• Korean Journal of Agricultural Science
• /
• v.37 no.2
• /
• pp.295-302
• /
• 2010

Electro-hydraulic transmission (HST) and an electronic control system was designed, and performance of the components were investigated through indoor tests. When input values for HST swash plate control were given at 3 levels (5, 10, 13 degrees) in forward and reverse directions, the errors were less than 0.6 degrees. Response time was in ranges of 0.14 ~ 0.16 s and 0.16 ~ 0.2 s for forward and reverse direction controls while driving, and the values were 0.23 ~ 0.25 s and 0.18 ~ 0.23 s at static condition, respectively. Similar experiments for left and right steering resulted errors less than 0.5 degrees. Resonse time was in ranges of 0.16 ~ 0.22 s and 0.11 ~ 0.23 s for left and right turns while driving, and the values were 0.07 ~ 0.21 s and 0.09 ~ 0.14 s at static condition, respectively. From frequency response experiments, control system appeared to follow sine waves appropriately at frequencies less than 0.8 Hz with gain of 0.11 dB and 0.09 dB for forward and reverse direction controls, respectively, and the gain decreased above the frequency. Phase difference showed a gradual increase and were less than 45 degree up to 0.8 Hz. Similar experiments for left and right streering showed that the control system appeared to follow sine waves appropriately at frequencies less than 0.8 Hz with gain of 0.28 dB and 0.26 dB for left and right steering controls, respectively, and the gain decreased above the frequency. Phase difference showed a gradual increase and were less than 45 degree up to 0.8 Hz, which was the same as for the forward and reverse controls.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.1
• /
• pp.186-194
• /
• 1997

The objective of this study is to develope knock control algorithms which can increase engine power without causing frequent knock occurrence. A four cylinder spark-ignition engine is used for the experiments to develop knock control algorithms which use block vibration signals. Knock occurrence is detected accurately by using knock threshold values which consider the difference of transmission path of each cylinder. Spark timing is controlled both simultaneously and individually. With the simultaneous control, torque gain is achieved by retarding the spark timing on knock occurrence in propotion to the knock intensity. The individual knock control algorithm results in higher torque gain than the simultaneous knock control algorithm. The knock occurrence frequency of the individual knock control algorithm is about twice the value of the simultaneous knock control algorithm results. Both control algorithms give similar torque gain of about 3% when they are optimized.

• Progress in Medical Physics
• /
• v.20 no.4
• /
• pp.244-252
• /
• 2009

The purpose of this study is to compensate for susceptibility and a ferromagnetic body artifact using CFA and TGV on MR Imaging. A total of 30 patients (15 men and 15 women, mean age: 45 years) were performed on head and neck diseases. MR Unit used a 1.5T superconducting magnet (GE medical system, High Density). This study have investigated by changing with CFA and TGV (70, 90, 110, 130, 150) searching for compensation values about susceptibility and a ferromagnetic body artifact in 60 kg standards of body weight (p<0.05). As a quality results, Image qualities were obtained at different score from CFA and TGV (70, 90, 110, 130, $150=3.23{\pm}0.35$, $4.31{\pm}0.02$ $4.23{\pm}0.21$, $5.12{\pm}0.25$, $7.13{\pm}0.72$, $8.31{\pm}0.01$, $5.21{\pm}0.15$, $6.14{\pm}0.08$, $5.23{\pm}0.72$, $5.91{\pm}0.06$, p<0.05). Absolute CNRs (TG, CNRpre, CNRpost) were acquired with (70:$-1.44{\pm}0.11$, $-2.7{\pm}0.04$, 90:$-2.18{\pm}0.42$, $-4.41{\pm}0.43$, 110:$-2.89{\pm}0.43$, $-5.23{\pm}0.02$, 130:$-2.34{\pm}0.05$, $-5.26{\pm}0.01$, 150: $-2.09{\pm}0.08$, $-3.87{\pm}0.12$, p<0.05). In conclusions, this study could be compensated for metal and flow artifacts surrounding the tissues having artifact by changing CFA and TGV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.233-235
• /
• 1997

A free sparse transmission method using X-band standard gain horn antenna is applied to measure the attenuation and phase shift of microwave signal through the wetted grain such as rough rice, brown rice and barley. The moisture content of grain varied from 11 to 25% based on its wetted condition. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The measured values of dielectric constants as a function of moisture density are compared with values of those obtained using the predicted model for estimating dielectric constants of grain.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.1450-1452
• /
• 2009

In this work, a plastic diffuser which has a surface similar to Sinusoidal wave profile for application of LC D backlighting is proposed. This new pattern diffuser is achieved the values of the transmission efficiency an d diffusion efficiency all over 70%, and it also has the value about gain over 1.1. Additionally, this new patter n diffuser has high uniformity when we put it in the LCD backlight module and its thickness is only 2mm. With these foregoing properties, this diffuser film can widely applied to LCD displays systems etc.

• Journal of Broadcast Engineering
• /
• v.4 no.2
• /
• pp.164-175
• /
• 1999

Based on the performance analyses for transmission channel and signal characteristics in digital satellite broadcasting system. the optimal design parameter values for system using QPSK modulation technique were proposed in this paper. The proper performance degradation were of 2.0dB for channel characteristics. O.4dB for transmission signal characteristics and 0.2dB for receiver characteristics. respectively. In this case. the design objectives for system parameters were within ${\pm}\;0.5dB$ for gain flatness in 27MHz bandwidth. and O.1nsec/MHz and $0.2sec/MHz^2$ for linear and parabolic group delay. respectively. Also. the optimal parameter values that provide the maximum availability were of OdB OBO for satellite transponder TWTA. and the optimal bandwidth for PLL circuit was of 40kHz with 0.707 damping factor. These analyses and design values can be available for high data rate transmission system via satellite.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.2 no.3
• /
• pp.32-40
• /
• 1991

A modified transmission line model is proposed for input impedance analysis of a square microstip antenna with single-circularly-polarized. Alog-periodic arrangement with microstrip antenna (LPMA) which consists of 3 resonant element ($3\times1$) is designed for broadband operation ranging from 11.2 GHz to 12.4 GHz, based on this pro- posed model from transmission line model. Aplanar array ($3\times4$array), in which 4sets of the above LPMA are in the same plane, is fabricated for high gain X-band satellite communication antennas. The optimum spacing between each LPMA is determined using computer simulation for the minimum bariation of far field pattern and null. This $3\times4$array has a measured values of gain greater than 8dBi, VSWR les then 2.3, and bandwidth greater than 7% respectively.

• Current Optics and Photonics
• /
• v.6 no.1
• /
• pp.32-38
• /
• 2022

Erbium-doped fiber amplifiers (EDFAs) have saturated the technological market but are still widely used in high-speed and long-distance communication systems. To overcome EDFA saturation and limitations, its erbium-doped fiber is co-doped with other materials such as zirconia and bismuth. This article demonstrates and compares the performance using three different fibers as the gain medium for zirconia-erbium-doped fibers (Zr-EDF), bismuth-erbium-doped fibers (Bi-EDF), and commercial silica-erbium-doped fibers (Si- EDF). The optical amplifier was configured with a double-pass amplification system, with a broadband mirror at the end of its configuration to allow double-pass operation in the system. The important parameters in amplifiers such as optical properties, optical amplification and noise values were also examined and discussed. All three fibers were 0.5 m long and entered with different input signals: 30 dBm for low input and 10 dBm for high input. Zr-EDF turned out to be the most relevant optical amplifier as it had the highest optical gain, longest transmission distance, highest average flatness gain with minimal jitter, and relevant noise figures suitable for the latest communication technology.

• Journal of Electrical Engineering and information Science
• /
• v.2 no.4
• /
• pp.72-78
• /
• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice ,brown rice and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The moisture content of grain varied from 11 to 25% based on this wetted condition. The measured values of dielectric constants as a function of moisture density are compared with values of those obtained using he predicted model for estimating dielectric constants of grain. The effect of density fluctuation, high is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation an moisture density is proposed of reducing the effects of density fluctuation on the moisture content measurement.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.8
• /
• pp.1599-1605
• /
• 2011

From now on, power line communication was made use of controling using 450 kHz narrow band, but as the PLC technology developing, in the near future get to the commercial step that is broadband PLC upto 30 MHz. In this paper, analyze the possibility of moving picture transmission for adapting surveillance camera which is among of the application of PLC. To analyze characteristics of channel, estimate the noise and impedance of lab, office, home. In case of noise, there is no problem to communicate each other because of 20 ~ 50 dB gain. In case of impedance, average impedance is about 100 ohm, it satisfy standards of designing modem but because max and min values get out of expectation there are some problem to acquire fully capacity of modems. Its condition is the same as transmission of multimedia data. In this test as more packets, as more handling rate, in lab, for the case that transmit 1,518 byte as the speed of 6 Mbps handling rate is upto 100%, it means possibility of moving picture transmission as the 6 Mbps speed. For delayed time there is no relationship about transmitted packets. As a result, there is no problem about applying surveillance camera via the PLC. And more cameras can work within PLC for considering the number of transmitted frames.