Journal of the Korean Society for Precision Engineering

Study on UV Energy Effects in High Aspect Ratio Patterning via the Self-propagating Photopolymer Waveguide (SPPW) Method: Jun Ho Song, Woo Young Kim, Seungwoo Shin, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2025;42(9):757-762.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.041

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This study quantitatively examines the impact of ultraviolet (UV) intensity and energy on the formation of high aspect ratio (HAR) microstructures using the Self-Propagating Photopolymer Waveguide (SPPW) process. This mechanism relies on the self-focusing of UV light within a refractive index gradient, allowing the light to propagate and polymerize vertically beyond the initial exposure zone. Experiments were performed at UV intensities of 7.5, 12.5, and 17.5 mW/cm², with energy levels ranging from 0.0375 to 13.5 J/cm². The results indicated that a lower UV intensity of 7.5 mW/cm² produced uniform and vertically elongated structures, achieving a maximum aspect ratio of 12.26 at 0.9 J/cm². In contrast, higher UV intensities led to lateral over-curing, base expansion, and shape distortion, primarily due to rapid polymerization and the oxygen inhibition effect. These findings emphasize the importance of precisely controlling both UV intensity and energy to produce uniform, vertically aligned HAR microstructures, offering valuable insights for optimizing the SPPW process in future microfabrication applications.

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Development of Drone-attached Spraying Device for Active Maintenance of Structures: Seung-Han Yang, Kwang-Il Lee; J. Korean Soc. Precis. Eng. 2023;40(12):975-980.
Published online December 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.086

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Exteriors of structures (apartments, buildings, bridges, dams, power plants, etc.) are subject to deterioration and damage (cracks, rust, etc.), mainly due to thermal expansion/contraction and environmental humidity. The damages shorten the lifespan of structures and cause unnecessary reconstruction, increasing social costs. The existing damage maintenance methods, which are directly constructed by the workers, have problems such as reduced work efficiency, increased work cost, lack of timely maintenance, and high work risks. In this paper, a spraying device attached to a drone for active and flexible maintenance of structures is developed. To simplify maintenance, the device consists of a solenoid motor, detachable parts for maintenance agent, and a lightweight-designed frame, manufactured with a 3D printer. In particular, the lever mechanism that amplifies the pushing force of the solenoid motor is designed to spray the maintenance agent when a switch comes into contact with the exterior of the structure. The prototype of a spraying device is attached to a commercial drone (Mavic3, DJI) and tested for effectiveness in structure maintenance. It demonstrates successful, cost-effective maintenance of structural damages in less than 10 minutes.

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Structural Integrity Improvement on Engine-Generator Support Structure for Hybrid Drone through Finite Element Analysis and Experimental Verification: Ki Beom Kim, Jae Nam Kim, Hyun Seock Lee, Hyun Cheol Kim, Tae-Wan Ku, Beom-Soo Kang; J. Korean Soc. Precis. Eng. 2022;39(12):913-921.
Published online December 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.076

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In this study, the structural integrity of an engine-generator support structure of hybrid drone is verified through finite element (FE) analysis and experimental investigation. From preliminary experiments, critical failures in four columns of the support structure were observed. Due to the repeated cyclic loads induced by the engine-generator operation, the results of the FE simulation pointed out that fatigue failure is the main cause. To improve the structural integrity, the geometric shape and the material of the structural members are modified and changed, and the safety factor is also reviewed using static structural analysis. The possibility of critical resonance is evaluated through FEM-associated modal analysis and a series of vibration tests. As result, it is confirmed that the re-designed support structure was structurally improved with enough safety margin through FE analysis and experimental investigation, and fatigue life by comparing the predicted value and S-N curve of the material used to the support structure was improved.

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Structural Design and Analysis of a Quadcopter Type CanSat for Diverse Launch Conditions
Yongseon Lee, Hyeongyu Lim, Hyeonchang Yang, Changbeom Choi, Jinsung Rho
Journal of the Korean Society for Precision Engineering.2026; 43(1): 29. CrossRef
A Study on Structural Integrity Improvement of Cargo Drone through FE Simulation and Topology Optimization
Jong Seop Seong, Ha-Young Shi, Beom-Soo Kang, Tae-Wan Ku
Journal of the Korean Society for Precision Engineering.2023; 40(9): 685. CrossRef

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The Suitability of Substructures of the Offshore Wind Power Complex: Dae Kyung Kim, Dong Soon Kang, Jong Hak Lim, Young Il Byun, Chul Ki Song; J. Korean Soc. Precis. Eng. 2022;39(4):299-305.
Published online April 1, 2022; DOI: https://doi.org/10.7736/JKSPE.021.104

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As the Paris Agreement on Climate Change came into effect in 2021, the Korean government set a target of 63.8 GW new renewable power generation until 2030 and announced “The 3020 Implementation Plan of Renewable Energy”, which was a policy to supply more than 95% of the new generation capacity as solar power and wind power. Continuous investment in new renewable energy will be required to reduce the greenhouse effect and to achieve sustainable growth. In particular, offshore wind power is advantageous for the construction of a large-scale power complex. This paper evaluates the suitability of the jacket-type substructure by analyzing the weather environment, marine environment, water depth survey, ground survey, and major equipment selection data. When the new offshore wind power complex is planned, it can be useful for selecting the suitable substructure and determining the turbine capacity to achieve good performance.

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A State-of-the-Art Review of Structural Monitoring Using Piezoelectric Paint Sensors: Hyunjin Bae, Kyungwho Choi; J. Korean Soc. Precis. Eng. 2021;38(12):927-934.
Published online December 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.092

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Recently, large-scale accidents caused by minor damage from fatigue failure and impact on structures have been frequently reported. Therefore, a real-time damage monitoring system of structures is considered to be one of the most important technologies to ensure safety in various types of research. The piezoelectric sensor, which has an advantage of converting deformation of a structure into an electrical signal without using an additional power source, has been reported as one of the most suitable methods for real-time monitoring systems. This review aims to describe the structural monitoring system utilizing piezoelectric paint sensors. First, we present the concept of a piezoelectric paint sensor with the advantages of flexibility and piezoelectric performance. Then, factors affecting the performance of the piezoelectric paint sensor are introduced. Finally, an overview of piezoelectric paint sensors for structural monitoring, such as vibration detection and impact monitoring, are provided. The state-of-the-art of the application of the piezoelectric sensor is also introduced, providing feasibility in industrial fields.

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Evaluation of MWCNT/PU sponge-based triboelectric nanogenerator for harvesting mechanical energy
Insik Jo, Byungchul Kim, Hyungsik Won, SunHee Kim, Kyungwho Choi, Dukhyun Choi
Functional Composites and Structures.2025; 7(3): 035010. CrossRef

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Stress Analysis of 100 kW Photovoltaic Plant Supporting Structure Considering Wind Load: Kwan-Yong Jeong, Sang-Young Kim; J. Korean Soc. Precis. Eng. 2020;37(7):493-501.
Published online July 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.156

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The photovoltaic power generation facility is usually installed outdoors and is extensively impacted by snow and wind power as well as external contact friction caused by snow and rain. In particular, since there is a markedly high possibility of damage from devastating wind power such as a typhoon, an overall safety evaluation is essential. However, most studies are conducted using cell-level stress analysis rather than cluster-wide stress analysis. Thus, in this study, a finite element analysis was performed on the entire support structure of the photovoltaic power generation facility, wherein the wind load was applied, and the portion wherein extensive stress was generated was identified. The results of the analysis showed that the stress in the rear side was relatively higher than in the front side of the support structure for the horizontal wind. Additionally, it was confirmed that a relatively high stress occurs in the lower side than the upper side of the support structure.

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The Study on the Vulnerable Part to Wind Load in Renewable Energy Photovoltaic Power Structures
Kwang Pil Park
International Journal of Highway Engineering.2023; 25(6): 27. CrossRef
Evaluation of Structural Integrity for Lifting-and-Lowering-Type Drone Station Using Fluid-Structure Interaction Analysis
Sang Ho Kim, Jae Youl Lee, Sung-Ho Hong, Jehun Hahm, Kap-Ho Seo, Jin-Ho Suh, Young Sik Joung, Se Hoon Jeung
Journal of the Korean Society for Precision Engineering.2021; 38(11): 841. CrossRef

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Fabrication of Anisotropically Oleophobic Surface with Inverse-Tapered Structure Using Micromolding in Capillaries and Microtransfer Molding: Ki Yeon Hong, Dong-Ki Lee, Sungdong Kim, Young Hak Cho; J. Korean Soc. Precis. Eng. 2019;36(4):413-418.
Published online April 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.4.413

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Fabrication of inverse-tapered structure remains as a problem in the fabrication of oleophobic surface mostly due to the complications and the high cost of processes. In this paper, we propose a simple and low-cost fabrication method of inverse-tapered structured oleophobic surface using micromolding in capillaries (MIMIC) and microtransfer molding followed by MEMS processes. Silicon wafer molds for the formation of inverse-tapered structure were made using MEMS processes such as photolithography and anisotropic KOH etching of silicon wafer. The geometry of structure could be changed by controlling the etching depth of the silicon wafer mold. After covering the surface of the mold using flat UV tape, the formed space between mold and UV tape was filled with pre-cured PDMS by capillary force and then cured in oven. The tapered structure on UV tape was transferred and bonded to glass wafer by O₂ plasma treatment. The fabricated inverse-tapered structure was coated with a fluoroalkylsilane monolayer to reduce its surface energy. The wetting behaviors were investigated by the contact angle (CA) measurement of hexadecane droplets. This study demonstrates that an inversetapered structure can be fabricated on a substrate using micromolding in capillaries and microtransfer molding, whose surface shows the superoleophobicity.

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Fabrication of Acoustophoretic Device with Lateral Polymer Wall for Micro-Particle Separation
Sungdong Kim, Su Jin Ji, Song-I Han, Arum Han, Young Hak Cho
Journal of the Korean Society for Precision Engineering.2022; 39(5): 379. CrossRef
Fabrication of anisotropic wetting surface with asymmetric structures using geometrical similarity and capillary force
Ye-Eun Lee, Dong-Ki Lee, Young Hak Cho
Micro and Nano Systems Letters.2019;[Epub] CrossRef

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Lightweight Design of Link Structures for Amphibious Boat using Topology Optimization Method: Jae Moon Im, Jong Yeon Kim, Kwang Bok Shin, Do Yeop Kim; J. Korean Soc. Precis. Eng. 2018;35(11):1085-1092.
Published online November 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.11.1085

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In this paper, the topology optimization method was used to describe the lightweight design of link structures for an amphibious boat. Topology optimization was used to determine the optimum density distribution of the structure. The analysis revealed that the link structures for amphibious boat can be reduced up to 31 percent by weight without altering the design of the connected and supported parts. The structural integrity of the proposed lightweight link structures was evaluated via topology optimization and verified by finite element analysis and static test. The structural integrity of lightweight link structures was found to meet the design requirements. The running stability of amphibious boat with lightweight link structures was verified via ground and water driving tests.

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Optimal Design and Experimental Validation of the Rib Structure of a Manufacturing Machine Bed Using Topology Optimization
Ji-Sang Hwang, Sung-Jae Kim, Jeong-Hyun Yoon, Chul-Hoon Sung
Journal of the Korean Society of Manufacturing Technology Engineers.2023; 32(6): 374. CrossRef
Study on the Optimal Design of Column Rib Structure of Horizontal Machine Tool Using Topology Optimization Technique
Ji-Sang Hwang, Sung-Jae Kim, Chul-Hoon Sung
Journal of the Korean Society of Manufacturing Technology Engineers.2023; 32(1): 1. CrossRef
Optimization Design of Student KSAE BAJA Knuckle Using SLM 3D Printer
Young Woo Im, Geon Taek Kim, Hyeon Sang Shin, Kang Min Kim, Bu Hyun Shin, Jong Won Lee, Jinsung Rho
Journal of the Korean Society for Precision Engineering.2023; 40(9): 719. CrossRef
Designing the internal reinforcements of a sailing boat using a topology optimization approach
Antonio Mancuso, Antonio Saporito, Davide Tumino
Applied Ocean Research.2022; 129: 103384. CrossRef
A Study on Injection Mold Design Using Topology Optimization
Mi-Jin Kim, Jae-Hyuk Choi, Gyeng-Yun Baek
Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(4): 100. CrossRef
Lightweight Design of a Vacuum Gripper for Inspection Equipment Using Topology Optimization
Euddeum Cha, Tae-Young Kim, Taeho Ha, Keun Park
Journal of the Korean Society for Precision Engineering.2021; 38(9): 683. CrossRef
Optimal Design for Strength Improvement of Support Bracket for Sanding Device of Railway Vehicle Using Topology Optimization
Yonho Cho, Woohyuck Yoon
Journal of the Korean Society for Precision Engineering.2020; 37(4): 263. CrossRef
Lightweight Design of a Sledge Frame for Para Ice Hockey Using Design for Additive Manufacturing
Eun-Ji Oh, Ju-Hye Lee, Jae-Eun Kim, Keun Park
Journal of the Korean Society for Precision Engineering.2020; 37(6): 407. CrossRef

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Study on Finite Element Modeling Method for Cylindrical Composite Lattice Structures with Hexagonal Cell: Jae Moon Im, Kwang Bok Shin, Sang Woo Lee; J. Korean Soc. Precis. Eng. 2018;35(6):609-613.
Published online June 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.6.609

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In this paper, finite element modeling methods for cylindrical composite lattice structures were verified through natural frequency test. Finite element models for cylindrical composite lattice structure were developed using beam, shell and solid elements. Natural frequency test was measured using impact test method under free-boundary condition. The analysis result of the beam element model showed up to 23% errors because the beam element could not consider the degradation of mechanical properties of non-intersection parts of the composite lattice structures. On the other hand, the natural frequencies of finite element analysis for shell and solid element models showed good results with natural frequencies test. From the analysis of the experiment, finite element model for composite lattice structures should use shell or solid element which takes into consideration the intersection and non-intersection parts.