• The Journal of Advanced Prosthodontics
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• v.15 no.5
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• pp.227-237
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• 2023

PURPOSE. This study aimed to assess and compare the color stability, flexural strength (FS), and surface roughness of occlusal splints fabricated from heat-cured acrylic resin, milled polymethyl methacrylate (PMMA)-based resin, and 3D-printed (PMMA) based-resin. MATERIALS AND METHODS. Samples of each type of resin were obtained, and baseline measurements of color and surface roughness were recorded. The specimens were divided into three groups (n = 10) and subjected to distinct aging protocols: thermomechanical cycling (TMC), simulated brushing (SB), and control (without aging). Final assessments of color and surface roughness and three-point bending test (ODM100; Odeme) were conducted, and data were statistically analyzed (2-way ANOVA, Tukey, P <.05). RESULTS. Across all resin types, the most significant increase in surface roughness (Ra) was observed after TMC (P < .05), with the 3D-printed resin exhibiting the lowest Ra (P < .05). After brushing, milled resin displayed the highest Ra (P < .05) and greater color alteration (∆E₀₀) compared to 3D-printed resin. The most substantial ∆E₀₀ was recorded after brushing for all resins, except for heat-cured resin subjected to TMC. Regardless of aging, milled resin exhibited the highest FS (P < .05), except when compared to 3D-printed resin subjected to TMC. Heat-cured resin exposed to TMC demonstrated the lowest FS, different (P < .05) from the control. Under control conditions, milled resin exhibited the highest FS, different (P < .05) from the brushed group. 3D-printed resin subjected to TMC displayed the highest FS (P < .05). CONCLUSION. Among the tested resins, 3D-printed resin demonstrated superior longevity, characterized by minimal surface roughness and color alterations. Aging had a negligible impact on its mechanical properties.

• Journal of Welding and Joining
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• v.26 no.3
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• pp.37-44
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• 2008

Charpy V-Notch test is commonly used to evaluate fracture toughness. However, since the region to be evaluated is limited to bulk material due to the specimen size required, individual evaluation of micro-structures on weldment is very difficult. In this study, ASP(Advanced Small Punch) test was carried out to evaluate material degradation and fracture toughness on the B.M, W.M and each micro-structures of HAZ for X20CrMoV121 and 2.25Cr1Mo steels with artificial aging time. In addition, to evaluate fracture toughness and material degradation of B.M and W.M of X20CrMoV121 steels with aging times, CVN (Charpy V-notch) test was performed. And then the correlation between ASP and CVN test on X20CrMoV121 steels was obtained. Furthermore, through this correlation, material degradation property of each micro-region of the HAZ in weldment, which was impossible to be evaluated by the CVN test, can be estimated and determined.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.25-30
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• 2011

In this paper, we analyzed the electrical characteristics with Micro-cracks in Photovoltaic module. Micro cracks are increasing the breakage risk over the whole value chine from the wafer to the finished module, because the wafer or cell is exposed to mechanical stress. And The solar cells have to with stand the stress under out door operation in the finished module. Here the mechanical stress is induced by temperature changes and mechanical loads from wind and snow. So, we experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. The first step, we made micro-cracks in PV module by mechanical load test according to IEC 61215. Next, PV modules applied the thermal cycling test, because micro-cracks accelerated aging by thermal cycling test, according to IEC61215. Before every test, we checked output and EL image of PV module. As the result of first step, we detected little power loss(0.9%). But after thermal cycling test increased power loss about 3.2%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.636-641
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• 2000

The purpose of this study is assessing the characteristics of surface aging and recovery of hydrophobicity for silicone rubber which takes a great interest as outdoor insulation recently subjected to the combined stressed of salt fog and AC power. The methods for assessing are contact angle ATR-FRIR, AFM and XRD. In addition salt fog method is adopted as the artificial contamination experiment and AC power is applied 24 hour on and 24 hour off repeatedly for 5 cycles. The results suggest that degraded surface was more rough than virgin but was restored water repellency through the off cycle. It was due to not only the formation of fractal surface but also maintenance of hydrophobic surface by diffusion of low molecular oil. Although surface recovers initial hydropohbicity there are possibilities of decreasing electrical performance due to irreversable changes such as depolymerization of surface and loss of filler particles. This fact is confirmed by surface conductivity measurement showing that the degradation is significant and the recovery of hydrophobicity is imperfect as the energized cycle increases.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.159-160
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• 2021

We are facing major changes such as an aging population along with the 4th industrial revolution based on ICT technologies such as artificial intelligence, the Internet of Things, autonomous driving, and factory automation. For the local governments that are indexed in high population extinction risk, it is essential to consider market expansion and re-education policies suitable for regional characteristics in order to respond to changes such as advanced industrial automation and population aging. For the reemployment of the elderly, we will analyze previous public strategies for elderly-friendly jobs, expand investment in age-friendly industries. In this study, we suggest to improvement direction of the elderly labor market in Cheonan-Si.

• 한국벤처창업학회:학술대회논문집
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• 2021.11a
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• pp.125-128
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• 2021

한국은 2025년 전체 인구 중 65세 이상 인구가 20%을 상회하는 초고령 사회 진입이 전망되면서 노화수준에 맞는 고령친화적인 제품서비스 공급이 요구된다. 특히 시니어 소비자가 사용하기 편리한 인터페이스를 갖춘 서비스가 필요하다. 이에 시니어들은 노화(aging)에 대한 문제의식에 비용을 지불하며 젊은 소비자들과 유사한 소비행태를 보이고, 노화 수준별 건강 유지 및 건강 불안, 돌봄 공백, 사회적 고립 증가 등 사회문제가 복합적으로 심화되면서 고령친화적인 스마트한 Aging Service 공급이 요구된다. 이러한 시기와 맞물려 with코로나시대 시니어 소비자가 사용하기 편리한 인터페이스를 갖는 제품·서비스로 4차 산업혁명의 중심인 AI(Artificial Intelligence)와 정보통신 기술의 노력이 가시화되고 있다. 따라서 IT 기술에 덧입혀 시니어들의 욕구에 부합하는 AI 음성인식 기능을 탑재한 제품 및 서비스가 향후 고령친화산업 성장을 주도할 것으로 전망된다. 이에 본 연구는 '고령친화 AI 음성 O2O 서비스'의 서비스 가치가 태도와 이용의도에 영향을 미치는가를 분석하기 위해 선행이론을 토대로 전문가 델파이 방법을 통해 고령친화 AI 음성 O2O 서비스의 정의를 도출하고 실증분석으로 '고령친화 AI 음성 O2O 서비스'의 서비스가치(상황기반 제공성, 즉시연결성, 위치정확성)와 태도 및 이용의도간의 인과관계를 조사하기 위해 본 연구를 진행하였다.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.6
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• pp.56-62
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• 2014

This study aims to investigate the applicability of supercritical fluid extraction as a dewaxing technique to restore the beeswax-treated volume of the Annals of the Joseon Dynasty in various deterioration and damage conditions. Thus, this study analyzed the dewaxing efficiency and changes in physical and morphological properties before and after dewaxing, by applying the optimal supercritical fluid extraction dewaxing condition ($70^{\circ}C$, 40 MPa, $CO_2$, Co-solvent 20% DCM, 2 hour) to 3 kinds of beeswax-treated paper with different deterioration rates (dry artificial aging of 10, 20 and 30 days at $120^{\circ}C$). After dry artificial aging at $120^{\circ}C$ for 30 days, the average molecular weight of the beeswax-treated specimen was $1.856{\times}10^5g/mol$, showing deterioration about 80% of the beeswax-treated paper before dewaxing. It was a similar level to the molecular weight of the bees-waxed volume of the Annals of the Joseon Dynasty that has a higher degree of damage. As a result of analyzing the dewaxing efficiency through FT-IR analysis, this study discovered that it was possible to effectively dewax beeswax-treated paper in the range of deterioration 20 to 80% with this supercritical fluid extraction dewaxing technique applied. As a result of analyzing changes in the physical and morphological properties before and after dewaxing, the viscosity tended to decrease to a slight degree, and since no morphological deformation or damage of stencil fibers was found, it was concluded possible to conduct stable dewaxing through this supercritical fluid extraction technique.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.51.1-51.13
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• 2021

Objectives: This study aimed to evaluate the effect of improper positioning single-peak and multi-peak lights on color change, microhardness of bottom and top, and surface topography of bulk fill and incremental composites after artificial aging for 1 year. Materials and Methods: Bulk fill and incremental composites were cured using multi-peak and single-peak light-emitting diode (LED) following 4 clinical conditions: (1) optimal condition (no angulation or tip displacement), (2) tip-displacement (2 mm), (3) slight tip angulation (α = 20°) and (4) moderate tip angulation (α = 35°). After 1-year of water aging, the specimens were analyzed for color changes (ΔE), Vickers hardness, surface topography (Ra, Rt, and Rv), and scanning electron microscopy. Results: For samples cured by single-peak LED, the improper positioning significantly increases the color change compared to the optimal position regardless of the type of composite (p < 0.001). For multi-peak LED, the type of resin composite and the curing condition displayed a significant effect on ΔE (p < 0.001). For both LEDs, the Vickers hardness and bottom/top ratio of Vickers hardness were affected by the type of composite and the curing condition (p < 0.01). Conclusions: The bulk fill composite presented greater resistance to wear, higher color stability, and better microhardness than the incremental composite when subjected to improper curing. The multi-peak LED improves curing under improper conditions compared to single-peak LED. Prevention of errors when curing composites requires the attention of all personnel involved in the patient's care once the clinical relevance of the appropriate polymerization reflects on reliable long-term outcomes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.496-498
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• 2022

With the prolonged spread of the new coronavirus infection worldwide and the entry of the super-aged society, smart health care, which combines IT technology for senior health care and the health care industry, is emerging as a solution to the aging problem. The development of non-face-to-face care services using Ai is on a global trend, not in some countries, and the form of care services for the elderly using AI artificial intelligence technology is changing rapidly. The convenience of AI-based care services for the elderly is expected to be highlighted, and the technology and market are expected to develop significantly. As the number of single-person households is increasing, the shortage of welfare workers for the elderly is emerging as a social issue. It is presented as a vision to solve long-term social problems such as the labor shortage of elderly care workers as well as the advantages of convenient care services using IT technology. Therefore, we would like to propose the development direction of care services for the elderly as a case study of care services for the elderly and a countermeasure against the super-aging age.

• Journal of the Korean Wood Science and Technology
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• v.51 no.3
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• pp.173-182
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• 2023

Color is an attribute of visual perception and can be an important factor that affects the preference of customers toward bamboo and wood products. Solar radiation can discolor bamboo surfaces and initiate cracking. The purpose of this study is to investigate the effects of an ultraviolet (UV)-protective coating on the photodiscoloration of untreated and heat-treated Phyllostachys bambusoides bamboo surfaces. Artificial UVA radiators are set at a UVA irradiance of 2,000 W/m² to accelerate the aging of the outer surfaces of hot-air-dried and heat-treated bamboo samples. Half of the samples are coated with transparent UV-protective paint. As the UVA radiation progresses, the discoloration prevention efficiency (DPE) of the UV-protective coating on all samples decreases gradually. The DPEs of the hot-air-dried samples are estimated to be 31.4% and 18.8% after 21 and 72 hours of artificial UVA radiation, respectively. The heat-treated samples exhibit similar trends (29.0% after 21 hours and 10.3% after 72 hours). Recoating the UV-protective paint periodically every six months is expected to minimize the discoloration of the bamboo's outer surface.