• 농업과학연구
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• 제37권2호
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• pp.295-302
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• 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.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.186-194
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• 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.

• 한국의학물리학회지:의학물리
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• 제20권4호
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• pp.244-252
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• 2009

자화율(susceptibility) 및 강자성체(ferromagnetic body)에 의한 인공물(artifact) 영향을 줄이기 위하여 중심주파수(center frequency) 정렬과 송 신호강도(transmission gain)값의 변화로 영상의 질을 보상하고자 한다. 본원에 내원한 환자 중 총 30명에 대하여 두 경부(head and neck)질환을 의심한 환자 중 남자 15명, 여자 15명으로 평균나이는 45세이었다. 사용된 장비는 GE 1.5T unit (GE, General Electric medical system, High Density)를 사용하여 Transmission gain (TG) 값을 평균 몸무게 60 kg을 기준으로 70, 90, 110, 130, 150까지 변환하여 검사를 하였다(p<0.05). 본 연구의 결과로서, 조영제 주입 전과 후의 지방소거 결과는 TG (70, 90, 110, 130, $150=3.23{\pm}0.35$, $4.31{\pm}0.02$, $4.23{\pm}0.21$, $5.12{\pm}0.25$, $7.13{\pm}0.72$, $8.31{\pm}0.01$, $5.21{\pm}0.15$, $6.14{\pm}0.08$, $5.23{\pm}0.72$, $5.91{\pm}0.06$)값에 다른 점수 분포를 나타났다(p<0.05). 절대값 대조도대 잡음비는 (TG, CNRpre, CNRpost, 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: $-2.09{\pm}0.08$, $-3.87{\pm}0.12$)을 얻었다(p<0.05). 본 실험에서 중심주파수 조정과 송 신호강도(transmission gain)값의 변화에 따라 인공물이 있을 때 영상의 질을 보상할 수 있다는 것을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.233-235
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• 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
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1450-1452
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• 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.

• 방송공학회논문지
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• 제4권2호
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• pp.164-175
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• 1999

본 논문에서는 QPSK 디지틀 전송 기술을 사용하는 위성방송 전송 시스템에 대한 위성 채널 특성과 전송 신호 특성에 대한 영향을 분석하여 전송 시스템의 설계 기준점을 결정할 수 있도록 하였다. 전송 채널 특성에 의한 열화도는 약 2.0dB, 전송 신호 스펙트럼 특성에 의한 열화는 0.4dB, 그리고 수신기 특성에 대해 약 0.2dB의 열화 특성을 갖는 위성 및 전송 시스템에 대한 가용 설계 파라미터 값들을 제안하였다. 열화 특성을 만족하는 설계 파라미터 값들은 ${\pm}\;0.5dB$ 이내의 진폭 응답 특성 그리고 0.1nsec/MHz, $0.2sec/MHz^2$ 이내의 전파 지연 특성을 나타내었다. 또한, 최대 서비스 가용도를 갖는 위성 전송 시스템의 TWTA 동작은 0dB OBO가 적당하며, 위상 잡음 영향을 최소화하기 위해서는 0.707 damping 계수 및 40kHz 대역폭을 갖는 PLL 회로가 최적의 동작 특성을 나타내었다. 본 논문의 시스템 성능 분석 및 설계 파라미터 값들은 위성을 통한 고속 데이터 전송 시스템에 대한 설계 기준점으로 활용될 수 있다.

• 한국전자파학회지:전자파기술
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• 제2권3호
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• pp.32-40
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• 1991

단일 급전으로 원형편파 특성을 얻을 수 있는 정사각형 마이크로스트립 안테나 소자에서의 입력 임피던스 해석을 위해 전송선로 모델을 수정 제안하였으며, 이를 기초로 11.2-12.4GHz의 광대역 주파수 범위에서 동작하는 대수주기형 마이크로스트립 배열 안테나를 3개의 공진 소자 ($3\times1$)로 구성하였다. 또한 X-band에서의 고이득 위성통신용 안테나로 응요하기 위해 이 대수 주기형 마이크로스트립 아네타 4로를 평면 배열 안테나 ($3\times4$배열)로 구성하였으며, 각 대수주기형 배열 사이의 간격을 조절하면서 원거리 전계 에서의 복사 패턴 및 null 변화를 시뮬레이션 하여 그 변화가 최적으로 도는 배열 간격을 결정하여, 8dBi의 이득과 VSWR 2.3이하로 약 7% 이상의 대역 특성을 얻었다.

• Current Optics and Photonics
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• 제6권1호
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• pp.32-38
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• 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
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• 제2권4호
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• pp.72-78
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• 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.

• 전기학회논문지
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• 제60권8호
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• pp.1599-1605
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• 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.