In this study, a four-axis platform capable of rolling, pitch, and yaw rotation was created for rehabilitation and exercise. Based on this, a virtual coach and a virtual reality game system were developed. The virtual coach is a 3D person model created with the Unity program that allows the user to exercise in the correct posture with the virtual coach, and recognizes the correct posture with the Kinect. Additionally, a virtual reality game has been developed, and in conjunction with this, the actual platform also moves to increase the rehabilitation effect. The upper body and lower body movement and plantar pressure measurement were used to associate with the four-axis platform to maintain strength and balance the body.
Free fall safety brakes against accidental cable failure such as in elevators may require friction, wedging action, eddy current, and other effects. An ideal safety brake system should be quick in its deployment with sufficient payload capacity in compact dimensions. In this study, a safety braking system with a quick deployment mechanism is proposed. The mechanism housed in a carrier is suspended by the cable and connected to the payload. At the onset of cable failure, a linkage system is driven by a pre-loaded spring to drive terminal cutting tools tips against the sacrificial braking pads on each side of the vertical track. Experiments showed that large braking force may be achieved by a compact mechanism. Several design issues of linkage deployment, braking force control, and drop dynamics are discussed.
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
In recent years, many soft wearable robots have been developed to overcome the limitations of conventional rigid wearable robots. Among the types of soft robots, soft pneumatic actuators (SPA) have been developed because of compliant characteristics that can guarantee safe human-robot interaction to improve one of the rigid wearable robot limitations. Especially, among various SPAs, inflatable actuators have been developed because they can be easily manufactured with various types of structures. However, the theoretical modelings proposed in the inflatable actuators are specific to apply to other joints, because their purpose is performance analysis. In this paper, we improve the theoretical modeling for the design of wrinkled inflatable actuators. The actuator’s design parameters such as height and number of layers were determined by the proposed theoretical model to provide the target torque. The soft actuator was manufactured with determined design parameters and then measure the torque for the various angles and pressures. The theoretical torque values acquired through the proposed theoretical model have an error of < 8% from the experimental torque values and showed higher accuracy than the previously proposed model.
This paper describes a new design method for constructing a heat exchanger computational model comprising TPMS (Triply Periodic Minimal Surface) core structures. These TPMS-Based core structures cannot be designed using the existing CAD systems, especially for heat exchangers with a high level of geometric complexity. This paper introduces a new implicit design algorithm based on the VDF (Volumetric Distance Field) calculation. All geometric components, including the TPMS-based core structures, heat exchanger exterior shapes, a set of parts for inlets and outlets, are represented by the VDF in a given design area. This enables the efficient design of computational models for the arbitrary-complex heat exchangers. The proposed design method extends the 2D flow pattern of the existing CHE into the 3D flow pattern, providing high heat transfer efficiency and low-pressure drop. Investigation of the design results and manufactured prototypes using the AM (Additive Manufacturing) technology showed that the proposed TPMS CHE design method can open a new paradigm for generating high-performance next-generation CHEs which cannot be designed and manufactured with the existing CAD and CAM technologies.
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A Study on Design and Fabrication Characteristics of TPMS Structures Hyun Kim, Kwang-Kyu Lee, Dong-Gyu Ahn Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(2): 52. CrossRef
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This research is to investigate the augmentation of cooling performance of water-cooling in the electric vehicle secondary battery. The research focused on the numerical study of heat transfer coefficients for cooling performance augmentation. To improve the water-cooling performance with three different inlet sections of water-cooling and five different mass flow rates, air-cooling, and water-cooling were compared. To compare the water-cooling performance, selected local positions for various temperature distributions were marked on the battery cell surface. The normalized local Nusselt number of the cooling area at the normalized height position indicated that the heat transfer coefficient of the combined section was averaging at 77.95 and 58.33% higher than that of the circle and square, respectively. The heat transfer coefficient with the normalized width by water-cooling at combined section was averaging at 5.15 times higher than that of the air-cooling. At the normalized height, the cooling performance at the water flow rates of 10 Lpm was averaging at 68-74% higher than that of 5 Lpm and 35-39% lower than that of 25 Lpm. Ultimately, the best cooling performance existed with the combined section, and the water flow rate of 10 Lpm was most appropriate, given the temperature difference and power consumption.
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This study is to investigate the cooling performance of the battery in the electric vehicle depending on the attachment of the cooling plates and materials to the battery cells. Research focused on the numerical comparison of forced convective heat transfer coefficients with case 1(cell-Al, cooling plate-None), case 2(cell-Al, cooling plate-Al), case 3(cell-Al, cooling plate-C), and case 4(cell-C, cooling plate-Al). Normalized local Nusselt number of the cooling area at the normalized width position indicated that the heat transfer coefficient of the case 1 was averaging at 7, 14.5, 11.9% lower than that of case 2, case 3, and case 4. Based on case 3, the cooling performance with six different types of mass flow rates (0.05, 0.075, 0.0875, 0.1, 0.125, 0.15 kg/s) were compared. Normalized local Nusselt number at the normalized width position indicated that the heat transfer coefficient of 0.0875 kg/s was averaging at 35.8, 11.9% higher than that of 0.05, 0.075 kg/s and 12.3, 36.4, 60% lower than that of 0.1, 0.125, 0.15 kg/s. Ultimately, the best optimization design for air-cooling performance was case 3 with mass flow rate of 0.125 kg/s.
In the case of dynamic sports activities such as skiing and sprints, it is difficult to apply optical motion capture systems because of measurement volume limitation. Alternatively, the use of inertial measurement unit (IMU) as a motion sensor has gained attention. This paper proposes a drift reduction method in the IMU-based joint angle estimation for dynamic motion-involved sports applications. To resolve the problem of conventional IMU-based methods significantly reducing performance under highly dynamic conditions, the proposed method applies a correction method using joint constraint. The proposed method is the complementary filter based on the previous drift reduction technique using the joint constraint, but performs in real time. The proposed method was validated by comparing the estimation accuracy with conventional methods under various dynamic conditions. The results showed that the proposed method was superior to the methods that did not use the constraint. While the proposed method was 0.19° less accurate than the non-realtime method of the reference, it is more practical due to its realtime correction capability.
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Motion capture and evaluation system of football special teaching in colleges and universities based on deep learning Xiaohui Yin, C. Chandru Vignesh, Thanjai Vadivel International Journal of System Assurance Engineering and Management.2022; 13(6): 3092. CrossRef
This study reports on the feasibility of applying polymer electrolyte membrane fuel cells (PEMFCs) system to an energy storage system (ESS). We modeled each constituting system to compute the overall efficiency of the ESS. As a result, it was verified that the power plants’ electric powering capability can be curtailed. The amount of reduction is equal to that of 2nd Gori Nuclear Power Plant currently under construction. We calculated that approximately 320.85 L/day · MW of hydrogen is produced on a national scale. Also, Seoul’s demand output power of PEMFC and the requisite area of sites to install the PEMFC system are approximately 236 MW and 59059 m² respectively. This study can contribute to preventing the upsurge of the entire electric powering installed capability. Based on the present technology level, this study diagnoses the use of hydrogen-based ESS which will be introduced in the upcoming hydrogen economy period. Considering the water electrolysis by polymer electrolyte membrane water electrolyzers are currently at the beginning of commercialization and the energy density per mass of hydrogen is exceedingly high, we anticipate that the future of hydrogen base ESS’ effectiveness will reach greater levels than the analysis of this study.
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Al₂O₃ catalysts, used for the hydrolysis of perfluorinated compounds (PFCs), have a limitation in that their lifetime is abruptly lowered by the generation of hydrogen fluoride (HF) during the reaction. In the PFCs hydrolysis plants, increasing replacement cycles is one of the major challenges in reducing maintenance costs. In this study, the Ca(OH)₂ layer, which decomposes the HF, was inserted between the Co-Zr/Al₂O₃ catalyst layers to increase the catalyst replacement cycle during the CF4 gas decomposition at 750℃. As a result, the decomposition rate was rapidly recovered through the replacement of the adsorbent, and the time to maintain a decomposition rate more than 90% improved by more than eight times compared to the bare catalyst layer without adsorbent.
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