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Changwon, South Korea

Xuan Z.,Konkuk University | Jin T.,Konkuk University | Ha N.S.,Konkuk University | Goo N.S.,Konkuk University | And 4 more authors.
Journal of Intelligent Material Systems and Structures | Year: 2014

Piezoelectric-hydraulic actuator is a hybrid device that consists of a hydraulic pump driven by piezoelectric stacks coupled with a conventional hydraulic cylinder and a set of fast-acting valves. Nowadays, such hybrid actuators are being researched and developed actively in many developed countries by requirement of high performance and compact flight system. In this research, operation principle and performance testing of the hybrid actuator were introduced. Two types of piezo-stacks are selected for experimental performance testing to identify the factors of piezo-stack which affect the performance of the hybrid actuator. The performance of piezo-stacks due to electrical power supply and self-heating was considered. Output no-load velocities and blocked force were measured on performance testing. The results showed that the maximum blocked force was 346 N and no-load velocity was 101 mm/s, resulting in maximum output power of 8.74 W at 1000 V applied voltage and 250 Hz pumping frequency. © The Author(s) 2014. Source


Kang H.,Korea University | Jung J.,Korea University | Jung M.,Korea University | Chi Y.,Bookwang Corporation and System Co. | And 6 more authors.
Transactions of the Korean Society of Mechanical Engineers, B | Year: 2013

A cooling system is adopted to control the thermal load from the avionic equipments in an aircraft for stable operation. In this study, an avionic cooling system was designed and manufactured by adopting a vapor compression cycle with a closed-loop air-circulation system to investigate the operating characteristics of an alternative refrigerant. The performance characteristics of a cooling system adopting R236fa as an alternative refrigerant were experimentally determined by varying the refrigerant charging amount, expansion valve opening, and compressor rotation speed. The experimental results were analyzed and compared with those of a cooling system adopting R124 as a refrigerant. The possibility of the adoption of R236fa as an alternative refrigerant was verified, and design solutions were suggested to improve the system efficiency. © 2013 The Korean Society of Mechanical Engineers. Source


Lee S.-T.,Firstec Co. | Kang D.-W.,Firstec Co. | Bae K.-H.,Firstec Co. | Jeon Y.-W.,Firstec Co.
2014 11th International Conference on Ubiquitous Robots and Ambient Intelligence, URAI 2014 | Year: 2014

Shuttle Robot Service means transport service for passengers or goods by autonomous robots(or unmanned vehicles) in a service area. This paper have suggested a safety system of shuttle robot service when the robot carries out a mission from the departure place to the destination place. Three sub systems would assure safe transportation, safe get into and get out of the robot. © 2014 IEEE. Source

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