Journal of the Korean Society for Precision Engineering

Suppression of Interfacial Side Reactions and Performance Enhancement of NCA Cathodes via LNO Deposition Using Particle ALD: Min-ji Kim, In-suk Song, Hyo-jun Ahn, Sun-min Kim, Young-Beom Kim; J. Korean Soc. Precis. Eng. 2025;42(10):851-859.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.025

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Improving the interfacial stability between cathode active material (CAM) and solid electrolyte (SE) is essential for enhancing the performance and durability of all-solid-state batteries (ASSBs). One promising method to achieve this is through surface coating with a chemically stable ion conductor, which helps suppress interfacial side reactions and improve long-term cycling stability. In this study, we deposited a uniform LiNbO3 (LNO) protective layer on NCA using particle atomic layer deposition (Particle ALD). This technique utilizes a self-limiting growth mechanism to ensure precise thickness control. We characterized the structural and chemical properties of the coated CAM with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), confirming the successful formation of a uniform LNO layer. Electrochemical evaluations revealed that LNO@NCA exhibited significantly improved capacity retention, maintaining 68.1% after 50 cycles at a 1C rate, compared to just 56.5% for the uncoated sample. This enhancement is attributed to the LNO layer's effectiveness in mitigating electrochemical side reactions. These findings demonstrate that Particle ALD-derived LNO coatings are an effective strategy for stabilizing CAM|SE interfaces and extending the cycle life of high-energy ASSBs.

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Manufacturing Process for Highly Stable Thermal Imprinting Transparent Electrode Using IPL Sintering: Yunseok Jang; J. Korean Soc. Precis. Eng. 2025;42(1):75-78.
Published online January 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.119

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This paper shows results of research on transparent electrode manufacturing processes using thermal imprinting and IPL technique. By using an IPL process instead of the existing heat sintering process, the sheet resistance value was reduced to about 1/ 10. Additionally, sintering time could be reduced from 1 hour to 1 ms. As a result of measuring the transmittance to determine the excellence of the transparent electrode produced in this way, it was confirmed that it had a high transmittance of 94.4% compared to the substrate with a very high bending stability compared to the existing ITO transparent electrode. These results show that the transparent electrode manufacturing method proposed in this study is very useful.

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Prediction of Falls Risk Using Toe Strength and Force Steadiness based on Deep Learning: A Preliminary Study: Jin Seon Kim, Seong Un Choi, Chang Yeop Keum, Jaehee Lee, Woong Ki Jang, Kwang Suk Lim, Hyungseok Lee, Byeong Hee Kim, Tejin Yoon; J. Korean Soc. Precis. Eng. 2023;40(7):519-526.
Published online July 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.050

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Falls are common among older people. Age-related changes in toe strength and force steadiness may increase fall risk. This study aimed to evaluate the performance of a fall risk prediction model using toe strength and force steadiness data as input variables. Participants were four healthy adults (25.5±1.7 yrs). To indirectly reproduce physical conditions of older adults, an experiment was conducted by adding conditions for weight and fatigue increase. The maximal strength (MVIC) was measured for 5 s using a custom toe dynamometer. For force steadiness, toe flexion was measured for 10 s according to the target line, which was 40% of the MVIC. A one-leg-standing test was performed for 10 s with eyes-opened using a force plate. Deep learning experiments were performed with seven conditions using long short-term memory (LSTM) algorithms. Results of the deep learning model were randomly mixed and expressed through a confusion matrix. Results showed potential of the model"s fall risk prediction with force steadiness data as input variables. However, experiments were conducted on young adults. Additional experiments should be conducted on older adults to evaluate the predictive model.

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Comparative Study of Gait Stability Using COM-COP Inclination Angle Changes of Elderly: Byeong Chan Cho, Tae Soo Bae; J. Korean Soc. Precis. Eng. 2021;38(7):521-528.
Published online July 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.001

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The current method of gait analysis has several limitations for determining gait stability, such as a complicated preparation process, repeated experimental procedures that are time-consuming, and financial burden of experiments. This study investigated whether gait stability could be analyzed using only the COM-COP (Center of Mass-Center of Pressure) inclination angle connecting COM and COP. COM and COP coordinates were obtained from a motion analysis system for a total of 40 elderly and young subjects. The COM-COP inclination angle that changed in real time during level walking was then analyzed to obtain gait stability on each of sagittal and frontal planes using these coordinates. As a result, the gait symmetry index on the sagittal plane did not show a statistically significant difference between young and elderly subjects (First Step, p = 0.189; Second Step, p = 0.711). On the frontal plane, elderly subjects showed 0.39 degrees (p = 0.058) and 0.5 degree (p = 0.03) larger side-to-side sway angles in the first and second steps than young subjects, respectively. Gait stability can be analyzed using a more simplified experimental method with minimum amount of data in future gait analysis.

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Controlling the Fluid Induced Instability of a Supercritical CO₂ Compressor Supported by Magnetic Bearing: Sheng-He Jin, Jae-Eun Cha, Jee-Uk Chang, Sang-Hyun Choi, Hyeong-Joon Ahn; J. Korean Soc. Precis. Eng. 2020;37(10):737-742.
Published online October 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.049

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Since sCO₂ (Supercritical Carbon Dioxide) turbomachinery are generally small and operate at high rotational speed, the bearings remain a significant challenge to the design of the turbomachinery for the sCO₂ power cycles. However, a fluid induced instability similar to the oil whirl may occur even with the magnetic bearing under high pressure and high speed conditions of the sCO₂ turbomachinery. This paper presents experimental investigation on the instability of a sCO₂ compressor supported by the magnetic bearing. First, we introduce the sCO₂ compressor supported by the magnetic bearing. The procedure to guarantee the rotordynamic performance of the sCO₂ compressor supported by the magnetic bearing is provided. Then, the effects of the working condition such as the pressure and rotating speed on the fluid induced instability are investigated experimentally. Finally, a strategy to resolve the fluid-induced instability with conventional PID control is proposed and experimentally verified.

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Turbomachine Operation with Magnetic Bearings in Supercritical Carbon Dioxide Environment
Alexander Johannes Hacks, Dieter Brillert
International Journal of Turbomachinery, Propulsion and Power.2022; 7(2): 18. CrossRef
A Study on the Efficient Optimization of Controller for Magnetic Bearings Supporting Oil-Free Turbo-Chiller Compressor
Eunsang Kwon, Myounggyu Noh, Namsoo Lee, Seongki Baek, Young-Woo Park
Journal of the Korean Society for Precision Engineering.2022; 39(2): 123. CrossRef

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Experimental Research on Running Stability of Swing Motion Bogie System for a Freight Car: Jeong Hwan Choi, Hae Young Ji, Jin Kyu Park, Seung Gie Jeon; J. Korean Soc. Precis. Eng. 2020;37(5):321-330.
Published online May 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.161

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The swing motion bogie system for a freight car is more effective regarding the vibration damping effect than other freight car bogie systems while operating, and it is a bogie system that can travel up to 120 km/h despite being a freight car. Imported in 2006 in Korea and operated for more than 10 years in the domestic railway environment, the performance and maintenance efficiency have been proven compared to the existing welding bogies. As a result, the domestic demand will continue increasing in the future, but it is now dependent on overseas imports. In the long term, it is expected to cause problems such as loss of foreign currency and delay in procurement during maintenance. For this reason, development of the localization of the swing motion bogie system is underway, and it requires accurate performance analysis and validation of operating behavior characteristics because the bogie system is one of the main devices of the railway vehicles. Thus, in this study, we could confirm the suitability of the swing motion bogie system in the domestic operating environment based on the analysis of the operating behavior characteristics, the validation at the laboratory environment, and the operating test on the track.

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Determination of the Gait Stability of the Lower-Limb Exoskeleton Robot Through the Stability Circle: Seung Hoon Hwang, Seung Chan Lee, Dong Bin Shin, Bum Soo Kim, Chang Soo Han; J. Korean Soc. Precis. Eng. 2019;36(6):537-542.
Published online June 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.6.537

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Patients with complete paralysis that only walk with the assistance of exoskeleton robots because they lost their ability to walk. However, robots do not allow the exoskeleton robot to grasp the current state before walking and change the walking pattern. A "Stability Circle Region" was proposed to determine the current state of the exoskeleton robot. The Stability Circle is an area that can determine the possibility of a fall situation before the next walk using the link parameters of the robot and the current center of gravity of the patients. This study verified the validity of "stability circle" by simulating the change in the center of mass. Simulation results can be used to determine the stability of walking depending on whether the position of the center of mass before the walking is included in the circle area.

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Design of Assistive Wearable System for Walking
Seong-Dae Choi, Sang-Hun Lee
Journal of the Korean Society of Manufacturing Process Engineers.2019; 18(12): 111. CrossRef

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Chattering-Free Second Order Sliding Mode Based Finite-Time Control of a Robot Manipulator Considering Uncertainty and Disturbance: Yook Hyun Yoon, Jae Min You, Jahng Hyon Park; J. Korean Soc. Precis. Eng. 2018;35(4):421-426.
Published online April 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.4.421

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This paper presents a finite-time tracking control for a robot manipulator in the presence of a modeling uncertainty and an external disturbance. To solve the large chattering phenomenon that is caused by the high switching gain of the slidingmode control, a novel second-order sliding-mode controller that generates a continuous control input is designed with a robust differentiator. The finite-time stability of the closed-loop system is ensured using a constructive Lyapunov-stability analysis. Finally, a numerical simulation of the 2-Axis Pan-Tilt system is performed to verify the effectiveness of the proposed controller.

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Driving Stability Analysis of Shelter Vehicles Passing by Each Other: Jeongroh Yoon, Donghun Son, Euibong Jeong, Joon Kim, Inkab Jang; J. Korean Soc. Precis. Eng. 2017;34(11):781-787.
Published online November 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.11.781

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Tactical devices and equipment are usually loaded on a trailer vehicle within a shelter system. When the vehicle is moving fast and passing other vehicles, side panels of the shelter are deformed and tilted by pressure waves. Also, the vehicle is subjected to the effects of wind load and centrifugal force with the pressure waves at severe conditions. In this study, a theoretical analysis of overturn calculated by CFD (Computational Fluid Dynamics) and experiments is applied to the vehicle. Deformations of the side panel are measured for experimental validation of the CFD model. As a result, the safety factor of the driving stability of the vehicle is derived by theoretical analysis in the severe situation predicted by the validated CFD model.

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Evaluation of Critical Speed for Active Steering Bogie Prototype: Hyun Moo Hur, Joon-Hyuk Park; J. Korean Soc. Precis. Eng. 2017;34(3):205-210.
Published online March 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.3.205

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Critical speed analysis was conducted for a active steering bogie prototype, developed to improve the curving performance of railway vehicles. The critical speed for the design concept was about 169.2 ㎞/h. To validate the analysis result, we performed a critical speed test for the prototype bogie using a roller-rig tester. The test results showed that the critical speed for the prototype bogie was about 165 ㎞/h. From the analysis and test results, The critical speed for the prototype bogie was determined to be 165 ㎞/h. Considering the maximum operating speed of the test vehicle is 100 ㎞/h, the prototype bogie is considered stable.