• Title/Summary/Keyword: surface aging

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The study of fractural behavior of repaired composite (수리된 복합 레진 수복물의 파괴 거동에 관한 연구)

  • Park, Sang-Soon;Nam, Wook;Eom, Ah-Hyang;Kim, Duck-Su;Choi, Gi-Woon;Choi, Kyoung-Kyu
    • Restorative Dentistry and Endodontics
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    • v.35 no.6
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    • pp.461-472
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    • 2010
  • Objectives: This study evaluated microtensile bond strength (${\mu}TBS$) and short-rod fracture toughness to explain fractural behavior of repaired composite restorations according to different surface treatments. Materials and Methods: Thirty composite blocks for ${\mu}TBS$ test and sixty short-rod specimens for fracture toughness test were fabricated and were allocated to 3 groups according to the combination of surface treatment (none-treated, sand blasting, bur roughening). Each group was repaired immediately and 2 weeks later. Twenty-four hours later from repair, ${\mu}TBS$ and fracture toughness test were conducted. Mean values analyzed with two-way ANOVA / Tukey's B test ($\alpha$= 0.05) and correlation analysis was done between ${\mu}TBS$ and fracture toughness. FE-SEM was employed on fractured surface to examine the crack propagation. Results: The fresh composite resin showed higher ${\mu}TBS$ than the aged composite resin (p < 0.001). Mechanically treated groups showed higher bond strength than non-mechanically treated groups except none-treated fresh group in ${\mu}TBS$ (p < 0.05). The fracture toughness value of mechanically treated surface was higher than that of non-mechanically treated surface (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. Specimens having high KIC showed toughening mechanism including crack deviation, microcracks and crack bridging in FE-SEM. Conclusions: Surface treatment by mechanical interlock is more important for effective composite repair, and the fracture toughness test could be used as an appropriate tool to examine the fractural behavior of the repaired composite with microtensile bond strength.

Protective Effects of Complex Diet of Korean red ginseng and fish oil on UV-induced Photoaging (홍삼과 어유(魚油) 복합식이에 의한 UV-유도 광노화 억제효과)

  • Mun, Yeun-Ja;Jeon, Byoung-Kook;Kim, Tae-Hyun;Lee, Jin-Ho;Choi, Hyung-Wook;Lim, Kyu-Sang;Woo, Won-Hong
    • The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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    • v.27 no.3
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    • pp.106-114
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    • 2014
  • Objective : UV irradiatiion causes skin-aging involving coarse wrinkles, thickning, dyspigmentation, and rough skin surface. This study was aimed to elucidate the anti-winkle activity of complex diet of Korean red ginseng (RG) and fish oil (FO) on UV-induced Photoaging. Methods : To investigated photo-protective effects of Korean red ginseng and fish oil on UV-induced damaged skins, SKH hairless female mice were randomly divided into six groups [control, UV, UV/RG, UV/FO, UV/RG/FO(low), UV/RG/FO(high)]and orally administered three times a week respectively. UV radiation was applied to the backs of the mice three times a week for 8 weeks. Expressions of matrix metalloproteinase (MMP)-3, MMP-13 and tissue inhibitor matrix metalloproteinase (TIMP)-1 in skin were measured by immunohistochemical staining. Results : In this study, UVB-induced epidermal hypertropy was diminished by RG group or FO group or complex group of RG and FO. Expression levels of MMP-3 and MMP-13 were reduced and expression level of TIMP-1 was increased by RG group or FO group or complex group of RG and FO. Especially MMP-3 and MMP-13 were markedly reduced by diet of FO and complex diet of RG and FO compared with untreated group. Conclusions : This results suggest that complex diet of RG and FO have a anti-wrinkle activity on UV-induced photo-aging and intrinsic aging.

The Effect of Residual Stress on Magnetoresistance in GMR Head Multilayers (자기기록 MR 헤드 용 다층박막의 자기저항에 미치는 잔류응력 효과)

  • Hwang, Do-Guwn
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.4
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    • pp.322-327
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    • 2003
  • Giant magnetoresistance(GMR) NiO multilayer, which has been used to reading head of highly dense magnetic recording, was fabricated, and oxidized in an air during 80 days to study the dependence of magnetoresistance properties on residual stress in the interfaces. The magnetoresistance ratio and the exchange biasing $field(H_{ex})$ of $NiO(60nm)/Ni_{81}Fe_{19}(5nm)/Co(0.7nm)/Cu(2nm)/Co(0.7nm)/Ni_{81}Fe_{19}(7nm)$ spin valves were increased from 4.9% to 7.3%, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity ${\rho}$ decreased from $28{\mu}{\Omega}m$ to $17{\mu}{\Omega}m$, but ${\Delta}p$ did not almost change after the oxidation. Therefore, the increase of MR ratio is due to the decrease in the sheet resistivity. the reduced resistance may result from the increase in the reflection of conduction electrons at the oxidized top surface. Also, the increase in the exchange biasing field is originated from the reduction of residual stress at the interface of $NiO/Ni_{81}Fe_{19}$ according as the aging time increases.

Mechanical reliability of Sn-37Pb BGA solder joints with high-speed shear test (고속전단 시험을 이용한 Sn-37Pb BGA solder joints의 기계적 신뢰성 특성 평가)

  • Jang, Jin-Kyu;Ha, Sang-Su;Ha, Sang-Ok;Lee, Jong-Gun;Moon, Jung-Tak;Park, Jai-Hyun;Seo, Won-Chan;Jung, Seung-Boo
    • Journal of the Microelectronics and Packaging Society
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    • v.15 no.4
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    • pp.65-70
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    • 2008
  • The mechanical shear strength of BGA(Ball Grid Array) solder joints under high impact loading was investigated. The Sn-37Pb solder balls with a diameter of $500{\mu}m$ were placed on the pads of FR-4 substrates with ENIG(Electroless Nickel Immersion Gold) surface treatment and reflowed. For the High Temperature Storage(HTS) test, the samples were aged a constant testing temperature of $120^{\circ}C$ for up to 250h. After the HTS test, high speed shear tests with various shear speed of 0.01, 0.1, 1, 3 m/s were conducted. $Ni_3Sn_4$ intermetallic compound(IMC) layer was observed at the solder/Ni-P interface and thickness of IMC was increased with aging process. The shear strength increased with increasing shear speed. The fracture surfaces of solder joints showed various fracture modes dependent on shear speed and aging time. Fracture mode was changed from ductile fracture to brittle fracture with increasing shear speed.

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The Physicochemical Characteristics of Marinated Beef Galbi under Different Cooking Conditions (양념 소갈비의 조리과정에서의 물리화학적 특성 평가)

  • Hong, Sang-Pil;Kim, Young-Ho;Lee, Nam-Hyouck;Heo, Yeong-Uk
    • Journal of the Korean Society of Food Culture
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    • v.28 no.1
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    • pp.78-88
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    • 2013
  • Marinated beef galbi is a traditional Korean dish cooked with soy sauce, pear juice, onion, sesame oil, and sugar. However, there are many differences in beef galbi, including flavor and physicochemical aspects, depending on cooking conditions. Therefore, the physicochemical characteristics of marinated beef galbi prepared through various recipes was evaluated for its effects on pH, texture, aging, proteolysis, heating conditions, cooking time, and flavor compounds (pyrazines, IMPs, or FAAs). There were significant differences in salt concentration (0.8~3.03%), pH (4.89~6.22), and solid soluble contents (1.34-6.31 Brix) between recipes in this study. In the Pearson assay for sensory evaluation, overall preference correlated well with texture (a well-known sensory attribute in meat evaluation). Controlling the pH of meat through soaking in lemon solution, alkali water, phosphate, and baking powder solution, improved water holding capacity as much as 9 to 15% compared with the control. The myofibril index (MFI) of marinated meat stored at $4^{\circ}C$ increased 32% with 24 hours of aging and reached 39% at 48 hours of aging, and its fragmentation was observed through microscopy. SDS-PAGE showed hydrolysis of acid-soluble collagen by the pear juice, possibly related to meat tenderness. On the basis of surface temperature, the cooking time was estimated to be 8 minutes with pan heating at $170^{\circ}C$, 6 minutes at $270{\sim}300^{\circ}C$, and 4 minutes with charcoal at $700{\sim}900^{\circ}C$. Different pyrazine compounds, such as 2-methyl-3-phenylpyrrol(2,3-b) pyrazine (the typical product of the browning reaction) was mainly detected, and IMP (one of the main taste compounds in beef) was in higher amounts with the charcoal treatment, potentially related to its flavor preference among treatments. Our results demonstrate an effective case study and cooking system for beef galbi.

Studies on the Interfacial Reaction between electroplated Eutectic Pb/Sn Flip-Chip Solder Bump and UBM(Under Bump Metallurgy) (전해 도금법을 이용한 공정 납-주석 플립 칩 솔더 범프와 UBM(Under Bump Metallurgy) 계면반응에 관한 연구)

  • Jang, Se-Yeong;Baek, Gyeong-Ok
    • Korean Journal of Materials Research
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    • v.9 no.3
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    • pp.288-294
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    • 1999
  • In the flip chip interconnection using solder bump, the Under Bump Metallurgy (UBM) is required to perform multiple functions in its conversion of an aluminum bond pad to a solderable surface. In this study, various UBM systems such as $Al 1\mu\textrm{m} / Ti 0.2\mu\textrm{m} / Cu 5\mu\textrm{m}, Al 1\mu\textrm{m} / Ti 0.2\mu\textrm{m} / Cu 1\mu\textrm{m}, al 1\mu\textrm{m}/Ni 0.2\mu\textrm{m} / Cu 1\mu\textrm{m} and Al 1\mu\textrm{m}/Pd 0.2\mu\textrm{m} / Cu 1\mu\textrm{m}$ for flip chip interconnection using the low melting point eutectic 63Sn-37Pb solder were investigated and compared to their metallurgical properties. $100\mu\textrm{m}$ size bumps were prepared for using an electroplating process. The effects of the number of reflows and aging time on the growth of intermetallic compounds(IMC) were investigated. $Cu_6Sn_5$ and $Cu_3Sn$ IMC were abserved after aging treatment in the UBM system with thick coper $(Al 1\mu\textrm{m}/Ti 0.2\mu\textrm{m}/Cu 5\mu\textrm{m})$. However only the $Cu_6Sn_5$ was detected in the UBM system with $1\mu\textrm{m}$ thick copper even after 2 reflow and 7 day aging at $150^{\circ}C$. Complete Cu consumption by Cu-Sn IMC growth gives rise to a direct contact between solder inner layer such as Ti, Ni and Pd, and hence to possibly cause reactions between two of them. In this study, however, only for the Pd case, IMC of PdSn. was observed by Cu consumption. UBM interfacial reactions with s이der affected the adhesion strength ot s이der balls after s이der reflow and annealing treatment.

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Application of Primary Rat Corneal Epithelial Cells to Evaluate Toxicity of Particulate Matter 2.5 to the Eyes (눈에 대한 미세먼지의 독성 평가를 위한 쥐 각막 상피 세포의 적용)

  • Kim, Da Hye;Hwangbo, Hyun;Lee, Hyesook;Cheong, Jaehun;Choi, Yung Hyun
    • Journal of Life Science
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    • v.32 no.9
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    • pp.712-720
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    • 2022
  • The purpose of this study was to investigate the efficacy of rat corneal-derived epithelial cells as an in vitro model to evaluate the harmfulness of the cornea caused by particulate matter 2.5 (PM2.5). To establish an experimental model for the effect of PM2.5 on corneal epithelial cells, it was confirmed that primary cultured cells isolated from rat eyes were corneal epithelial cells through pan-cytokeratin staining. Our results showed that PM2.5 treatment reduced cell viability of primary rat corneal epithelial (RCE) cells, which was associated with the induction of apoptosis. PM2.5 treatment also increased the generation of reactive oxygen species due to mitochondrial dysfunction. In addition, the production of nitric oxide and inflammatory cytokines was increased in PM2.5-treated RCE cells. Furthermore, through heatmap analysis showing various expression profiling between PM2.5-exposed and unexposed RCE cells, we proposed five genes, including BLNK, IL-1RA, Itga2b, ABCb1a and Ptgs2, as potential targets for clinical treatment of PM-related ocular diseases. These findings indicate that the primary RCE cell line is a useful in vitro model system for the study of PM2.5-mediated pathological mechanisms and that PM2.5-induced oxidative and inflammatory responses are key factors in PM2.5-induced ocular surface disorders.

Evaluation on Undrained Shear Strength considering Consolidation Characteristics for Busan Clay (부산 점토의 압밀특성과 연계한 비배수전단강도 평가)

  • Kim, Ju-Hyun
    • Journal of the Korean Geosynthetics Society
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    • v.16 no.3
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    • pp.41-49
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    • 2017
  • In this study, a series of laboratory and in-situ tests such as FVTs and CPTUs were carried out to evaluate undrained shear strength related to quasi overconsolidated characteristics in the near-surface clay at Busan new port. Using unconfined compression and field vane test results, correlation between undrained shear strength and effective overburden pressure, that is, equation of $10+0.262{\sigma}^{\prime}v_0$ (kPa) was obtained. From oedometer tests, OCR is around 1.9 at depths lower than 7 m and OCR below this depth is very close to unit. As stated by Hanzawa et al. (1983), a natural clay deposit in the near-surface, even in normally consolidated state, is more and less apparently overconsolidated due to aging effects such as chemical bonding. Based on this concept, it can be inferred that intercept of equation is mobilized due to chemical bonding irrespective of effective overburden pressure and strength incremental ratio in normally consolidated state is 0.262. From CPTU results, same trend was confirmed. The further study should be necessary to judge whether upper clay is under overconsolidated state due to chemical bonding or not based on the depositional environment.

Evaluation of the Thermal Degradation in Co-based Superalloy using High frequency Transducer of Scanning Acoustic Microscope (초음파현미경의 고주파 초음파 탐촉자를 이용한 코발트기 초내열합금강의 열화평가)

  • Park, Ik-Keun;Cho, Dong-Su;Kim, Yong-Kwon;Lim, Jae-Seang;Kim, Chung-Seok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.5
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    • pp.518-524
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    • 2004
  • The feasibility of Y(z) curve method of scanning acoustic microscope using high frequency transducer was experimentally studied for assessment of the thermal degradation in Co-based superalloy. Thermal degradation was performed to simulate the microstructural changes in Co-based superalloy arising from long term exposure at high temperature. Longitudinal wave velocity measured by pulse echo method using 10MHz transducer and leaky surface acoustic wave (LSAW) velocity measured by V(z) curve method using 200MHE transducer were measured to investigate the effect on thermal degradation. Ultrasonic velocity decreased as the aging time increased in both ultrasonic waves. Moreover, the low frequency longitudinal wave velocity decreased a little. Otherwise, the high frequency LSAW velocity drastically decreased up to a maximum of 4.7% at the aging time of 4,000hours. A good correlation was found between LSAW and Vickers hardness. Consequently, V(z) curve method of SAM using high frequency transducer could be a potential tool for assessing thermal degradation.

Effect of TESPT Silane Coupling Agent on Mechanical Properties of Precipitated Silica Filled NBR Compound for Oil Seal (TESPT 실란커플링제가 침전 실리카로 보강된 오일씰용 NBR복합소재의 기계적 물성에 미치는 영향)

  • Lee, Young-Seok;Hwang, Ki-Seob;Lee, Jong-Cheol;Kim, Tae-Geun;Ha, Ki-Ryong
    • Elastomers and Composites
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    • v.46 no.1
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    • pp.45-53
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    • 2011
  • The effect of the silane coupling agent, bis(triethoxysilypropyl)tetrasulfide (TESPT), on mechanical properties of a silica-filled NBR compound for oilseal was investigated. Curing behavior and crosslinking density of the compounds were measured using ODR (oscillating disk rheometer) and swelling ratio in toluene. UTM (universal testing machine) and shore A hardness tester were used in order to study the characteristics of mechanical properties of original vulcanizates and aged ones with heated air and ASTM No. 3. oil. Recovery of elasticity which influences the performance and service life of oilseal was investigated by giving bending deformation to vulcanizates in aging condition. After bending aging test, recovery distance was measured and calculated angle of recovery from it. TR (temperature retraction) test was performed on these vulcanizates to determine the low temperature recovery behavior. Wear resistance was measured by Taber type abrasion tester. In addition, SEM was used to characterize the morphology of the worn surface of vulcanizates. The result showed that addition of TESPT into silica-filled compound improves not only compound flow-ability, interaction between NBR and silica and crosslinking density, but also hardness, 100% modulus, recovery of elasticity, wear resistance, heat resistance and ASTM No.3 oil resistance of vulcanizates.