https://pubs.kist.re.kr/handle/123456789/75389 Wed, 15 Apr 2026 17:39:43 GMT 2026-04-15T17:39:43Z https://pubs.kist.re.kr/handle/201004/115770 Title: ROTORDYNAMIC PERFORMANCE MEASUREMENT OF AN OIL-FREE TURBOCOMPRESSOR SUPPORTED ON GAS FOIL BEARINGS Authors: Lee, Yong-Bok; Cho, Sang-Beom; Kim, Tae-Young; Kim, Chang Ho; Kim, Tae Ho Abstract: This paper presents the results of speed-up and coastdown tests with a variation in the radial clearance of gas foil bearings. The test facility includes a high speed driving motor and a two-stage turbocompressor whose shafts are coupled using a flexible coupling. The rate power of the permanent magnet synchronous (PMS) motor is 300 HP (225kW) at the maximum rotating speed of 60krpm. The turbocompressor shaft has two impellers at its side ends and compresses air while it rotates at the same speed as the motor. Four gas foil bearings (GFBs) support the coupled multi-shafts at the motor and compressor sides. To determine the rotordynamic performance of the coupled motor - compressor system, a series of experiments are conducted for increasing radial clearances of the motor side test GFBs from 150 mu m to 300 mu m with a 50 mu m increment, while the radial clearance of the compressor side GFBs are fixed at 150 mu m. The test results show that increasing radial clearance delays the onset speed of rotor subsynchronous whirl motions and decreases the whirl frequency. As the radial clearance decreases, the rotor peak amplitude at the critical speed similar to 15 krpm decreases significantly. Wed, 01 Sep 2010 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/115770 2010-09-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/115769 Title: Highly-Accurate, Implantable Micromanipulator for Single Neuron Recordings Authors: Yang, Sungwook; Lee, Semin; Park, Kitae; Kim, Jinseok; Cho, Jeiwon; Shin, Hee-Sup; Yoon, Eui-Sung Abstract: A precise and implantable micromanipulator is presented for automatically advancing electrodes during single unit recordings in freely-behaving animals. The modular design and enhanced clamping mechanism with simple mechanical components are designed to provide reliable linear motion using a piezo motor with a stroke of 3 mm. To be specific, a closed loop control system, based on the position feedback from a magnetoresistive (MR) sensor, was implemented to overcome the non-linear characteristics of the piezo motor and to locate electrodes precisely at the targeted position with the accuracy of 1 mu m, even under load. The weight of the micromanipulator is only 0.84 g when it is fully assembled with the MR sensor, PCBs, and connectors. In addition, a protective cover is employed to prevent breakage during semi-chronic recording. The positioning performance of the micromanipulator was tested at various loading conditions using various control methods. Finally, the activities of a single unit were isolated successfully using small step adjustments, such as 1 to 5 mu m, in freely-moving mice. Fri, 01 Jan 2010 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/115769 2010-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/115768 Title: DSP Integration of Sound Source Localization and Multi-channel Wiener Filter Authors: Lee, Byoung-gi; Kim, Hyun-dong; Choi, Jong-suk; Kim, Seyun; Cho, Nam Ik Abstract: This paper describes a DSP integration of sound source localization (SSL) and multi-channel Wiener filter (MWF). To develop a robot audition system, we integrated SSL module and MWF module into a DSP system. SSL is a module to perceive the direction of a human user's call. It measures time delay of arrival among microphones and estimates the direction of sound source. Also, it post-processes the resulted estimations of direction by histogram to perceive the direction robustly under noisy environment. MWF is a module to reduce background noises from raw voice signal to enhance the performance of robot's speech recognition. It gathers information of background noises during noise-period and then reduces noises during voice-period. This SSL-MWF combination system will be a cheap, high-performing and convenient solution for robot audition. Fri, 01 Jan 2010 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/115768 2010-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/115767 Title: Characteristics of Conducting Polymer-Coated Nanosized LiFePO4 Cathode in the Li+ Batteries Authors: Dinh, Hung-Cuong; Yeo, In-Hyeong; Cho, Won Il; Mho, Sun-il Abstract: Both nano-sized and micron-sized LiFePO4 crystalline particles with rhombus structure were synthesized by a hydrothermal method for the cathode materials. Coating conductive polymers, such as polypyrrole (PPy) and poly-3,4-ethylenedioxythiophene (PEDOT), on the surfaces of LiFePO4 particles improved the battery capacities by increasing the ionic and electric conductivities of the cathode materials. The nano-sized LiFePO4 coated with PEDOT shows the largest specific capacity (167 mAhg(-1) for initial to 158 mAhg(-1) after 50 cycles), compared to the cases coated with PPy (165 mAhg-1 to 127 mAhg(-1)) and with carbon (152 mAhg(-1) to 147 mAhg(-1)). Compared to the nano-sized particles, the micron-sized particles have much smaller surface-tovolume ratios, which resulted in increased diffusion distance requirements for lithium ions and, also, reduced accessibility of lithium ions. Fri, 01 Jan 2010 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/115767 2010-01-01T00:00:00Z