.5 mm in Type I, and greater than 2 mm in Type II implants. Conclusion: These results indicate that the marginal bone may be at the risk of resorption on receiving the implant for all 3 implant models studied. Yet, the risk was greater for Type I and Type II implants, which had microthread at the cervical 1/3.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.289-296
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• 2008

Electrochemical studies were performed by a half-cell test for the nickel hydroxide (cathode) and hydrogen storage alloy(anode) electrodes for the sealed Ni-MH batteries applicable to industrial use. The electrodes were fabricated and checked a charge efficiency and an internal pressure of the battery during charge-discharge cycling. In order to reduce the internal pressure of the sealed Ni-MH battery, cyclic voltammetry (CV) were performed on the electrodes of nickel hydroxide(cathode) and hydrogen storage alloy(anode), respectively. The results of the test showed clearly the oxidation/reduction and oxygen evolution reaction in a nickel hydroxide electrode and the hydrogenation behavior of a hydrogen storage electrode. The sealed Ni-MH battery of 130Ah was fabricated by using nickel hydroxide of a high over-voltage for an oxygen gas evolution and hydrogen storage alloy of a good performance for activation The battery showed a good characteristics such as a high charge efficiency of 98% at 1 C charge current, a low level internal pressure of 4 atm on a continuous over-charging and a large preservation capacity of 95% at 400 cycle.

• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.397-413
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• 2008

In Gaya area, the Boseong kaolin deposits exhibit locally unusual occurrences such as downward enrichment of kaoin minerals, characteristic hydrothermal alterations (illite and stilbite), and phase relations among kaolin minerals in addition to the extensive weathering of anorthositic country rocks. This indicates that the kaolin deposits seem to be genetically formed as a mixed hydrothermal and residual model. The kaolin ores can be divided into five types on the basis of differences in occurrence, mineral composition and characters. These consist of two types of high-grade ores ranging above 80% in grade and low-grade ores as low as less than 80% including feldspar residuals or the peculiar impurity phase of illite-vermiculite-stilbite. Halloysite and kaolinite are mostly coexisted in the Boseong kaolin, and these kaolin minerals exhibit diverse appearances in crystallinity and morphology. Such a diversity in mineral phase and crystallinity seems to be originated from the complexity in genesis. In addition to these diverse characters of the kaolin, its applied-mineralogical characteristics such as chemical composition, thermal properties, whiteness, viscosity, and etc. made it disadvantageous in terms of ore quality.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.6
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• pp.445-452
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• 2015

Software reliability in the software development process is an important issue. Software process improvement helps in finishing with reliable software product. Infinite failure NHPP software reliability models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, proposes the reliability model with log and power intensity function (log linear, log power and exponential power), which made out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on mean square error (MSE) and coefficient of determination($R^2$), for the sake of efficient model, was employed. Analysis of failure, using real data set for the sake of proposing log and power intensity function, was employed. This analysis of failure data compared with log and power intensity function. In order to insurance for the reliability of data, Laplace trend test was employed. In this study, the log type model is also efficient in terms of reliability because it (the coefficient of determination is 70% or more) in the field of the conventional model can be used as an alternative could be confirmed. From this paper, software developers have to consider the growth model by prior knowledge of the software to identify failure modes which can be able to help.

• Membrane Journal
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• v.21 no.1
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• pp.30-38
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• 2011

Composite membranes based on sulfonated poly(aryl ether) sulfone (SPAES) with different sulfated zirconia nanoparticles ($s-ZrO_2$) ratio are synthesized and investigated for the improvement of the hydration and the proton conductivity at high temperature and no humidification for fuel cell applications. X-ray diffraction technique is employed to characterize the structure and the size of $s-ZrO_2$ nanoparticles. The sulfation effect of $s-ZrO_2$ nanoparticles is verified by FT-IR analysis. The properties of the SPAES composite membranes with the various $s-ZrO_2$ ratio are evaluated by ion exchange capacity and water content. The proton conductivities of the composite membranes are estimated at room temperature with full hydration and at the various high temperature without external humidification. The composite membrane with 5 wt% $s-ZrO_2$ shows the highest proton conductivity. The proton conductivities are $0.9292\;S\;cm^{-1}$ at room temperature with full hydration and $0.0018\;S\;cm^{-1}$ at $120^{\circ}C$ without external humidification, respectively.

• Journal of Korean Philosophical Society
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• v.123
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• pp.87-110
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• 2012

The kitsch was emerged from the people's cultural desire in the conditions of the various duplicating technology, the capital economy system, and the civil revolution in the western modern mass society. But it is underestimated constantly because of the conspicious consumption and the aesthetic inadequacy. Even though some kitsches are elevated to the 'kitsch arts' in the historical description of the modern arts, still the most of kitsches are remained as 'just kitsches' and excluded from the aesthetic research according to the double standard. In this essay, I research for whether anti-kitsch theory is convincing theoretically and practically. Anti-kitsch theory criticizes the kitsch on the basis of the modernist aesthetics, in which the 'fine art' provokes the aesthetic pleasure in the disinterested contemplation. But kitsch purposes for the sensual gratification and the sentimentality. So the anti-kitish theorists conclude that the kitsch is the bad taste. In critically analyzing the argumentation of Greenberg's. Kaplan's and $C{\tilde{a}}linescu^{\prime}s$, I refute the privileged prejudice of the ideal critic. They don't justify the criteria of the classification of 'art'/ 'kitsch'. They supplement the economical and the political grounds for the evaluative theory of the kitsch. But the argumentation of the kitsch is consumed conspicuously and results in the unlettered masses is not sufficient. People produce and enjoy the kitsches in the various ways. People envelope the genres, styles and media of the kitsches and they try to suggest the new horizon of the popular aesthetics. So anti-kitsch theories cannot be accepted because they adhere to the elitism and formalism. The exclusion of the kitsch is the derogation for people's taste. Also they didn't reflect the contemporary cultural practice and the aesthetic needs in the system of post-art. The alternative aesthetics of the kitsch is the topic of my next essay.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.512-518
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• 2019

To develop a membrane electrode assembly (MEA) with lower Pt loading and higher performance in proton exchange membrane fuel cells (PEMFCs), it is an important research issue to understand interfacial structure of Pt/C catalyst and ionomer and design the catalyst layer structure. In this study, we prepared short-side-chain Nafion-based ionomer dispersion using propylene glycol (PG) as a solvent instead of water which is commonly used as a solvent for commercially available ionomers. Cathode catalyst layers with different ionomer content from 20 to 35 wt% were prepared using the ionomer dispersion for the fabrication of four different MEAs, and their fuel cell performance was evaluated. As the ionomer content increased to 35 wt%, the performance of the prepared MEAs increased proportionally, unlike the commercially available water-based ionomer, which exhibited an optimum at about 25 wt%. Small size micelles and slow evaporation of PG in the ionomer dispersion were effective in proton transfer by inducing the formation of a uniformly structured catalyst layer, but the low oxygen permeability problem of the PG-based ionomer film should be resolved to improve the MEA performance.

• Journal of Oral Medicine and Pain
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• v.36 no.4
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• pp.225-234
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• 2011

Tobacco smoking is a major risk factor of systemic health and also impairs oral health, which is related to development of oral cancers, periodontitis, delayed wound healing, tooth loss, failure of implant, etc. Aside from smoking, many other risk factors can be related to oral health and long-term effects of smoking on salivary flow and taste threshold are still in controversy. Authors considered dental students to be an appropriate group with good oral hygiene for a long-term study to reveal effects of smoking on oral health. This study was performed to compare smoking patterns and current oral health conditions between smokers and nonsmokers in dental students prior to long-term evaluation. 192 volunteers (85.7%) of 224 male dental students in Dankook University were evaluated through questionnaires and clinical examination in 2010. Questionnaires included smoking pattern, alcohol use, nicotine dependence, preventive care, psychological profile and clinical examinations comprised assessment of teeth or periodontal status, nicotine pigmentation, salivary flow, electrical taste thresholds and halitosis. From the study, (current) smokers were older, and drank more frequently with more alcohol intake compared to former smokers and nonsmokers(p<0.05). There was no significant difference among them in salivary flow rate, halitosis and electrical taste threshold. However, there was significant difference in DMFT rate, periodontal treatment need, nicotinic pigmentation between smokers and nonsmokers(p<0.05), irrespective of their levels of preventive care. The smokers in this study, who are young dental students with relatively shorter duration of smoking, less use of cigarettes and low level of nicotine dependence, did not reveal significant impairment of oral health. However, their oral health was found to be relatively impaired compared to nonsmokers', which suggests negative effect of smoking on the oral health and a need of smoking cessation.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.2
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• pp.95-101
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• 2019

Purpose: The aim of this study is to evaluate the effects of various primers on the microtensile bond strength (${\mu}TBS$) of resin cements to cobalt-chromium (Co-Cr) dental casting alloy. Materials and methods: Four adhesive primers (Universal primer, Metal primer II, Alloy primer, and Metal/Zirconia primer) and two resin cements (Panavia F2.0, G-CEM LinkAce) were tested. One hundred fifty Co-Cr beams were prepared from Co-Cr ingots via casting ($6mm\;ength{\times}1mm\;width{\times}1mm\;thick$). The metal beams were randomly divided into ten groups according to the adhesive primers and resin cements used; the no-primer groups served as the control (n = 15). After sandblasting with aluminum oxide ($125{\mu}m$ grain), the metal and resin cements were bonded together using a silicone mold. Prior to testing, all metal-resin beams were examined under stereomicroscope, and subjected to the ${\mu}TBS$ test. The mean value of each group was analyzed via one-way ANOVA with Tukey's test as post hoc (${\alpha}=.05$) using SPSS software. Results: The mean ${\mu}TBS$ of all groups was ranged from 20 to 28 MPa. There is no statistically significant difference between groups (P > .05). Mixed failure, which is the combination of adhesive and cohesive failures, is the most prevalent failure mode in both the Panavia F2.0 and G-Cem LinkAce groups. Conclusion: The ${\mu}TBS$ of all tested groups are relatively high; however, the primers used in this study result in no favorable effect in the ${\mu}TBS$ of Panavia F2.0 and G-Cem LinkAce resin cement to Co-Cr alloy.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.85-93
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• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.