• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.300-309
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• 2012

Long endurance is a key issue in the application of unmanned aerial vehicles. This study presents feasibility test results when fuel cell system as an alternative to the conventional engine is applied for the power of the UAV after the 150W fuel cell system is developed and packaged to the 1/4 scale super cub airplane. Fuel cell system is operated by dead-end method in the anode part and periodically purged to remove the water droplet in flow field during the operation. Oxygen in the air is supplied to the stack by the two air blowers. And fuel cell stack is water cooled by cooling circuit to dissipate the heat generated during the fuel cell operation. Weight balance is considered to integrate the stack and balance of plant (BOP) in package layout. In flight performance test, we demonstrated 4 times standalone take-off and landing. In the laboratory test simulating the flight condition to quantify the energy flow, the system is analyzed in detail. Sankey diagram shows that electric efficiency of the fuel cell system is 39.2%, heat loss 50.1%, parasitic loss 8.96%, and unreacted purged gas 1.67%, respectively compared to the total hydrogen input energy. Feasibility test results show that fuel cell system is high efficient and appropriate for the power of UAV.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.12 no.1
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• pp.53-62
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• 2018

In this study, we developed a smart 1RM system for national health management and physical fitness, which enables quantitative 1RM measurement in various types of exercise using digital pulley technology, and to test the effect on training by using it. We developed the smart 1RM system, which is composed of portable muscle strength measuring device, Bluetooth communication based mobile phone data transmission and circuit diagram, and height adjustable system body. We recruited the 30 participants with 20th aged and divided into training and non-performing groups with 15 participants randomly. The participants performed 5 sets of elbow, lumbar, knee extension / flexion 10 times using smart 1RM system and the experimental period was 3 days a week for a total of 8 weeks. The experimental results showed that the maximum strength of the elbow, lumbar, and knee joints was significantly improved before and after maximal muscle strength training in the training group. Oxygen intakes during 1RM exercise mode showed 10.91% than endurance. To verify the validity of the smart 1RM maximal strength data, the reliability was 0.895 (* p <0.00). This study can be applied to the early rehabilitation treatment of the elderly and rehabilitation patients more quantitatively using the national health care.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.913-920
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• 2011

We describe the evaluation of the fatigue life and strength of a lightweight railway bogie frame made of glass fiber/epoxy 4-harness satin-woven composites. To obtain the S-N curve for the evaluation of the fatigue characteristics of the composite bogie frame, we performed a tension-compression fatigue test for composite specimens with different stacking sequences of the warp direction, fill direction, and $0^{\circ}/90^^{\circ}$ direction. We used a stress ratio (R) of -1, a frequency of 5 Hz, and an endurance limit of $10^7$. The fatigue strength of the composite bogie frame was evaluated by a Goodman diagram according to JIS E 4207. The results show that the fatigue life and strength of the lightweight composite bogie satisfy the requirements of JIS E 4207. Given its weight, its performance was better than that of a conventional metal bogie frame based on an SM490A steel material.