• 대한치과기공학회지
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• 제46권3호
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• pp.84-92
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• 2024

Purpose: To evaluate the effect of post-curing on the three-dimensional (3D) accuracy of artificial teeth, denture bases, and denture base monoblock manufactured using digital light processing (DLP) technology. Methods: Using an edentulous model, a 3D design was made for complete dentures. Three groups were printed by DLP: artificial teeth, denture bases, and denture base monoblock. The models were scanned, subjected to post-curing, and scanned again. Three-dimensional analysis was performed based on the post-treatment differences among the three groups. Statistical analysis was performed using SPSS Statistics ver. 22.0 (IBM), and the Mann-Whitney U-test and Kruskal-Wallis test were employed as nonparametric tests. Results: The complete denture monoblock (CM) and complete denture artificial teeth (CA) groups showed the lowest and highest errors at 15.13 and 23.37 ㎛, respectively. The groups did not show significant differences (p>0.05). In the significance test among the three groups, no significance was found in the CA group; however, significant differences were found between the complete denture base (CB) and CM groups. In addition, the three groups showed significant differences (p<0.05). Conclusion: Although deformation may occur during the post-curing process, it is within the clinically acceptable range. Future comparative studies using different 3D printers and searching for ways to minimize errors through optimization of the post-curing process are warranted.

• 한국전기전자재료학회논문지
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• 제37권5호
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• pp.554-561
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• 2024

Micro light-emitting diodes (µLEDs) have been utilized in various fields such as displays, and smart devices, due to their superior stabilities. Since the applications of the µLEDs have been extended to medical devices and wearable sensors, excellent optical properties and uniformity of the µLEDs are important. Hence, several researchers have investigated to enhance the optical efficiency of the µLEDs through micro/nano lens. However, the reported methods for realizing the micro/nano lens have some drawbacks such as complex and high-cost manufacturing processes. Herein, we developed µLEDs with 3D-printed hydrogel microlenses. The printed hydrogel had high transparency and excellent adhesive strength, allowing it to attach onto top surface of the µLEDs without any additional adhesives. Microscale printing technology using a 3D printer achieved quick and fine printing in desired shapes and arrangements, showing the possibility of mass production. The 3D-printed microlens can be applied to improve not only the optical properties of µLEDs but also other optical devices.

• Advances in concrete construction
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• 제17권2호
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• pp.93-110
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• 2024

The process of concrete production consumes an immense volume of water, with approximately one billion metric tons of freshwater being utilized for tasks such as aggregate washing, fresh concrete production, and concrete curing. The accessibility of clean water for the public is hindered by the limited availability of water resources, primarily due to the rapid expansion of industries such as tanneries, stone quarries, and concrete manufacturing. These industries not only consume substantial amounts of freshwater but also generate significant volumes of various types of waste. Therefore, the use of fresh water in concrete production should be minimized. Few studies have reviewed the production of concrete using wastewater to derive practical and applicable findings for the industry. Thus, this study thoroughly explores the physical and chemical effects of wastewater on concrete, examining aspects like durability, hardened properties, and rheological characteristics. It identifies key factors that can compromise concrete properties when exposed to wastewater. The scarcity of research on integrating wastewater into concrete production underscores the urgent necessity for innovative approaches and methodologies in this field. While the inclusion of wash water typically reduces the workability of fresh concrete, it often enhances its compressive strength. Notably, significant improvements have been observed when using tertiary processed wastewater, wash water, polyvinyl alcohol-based wash water (PVAW), and reclaimed water in the concrete mixing process. The application of tertiary treatment to wastewater resulted in a notable enhancement of compressive strength, showing increases of up to 7%. In contrast, wastewater treated through secondary methods experienced a decline in strength ranging from 9% to 18% over a period of six months. However, the use of reclaimed wastewater demonstrated an improvement in strength by 8% to 17%, depending on the concentration level ranging from 25% to 100%. In contrast, the utilization of secondary processed wastewater and industrial water has a minimal impact on the concrete's strength.

• Design & Manufacturing
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• 제18권3호
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• pp.15-21
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• 2024

This study investigates the causes of wrinkle defects in PA12-insulated busbars used in electric vehicles and proposes an improvement method to address these issues. Busbars, essential components for efficient current transmission in electric vehicle battery modules, require complex three-dimensional bending to optimize internal layouts. For this study, oxygen-free copper busbars with a 0.8 mm PA12 insulation coating were subjected to three types of bending tests: flat bending, edge bending, and torsional bending. Experimental results showed that wrinkle defects only occurred during edge bending, while flat and torsional bending modes exhibited no significant issues. Cross-sectional analysis revealed that the PA12 insulation layer's thickness was uneven, with thinner sections on flat areas and thicker accumulation at the comers. This uneven distribution led to poor adhesion between the insulation and copper layers, resulting in the formation of wrinkles, particularly in areas with air gaps ranging from 75 to 250 ㎛. To further analyze the issue, finite element analysis (FEA) of the bending process was performed under adhesive and non-adhesive conditions. The results confirmed that wrinkles formed when the adhesion between the copper and PA12 coating was insufficient. Improved adhesion conditions, achieved through a heat treatment process at 120℃ for 2 hours, significantly reduced the occurrence of wrinkles during edge bending. This study demonstrates that optimizing the adhesion between the insulation coating and the copper busbar, through controlled heat treatment, can prevent wrinkle defects. The findings provide a pathway for enhancing the durability and performance of insulated busbars in electric vehicle applications.

• 마이크로전자및패키징학회지
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• 제31권3호
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• pp.80-86
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• 2024

Polyimide는 열안정성과 내열성이 우수하고 뛰어난 내화학성을 가지는 등 기존 폴리머들과는 차별화된 장점을 가진다. 이러한 Polyimide를 다양하게 응용하는 방안이 연구되고 있는데, 본 연구에서는 이러한 Polyimide를 필름으로 제조하기 위한 연구를 수행하였다. 최적화된 제조 조건을 통해 부착력과 연필 경도가 우수한 Polyimide 필름을 구현하는 한편, glass flake를 첨가하여 산소 투과도도 감소시켜 패키징 재료로의 응용 가능성을 모색하였다. 그 결과, 약 50 ㎛ 두께의 glass flake 및 (3-Aminopropyl)triethoxysilane이 첨가된 Polyimide 필름을 균질하게 구현할 수 있었으며, 해당 Polyimide 필름의 부착력은 4B, 연필 경도는 5H, 그리고 산소 투과도는 8.795 × 10^-9 cc/s 미만임을 확인하였다.

• 한국산업보건학회지
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• 제34권3호
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• pp.238-246
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• 2024

Objectives: A collective of workers in the company's cafeteria encountered symptoms such as stinging and watering in and around the eyes, a sensation of sand in the eyes, erythema, swelling, and peeling of the skin on the face and neck. The objective of this study is to pinpoint the causes of these symptoms and propose preventive measures. Methods: Following preliminary on-site investigations, worker interviews, and literature research, it was determined that the most probable cause of the symptoms was ultraviolet rays emitted from a UV sterilizer. Consequently, the study measured and assessed the effective amount of ultraviolet radiation emitted by the sterilizer. Results: When operating with the curtain-type door of the ultraviolet sterilizer open, it was observed to surpass the 0.1 μW/cm2 8-hour work exposure standard recommended by ACGIH TLV in most kitchen workspaces. The evaluation of the maximum allowable exposure time based on the distance from the ultraviolet sterilizer indicated only 4.2 seconds at a distance of 0.2 m with the curtain door open, and merely 1.7 minutes at a distance of 1 m. Conclusions: This study confirmed that the symptoms among restaurant workers emerged immediately after the installation of the ultraviolet sterilizer, and these symptoms were consistent with those associated with exposure to ultraviolet rays. Furthermore, the assessment revealed that the exposure level to ultraviolet rays could be exceeded established exposure standards. It was recommended that the existing ultraviolet sterilizer be replaced with one featuring a glass door, and facility improvements should be made, such as implementing an automatic mechanism to turn off the ultraviolet lamp when the door is opened.

• 품질경영학회지
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• 제52권3호
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• pp.413-428
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• 2024

Purpose: This study aims to optimize the adhesive strength of epoxy adhesive when applied to tiles, addressing frequent issues of adhesion degradation observed in indoor interiors. The degradation often leads to costly repairs and maintenance, highlighting the need for improved adhesive formulations and application techniques. Methods: Employing the DMAIC (Define, Measure, Analyze, Improve, Control) methodology integral to Six Sigma and utilizing MINITAB for data analysis, this research focused on critical factors like curing time, application method, and mixing ratio. The Taguchi Experimental Design within the Design of Experiments (DOE) framework was applied to determine the impact of these parameters on adhesive strength. Results: The analysis facilitated by Taguchi's method led to notable improvements in adhesive workability and consistency. It identified the optimal combination of factors that significantly increase adhesive strength, evidenced by the improvement in signal-to-noise ratio and I-MR control charts. Conclusion: By applying a structured statistical approach through Six Sigma and the Taguchi method, the study successfully pinpointed optimal conditions for epoxy adhesive application on tiles. This contributes to quality management in the manufacturing and application processes of epoxy adhesives, ensuring enhanced durability and reliability in indoor tiling applications. The findings offer a significant methodological framework for future material optimization research.

• 국제학술발표논문집
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• The 10th International Conference on Construction Engineering and Project Management
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• pp.585-594
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• 2024

In recent years, the construction industry has rapidly adopted offsite-manufacturing and distributed construction methods. This change brings a variety of challenges requiring innovative solutions, such as the utilization of AI-driven and generative design. Numerous studies have explored the concept of multi-objective generative design with genetic algorithms in construction. However, this paper highlights the challenges and proposes a solution for combining generative design with distributed construction to address the need for agility in design. To achieve this goal, the research delves into the development of a multi-objective generative design optimization using a weighted genetic algorithm based on simulated annealing. The specific design case adopted is an educational complex. The proposed process strives for scalable economic viability, environmental comfort, and operational efficiency by optimizing modular configurations of architectural spaces, facilitating affordable, scalable, and optimized construction. Rhino-Grasshopper and Galapagos design tools are used to create a virtual environment capable of generating architectural configurations within defined boundaries. Optimization factors include adherence to urban regulations, acoustic comfort, and sunlight exposure. A normalized scoring approach is also presented to prioritize design preferences, enabling systematic and data-driven design decision-making. Building Information Modeling (BIM) tools are also used to transform the optimization results into tangible architectural elements and visualize the outcome. The resulting process contributes both to practice and academia. Practitioners in AEC industry could gain benefit through adopting and adapting its features with the unique characteristics of various construction projects while educators and future researchers can modify and enhance this process based on new requirements.

• 디자인학연구
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• 제11권2호
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• pp.129-140
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• 1998

본 연구는 국내 중소제조업 경영자가 처음으로 산업디자인도입을 시도할 때 보다 손쉽게 효과적인 방법으로 어프로우치할 수 있는 가이드라인적인 방법을 모색, 제시하는데 목표를 둔 것이다. 연구방법으로서는, 먼저 중소기업의 역할과 중요성에 대한 고찰을 통해 산업디자이 도입의 필요성을 검토하고, 다음은 국내 중소제조업 경영자를 대상으로 실시한 앙케트 조사결과를 분석.고찰하였으며, 그 결과로서 산업디자인의 효과적 도입을 위한 전제조건을 도출하였다. 그리고 앙케트조사 결과로서 도출된 전제조건을 토대로 하여 어프로우치 가능한 도입방법을 검토하고, 최종적으로는 국내중소제조업에 유효한 것으로 판단되는 산업디자인 도입방법을 시각적인 가이드라인수준의 모델로서 구조화하였다. 연구과정 및 결과로서의 성과는 다음과 같다. 첫째, 산업디자인 도입을 처음으로 시도하는 중소기업 경영자는 효과적인 어프로우치를 위한 전제로서 다음 6가지 조건을 숙지할 필요가 있음이 발견되었다. 1) 자사의 대 국가적.국민적 역할 및 중요성이 자각 필요 2) 창조적 경영사고와 그 촉매제로서의 산업디자인 도형 필요성 검토 3) 산업디자인의 본질 및 가치에 대한 확실한 이해 4)산업디자인 도입의 성공사례 및 타 기업의 공통적인 도입방법에 대한 면밀한 연구, 검토 5) 상담창구, 디자인 전문기관을 이용한 도입방법의 사전검토 6) 디자이너 정보, 디자이너의 기용목적 및 방법에 대한 신중한 검토 둘째, 처음으로 산업디자인을 도입하여 중소기업 입장에서는 산업디자인도입의 필요성 발생상황 및 도입범위를 동시에 고려한 도입필요성에 의한 어프로우치, 즉 예비적 도입.부분적 도입.본격적 도입.전사 적 도입의 방법으로 필요에 따라 어프로우치하는 것이 효과적인 것으로 확인되었다. 이 방법은 단계적으로도 어프로우치가 가능하며, 산업디자인 도입의 필요성 또는 목적 및 범위에 따라 그 방법을 자유롭게 선택할 수 있는 점과, 시각적인 형태로 구조화되어 있어 쉽게 이해할 수 있다는 점등에 그 특징이 있는 것으로 확인되었다.

• Journal of the Korean Wood Science and Technology
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• 제2권3호
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• pp.3-16
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• 1974

One of the disadvantages of. wood and wood products is their hydroscopicity or dimensional instability. This is responsible for the loss of green volume of lumber as seasoning degrade. Dimensional stabilization is needed to substantially reduce seasoning defects and degrades and for increasing the serviceability of wood products. Recently, considerable world-wide attention has been drawn to the so-called Wood-Plastic Composites by irradiation-and heat-catalyst-polymerization methods and many research and developmental works have been reported. Wood-Plastic Composites are the new products having the superior mechanical and physical properties and the combinated characteristics of wood and plastic. The purpose of this experiment was to obtain the basic data for the improvement of wooden materials by manufacturing WPC. The species examined were Mulpurae-Namoo (Fraxinus, rhynchophylla), Sea-Namoo (Carpinus laxiflora), Cheungcheung-Namoo (Cornus controversa), Gorosae-Namoo (Acermono), Karae-Namoo(Juglans mandshurica) and Sanbud-Namoo (Prunus sargentii), used as blocks of type A ($3{\times}3{\times}40cm$) and type B ($5{\times}5{\times}60cm$), and were conditioned to about 10~11% moisture content before impregnation in materials humidity control room. Methyl methacrylate (MMA) as monomer and benzoyl peroxide (BPO) as initiator are used. The monomer containing BPO was impregnated into wood pieces in the vacuum system. After impregnation, the treated samples were polymerized with heat-catalyst methods. The immersed weights of monomer in woods are directly proportionated to the impregnation times. Monomer impregnation properties of Cheungcheung-Namoo, Mulpurae-Namoo and Seo-Namoo are relatively good, but in Karae-Namoo, it is very difficult to impregnate the monomer MMA. Fig. 3 shows the linear relation between polymer retentions in wood and polymerization times; that is, the polymer loadings are increasing with polymerization times. Furthermore species, moisture content, specific gravity and anatomical or conductible structure of wood, bulking solvents and monomers etc have effects on both of impregnation of monomer and polymer retention. Physical properties of treated materials are shown in table 3. Increasing rates of specific gravity are ranged 3 to 24% and volume swelling 3 to 10%. ASE is 20 to 46%, AE 14 to 50% and RWA 18 to 40%. Especially, the ASE in relation to absorption of liquid water increases approximately with increase of polymer content, although the bulking effect of the polymerization of monomer may also be influential. WPCs from Mulpurae-Namoo and Cheungcheung-Namoo have high dimensional stability, while its of Karae-Namoo and Seo-Namoo are-very low. Table 4 shows the mechanical properties of WPCs from 6 species. With its specific gravity and polymer loading increase, all mechanical properties are on the increase. Increasing rate of bending strength is 10 to 40%, compression strength 25 to 70%, ;impact bending absorbed energy 4 to 74% and tensile strength 18 to 56%. Mulpurae-Namoo and Cheungcheung-Namoo with high polymer content have considerable high increasing rate of strengths. But incase of Karae-Namoo with inferior monomer impregnation it is very low. Polymer retention in cell wall is 0.32 to 0.70%. Most of the polymer is accumulated in cell lumen. Effective. of polymer retention is 58.59% for Mulpurae-Namoo, 26.27% for Seo-Namoo, 47.98% for Cheungcheung-Namoo, 25.64% for Korosae-Namoo, 9.96% for Karae-Namoo and 25.84% for Sanbud-Namoo.