This study is about the design and simulation of an f-theta lens, one of the main components used in laser printers and laser scanning systems. To design an f-theta lens, the optical paths of the components of the laser scanning unit, the ftheta lens, the cylinder lens, and the collimator lens must be identified. Simulations were performed on the performance of aspherical and beam size optical systems while considering the f-theta lens optical design and optical properties. And while considering the optical design and optical characteristics of the f-theta lens, simulation was conducted on the performance of the optical system for aspherical surface and ray aberrations by location, point spread function, spot diameter, and beam size. Optical system simulation was implemented by applying the collimator lens, polygon mirror, and cylinder lens to the design formula of an f-theta lens using the Code-V and design verification was performed with these results.
The purpose of this study was to design a sledge frame for para ice hockey in which an athlete sits and plays on a sledge. A sledge comprises a bucket, a blade carrier, and a frame. A sledge frame is usually fabricated by welding a number of pipes, and thus its structural safety is degenerated at the welded joints. In this study, the sledge frame was redesigned using the principle of DfAM (Design for Additive Manufacturing), to reduce the frame weight as well as to have sufficient structural safety. As an application of DfAM, the part consolidation was performed for six joints from which the number of welding spots was reduced to 56% (From 16 to 9). Among the resulting four consolidated joints, topology optimization was performed for three joints to reduce their weight while maintaining higher structural stiffness and safety. As a result, the structural stiffness and safety of the joints improved remarkably, and the resulting frame weight was reduced by 20% (From 1.66 to 1.34 kg). This weight reduction with structural enhancement is expected to improve athletes’ performance and safety in para ice hockey games.
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A Study on Improvement of Flow Characteristics of TPMS Heat Exchanger based on Mathematical Filtering Seo-Hyeon Oh, Jeong Eun Kim, Ji Seong Yun, Do Ryun Kim, Jungwoo Kim, Chang Yong Park, Keun Park Journal of the Korean Society for Precision Engineering.2024; 41(7): 541. CrossRef
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Tool condition monitoring is one of the key issues in mechanical machining for efficient manufacturing of the parts in several industries. In this study, a tool condition monitoring system for milling was developed using a tri-axial accelerometer, a data acquisition, and signal processing module, and an alexnet as deep learning. Milling experiments were conducted on an aluminum 6061 workpiece. A three-axis accelerometer was installed on a spindle to collect vibration signals in three directions during milling. The image using time-domain, CWT, STFT represented the change in tool wear of X, Y axis directions. Alexnet was modified to learn images of the two directional vibration signals, to predict the tool condition. From an analysis of the results of learning based on the experimental data, the performance of the monitoring system could be significantly improved by the suitable selection of the data image method.
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Anomaly Detection Method in Railway Using Signal Processing and Deep Learning Jaeseok Shim, Jeongseo Koo, Yongwoon Park, Jaehoon Kim Applied Sciences.2022; 12(24): 12901. CrossRef
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Three-dimensional printing technology has technical limitations limited to the development of prototypes focusing on functional realization. Because of these limitations, there are problems such as mechanical strength and rigidity in entering the commercialization market. However, the industry is working to overcome these obstacles in the future and apply them directly to the field for mass production in the manufacturing process. In particular, research to secure physical properties such as mechanical strength, the major problem of 3D printing products, has been initiated in the automobile industry, aviation, and medical fields. Thus, this study focused on the mechanical strength required for commercialization of 3D printing technology. To achieve this goal, a tensile specimen was fabricated by an FDM (Fused Deposition Modeling) type 3D printer. Tensile specimens were produced of round bar type and the deposition direction, layer height, and printing speed of the layers were considered. Finally, the effects of variables for each printing condition on tensile strength and fracture behavior were compared and analyzed. Also, the fracture surface of the tensile specimen was observed to investigate the effect of the deposition direction on the fracture behavior.
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When the penetrator collides with the target, the penetrator has different penetrating characteristics and residual velocity after penetration, according to the geometry of the penetrator. In this study, we optimized the geometry of the penetrator using the artificial neural network and the genetic algorithm to derive the best penetration performance. The Latin hypercube sampling method was used to collect the sample data, Simulation for predicting the behavior of the penetrator was conducted with the finite cavity pressure method to generate the training data for the artificial neural network. Also, the optimal hyper parameter was derived by using the Latin hypercube sampling method and the artificial neural network was used as the fitness function of the genetic algorithm to optimize the geometry of the penetrator. The optimized geometry presented the deepest penetration depth.
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A Study on 3D Printing Conditions Prediction Model of Bone Plates Using Machine Learning Song Yeon Lee, Yong Jeong Huh Journal of the Korean Society for Precision Engineering.2022; 39(4): 291. CrossRef
Recently, there has been increasing demand for flexible electronic applications such as flexible displays, foldable smartphones, and flexible batteries based on flexible substrates. The roll-to-roll additive process has attracted tremendous attention regarding manufacturing such flexible electric devices because of its characteristics of eco-friendliness, large area of compatibility, and high flexibility, in contrast to traditional lithography or vaper evaporation methods. The mass production of roll-to-roll process tension control in precision is the most crucial assignment to be achieved. For the tension control, the load cell and dancer systems are used to regulate tension disturbance. A pendulum dancer system was extensively applied for unwinder or rewinder whose span length varied in the roll-to-roll printing and coating process. However, there have been an inadequate number of studies regarding tension control using the dancer system for mass production. In this paper, we propose a mathematical model of center pivot rotary dancer system revolving dual idle rolls around the pivot. Parametric studies are conducted as a function of inertia, span length, width of substrate, and operation velocity. Additionally, an impulse response was conducted for the time domain analysis. These results can be used for the mass production of roll-to-roll additive process.
Among the various next-generation solar cells, a perovskite solar cell can solve the economic problem because it can perform the low temperature solution process and the material is inexpensive. Photovoltaic conversion efficiency is comparable to silicon solar cells and thin-film solar cells. However, to commercialize the perovskite solar cells, there are many problems to be resolved, such as stability, upscaling, and efficiency. Thus, in this study, perovskite crystallization experiments were conducted according to the coating conditions such as the coating speed of the meniscus solution sheared coating process, and large-area perovskite solar cells with p-i-n structures were fabricated. Perovskite crystallization is one of the crucial factors that determine the efficiency of solar cells, and it is an integral process condition for manufacturing large-area perovskite solar cells.
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A Study on Crystallization of Perovskite Using a High-Speed Meniscus Solution Shearing Coating Visualization Device I-Ji Kim, Hyun Ah Lee, Dong Soo Kim Journal of the Korean Society for Precision Engineering.2021; 38(12): 965. CrossRef
The motion platform supports the trainee in experiencing a sense of reality in virtual space by performing a motion on the available degrees of freedom for a motion that mimics a specific motion in connection with a virtual reality content or a simulator. The required specification of the motor and driver of motion platform is determined by the target specification for the upward motion of the motion plate. The reason is that the weight of the upper plate always applies gravity in the direction of the downward motion. As a result, the downward motion has an excessive specification compared to the upward motion specification, resulting in an unbalanced motion specification. Additionally, a problem may occur in which a volume increases from the application of a high specification driving unit. In this paper, the motion platform was designed capable of three-axis motion in roll, pitch, and gravity directions using a compression spring to apply a load compensation mechanism. Based on the design results, the specifications of the compression spring for motion platform to satisfy the operating specifications do not excessively move the upward and downward direction derived by the analysis.
In this paper, the boom structure of a telescopic boom-type forklift truck was analyzed using ANSYS, a finite element analysis program. As a result, 494.22 MPa exceeded 456.08 MPa, allowable stress of the material, in the second boom. Thus, structural analysis was performed by reinforcing the thickness of the boom and stress was reduced. The experiment was conducted by selecting four factors of the thickness of the boom T1, T2, T3, and T4. Through response surface analysis, the curvature of the factors for stress was confirmed, and T1 was the most influential factor. Through regression equations from the variance analysis of each response, response maximization was performed to optimize mass and stress. As a result, 467.65 MPa was predicted. This exceeded allowable stress of 456.08 MPa. To obtain the result that does not exceed allowable stress, the mass was fixed at 118 kg, the initial value, and multiple response optimization was performed to limit target value and minimize stress. As a result, 432.96 MPa was expected to occur, and structural analysis resulted in 428.87 MPa stress demonstrating 13.22% reduction of stress compared to the existing model, and it is safe because allowable stress was less than 456.08 MPa.
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Design and fabrication of a device for cleaning greenhouse roofs Ahmed Amin, Xiaochan Wang, Zhao Lianyuan, Yinyan Shi, Ren Xiaoyan, Mahmoud Okasha, Reda Hassanien Emam Hassanien Heliyon.2025; 11(2): e41991. CrossRef
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On-Line Model Predictive Control for Energy Efficiency in Data Center Min Sik Chu, Hyun Ah Kim, Kyu Jong Lee, Ji Hoon Kang Journal of the Korean Society for Precision Engineering.2021; 38(12): 943. CrossRef
Precision positioning stages are devices for precisely positioning objects according to required degrees of freedom and performance. Precision positioning stages are classified into serial and parallel mechanisms. Except for specific applications, the parallel mechanism is preferred. In serial mechanism, dynamic characteristics such as resonant frequency are clearly different from axis to axis and the first resonance frequency is distinctly low compared to the second. These make the control performance different for each axis and incurs limitation in control. In this study, the first and second resonant frequencies in a serial 2-DOF precision positioning stage were increased while maintaining their approximal value. Compliance analysis for the stage was performed by applying the matrix based method. A new concept of resonant frequency isotropy (RFI) was introduced and design optimization was performed in which first and second resonant frequencies almost coincided. This optimization allowed for the design of a serial 2-DOF precision positioning stage with enhanced first resonance frequency by 50.8% and RFI by 80.2% compared to the initial design. This paper is expected to increase the use of precision positioning stages based on serial mechanism and apply the concept of RFI to the positioning stages with more than 2-DOF.
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