Deaf people use their own national sign or finger languages for communication. They have a lot of inconvenience in both social and financial problems. In this study, a finger language recognition system using an ensemble machine learning algorithm with an armband sensor of 8 channel surface electromyography (sEMG) is introduced. The algorithm consisted of signal acquisition, digital filtering, feature vector extraction, and an ensemble classifier based on artificial neural network (EANN). It was evaluated with Korean finger language (14 consonants, 17 vowels and 7 numbers) in 20 normal subjects. EANN was categorized with the number of classifiers (1 to 10) and the size of training data (50 to 1500). Mean accuracies and standard deviations for each structure were then obtained. Results showed that, as the number of classifiers (1 to 8) and the size of training data (50 to 300) were increased, the average accuracy of the E-ANN classifier was increased while the standard deviation was decreased. Statistical analysis showed that the optimal E-ANN structure was composed with 8 classifiers and 300 training data. This study suggested that E-ANN was more accurate than the general ANN for sign/finger language recognition.
In soccer, sports science aims to prevent injuries and improve performance by biomechanically analyzing a series of the kick processes. In order to understand the kick processes biomechanically, studies on kinematic, kinetic, and EMG have been conducted. However, these studies have limitations due to absence of integrated theory defining interactions between the segments. In the present work, we propose a model to understand dynamic characteristics of the kicking leg based on the biomechanical features of the instep kick. Five healthy men participated in an experiment to perform four-level instep kick. We collected kinematic and kinetic information of the hip and knee joints. Based on the passive dominance of the knee joint, we devised the knee joint torque model proportional to angle and angular velocity. RMSE between simulated and real torque was 4.17%, and exhibited a tendency to decrease linearly with the kick speed. Henceforth, it is apparent that the faster the kick, the greater the load on the hip; and the slower the kick, the greater the load on the knee joint. We anticipate that this model will be applied to the kick monitoring equipment and for the prevention of injuries by measuring the load.
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Ablation Behavior of ZrB2-SiC UHTC Composite under Various Flame Angle Using Oxy-Acetylene Torch Seung Yong Lee, Jung Hoon Kong, Jung Hwan Song, Young Il Son, Do Kyung Kim Korean Journal of Materials Research.2022; 32(12): 553. CrossRef
Recently, a Total Ankle Arthroplasty (TAA) has been commonly used when no other options are available for patients with severe arthritis at the ankle joint. But bone resorption, aseptic loosening, instability, malalignment and fractures are generally known as the main reasons of TAA failures. Those TAA which have been designed up until now are generally based on the morphological and kinesiological characteristics of the ankle joint. They are adjusted by the ankle joint size of Westerners, although both the morphological and mechanical (strength) characteristics of the ankle joints of Asian are important in the development of a TAA suitable to Asians. Little information about the morphological and mechanical characteristics of the ankle joint of Asians is available for the development of a TAA suitable to Asians. The purpose of this study was, therefore, to analyze the morphological and mechanical characteristics of the ankle joints of Asians. Computed tomography data obtained from 50 patients (mean age: 64.14 ± 9.34 years) were analyzed.
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Evaluating the validity of lightweight talar replacement designs: rational models and topologically optimized models Yeokyung Kang, Seongjin Kim, Jungsung Kim, Jin Woo Lee, Jong-Chul Park Biomaterials Research.2022;[Epub] CrossRef
The purpose of this study was to examine the effect of gender and foot landing type (forefoot vs. rearfoot landing) on kinematics, kinetics, and energy absorption of lower extremity joint. Twenty males and twenty females performed single-leg landing with two different foot landing types: forefoot landing and rearfoot landing. Three-dimensional kinematic and kinetic parameters were measured using motion capture system. Greater knee valgus angle at peak vertical ground reaction force (p = 0.034) during rearfoot landing increased the risk of anterior cruciate ligament (ACL) injury in females as increasing valgus positioning from neutral alignment could increase the load on ACL. Greater contribution of ankle joint and less contribution of hip joint in energy dissipation were found in females during both forefoot (p = 0.029 and p = 0.016, respectively) and rearfoot landing (p = 0.003 and p = 0.016, respectively). These results suggest that increasing muscular activity of ankle plantarflexor could reduce shock transmission to the proximal joint in females. In addition, greater hip joint’s contribution to total negative work in males induced lower hip flexion angle found in both forefoot and rearfoot landing by elevated activation of the hip extensor. In conclusion, landing strategy differs between genders in both forefoot and rearfoot landing.
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Predicting Three-Dimensional Gait Parameters with a Single Camera Video Sequence Jungbin Lee, Cong-Bo Phan, Seungbum Koo International Journal of Precision Engineering and Manufacturing.2018; 19(5): 753. CrossRef
Gait analysis is the best objective measurement tool for monitoring rehabilitation. However, it has limitations to evaluate gait recovery. Previous studies have evaluated the effect of gait training using continuous relative phase. The objective of this study was to determine the effect of gait recovery by rehabilitation gait training on lower limb coordination. We analyzed spatio-temporal parameters and CRP values of hip and knee joints based on gait analysis data obtained by 3D motion analysis system at 15 days intervals in 24 uni-lateral transfemoral amputees participated in IRP. Our results revealed that walking velocity of uni-lateral transfemoral amputees who participated in the program during a mean of 107.1 days was 49.2% faster than that at initial stage. The walking velocity showed a 46% increase at the end of 30 days after training. In gait coordination, values of CRP-RMS and CRP-SD were increased and maintained in-phase pattern. CRP showed symmetry in both limbs at the end of 90 days after training. Therefore, CRP is a significant factor in the gait recovery process. Effects of various rehabilitation training methods can be determined through CRP analysis.
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Changes in Gait Characteristics after Completion of Prosthetic Gait Training in Patients with Unilateral Transfemoral Amputation: Follow-Up after 1 Year Bo Ra Jeong, Gyoo Suk Kim, Yun Hee Chang Journal of the Korean Society for Precision Engineering.2022; 39(11): 849. CrossRef
The purpose of this study was to analyze dynamic postural balance against tilting perturbation in the young and the elderly. Twenty-eight young subjects and 22 elderly subjects participated in this study. Subjects performed dynamic balance test on a force plate during tilting perturbations (tilt-up and tilt-down). As outcome measures, peak distance and velocity were calculated from center of pressure (COP). Two-way ANOVA were performed for the outcome measures with the independent factors of age and gender. COP peak distance of the elderly was significantly greater than that of the young (p < 0.05). Velocity of COP showed age difference (p < 0.001) and also interaction effects only in tilt-up perturbation (p < 0.05). Especially, age-related difference existed in only women (p < 0.001). The age-related changing of women in the dynamic balance may be related to the greater fall rate of elderly women.
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Enhancing tool longevity through TiN coating in multistage cold forging: implementation and analysis using Archard’s wear theory and FEA V. P. Kulkarni, S. M. Kulkarni, S. B. Patil, Aseem Anshul International Journal on Interactive Design and Manufacturing (IJIDeM).2025; 19(12): 8773. CrossRef
Predicting Three-Dimensional Gait Parameters with a Single Camera Video Sequence Jungbin Lee, Cong-Bo Phan, Seungbum Koo International Journal of Precision Engineering and Manufacturing.2018; 19(5): 753. CrossRef
The purpose of this study was to develop and verify the smart insole based FSR sensor for measurement and improvement of the muscle strength imbalance. We recruited 15 subjects with muscle strength difference over 20% and 15 subjects with muscle strength balance below 10%. We developed the human body load insole and integrated modules using FSR sensor. Subjects walked for 5 minutes at a slope of 0% and a speed of 3 km / h on a treadmill with a smart insole. We measured the real-time muscle activity and foot pressure according to the muscle strength imbalance during gait. FSR data of the developed smart insole showed that the insole had similar accuracy and efficacy as muscle activity and foot pressure. This is the interval in which the muscle imbalance shifts from the stance phase to the load reaction, and the weight support is the largest, and the center of gravity of the human body passes over the whole foot, which is considered to cause the greatest imbalance. This suggests that there is a direct or indirect correlation between muscle strength imbalance of the lower limb and the imbalance of the body weight distribution during gait.
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Design and manufacturing of a smart insole Seung Joo Lee, Chae Young Park, In Hwan Lee Sensors and Actuators A: Physical.2026; 397: 117225. CrossRef
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STUDY ON VISION-BASED MULTIDIRECTIONAL POSTURE AND MOTION ANALYSIS SYSTEM DEVELOPMENT WOO SUK CHONG, MI YEON SHIN, CHANG HO YU Journal of Mechanics in Medicine and Biology.2019; 19(08): 1940059. CrossRef
In laser polishing, a laser beam is used to melt the surface of a work piece to improve surface quality. An optimum combination of process controlling parameters and state of laser beam output is the key strength of laser polishing. Laser beam output power, feed rate, path interval, and spot size are critical parameters in the laser polishing process effect on the thermal state of surface quality. In this study, experimental tests demonstrate that it is an optimum value of the proper processes condition in the pulse laser and CW laser system. The proposed dominant controlling parameters, method for examining morphology; several experimental conditions; and details from performance improvement of surface roughness are presented.
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Effect of laser remelting on the surface characteristics of 316L stainless steel fabricated via directed energy deposition Seung Yeong Cho, Gwang Yong Shin, Do Sik Shim Journal of Materials Research and Technology.2021; 15: 5814. CrossRef
In mobile phone cameras, usually a voice coil motor (VCM) is used as a micro-positioning device for the image autofocus (AF) because of its low cost, simplicity, and reliability. Measuring the actual displacement of the VCM is important when we assemble the camera and test the AF performance for distant objects. In this paper, we propose using a confocal displacement sensor for calibrating the VCM displacement, where the axial chromatic aberration of a confocal objective lens is used to measure the target position. The tolerance angle for the dynamic tilt of a VCM increased up to ±15o because of the large numerical aperture of the confocal objective lens, which increased the stability of the repeatable in-line inspection. We compared the measurement robustness of the confocal displacement sensor with that of the laser displacement sensor in a mass production line to verify its performance superiority.
Three-axis magnetometers are widely used in various fields requiring azimuth information. However, accuracy of azimuth estimation based on magnetometer signals may be degraded because of errors such as offset, scale factor, nonorthogonality, hard-iron distortion, and soft-iron distortion. Recently, several ellipsoid-fitting calibration techniques have been proposed and have received much attention. However, comparative analysis of calibration accuracies between these techniques has not been conducted. This study compared and analyzed performance of four ellipsoid-fitting magnetometer calibration techniques such as the linear least square method, the two-step algorithm, and two different nonlinear least square methods. Our analysis and experimental results reveal superiority of the linear least square method compared to other methods in terms of calibration accuracy as well as ease of use in practice.
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Real-time estimation of roll angles by magnetometer based on two-step adaptive Kalman filter Xiaofen Dong, Guoguang Chen, Xiaoli Tian, Xiaolong Yan Measurement.2022; 198: 111349. CrossRef
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The parallel slider system can be configured as a parallel robot by combining with other link devices. Therefore, the degree of positioning of the parallel slider would have considerable influence on the smooth operation of the parallel robot. In order to examine the degree of positioning of each slider, the following trajectory is equally presented, and the possibility of tracking the slider trajectory examined by application of the PD and PND control. From the experimental results, the dynamic characteristics of the slider show different responses to differing equivalent frictional forces acting on the slider. The PND control can make the rise time shorter than the PD control, and the PND control and PD control can smoothly follow the same trajectory given to each slider. It is therefore anticipated that the PND control and the PD control could be successfully implemented to follow the trajectory of a parallel robot based on a parallel slider system. It would then be necessary to fabricate slider experimental equipment capable of generating torque of sufficient magnitude to successfully reduce the trajectory error of the slider.
Complex parts are manufactured with high production rates using plastic injection. Defects in injection moulded parts are typically caused by non-uniform cooling. The design of cooling channels is a key step in the mould tool design process. Laser sintering allows for the direct fabrication at reasonable price, complex 3D tools with integrated cooling channels without the need of fixtures. This technique allows the designer to optimise the position of cooling channels relative to the heat source. This paper presents a simulation study for a non-constant thickness threaded screw cap. Results comparing conventional to conformal cooling channel show that the range between the highest and the lowest part surface temperatures is reduced by 18.8%. On the other hand, there is only a decrease of 3.9% for the maximum temperature in the interior of the threaded screw cap. Conformal cooling using laser sintering in tool manufacturing achieves an improved heat transfer leading to a better part quality.
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The Impact of Surface Roughness on Conformal Cooling Channels for Injection Molding Jan Hanzlik, Jiri Vanek, Vladimir Pata, Vojtech Senkerik, Martina Polaskova, Jan Kruzelak, Martin Bednarik Materials.2024; 17(11): 2477. CrossRef
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A comprehensive review of injection mold cooling by using conformal cooling channels and thermally enhanced molds Samaneh Arman, Ismail Lazoglu The International Journal of Advanced Manufacturing Technology.2023; 127(5-6): 2035. CrossRef
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The goal of this study is to develop a fast, controllable PZT-driven depth adjustment device with a flexure hinge. The device can be used to trace rapidly a flat or curved surface with several hundreds of micrometers’ variance in height. The lever type flexure hinge designed for a magnification ratio of 10 and no other axes motion has been confirmed through FEM analysis; the actual performance has been verified through static/dynamic experiments. A micro-depth control system, which is comprised of a DAQ with a LabVIEW, PZT amplifier, PZT actuator, flexure hinge, and laser displacement sensor, is implemented, and its static/dynamic characteristics of depth control is investigated with a PID gain tuned control algorithm on LabVIEW. It has been verified that the developed device can trace a micro-depth command as fast as 0.5 s to get an accurate position of 0.1 μm, even under a load of 1 N.
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Optimal Design of a Multi-Layer Lever Type Flexure Hinge for High Magnification Cui Xun, Hwa Young Kim, Jung Hwan Ahn Journal of the Korean Society for Precision Engineering.2018; 35(12): 1191. CrossRef
In this study, we propose a fabrication method of three-dimensional complex shape polydimethylsiloxane microstencils. Three-dimensional complex shape polydimethylsiloxane (PDMS) microstencils were fabricated by an air-knife system and PDMS casting form preparing master mold by photolithography, diffuser lithography and polyurethane acrylate (PUA) replication. PDMS microstencils shape was a production of the hemispherical and quadrangular pyramid. When the prepolymer of PDMS was spin-coated onto the three-dimensional complex shape master mold, a thin layer of prepolymer remained on top of the master"s structure and consequently prevented formation of perforated patterns. This residual layer was easily removed by the air-knife. The air-knife system was controlled by the flow rate of N2 gas and conveying speed of the master mold. Results revealed the fabricated three-dimensional complex shape PDMS microstencils, could be useful for application of three-dimensional cell culture device.
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Review on Microstencil Lithography Technologies Jin Ho Choi, Hye Jin Choi, Gyu Man Kim Journal of the Korean Society for Precision Engineering.2018; 35(11): 1043. CrossRef
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