• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.79-88
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• 2019

Objective: The aim of this study was to determine the peak torques of the knee and ankle joint and local stability of the lower extremity's joints, and muscle activation patterns of the lower extremity's muscles between fallers and non-fallers in the elderly women during walking. Method: Four elderly women (age: $74.5{\pm}5.2yrs.$; height: $152.1{\pm}5.6cm$; mass: $55.3{\pm}5.4kg$; preference walking speed: $1.19{\pm}0.06m/s$) who experienced falls within six months since experiment had been conducted (falls group) and thirty-six subjects ($74.2{\pm}3.09yrs.$; height: $153.6{\pm}4.9cm$; mass: $56.7{\pm}6.4kg$; preference walking speed: $1.24{\pm}0.10m/s$) who had no experience in falls (non-falls group) within this periods participated in this study. They were measured torque peaks of the knee and ankle joint using a Human Norm and while they were walking on a treadmill at their natural pace, kinematic variables and EMG signals were collected with using a 3-D motion capture system and a wireless EMG system, respectively. Lyapunov Exponent (LyE) was determined to observe the dynamic local stability of the lower extremity's joints, and muscles activation and their co-contraction index were also analysed from EMG signals. Hypotheses between falls and non-falls group were tested using paired t-test and Mann-Whitey. Level of significance was set at p<.05. Results: Local dynamic stability in the adduction-abduction movement of the knee joint was significantly lower in falling group than non-falling group (p<.05). Conclusion: In conclusion, muscles which act on the abduction-adduction movement of the knee joint need to be strengthened to prevent from potential falls during walking. However, a small number of samples for fallers make it difficult to generalize the results of this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.170-177
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• 2020

This study examined the clamping force control method and the braking performance test results of an electromechanical brake (EMB) using braking test equipment. Most of the studies related to EMBs have been carried out in the automotive field, dealing mainly with the static test results for various control methods. On the other hand, this study performed a dynamic performance evaluation. The three-phase interior permanent magnet synchronous motor (IPMSM) was applied to drive the actuator of the EMB, and the analysis was verified by JMAG(Ver. 18.0), which is finite element method (FEM) software. The current control, speed control, and position control were used for clamping force control of the EMB, and the maximum torque per ampere (MTPA) control was applied to the current controller for efficient control. The EMB's emergency braking deceleration performance was tested in the same way as conventional pneumatic brake systems when the wheel of a train rotates at 110 km/h, 230 km/h, and 300 km/h. The emergency braking time, with the wheel stopped completely at the maximum rotational speed, was approximately 73 seconds. The similarity of the braking time and deceleration pattern was verified through a comparison with the performance test results of the pneumatic brake system applied to the next generation high-speed railway vehicle (HEMU-430X).

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.503-518
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• 2003

Statement of problem : There have been previous studies about considerable variations in machining accuracy and consistency in the implant-abutment-screw interfaces. Purpose : The purpose of this study was to evaluate the machining accuracy and consistency of implant/abutment/screw combinations on two randomly selected implants from each of four manufactures. Material and methods : In this study, screws were respectively used to secure a cemented abutment, to a hexlock implant fixture ; teflon coated titanium alloy screw(Torq-Tite) and titanium alloy screw in Steri--Oss system, gold-plated gold-palladium alloy screw(Gold-Tite) and titanium alloy screw in 3i system gild screw ana titanium screw in AVANA Dental Implant system, and titanium screws in Paragon System. The implants were perpendicularly mounted in polymethyl methacrylate autopolymerizing acrylic resin block(Orthodontic resin, Densply International Inc. USA) by use of dental surveyer. Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10 minutes. All samples were cross sectioned with grinder-polisher unit(Omnilap 2000 SBT Inc) after embeded in liquid unsaturated polyester (Epovia, Cray Valley Inc) Results : There were the largest gaps in the neck areas of screws in hexagonal extension implants which were examined in this study. The leading edge of the abutment screw thread (superior surface) was in contact with the implant body thread, and the majority of the contacting surfaces were localized to the middle portion of the mating threads. Considerable variation in the contacting surfaces was noted in the samples evaluated. Amounts of contact in the abutment screw thread were larger for assemblies with Gold-Tite screw, gold alloy screw. Torq-Tite screw than those with titanium screws. The findings of intimate contact between the screw and screw seat were seen in all samples, regardless of manufacturers. However, microgap between the head and lateral neck surface of the screw and the abutment could be dectected in all samples. The findings of intimate contact between the platform of the implant and the bottom of the abutment were consistent in all samples, regardless of manufacturers. However, microgaps between the lateral surface of external hex of the fixture and the abutment could be dectected in all samples. Conclusion : Considerable variations in machining accuracy and consistency were noted in the samples and the implant-abutment-screw interfaces were incomplete. From the results of this study, further development of the system will be required, including improvements in pattern design.

• Journal of Biomedical Engineering Research
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• v.24 no.6 s.81
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• pp.523-531
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• 2003

We developed a PC-based 8-channel electrical stimulation system for transcutaneous functional electrical stimulation (FES), and applied it to FES exercise and paraplegic walking. The PC program consists of four parts: a database, a stimulation pattern generator, a stimulus parameter converter, and an exercise program. The stimulation pattern can be arbitrarily generated and edited by using the mouse on the PC screen, and the resulting stimulus parameters arc extracted from the recruitment curves, and transmitted to the 8-channel stimulator through the serial port. The stimulator has nine microprocessors: one master and eight slaves, Each channel is controlled by the slave microprocessor, and is operated independently. Clinical application of the system to a paraplegic patient showed significant increase in the knee extensor torque, the fatigue resistance, and the leg circumference, The patient can now walk about 50 meters for more than 2 minutes.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2357-2364
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• 2011

Diesel locomotive operates the generator with the power from the diesel engine, and it consists of the typical serial-hybrid system which operates the train wheels by converting its generated electric energy into the torque of DC (or AC) motor. However, the technology of locomotives is only focused on trains' controlling power generation mechanism. Hence, it is a current issue that the efficiency of its engine and its generator is relatively lower than that of auto vehicles'. Particularly, since there are no proper equipment to measure the amount of fuel which is essentially necessary for the efficient use of fuel, it is not easy to confirm the instant amount of fuel use as well as the exact average fuel consumption per an hour. Due to those difficulties, it is urgent to develop the device that measures the fuel consumption. Plus, this use of the developed measuring device allows the various and useful analysis relating to the fuel consumption, and this could lead to establishing the efficient driving pattern regarding to fuel saving. This device consists of two flux (fuel level) measuring censors, MCU for calculating the measured values, the information recorder for saving measured values, and the display device for indicating the fuel amount consumed during driving.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.184-189
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• 2006

Tumble flow test rig has been used as the useful tool in the developing intake system because major flow pattern induced by intake port of DOHC engine is tumble. Angular momentum of in-cylinder tumble flow can not be directly measured by impulse torque meter in the test rig like that of in-cylinder swirl flow due to rotational axis of the flow. Therefore the adaptor to transform tumble to swirl flow must be adapted in the test rig. In this study, using the commercial CFD code STAR-CD, we studied the effects on measured results due to the variation of the major design variables in the adaptor, tube length(L), tube diameter(D) and cylinder height(H). The effect of the attached angle($\theta$) of the test head to the adaptor also was simulated.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.238-243
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• 2013

This paper analyzes a virtual work of the knee and hip joints of bipedal walking robots. For the purpose, we consider a model of bipedal leg mechanism with a compliant foot and a typical walking pattern. We also check the torque characteristics at the joint space propagated from the space of the foot contacting a flat and stiff surface, and present the works accumulated at the joint space. As a result, it is shown that this analysis is useful for evaluating the fatigue of the leg mechanism by the physical walking contact between the foot and the surface, and it is applicable for improving the compliant characteristics at the foot space by employing a proper footgear.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1021-1024
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• 2001

Out of all metal-cutting processes, the hole-making process is the most widely used. It is estimated to be more than 30% of the total metal-cutting process. It is therefore desirable to monitor and detect drill wear during the hole-drilling process. In this paper, the vision system of the sensing methods of drill flank wear on the basis of image processing is used to detect the wear pattern by non-contact and direct method and get the reliable wear information about drill. In image processing of acquired image, median filter is applied for noise removal. The vision flank wear area of the drill was measured. Backpropagation neural networks (BPns) were used for no-line detection of drill wear. The neural network consisted of three layers: input, hidden and output. The input vectors comprised of spindle rotational speed, feed rates, vision flank wear, thrust and torque signals. The output was the drill wear state which was either usable or failure. Drilling experiments with various spindle rotational speed and feed rates were carried out. The learning process was peformed effectively by utilizing backpropagation. The detection of the abnormal states using BPNs achieved 96.4% reliability even when the spindle rotational speed and feedrate were changed.

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.93-101
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• 2015

This paper provides numerical results of the simulation for the flow around the hull and the propeller of KCS model ship advancing in shallow water conditions. A finite volume method is used to solve the unsteady Reynolds averaged Navier-Stokes(RANS) equations, where the wave-making problem is solved by using a volume-of-fluid(VOF) method. The wave formed near the hull surface in shallow water conditions shows a deep trough dominant pattern that causes the loss of buoyancy followed by hull squat. The flow past the hull increases as the depth of water decreases. However, the axial flow velocity around the stern shows a reduction in magnitude by the effect of shallow water accompanied by the hull-propeller interaction. As a results, the thrust and torque coefficient increase about 8.3% and 6.2%, respectively for a depth of h/T=3.0 corresponding to a depth Froude number of $F_h=0.693$. The resistance coefficient increases about 11.6% at this Froude number condition.

• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.20-28
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• 2008

Recently, butterfly valves are used as control valves for industrial process. However, there are not so many reports on cryogenic butterfly valves in spite of broad application in LNG storage station and LNG carriers. Present study is focused on the investigation of the detailed hydrodynamic and aerodynamic characteristics of cryogenic butterfly valves to contribute to the operation during the handling on LNG transportation system, and to the practical utilization in design of butterfly valves and actuators. The results show that large recirculation vortices in the region downstream of the valve are founded and the cavitation flows are intensively generated on the surface of valve disc at the relatively small opening angle. The aerodynamic characteristics, lift, drag and torque, acting on the valve disc are calculated. The pressure distribution and the pressure loss coefficient of the cryogenic butterfly valve show almost similar pattern with those of the butterfly valve which is used on the normal temperature.