• Journal of Welding and Joining
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• v.16 no.1
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• pp.77-87
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• 1998

This paper deals with the effect of laser welding parameters on the weld formation. Thin steels for automotive application were prepared so as to be welded with high power carbon dioxide laser system. Major process parameters were position of focus and travel speed. The effect of shielding gas was also discussed by employing the high speed photometry. Test results showed that the optimal position of focus varied in accordance with the joint configuration; bead-on-plate, butt or lap welding. It was recommended that the position of focus for the lap welding be located at slightly inner part of the material to be welded. In this case, however, it was noticeable that the weld penetration ratio, d/t$_{0}$ dropped drastically at the critical region. Results also demonstrated that both the bead width and penetration reduced as the travel speed increased. The penetration ratio showed two distinct regions; stabilized zone at the lower range of the travel spped and sudden drop zone at the higher range of travel speed. Lower limit of the penetration for acceptable weld was proved to be about 90% of the parent metal thickness based on the physical properties of the weld. Mixed gas application for both the shielding of molten metal and laser induced plasma control was recommended as far as the penetration was concerned.d.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.2063-2081
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• 2018

A resource allocation algorithm is proposed in this paper to simultaneously minimize the total system power consumption and maximize the system throughput for the downlink of multi-user multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. With the Lagrange dual decomposition method, we transform the original problem to its convex dual problem and prove that the duality gap between the two problems is zero, which means the optimal solution of the original problem can be obtained by solving its dual problem. Then, we use convex optimization method to solve the dual problem and utilize bisection method to obtain the optimal dual variable. The numerical results show that the proposed algorithm is superior to traditional single-objective optimization method in both the system throughput and the system energy consumption.

• Journal of Drive and Control
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• v.13 no.2
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• pp.26-33
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• 2016

This paper describes of a mathematical and real experimental analysis for a walking robot which uses servo valve driven hydraulic actuator. Recently, many researchers are developing a walking robot based on hydraulic systems for the difficult and dangerous missions such as walking in the rough terrain and carrying a heavy load. In order to design and control a walking robot, the characteristics of the hydraulic actuators in the joint through the view point of walking such as controllability and backdrivability must be analyzed. A general mathematical model was used for analysis and proceeds to position and pressure changes characteristic of the input and backdrivability experiment. The result shows the actuator is a velocity source, had a high impedance, the output stiffness is high in contact with the rigid external force. So stand above the controller and instruments that complement the design characteristics can be seen the need to apply a hydraulic actuator in walking robot.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3133-3150
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• 2021

This work deals with the validation of a high-fidelity multiphysics system coupling the Serpent 2 Monte Carlo neutron transport code with SUBCHANFLOW, a subchannel thermalhydraulics code, and TRANSURANUS, a fuel-performance analysis code. The results for a full-core pin-by-pin burnup calculation for the ninth operating cycle of the Temelín II VVER-1000 plant, which starts from a fresh core, are presented and assessed using experimental data. A good agreement is found comparing the critical boron concentration and a set of pin-level neutron flux profiles against measurements. In addition, the calculated axial and radial power distributions match closely the values reported by the core monitoring system. To demonstrate the modeling capabilities of the three-code coupling, pin-level neutronic, thermalhydraulic and thermomechanic results are shown as well. These studies are encompassed in the final phase of the EU Horizon 2020 McSAFE project, during which the Serpent-SUBCHANFLOW-TRANSURANUS system was developed.

• Journal of the Korean Institute of Gas
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• v.25 no.4
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• pp.57-62
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• 2021

In this study, risk assessment was conducted in case of leakage of storage facilities (tube trailer) using the HyKoRAM program developed through international joint research. The high-pressure gas facilities in the hydrogen filling station are divided into four main categories: storage facilities (tube trailers), processing facilities (compressors), compressed gas facilities, and filling facilities (dispensers). Among them, the design specifications of the tube trailer, which is a storage facility, and the surrounding environmental conditions were reflected to construct an accident scenario with previously occurring accidents and potential accidents. Through this, we identify the risks of storage facilities at hydrogen refueling stations and suggest measures to improve the safety of hydrogen charging stations.

• Journal of TMJ Balancing Medicine
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• v.10 no.1
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• pp.21-25
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• 2020

Objectives: The aim of this study was to report the effectiveness of TMJ balancing therapy and Traditional Korean Medicine (TKM) treatments on a thalamus cerebral infarction patient with hemiparesis and gait disturbance. Methods: The patient was treated with TMJ balancing therapy, along with korean herbal medicine, acupuncture, moxibustion, cupping and physical therapy. The motor function was evaluated through the Manual Muscle Test (MMT), Grasp power and Functional Ambulatory Category (FAC). And the daily life ability was evaluated by the Korean version of the Modified Barthel Index (K-MBI) and Korean National Institute of Health Stroke Scale (K-NIHSS). Results: After 17 days of TMJ balancing therapy and TKM treatments, the score of MMT did not improved, but the score of FAC, K-MBI, K-NIHSS improved. Conclusions: This study suggested that TMJ balancing therapy and TKM treatments could be effective for hemiparesis and gait disturbance in patients with thalamus cerebral infarction.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.3
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• pp.141-148
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• 2019

Purpose: The present study investigated the effects of 12-week aquatic exercise training on isokinetic muscle function of the shoulder in adolescents with cerebral palsy. Methods: The study included four male and four female adolescents with cerebral palsy. Isokinetic muscle function was measured at an angular velocity of $60^{\circ}/s$, using Biodex System VI Pro. The peak torques of internal rotation and external rotation were measured before and after training. Aquatic exercise training was performed once a day for 120 min, 4 times a week for 12 weeks. Results: The peak torque of external rotation according to body weight and mean power of internal rotation were significantly higher after training (p < 0.05). Conclusion: Our findings suggest that 12-week aquatic training for adolescents with cerebral palsy can improve isokinetic muscle function of the shoulder. Future studies should analyze the changes in isokinetic muscle function of the shoulder in more detail using various aquatic exercise programs to investigate their effects on individuals with cerebral palsy.

• Biomedical Engineering Letters
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• v.8 no.4
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• pp.345-353
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• 2018

This study suggested a new EMG-signal-based evaluation method for knee rehabilitation that provides not only fragmentary information like muscle power but also in-depth information like muscle fatigue in the field of rehabilitation which it has not been applied to. In our experiment, nine healthy subjects performed straight leg raise exercises which are widely performed for knee rehabilitation. During the exercises, we recorded the joint angle of the leg and EMG signals from four prime movers of the leg: rectus femoris (RFM), vastus lateralis, vastus medialis, and biceps femoris (BFLH). We extracted two parameters to estimate muscle fatigue from the EMG signals, the zero-crossing rate (ZCR) and amplitude of muscle tension (AMT) that can quantitatively assess muscle fatigue from EMG signals. We found a decrease in the ZCR for the RFM and the BFLH in the muscle fatigue condition for most of the subjects. Also, we found increases in the AMT for the RFM and the BFLH. Based on the results, we quantitatively confirmed that in the state of muscle fatigue, the ZCR shows a decreasing trend whereas the AMT shows an increasing trend. Our results show that both the ZCR and AMT are useful parameters for characterizing the EMG signals in the muscle fatigue condition. In addition, our proposed methods are expected to be useful for developing a navigation system for knee rehabilitation exercises by evaluating the two parameters in two-dimensional parameter space.

• Journal of the Korean Society of Systems Engineering
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• v.17 no.1
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• pp.53-64
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• 2021

Wargame is a simulated military operation with certain rules, specifications, and procedures, in which soldiers can virtually and indirectly experience the war. The ROK Navy operates the Cheonghae model, a training wargame model for helping commanders and staff master the procedures for conducting the war. It is important for commanders, staff and analysts to know whether a warship can perform its missions and how long it can last during a war. In existing model, the Cheonghae, the probability of kill of a warship is calculated simply considering the number of tonnage without any stochastic elements, and the warship's mission availability is also determined based on predetermined values. With this model, it is difficult to get a value of the probability of kill that makes sense. In this dissertation, the author has developed a probabilistic model in which the warship vulnerability data of ROK-JMEM can be used. A conceptual model and methodology that can evaluate the mission performance of personnel, equipment, and supplies has been proposed. This can be expanded to a comprehensive assessment of wartime warship loss rates by integrating damage rates for personnel, equipment, and supplies in wartime.

• Journal of Information Processing Systems
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• v.17 no.3
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• pp.615-629
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• 2021

With the development of mobile edge computing, how to utilize the computing power of edge computing to effectively and efficiently offload data and to compute offloading is of great research value. This paper studies the computation offloading problem of multi-user and multi-server in mobile edge computing. Firstly, in order to minimize system energy consumption, the problem is modeled by considering the joint optimization of the offloading strategy and the wireless and computing resource allocation in a multi-user and multi-server scenario. Additionally, this paper explores the computation offloading scheme to optimize the overall cost. As the centralized optimization method is an NP problem, the game method is used to achieve effective computation offloading in a distributed manner. The decision problem of distributed computation offloading between the mobile equipment is modeled as a multi-user computation offloading game. There is a Nash equilibrium in this game, and it can be achieved by a limited number of iterations. Then, we propose a distributed computation offloading algorithm, which first calculates offloading weights, and then distributedly iterates by the time slot to update the computation offloading decision. Finally, the algorithm is verified by simulation experiments. Simulation results show that our proposed algorithm can achieve the balance by a limited number of iterations. At the same time, the algorithm outperforms several other advanced computation offloading algorithms in terms of the number of users and overall overheads for beneficial decision-making.