• Korean Journal of Materials Research
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• v.8 no.6
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• pp.538-544
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• 1998

The spallation of a thermal barrier coating layer depends on the formation of brittle spinels. thermal expansion mismatch between ceramic and metal. the phase transformation of a ceramic layer and residual stress of coating layer. In this work. the formation mechanism of oxide scale formed by oxidation treatment at 90$0^{\circ}C$ was investigated in order to verify oxidation behavior at the interface between E-beam coated $Zr0_2$-7wt.% $Y_20_3$ and plasma sprayed CoNiCrAIY. Some elements distributed in the bond coating layer were selectively oxidized after oxidation. At the initial time of oxidation. AI-depletion zone and $\alpha$-$Al_O_3$,O, were formed at the bond coating layer by the AI-outward diffusion. After layer grew until critical thickness. spinels. $Cr_20$, and $C0_2CrO_4$ by outward diffusion of Co. Cr, Ni were formed. It was found that the formation of spinels may be related to the spallation of $Zr0_2$-7wt.% $Y_20_3$ during isothermal oxidation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.1
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• pp.95-101
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• 2018

The epidermis which is stratified by epithelial tissue renewal based on keratinocyte differentiation protects the organism from various environmental insults by forming a physical barrier. Autophagy is a mechanism which mediates lysosomal delivery and degradation of protein aggregates, damaged organelles and intracellular microorganisms. Recent reports have shown that autophagy has critical roles for proper terminal differentiation to stratum corneum via removing metabolic organelles and nuclei. However, whether increasing autophagy can activate epidermal differentiation is unknown. Here, we screened a library of natural single compounds and discovered that betaine specifically increased the LC3 positive cytosolic punctate vesicles and LC3-I to LC3-II conversion in HaCaT human keratinocyte cell line, indicating increased autophagy flux. mTOR pathway, which negatively regulates autophagy, was not affected by betaine treatment, suggesting betaine-induced autophagy through an mTOR-independent pathway. Betaine-induced autophagy was also observed in primary human keratinocyte and skin equivalent. Furthermore, epidermal thickness was increased in skin equivalent under betaine treatment. Overall, our finding suggests that betaine as a novel regulator of autophagy may induce epidermal turnover and improve the skin barrier abnormality of the aged epidermis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.7-11
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• 2010

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.22 no.1
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• pp.1-14
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• 2000

The purpose of this study was to evaluate the efficacy of adding autogenous bone to the toothash-plaster mixture in the healing process of bone. Full-thickness round osseous defects with the diameter of 20mm were made at the calvarial bone of adult dogs (n=19) bilaterally, which were thought to be critical size defect. The right defects were repaired with the toothash-plaster mixture plus autogenous bone (compressed volume 0.3cc) and the left defects with only toothash-plaster mixture. At 2-, 4-, 8-, 12- and 20- week after implantation, dogs were sacrificed and evaluated the osseous healing of bony defects clinically, radiographically, and microscopically. The results were as follows; 1. At the clinical observation, the wound healed very well without any problem except severe swelling in the early period after operation. Slight depression was recognized at the both sides when the portions of cranial defect were palpated. 2. There were statistically significant differences between toothash-plaster mixture groups and autogenous bone added groups at the same period, and among the groups in the bone density of the digital radiograms (P<0.001). There was a tendency that bone density was increasing with time. 3. In light microscopic examination, new bone formation was more active in the autogenous bone added groups than toothash-plaster mixture groups at the early period after implantation but there is little difference at 20-week after implantation. 4. In fluorescent microscopic examination, the fluorescent band could be observed at the area of active bone formation and the band was more distinct in the autogenous bone added groups then toothash-plaster mixture groups. 5. In transmitted electron microscopic examination, organelles such as rER, Golgi complex and secretory granule and osteoblast were observed. In summary higher volume ratio of autogenous bone is needed to improve the bone healing in that there is little difference between toothash-plaster mixture group and autogenous bone added group at the 20-week after implantation in spite of new bone formation was more active in the autogenous bone added groups than toothash-plaster mixture groups at the early period after operation.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.531-554
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• 2006

Oral implants must fulfill certain criteria arising from special demands of function, which include biocompatibility, adequate mechanical strength, optimum soft and hard tissue integration, and transmission of functional forces to bone within physiological limits. And one of the critical elements influencing the long-term uncompromise functioning of oral implants is load distribution at the implant- bone interface, Factors that affect the load transfer at the bone-implant interface include the type of loading, material properties of the implant and prosthesis, implant geometry, surface structure, quality and quantity of the surrounding bone, and nature of the bone-implant interface. To understand the biomechanical behavior of dental implants, validation of stress and strain measurements is required. The finite element analysis (FEA) has been applied to the dental implant field to predict stress distribution patterns in the implant-bone interface by comparison of various implant designs. This method offers the advantage of solving complex structural problems by dividing them into smaller and simpler interrelated sections by using mathematical techniques. The purpose of this study was to evaluate the stresses induced around the implants in bone using FEA, A 3D FEA computer software (SOLIDWORKS 2004, DASSO SYSTEM, France) was used for the analysis of clinical simulations. Two types (external and internal) of implants of 4.1 mm diameter, 12.0 mm length were buried in 4 types of bone modeled. Vertical and oblique forces of lOON were applied on the center of the abutment, and the values of von Mises equivalent stress at the implant-bone interface were computed. The results showed that von Mises stresses at the marginal. bone were higher under oblique load than under vertical load, and the stresses were higher at the lingual marginal bone than at the buccal marginal bone under oblique load. Under vertical and oblique load, the stress in type I, II, III bone was found to be the highest at the marginal bone and the lowest at the bone around apical portions of implant. Higher stresses occurred at the top of the crestal region and lower stresses occurred near the tip of the implant with greater thickness of the cortical shell while high stresses surrounded the fixture apex for type N. The stresses in the crestal region were higher in Model 2 than in Model 1, the stresses near the tip of the implant were higher in Model 1 than Model 2, and Model 2 showed more effective stress distribution than Model.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.2
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• pp.212-234
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• 1999

Dental restorative materials must have the physical properties to withstand wear and corrosion. Base metal alloys possess better mechanical properties and lower price than the gold alloys. For these reasons such alloys have largely replaced the precious metal alloys. One aspect to con-sider is the release of metal substances to oral environment. The release of elements from dental alloys is a continuing concern because the elements may have the potentially harmful biological effects on local tissues. The purpose of this study was to minimize metal release on the nonprecious metal surfaces by ion beam assisted deposition(IBAD) of titanium nitride (TiN) Ni-Cr-Be alloys with and without TiN coatings were secured in an wear test machine opposing ruby ball to determine their relative resistance to wear with loom, 200m, 300m and 400m sliding distance. And the corrosion behavior of the Ni-Cr-Be alloys with and without TiN coatings and 3 dental noble alloys have been studied. Potentiodynamic curves were used to analyse the corrosion characteristics of the alloys. The measurement of the released Ni and Cr ions was conducted by analysis of the electrolyte solution with atomic absorption spectroscopy. The results were as follows : 1. The critical sliding distance that wore down TiN coatings of $2.5{\mu}m$ thickness in this study condition was 300m. 2. Ion beam assisted deposition of TiN showed a good surface modification with respect to the properties of wear and corrosion resistance. 3. X-ray diffraction showed that the strongest peak of TiN is TiN(111) in the coatings. 4. The release of Ni and Cr ions from alloys measured by means of atomic absorption spectroscopy was reduced by ion beam assisted deposition of TiN.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.2
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• pp.136-147
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• 2003

Statement of problem : Ceramic and composite resin have been used to fulfill the demand for esthetic prosthesis. However, ceramic is easy to break and wears off the opposite natural teeth. Conventional composite resin also has low abrasive resistance and color stability. Ceramic Optimized Polymer (ceromer) was developed in mid-1990s to overcome the shortfalls of ceramic and composite resin. Ceromer has similar abrasiveness with the natural tooth and has relatively high strength. Color stability affects esthetics and long-term prognosis of the prosthesis. Purpose The purpose of this study was to compare color stability of ceromers(2 types : $Artglass^{(R)}$. $Targis^{(R)}$) with ceramics ($Vintage^{(R)}$-polishing, $Vintage^{(R)}$-glazing). Material and Method : The color difference(${\Delta}E^*$) was measured by spectrophotometer with different immersion time. Twenty disks, 3mm in thickness and 10mm in diameter, were fabricated for each specimen in shade A2(Vita Lumin shade guide), Specimens (5 samples in each group) were immersed in the food colorants (Red no.3. Yellow no.4, Blue no.1, Distilled water) for 24 hours, 48 hours and 72 hours respectively. $L^*,\;a^*$ and $b^*$ value were measured with spectrophotometer (CM 503i : Minolta Co., Japan) and mean ${\Delta}E^*$ value was calculated for statistical analysis Results : The results of this study were obtained as follows. 1. The ${\Delta}E^*$ values of all test samples increased with the time of immersion. 2. The ${\Delta}E^*$ values of all materials increased in order of Distilled Water, Yellow no.4, Blue no.1 and fed no.3. There was significant difference between Red no.3 and the other food colorants(p<0.05). 3. The ${\Delta}E^*$ values increased in order of $Vintage^{(R)}$-glazing, $Vintage^{(R)}$-polishing. $Artglass^{(R)}$ and $Targis^{(R)}$. There was significant difference between $Vintage^{(R)}$-glazing and the other materials (p<0.05). Conclusion : By means of the above results, immersion time was found to be a critical factor for color stability of ceromer. For the long-term color stability of prosthesis it is recommended patients having ceromer prosthesis ($Artglass^{(R)},\;Targis^{(R)}$) to reduce the habitual intake of Red no.3 colorants con taming foods.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.1
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• pp.23-33
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• 2011

This experimental focus to characterize luminescence properties related to CNT (Carbon Nano Tube) element dispersedly implanted in ZnS-based phosphor thin film panel fabricated by a screen printing method. More specifically FE-SEM measurements, L-V(Luminescence vs. Voltage) and photo luminescence were carried out to determine an optimum value of CNT concentration and film thickness for the thin film structure of CNT-ZnS:(Cu, Al) by the screen printing method. We confirmed that an optimum value of CNT concentration in the ZnS:(Cu, Al) film panel is about 0.75 wt% resulting that the electric conductivity is 1.6 times higher than that of pure CNT sample and showing that the luminescence intensity is increasing until the optimum concentration. Clearly, CNT is presenting in the luminescence process providing a pathway for the creation of hot electron and a channel for the electron-hole recombination but overly inserted CNT may hinder to produce the hot electron for making an avalanching process. In case of the overly doped CNT 1.0 wt% in the ZnS-based phosphor, the luminescence intensity is decreasing although the electric conductivity is exponentially increasing. Based on these results, we realized that hot electron occurred by the external electric field or exciton arose by the external photon source are reduced dramatically over the critical value of CNT concentration because CNT element provide various isolated residues in the composites of ZnS based phosphor rather than pathway or channel for the D-A(Donnor to Acceptor) pair transition or the radiative recombination of electron-hole.

• The Journal of Engineering Geology
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• v.11 no.2
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• pp.175-190
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• 2001

This study investigates the existing theoretical backgrounds in order to examine the behavior of lateral flow according to the plasticity of soils when unsymmetrical surcharge is worked on polluted soft soils by comparing and analyzing the results measured through model tests. Model tests are canied out as follows soil tank, bearing frame and bearing plate are made. By increasing unsymmetrical surcharge to the ground soils with the consistent water content and with gradually increased polluted materials at intervals, the amounts of settlement, lateral displacement and upheaval were respectively observed. In conclusion, the value of critical surcharge was expressed as q$_{cr}$=2.78$_{cu}$ which was similar to those Tschebotarioff(q$_{cr}$=3.0$_{cu}$) and Meyerhof(q$_{cr}$=(B/2H+$\pi$/2)$_{cu}$) had been proposed. The value of ultimate capacity was expressed as q$_{ult}$=4.84$_{cu}$ which was similar to that of Prandtl. The lateral flow pressure is adeQuately calculated by the eQuation(P$_{max}$=K$_o$ r H) and the maximum value of lateral flow pressure is found near O.3H of layer thickness(H) and is higher to ground surface than the ones in composition pattern, Poulos distribution pattern and softclay soils (CL, CH) which is not polluted. The stability control method used in this research followed the management diagram of Tominaga.Hashimoto, Shibata.Sekiguchi, Matsuo.Kawamura who use the amounts of plasticity displacement by lateral flow. As a result, the ultimate capacity values in the diagram {S$_v$-(Y$_m$/S$_v$)} of Matsuo.Kawamura and in the diagram {(q/Y$_m$)-q} of Shibata. Sekiguchi were smaller than in the ones of load-settlement curve (q-S$_v$).

• Applied Microscopy
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• v.15 no.2
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• pp.111-129
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• 1985

The morphology and histology of the gastrointestinal mucosa of the mole, Talpa micrura coreana (Thomas), were studied using light and scanning electron microscopes. Tissue specimens were taken from body and pyloric portions of the stomach, and from the initial, proximal, middle, distal and terminal portions of the intestine. For light microscopy, tissue blocks were fixed in 10% buffered neutral formalin, embedded in paraffin wax, and sectioned at a thickness of $5{\mu}m$. These sections were stained with hematoxylin-eosin. For scanning electron microscopy, tissue blocks were fixed in 1% glutaraldehyde-1.5% paraformaldehyde, and postfixed in 1% osmium tetroxide, dehydrated in graded alcohol, transferred to isoamylacetate and dried by the critical point drier(Polaron E 3000). Subsequently, specimens were coated with gold and observed with a JSM-35C scanning electron microscope. The results were as follows: The mucous membrane of the body portion of the stomach had numerous irregular folds and the pyloric mucosa formed the strawberry-shaped folds, and general histological structures of each portion were similar to those of man. The intestine could not be differentiated macroscopically and microscopically into small and large intestines. There was no cecum, appendix, taenia coli, haustra coli or appendices epiploicae. In the initial portion (4 mm long), conical or tongue-shaped villi with the height of $143.3{\pm}10.7{\mu}m$ were present, and large mucous glands were seen in the submucosa. In the proximal, middle and distal portions, wavy folds composed of the epithelium and lamina propria were densely and transversely arranged, and their heights were $440.4{\pm}45.5{\mu}m,\;454.4{\pm}19.9{\mu}m\;and\;205.2{\pm}33.5{\mu}m$, respectively. The mucosa of the terminal portion (3 cm long) formed several longitudinal folds, and the intestinal glands were directly opened on the smooth surface of the folds. Aggregated lymphoid follicles were observed in the major portions of the intestine except the initial and terminal portions. There was no circular or semilunar fold throughout the intestine.