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Yoonseok Choi,Hoon Bock Lee,Sung-Bum Park,Bong-Hyun Hong,Sang-Yoon Lee,Kyun Hyon Tchah 한국물리학회 2006 Current Applied Physics Vol.6 No.5
For transmission of multimedia data via ad-hoc networks, the next-generation Bluetooth specication, Bluetooth EDR(Enhanced Data Rate) was developed recently. The design issues of the Bluetooth EDR are how area-eciently three modulationschemesGFSK,p/4-shifted DQPSK and 8-DPSKare combined, and how fast and simply they perform seamless timing and car-rier recovery as the demodulation scheme is changed to receive enhanced-rate data. So we proposed 6 hardware or software schemesfor area reduction and simple implementation, and designed a Bluetooth EDR baseband controller using those schemes. We espe-cially proposed and designed a simple scheme that compensates carrier frequency oset by using an average of phase errors betweenadjacent symbols. The FPGA implementation integrated with link manager software was tested with Bluetooth EDR specication,and was shown to be fully functional with enhanced data rates of 2 Mbps and 3 Mbps in spite of switching of modulation methodduring packet transmission. Timing recovery was completed within 10l s which is shorter than 11l s assigned to synchronizationsequence after GFSK demodulation, and the coverage of frequency oset was 100 kHz which is wider than 40 kHz of the specication.
Yoonseok Choi,Jaerok Kim,Eunok Han 한국영양학회 2016 Nutrition Research and Practice Vol.10 No.2
BACKGROUND/OBJECTIVES: The current South Korean government policy on food irradiation technology should be reformed based on an in-depth investigation of the communications aspect, because the issue is no longer of a technological nature, given the proven safety and efficacy of the processes. SUBJECTS/METHODS: The target population of the education program consisted of elementary, middle, and high school students attending 310 schools in South Korea (2013: 63 schools, 2014: 104 schools, 2015: 143 schools). Data subjected to analysis were 13,327 pre-education and 12,641 post-education questionnaires received from 7,582 elementary, 2,671 middle, and 3,249 high school students who participated in the education program from May 2012 to April 2015 (n = 12,831), after the exclusion of inadequately filled-in questionnaires. RESULTS: Analysis of the three-year educational effect trend was conducted by comparing levels of variables before and after food radiation education. The analysis yielded the finding that the post-education levels were significantly higher for all variables. That is, for interest in education, perception (necessity, safety, subjective knowledge, and information acquisition), objective knowledge, and attitude, with the sole exception of objective knowledge in 2013. CONCLUSIONS: Given that post-education levels of perception, knowledge, and attitude concerning irradiated foods increased considerably compared to pre-education levels, behavior change should be induced by providing continuous education to enhance, these primary variables.
A Study on the Flow-Accelerated Corrosion Characteristics of Galvanically Coupled Dissimilar Metals
Choi, YoonSeok,Kim, JungGu 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.2
The flow-accelerated corrosion characteristics of a carbon steel(CS) coupled to stainless steel(SS) were investigated in deaerated alkaline-chloride solutions with velocities (0, 0.2, 0.4 and 0.6 m/s), pH (8, 9 and 10) and temperatures (25, 50 and 75℃). The electrochemical properties of specimens were investigated by potentiodynarnic test and galvanic corrosion test using RCE (Rotating Cylinder Electrode). CS did not show passive behavior while SS show passive behavior in the alkaline-chloride solution. Galvanic corrosion tests were conducted as a function of flow velocities, pH and temperature. The galvanic current density increases with increasing flow velocity and temperature, but decreased with increasing pH. Flow velocity had a small effect on the galvanic current density at 25℃, whereas the flow velocity increased galvanic current density significantly at 50 and 75℃. This might be due to the increased solubility of magnetite at the higher temperature.