• Journal of Astronomy and Space Sciences
• /
• v.40 no.4
• /
• pp.237-245
• /
• 2023

Laser communication has been considered as a novel method for earth observation satellites with generation of high data volume. It offers faster data transmission speeds compared to conventional radio frequency (RF) communication due to the short wavelength and narrow beam divergence. However, laser beams are refracted due to atmospheric turbulence between the ground and the satellite. Refracted laser beams, upon reaching the receiver, result in angle-of-arrival (AoA) fluctuation, inducing image dancing and wavefront distortion. These phenomena hinder signal acquisition and lead to signal loss in the course of laser communication. So, precise alignment between the transmitter and receiver is essential to guarantee effective and reliable laser communication, which is achieved by pointing, acquisition, and tracking (PAT) system. In this study, we simulate the effectiveness of tip/tilt compensation for more efficient laser communication in the satellite-ground downlink. By compensating for low-order terms using tip/tilt mirror, we verify the alleviation of AoA fluctuations under both weak and strong atmospheric turbulence conditions. And the performance of tip/tilt correction is analyzed in terms of the AoA fluctuation and collected power on the detector.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.2
• /
• pp.167-174
• /
• 2012

The circuits including with Optical transceiver and clock data recovery, in this paper, SERDES (SERializer-DESerializer) are implemented to construct a GE-PON burst-mode transceiver supporting IEEE 802.3ah and a jig for measuring the burst-mode characteristics, that is to say, PON upstream optical transmission environment are manufactured to evaluate the performance of transceiver. we verified that the limiting amplifier compensated the gap of max. 26dB optical power by experiments. The startup acquisition lock time is 670ns in case of using VSC7123 and 2300ns in case of S2060 and the data acquisition lock time were measured to be 400ns and 600ns, respectively, in the upstream channel transmission in this work. While on the other, VSC7123 is satisfied with IEEE802.3ah recommendations.

• Journal of the Ergonomics Society of Korea
• /
• v.14 no.2
• /
• pp.75-85
• /
• 1995

The purpose of this study is to develop a force-platform system suitable for real situations in industry. The developed system is a 3-axis measurement type. It consists of force-transmission, force measuring circuit, and the software that analyzes the measured force. The force-transmission transmits forces to 3 axes, which has a physical structure to minimize the interference among those axes. Force measuring circuit consists of DSP (digital signal processor) for flexible disposal of change of measurement algorithm, elimination of noise and maintenance of precision. The functions of the software are the calibration which revises the measurement error occuring during data acquisition, and various analyses of forces. The result of the experiment shows that the developed system has about 1% measurement error, is stable for repeated experiments, and is not effected by temperature change.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.319-320
• /
• 1998

We have developed algorithm for calculating tumor dose from transmission dose in radiation therapy. Using data acquisition card and LabVIEW programming language, we acquired the signal from 9 ion chambers, processed and displayed it in real time. And we also developed GUI(Graphic User Interface) for system operation.

• 유공압시스템학회:학술대회논문집
• /
• 2010.06a
• /
• pp.33-38
• /
• 2010

As for an oil hydraulic vane pump of vehicle hydraulic systems, the highest of planning technique required by the acquisition of optimum profile data which can be available to predict noises and vibrations. Pressure pulsation may result in considerable vibration and noise of pump component as well as cavitation in hydraulic system. The influences of the discharge pressure and rotating speed of the vane on the dynamic pressure in chamber surrounding a vane have been investigated. It is very important to predict pressure pulsation in vane pump. This paper presents analysis of technique of vane pump for automatic transmission. The predicted result using AMESim model were good agreement with the experimentally obtained results.

• Journal of the Semiconductor & Display Technology
• /
• v.3 no.1
• /
• pp.31-34
• /
• 2004

We develop Mueller-matrix spectroscopic ellipsometry based on dual compensator configuration. This technique is very powerful for measuring surface anisotropy in nano-scale, especially when materials show depolarization. Dual-rotating compensator configuration is adopted with the rotational ratio of 5:3 originally developed by Collins et al[1]. The instrument can provide 250-point spectra over the wavelength range from 230 nm to 820 nm in one irradiance waveform with minimum acquisition time of Tc=10 s. In this work, the results obtained in transmission modes are presented for the initial attempt. We present calibration procedures to diagnose the system from the utilized data collected in transmission mode without sample. We expect that the instrument will have important applications in thin films and surfaces that have anisotropy and inhomogeneity.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2003.12a
• /
• pp.12-17
• /
• 2003

We develop Mueller-matrix spectroscopic ellipsometry based on dual compensator configuration. This technique is very powerful for measuring surface anisotropy in nano-scale, especially when materials show depolarization. Dual-rotating compensator configuration is adopted with the rotational ratio of 5:3 originally developed by Collins et al [1]. The instrument can provide 250-point spectra over the wavelength range from 230 nm to 820 nm in one irradiance waveform with minimum acquisition time of $Tc{\approx}10 s$. In this work, the results obtained in transmission modes are presented for the initial attempt. We present calibration procedures to diagnose the system from the utilize data collected in transmission mode without sample. We expect that the instrument will have important applications in thin films and surfaces that have anisotropy and inhomogeneity.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.04a
• /
• pp.213-217
• /
• 2000

It is essential to establish an earthquake alert system real-time seismographic data acquisition and data transmission by dedicated communications,. Up to now approximately 60 earthquake stations are installed in Korea and being operated by KMA. KEPRI,. KINS and KIGAM and its number will be increased in time. The earthquake data recorded in half of these stations are transmitted to data center and analysed in quasi real-time. Therefore if these real-time seismographic stations be connected to each organization by dedicated lines and we will develop an algorithm which we can calculate the magnitude and epicenter within 25-30 seconds after an earthquake occurred it will be possible to develop an Earthquake Alert System giving several tens of seconds warning in advance.

• Journal of Broadcast Engineering
• /
• v.22 no.4
• /
• pp.509-518
• /
• 2017

High-resolution digital holograms can be quickly generated by using a PC cluster that is based on server-client architecture and is composed of several GPU-equipped PCs. However, the data transmission time between PCs becomes a large obstacle for fast generation of video holograms because it linearly increases in proportion to the number of frames. To resolve the problem with the increase of data transmission time, this paper proposes a multi-threading-based method. Hologram generation in each client PC basically consists of three processes: acquisition of light sources, CGH operation using GPUs, and transmission of the result to the server PC. Unlike the previous method that sequentially executes the processes, the proposed method executes in parallel them by multi-threading and thus can significantly reduce the proportion of the data transmission time to the total hologram generation time. Through experiments, it was confirmed that the total generation time of a high-resolution video hologram with 150 frames can be reduced by about 30%.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.53 no.11
• /
• pp.786-792
• /
• 2004

A wavelet based ECG data compression has become an attractive and efficient method in many mobile tele-cardiology applications. But large data size required for high compression performance leads a serious delay. In this paper, new wavelet compression method with minimum delay is proposed. It is based on deciding the type and compression ratio(CR) of block organically according to the standard deviation of input ECG data with minimum block size. Compression performances of the proposed algorithm for different MIT ECG Records were analyzed comparing other ECG compression algorithm. In addition to the processing delay measurement, compression efficiency and reconstruction sensitivity to error were also evaluated via random noise simulation models. The results show that the proposed algorithm has both lower PRD than other algorithm on same CR and minimum time in the data acquisition, processing and transmission.