Ni기 단결정 초내열합금 액상확산접합부의 크리프 파단특성에 미치는 회전각의 영향

김대업 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9

The effect of rotating angle on creep rupture properties of transient liquid phase (TLP) bonded joints at elevated temperature of Ni base single crystal superalloy CMSX-2 was investigated using MBF-80 as a insert metal. The rotating angle was defined by <100> twist angle at bonded interface. The post-bonded heat treatment, consisting of the solution treatment and sequential two-step aging, was carried out in the Ar or vacuum atmosphere prior to creep rupture testing. Creep rupture properties of joints were comparable to those of base metal in case of the rotating angles less than 3 degree while drastically fell down with increasing the rotating angle more than 5 degree. The grain boundary energy and oxygen content at bonded interface increased with increasing the rotating angle. Creep rupture properties of joints could be improved with lowering the oxygen partial pressure during post bonded heat treatment attributed to the restraint of grain boundary oxidation of bonded interface.

불소가 함유된 세마제가 법랑질의 내산성에 끼치는 영향에 관한 생체외 연구

조중한,김대업,이광희 大韓小兒齒科學會 1995 大韓小兒齒科學會誌 Vol.22 No.1

The purpose of study was to know the effect of addition of fluoride to prophylaxis paste on caries prevention. 2% sodium fluoride solution and 8% stannous fluoride solution were applied topically to enamel blocks made from human teeth. Also, 2% sodium fluoride-containing pumice and 8% stannous fluoride-containing pumice was applied to enamel blocks using rubber cup for ten seconds. Enamel surface hardness was measured before and after demineralization by 0.01 N lactic acid. The results were as follows ; 1. Enamel solubility was increased in NaF group and nearly unchanged in SnF₂group by prophyaxis with plain pumice after fluoride application. 2. Enamel solubility was increased in NaF group and decreased in SnF₂group by prophylaxis with fluoride-containing pumice after fluoride application. 3. Enamel solubility was lower in case of prophylaxis with fluoride-containing pumice after fluofied application and after no fluoride application than in case of prophyalxis with plain pumice after fluoride application. 4. Enamel solubility was lower incase of no prophylaxis after fluoride application than in case of prophylaxis with fluoride-containing pumice in NaF group, and vice versa in SnF₂group.

불화물의 첨가가 아연화유지놀의 압축강도, 이차 우식에 대한 저항성, 변연누출에 미치는 영향에 관한 실험적 연구

정호석,김대업,이광희 大韓小兒齒科學會 1995 大韓小兒齒科學會誌 Vol.22 No.1

The purpose of this study was to investigate the effect of addition of fluoride to conventional zinc oxide eugenol on compressive strength, resistance of enamel to secondary caries and marginal leakage. Groups were divided by adding materials and their content. Group 1 was control group that did not contain fluoride, Group 2 was 10% sodium fluoride group, Group 3 was 20% sodium fluoride group, Group 4 was 10% stannous fluoride group and Group 5 was 20% stannous fluoride group. Each of four experimental groups was compared with control group. The results were as follows : 1. In compressive strength after 3 days, 10% stannous fluoride group was highest and then 20% sodium fluoride group, 10% stannous fluoride group, 10% sodium fluoride group, and non-fluoride group were in order. Compressive strength after 1 day water soakong after 3 days was stastically not significant(p>0.05). 2. In resistance of enamel to secondary caries, hardness reduction rate of experimental groups was lower than control group. There was no significant difference among groups (p>0.05). 3. Sodium fluoride group showed less marginal leakage than stannous fluoride group(p<0.05). 4. The amount of fluoride release was largest in 20% sodium fluoride group, and then 10% sodium fluoride group, 20% stannous fluoride, 10% stannous fluoride group were in order.

비진료방문이 미취학 아동의 불안에 미치는 영향에 관한 연구

오세영,김대업,이광희 大韓小兒齒科學會 1995 大韓小兒齒科學會誌 Vol.22 No.1

The purpose of this study was to measure preschool children' anxiety about educational dental visit. This study was undertaken in 511 preschool children, 241 with educational dental visit and 270 without educational dental visit,whose age ranged from 3 to 7 years old. Preschool children during educational dental visit observated dental enviornment, directly touched dental instrument, and were surveyed oral condition. After they had gone to their preschool, they drew dentist. Drawings were analyzded using Human Figure Drawing Scoring System developed By Sonnenberg and Venham. The results were as follows ; 1. The anxiety score of group with educational dental vfisit was higher than that of group without dental visit(P<0.01). 2. The anxiety score was 9.28 in 4 year old, 6.78 in 5 year old, 4.79 in 6 year old, and 3.57 in 7 year old. There were significant difference in each groups(P<0.01). 3. The anxiety score of boys was higher than that of girls(P<0.05). 4. The anxiety score of untreated preschool children was higher than that of treated preschool children(P<0.01). 5. There was not the effect of relation between age and educational dental visit, between gender and educational dental visit, between treatment experience and educational dental visit(P<0.05).

어린이 그림에 투사된 치과치료 불안의 분석에 관한 연구

양계식,김대업,이광희 大韓小兒齒科學會 1995 大韓小兒齒科學會誌 Vol.22 No.1

The purpose of study was to develop the method of analysis of drawings to assess the level of anxiety of children for dental treatment. 702 school children from second to fourth grade drawed pictures representing the dental treatment situation. Caries experience and dental treatment experience were investigated. Drawings were analyzed using criteria modified from Dental Anxiety Scale by Sheskin et al. The index 'drawing of the dentist' was replaced by 'drawing of smile of the dentist' and the index 'number of colors used' was replaced by 'number of persons drawed'. The results were as follows : 1. The mean anxiety score was 2.19, and the range was from 0 to 6.00. 2. The anxiety score was 2.27 inboys and 2.13 in girls. 3. The anxiety score was 1.93 in second grade, 2.30 in third grade, and 2.40 in fourth grade. There were siginificant difference between second grade and the other grades(P<0.01). 4. The anxiety score by theme color was 2.50 in black, 2.37 in brown, 2.36 in red, 2.33 in white, 2.22 in orange, 2.18 in yellow, 2.15 green, 2.12 in ocher yellow, 2.11 in gray, 2.08 in pick, and 2.03 in violet. 5. The anxiety score was 2.21 in treated children and 2.03 in untreated children. 6. Pearson correlation coefficent was -0.1170 (P<0.01) between anxiety score and dt index and 0.078(P<0.05) between anxiety score and ft rate. 7. The index 'height' was highest in the anxiety score and then 'smile', 'omission', 'instrument', 'number of person', and 'treatment situation' were in order. 8. The indexes 'smile' and 'omission' had the most high correlation with the total anxiety score.

건식경량벽체의 내충격성능 평가방법에 관한 연구 (Ⅰ) : 인간이 벽체에 가하는 충격하중의 분석을 위한 실험 및 고찰 An Experiment to Analyze the Human Impact Load Applied to Framed Walls

신윤호,안정업,김대희,최수경 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

The purpose of this study is to establish an evaluation method of fracture of light-weight framed walls by human impact load. In this paper, part (I), we analyzed human impact load applied to framed walls. At first, we made original measuring equipment of impact load, and carried out the experiment on human impact load in various action. After the experiment, we extracted the essential characteristics. And grasped the property of human impact load systematically based on the relation between maximum load and load velocity.

PE-162: The Degree of Liver Fibrosis Assessed Using Transient Elastography Independently Correlates with the Risk of Stroke: A Case-control Study

( Young Dae Kim ),( Dongbeom Song ),( Ji Hoe Heo ),( Beom Kyung Kim ),( Jun Yong Park ),( Do Young Kim ),( Sang Hoon Ahn ),( Kwang-hyub Han ),( Kwang Joon Kim ),( Seung Up Kim ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: Transient elastography (TE) assess the degree of liver fibrosis and steatosis. The degree of liver fibrosis was associated with the presence and burden of cerebral microbleeds in healthy, asymptomatic participants. We investigated the correlation between the degree of liver fibrosis, as assessed using TE, and the risk of stroke. Methods: Patients who were admitted due to the management of stroke and received TE examination from April 2013 to August 2014 and subjects who underwent a medical health check-up including TE during the same period were recruited. Significant fibrosis was defined as a liver stiffness (LS) value of ≥8 kPa and hepatic steatosis was defined as a controlled attenuation parameter (CAP) of ≥250 dB/m. Subjects with inappropriate TE results and alcoholic/ chronic viral liver diseases were excluded. Further, we conducted propensity score matching to reduce the potential effects of selection bias and confounding factors. Results: A total of 295 patients with stroke and 2,936 subjects with health check-up were analyzed. The mean age and the proportion of hypertension, diabetes, hypercholesterolemia, chronic kidney disease, and metabolic syndrome were significantly higher in patients with stroke than those of subjects with health check-up (all P<0.05). The mean LS value (5.6 kPa, vs. 4.2 kPa) and the proportion of significant fibrosis (9.2% vs. 2.7%) were significantly higher in patients with stroke than those of subjects with health check-up (all P<0.05), whereas the mean CAP value and the proportion of hepatic steatosis were statistically similar between two groups (all P>0.05). When fibrotic burden was assessed using TE, it was significantly higher in patients with stroke than that of subjects with health check-up, regardless of body mass index (BMI) (mean 5.3 kPa vs. 3.9 kPa in BMI<25 kg/m2 and 6.3 kPa vs. 4.7 kPa in BMI ≥25 kg/m2), CAP value (mean 5.3 kPa vs. 3.9 kPa in CAP<250 dB/m and 6.3 kPa vs. 4.7 kPa in CAP≥250 dB/m), and metabolic syndrome (mean 5.3 kPa vs. 4.1 kPa in the absence of metabolic syndrome and 5.9 kPa vs. 5.0 kPa in the presence of metabolic syndrome) (all P<0.05). As a continuous variable, unadjusted odd ratio (OR) of LS value for stroke was 1.161 and adjusted ORs were calculated as between 1.132 to 1.213 according to varying multivariate models. As a categorical variable, unadjusted OR of significant fibrosis was 4.388 and adjusted ORs were calculated as between 3.474 to 6.397 according to varying multivariate models. In a propensity matched analysis using 1:1 ratio (n=197 for each group), LS value was independently associated with the risk of stroke (OR of 1.080 as a continuous variable and 8.488 as a categorical variable) (all P<0.001). Conclusions: In our case-control study, we found that the degree of liver fibrosis, as assessed using TE, was significantly associated with the risk of stroke. Further studies investigating the dynamic link between these two disease entities are required.

Revisiting the thickness reduction approach for near-foldable capacitive touch sensors based on a single layer of Ag nanowire-polymer composite structure

Kim, Kwang-Seok,Kim, Sun Ok,Han, Chul Jong,Kim, Dae Up,Kim, Jin Soo,Yu, Yeon-Tae,Lee, Cheul-Ro,Kim, Jong-Woong Elsevier 2018 Composites science and technology Vol.165 No.-

<P><B>Abstract</B></P> <P>Although a percolated network of silver nanowires (AgNWs) is considered the most promising flexible transparent electrode because of its high conductivity, high transmittance, excellent flexibility, and facile patternability, it has encountered a serious delay in its application to most optoelectronic devices. Here, we analyzed the reasons and tried to resolve the current issues to achieve near-foldable transparent touch sensors by employing an inverted layer processing method. A hydroxylated polydimethylsiloxane (PDMS) was used as a preliminary substrate for deposition and patterning of AgNWs, and then the nanowires were completely transferred to the newest version of colorless polyimide (cPI) by hydrophobic recovery of the PDMS surface. For the first time, we designed an automatic apparatus for testing the foldability of the fabricated composite film by a spacer inserting method. The testing of various AgNWs/cPI films with this method revealed that the thickness reduction approach could be an efficient and powerful tool to attain near-foldable electrodes if the AgNWs are solidly adhered to the substrate. Based on these findings, we could successfully demonstrate a near-foldable touch sensor, which is capable of sensing human touches even in the folded state.</P>

Bonding Phenomena of Transient Liquid Phase Bonded Joints of a Ni Base Single Crystal Superalloy

Kim, Dae-Up,Kazutoshi, Nishimoto 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.4

The bonding phenomena of Ni base single crystal superalloy CMSX-2 during transient liquid phase (TLP) bonding have been investigated using MBF-80 and F-24 insert metals. TLP bonding of the superalloy was carried out at 1373-1548K for 0-19.6ks in vacuum and the (100) plane of each test specimen was always aligned perpendicular to the joint interface. The dissolution width increased when the bonding temperature and holding time increased. The eutectic width decreased linearly with the square root of holding time during isothermal solidification. After homogenization treatment, the microstructure, distributions of hardness and alloying elements in the bonded interlayer become similar to those of the base metal.

Photo-induced healing of stretchable transparent electrodes based on thermoplastic polyurethane with embedded metallic nanowires

Kim, Kwang-Seok,Choi, Su Bin,Kim, Dae Up,Lee, Cheul-Ro,Kim, Jong-Woong The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.26

<P>The incorporation of self-healing functionalities into stretchable thermoset systems can be associated with challenges such as large accumulation of inelastic strain as a result of repeated stretching or dramatic changes in modulus during repeated damage-self-healing cycles. Here, we successfully fabricate a stretchable and transparent electrode with photo-irradiation mediated self-healing capacity. This electrode was realised using Ag nanowires (AgNWs) and thermoplastic polyurethane (TPU) without employing any of the established dynamic self-healing chemistries. First, the AgNWs deposited on a cured TPU film were irradiated with intense-pulsed-light (IPL) to induce plasmonic heating, resulting in a large enhancement in conductivity and mechanically stable, stretchable transparent electrodes. Subsequent rounds of IPL irradiation were employed to repair the artificial cracks formed on the surface of the AgNW/TPU electrodes and the micro-cracks induced by repeated rounds of stretch-and-release testing. The surface analysis confirmed that both types of defects were successfully repaired by the IPL treatment owing to the enhanced flowability and thermal expansion of TPU during IPL irradiation. Multiple scratching with a cutting knife and healing demonstration revealed that the cracks formed at the same locations were healed repeatedly up to five times.</P>