• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.638-647
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• 2006

Recently, the DFT-Spread OFDM has been studied for the PAPR reduction. However, the DFT-Spread OFDM produces more ICI and SCI problems than OFDM because phase offset mismatch of the DFT spreading code results from the random phase noise in the oscillator. In this paper, at first, phase noise influence on the DFT-Spread OFDM system is theoretically analyzed in terms of the BER performance. Then, the conventional ICI self-cancellation methods are discussed and two kinds of ICI self-cancellation methods are newly proposed. Lastly, a new DFT-Spread OFDM system which selectively adopts the ICI self-cancellation technique is proposed to resolve the interference problem and PAPR reduction simultaneously. Proposednew DFT-Spread OFDM system can minimize performance degradation caused by phase noise, and still maintain the low PAPR property. Among the studied methods, DFT-Spread OFDM with data-conjugate method or newly proposed symmetric data-conjugate method show the significant performance improvements, compared with the DFT-Spread OFDM without ICI self-cancellation schemes. The data-conjugate method is slightly better than symmetric data-conjugate method.

• Korean Journal of Applied Biomechanics
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• v.31 no.4
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• pp.241-248
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• 2021

Objective: The purpose of this study was to investigate the difference in muscle strength, kinematics, and kinetics between injured and non-injured sides of the leg after Achilles Tendon Rupture surgery during walking and running. Method: The subjects (n=11; age = 30.63 ± 5.69 yrs; height = 172.00 ± 4.47 cm; mass = 77.00 ± 11.34 kg; time lapse from surgery = 29.81 ± 10.27 months) who experienced Achilles Tendon Rupture (ATR) surgery participated in this study. The walking and running trials were collected using infrared cameras (Oqus 300, Qualisys, Sweden, 100 Hz) on instrumented treadmill (Bertec, U.S.A., 1,000 Hz) and analyzed by using QTM (Qualisys Track Manager Ver. 2.15; Qualisys, U.S.A). The measured data were processed using Visual 3D (C-motion Inc., U.S.A.). The cutoff frequencies were set as 6 Hz and 12 Hz for walking and running kinematics respectively, while 100 Hz was used for force plate data. Results: In ATR group, muscle strength there were no difference between affected and unaffected sides (p> .05). In kinematic analysis, subjects showed greater ROM of knee joint flexion-extension in affected side compared to that of unaffected side during walking while smaller ROM of ankle dorsi-plantar and peak knee flexion were observed during running (p< .05). In kinetic analysis, subjects showed lower knee extension moment (running at 2.2 m/s) and positive ankle plantar-flexion power (running at 2.2 m/s, 3.3 m/s) in affected side compared to that of unaffected side (p< .05). This lower positive ankle joint power during a propulsive phase of running is related to slower ankle joint velocity in affected side of the subjects (p< .05). Conclusion: This study aimed to investigate the functional evaluation of the individuals after Achilles tendon rupture surgery through biomechanical analysis during walking and running trials. Based on the findings, greater reduction in dynamic joint function (i.e. lower positive ankle joint power) was found in the affected side of the leg compared to the unaffected side during running while there were no meaningful differences in ankle muscle strength and walking biomechanics. Therefore, before returning to daily life and sports activities, biomechanical analysis using more dynamic movements such as running and jumping trials followed by current clinical evaluations would be helpful in preventing Achilles tendon re-rupture or secondary injury.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.3
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• pp.276-282
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• 2003

OFDM is effective for the high speed data transmission. However, the nonlinear distortion is a serious problem because of the high PAPR due to many subcarriers. The conventional SLM selects the OFDM signal with the lowest PAPR. In this method, OFDM data can be correctly recovered only if the side information about the phase sequence is transmitted to receiver. This paper proposes a new method of side information insertion into the conventional SLM and reduces the computational complexity by adaptive method. Performances are compared in case that three kinds of phase sequences are used for phase rotation factor. The adaptive SLM method has the same PAPR reduction as the conventional SLM method. The required BER can be guaranteed by the proposed method. When subcarrier number N=32, computational complexity is reduced to 48 %, 72 % and 51 % for the branch number U=4, 8 and 16, respectively.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1216-1220
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• 1999

The effects of low-temperature blanching on the physical properties of chestnut powder were studied. Chestnuts were blanched in water for 15, 30 and 60 min., each at three temperatures viz. $45^{\circ}C,\;55^{\circ}C$ and $65^{\circ}C$. The particle size of chestnut powder was prepared smaller than 60 mesh$(250\;{\mu}m)$. Higher blanching time and temperature increased water binding capacity(WBC) of chestnut powder. Water soluble index(WSI) was the highest for chestnuts blanched at $65^{\circ}C$ for 30 min. As with water binding capacity(WBC), swelling power of chestnut powder increased with increasing blanching time and temperature but solubility showed an reduction by increasing blanching temperature. In Brabender amylographic examination, peak viscosity of chestnut powder showed great change, but the gelatinization temperature showed no significant differences by blanching conditions.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.234-239
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• 2012

Next generation mobile communication systems have been studied and applied to support various services. In next generation mobile communication systems, the most interested research is the integration of various communication systems and the offer of various services by using high-speed data transmission. The integration of communication systems has been researched by using multi standard modem, while the high-speed data transmission for the offer of various services has been applied by using OFDM. This paper has proposed the method to reduce PAPR by using multi standard modem. with EVM, this paper has also suggested the method to compensate in-band distortion while reducing PAPR. By using the proposed methods, this paper has analyzed and simulated the decrease efficiency of PAPR, the performance of CCDF, and the performance of BER in next generation mobile communication systems. The simulation results improved the performance of next generation mobile communication system can be seen that.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.4
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• pp.234-244
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• 2014

Recently it has been focused that the automobile engine has developed in a strong upward tendency for the use of the high viscosity and poorer quality fuels in achieving the high performance, fuel economy, and emission reduction. Therefore it is not easy to solve the problems between low specific fuel consumption and exhaust emission control at motor cars. In this study, it is designed and used the engine test bed which is installed with turbocharger and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters, and they were engine speeds(rpm), injection timing(bTDC), and engine load(%). From the result of an experimental analysis, peak cylinder pressure and the rate of pressure rise were increased, and the location of it was closer toward top dead center according to the increasing of engine speed and load, and with advancing injection timing. The combustion characteristics are effected by fuel injection timing due to be enhanced the mass burned fraction. Using the engine dynamometer for analyzing the engine performance, the engine torque and power have been enhanced according to advancing the fuel injection timing. In analyzing of exhaust emission, there has been a trade-off between PM and NOx with increasing of engine speed and load, and with advanced injection timing. The experimental data are shown that the formation of NOx has increased and PM, vice versa.

• Journal of electromagnetic engineering and science
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• v.9 no.1
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• pp.17-24
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• 2009

In recent years, OFDMA(orthogonal frequency division multiple access) and SC-FDMA(Single Carrier Frequency Division Multiple Access) have been widely studied for the uplink of a mobile communication system. In this paper, PAPR(Peak-to-Average Power Ratio) and BER(Bit Error Rate) performance of the OFDMA and SC-FDMA systems are studied in relation to the uplink of a mobile communication system. Three kinds of sub-carrier allocation methods in the OFDMA system and 2 kinds of sub-carrier allocation methods in SC-FDMA system are suggested to compare and improve system performance. Simulation results show that in the OFDMA system, the first sub-band allocation method has better PAPR reduction performance than the other methods. In the SC-FDMA system, the distributed allocation method offers similar P APR, compared with the sub-band allocation method. P APR can be further reduced by adding a spectrum shaping filter with an appropriate roll of factor. Furthermore, it is found that on average, SC-FDMA can reduce the PAPR by more than 5 dB compared to OFDMA, when the total sub-carrier number is 1,024 and the sub-carrier number allocated to each user changes trom 8 to 512. Because of the frequency diversity and low PAPR characteristics, SC-FDMA system of the distributed sub-carrier allocation method can achieve better BER performance than the OFDMA system.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.5
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• pp.700-706
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• 2005

The objectives of this research were to analyze physicochemical properties of physically modified rice starch which was prepared by hydro-shear homogenizer and ultrasonic homogenizer. The 5:1 of water to starch ratio, 20,500 rpm of hydro-shear homogenizer, and 5 sec of pulse and 40 kHz of frequency of ultrasonic homogenizer, which were operated for 10 min. The 1/3 of size reduction of raw rice starch and gelatinized rice starch, and reduced of particle size were achieved by above processing conditions. The homogenization of raw rice starch and gelatinized rice starch were higher values of specific area, transmittance, solubility and swelling power than control. While, these had lower value of apparent viscosity than control. In raw rice starch, the gelatinization characteristics of ultrasonic homogenizer treated rice starch had some higher values of gelatinization temperature, peak temperature and enthalpy than those of control. While, those of hydro-shear homogenizer treated rice starch had similar values to those of control.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.113-119
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• 2013

We developed a transformed, symmetrical, mushroom-like surface without via holes in cells focused on a 2.4-GHz WLAN band. Each slot in the novel type structure plays a key role in modeling at the desired frequencies. The designed artificial magnetic conductor (AMC) has several advantages, including a small size, a wider bandwidth, a short reflecting distance to the antenna, and easy fabrication because there are no via holes. Overall dimensions of the AMC cell are 21 mm $(Width){\times}21mm$ $(Height){\times}2.6mm$ (Thickness), and the bandwidth is about three times wider (11.7%) compared to that of a conventional AMC (4.0%). For evaluating the performance of the proposed structure, a reflector, which periodically consists of the designed AMC cells, was developed. The antenna with the investigated AMC reflector not only works within a quarter of the wavelength because of the extremely high wave impedance generated by the AMC cells on the surface of the structure but also reduces the specific absorption rate (SAR). Electromagnetic field (EMF) exposure to a human phantom was analyzed by applying the designed reflector to the 2.4-GHz dipole antenna in a tablet PC. The calculated peak SAR averaged over 1 g was 0.125 W/kg when the input power was 1 W and the antenna was located at 20 cm from the human phantom. However, the SAR value was only 0.002 W/kg (i.e., 98.4% blocked) when the designed reflector was inserted in front of the antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1181-1185
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• 2005

A combining of MIMO signal processing with OFDM is regarded as a promising solution of enhancing the performance of next generation wireless system. Therefore, in this paper, an OFDM-based wireless system employing layered space-time architecture is considered for a high-rate transmission. In the MIMO-OFDM system, we evaluate the PAR performance using the SLM approaches. The investigated SLM scheme for MIMO-OFDM signals selects the transmitted sequence with lowest average PAR over all transmitting antennas and retrieves the side information very accurately at the expense of a slight degradation of the PAR performance. The low probability of false side information can improve the overall detection performance of the MIMO-OFDM system with erroneous side information compared to the ordinary SLM approache, respectively. Also, we provide closed form of the average BER performance in MIMO-OFDM system using analytic approach.