• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.60-64
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• 2014

We report the generation of 3.3-mW single-cycle terahertz (THz) pulses at 1-kHz repetition rate via optical rectification in MgO-doped prism-cut stoichiometric LiNbO3. Efficient pulse-front tilting of 800-nm pulses was realized by an optimized single-lens focusing scheme for radially-symmetric propagation of THz beams. In this geometry, nearly-diffraction-limited THz Gaussian beams with electric field strength as high as 350 kV/cm were generated. The pump-to-THz energy conversion efficiency of $1.36{\times}10^{-3}$ and the extremely high signal-to-noise ratio of ~1:15000 achieved are among the best results for 1-kHz single-cycle terahertz pulse generation ever demonstrated in room temperature operation.

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.89-98
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• 2015

PURPOSES : This study evaluated the feasibility of implementing protected-permissive left-turn (PPLT) signals at three-leg signalized intersections. METHODS: A three-leg signalized intersection with permissive left-turn was first selected. A VISSIM simulation model was constructed using data collected from the test site. The VISSIM network was calibrated by adjusting related parameter values in order to minimize the difference between the simulated and surveyed critical gap. The calibrated network was validated by the number of waiting left-turning vehicles per cycle. Finally, the mobility and safety measures were extracted from simulation runs in which permissive, protected left turns as well as PPLTs were realized based on diverse traffic volume scenarios. RESULTS : The mobility-related measures of effectiveness (MOEs) of the case with PPLT outperformed the other two left-turn treatment scenarios. In particular, the average waiting time per cycle for the left-turn vehicles in the case with PPLT was reduced by 30 s. The safety-related MOEs of the case with PPLT were somewhat higher than those in the case with protected left-turns and much higher than those in the case with permissive left-turns. CONCLUSIONS : Based on the mobility- and safety-related MOEs generated from the VISSIM simulation runs, the use of PPLT seems to be feasible at three-leg signalized intersections where the left-turn is permissive and a pedestrian signal exists at the conflicting approach. However, in order to use the PPLT in earnest, it is necessary to revise the road traffic act, traffic signs, and related manuals.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.11
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• pp.74-84
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• 2000

This paper deals with procedures for design and implementation of a DSP, which is compatible with TMS320C30 DSP. CBS(Cycle Based Simulator) is developed to study the architecture of the target DSP. The simulator gives us detailed information such as function block operation, control signal values, register condition, bus and memory values when a instruction is being carried out. RTL design is carried out by VHDL. Logic simulation and hardware emulation are employed to verify proper operation of the design. The DSP is fabricated with 0.6${\mu}m$ CMOS technology. The Chip has 450,000 gates complexity, $9{\times}9mm^2$ area, 20 MIPS operation speed. It is confirmed by running 109 instructions out of 114 instructions and 13 kinds of algorithm that the developed DSP has compatibility with TMS320C30.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.549-557
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• 2019

In this paper, we focus on the real-time detection method of a seismic ionospheric disturbance using Global Navigation Satellite System (GNSS) signal. First, the monitor for the detection of the seismic ionospheric disturbance is studied based on the estimated ionospheric delay using the GNSS signals. And then, the threshold for the automatic detection is computed. Moreover, to discriminate the seismic ionospheric disturbance against the other ionospheric anomalies due to other error sources such as cycle slips, the signatures of the ionospheric perturbation caused by the seismic wave is investigated. Based on the observation, the detection strategy is proposed. Using GPS observations collected from the 47 permanent stations in South Korea and Japan, the proposed real-time detection method is evaluated.

• Wind and Structures
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• v.37 no.6
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• pp.445-460
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• 2023

Accurate estimation of modal parameters (i.e., natural frequency, damping ratio) of tall buildings is of great importance to their structural design, structural health monitoring, vibration control, and state assessment. Based on the combination of variational mode decomposition, smoothed discrete energy separation algorithm-1, and Half-cycle energy operator (VMD-SH), this paper presents a method for structural modal parameter estimation. The variational mode decomposition is proved to be effective and reliable for decomposing the mixed-signal with low frequencies and damping ratios, and the validity of both smoothed discrete energy separation algorithm-1 and Half-cycle energy operator in the modal identification of a single modal system is verified. By incorporating these techniques, the VMD-SH method is able to accurately identify and extract the various modes present in a signal, providing improved insights into its underlying structure and behavior. Subsequently, a numerical study of a four-story frame structure is conducted using the Newmark-β method, and it is found that the relative errors of natural frequency and damping ratio estimated by the presented method are much smaller than those by traditional methods, validating the effectiveness and accuracy of the combined method for the modal identification of the multi-modal system. Furthermore, the presented method is employed to estimate modal parameters of a full-scale tall building utilizing acceleration responses. The identified results verify the applicability and accuracy of the presented VMD-SH method in field measurements. The study demonstrates the effectiveness and robustness of the proposed VMD-SH method in accurately estimating modal parameters of tall buildings from acceleration response data.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.101-105
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• 2006

Disk radial runout creates a periodic relative motion between the laser beam spot and tracks formed on an optical disk. While only focus control is activated, the periodic relative motion yields sinusoid-like waves in the tracking error signal, where one cycle of the sinusoid-like waves corresponds to one track. The frequency of the sinusoid-like waves varies depending on the disk rotational speed and the amount of the disk radial runout. If the frequency of the tracking error signal in the off-track state is too high due to large radial runout of the disk, it is not a simple matter to begin track-following control stably. It might take a long time to reach a steady state or tracking control might fail to reach a stable steady state in the worst case. This article proposes a simple method for reducing the relative motion caused by the disk radial runout in the off-track state. The relative motion in the off-track state is effectively reduced by a drive input obtained through measurements of the tracking error signal and simple calculations based on the measurements, which helps reduce the transient response time of the track-following control. The validity of the proposed method is verified through an experiment using an optical disk drive.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.158-165
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• 1994

A fiber optic voltage sensor is demonstrated with a new signal processing scheme that displays the magnitude and the waveform of applied voltage with immunity from the signal frequency change. The sensor is based on a Mach-Zehnder interferometer with a PZT phase modulator as a sensing element. We observed a linear relationship between applied voltage and the number of fringe shift during a half cycle of the ac signal. The temperature dependence of the sensor output is experimentally evaluated over the temperature range from $-20^{\circ}C to 80^{\circ}C$. It is demonstrated that the detrimental polarization modulation effect can be overcome by using polarization maintaining fibers or a half-wave plate. plate.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.51-53
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• 2006

This paper proposes a portable ECG monitoring system, which integrates uptodate PDA and RF communication technology. The aim of the study is to acquire the subject's biomedical signal without any constraint. It has two types of transmission mode, which are total signal transmission mode and HR(heart rate)/SC(step count) transmission mode. In audition, wireless communication technology uses Zigbee Wireless PAN and can work in low-power mode, which is one of the advantages of ZiBbee communication technology. The developed system is composed of a transmitter and a receiver. The transmitter has three-axial acceleration sensor. ECG amplifier and Zigbee communication controller. In total signal transmission mode, it can send data 50 packets per second whose transmission speed corresponds to 300 ECG samples and 60 acceleration samples. In HR/SG transmission mode, it can calculate heart rate from EEG data with 216 samples per second and step count from acceleration data and send a packet every cardiac cycle. The receiver forwards the received data to PDA, where the data can be stored and displayed. Therefore, the developed device enables to continuous monitoring for Activities of Daily Living(ADL). Also, this method will reduce medical costs in the aged society.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.10
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• pp.1123-1130
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• 2015

Network on a chip(NoC) is a communication subsystem between intellectual property(IP) cores in a SoC and improves high performance in the scalability and the power efficiency compared with conventional buses and crossbar switches. NoC needs a synchronizer to overcome the metastability problem between data links. This paper presents a new mesochronous synchronizer(MS) which is composed of selection window generator, selection signal generator, and data buffer. A delay line circuit is used to build selection window in selection window generator based on the delayed clock cycle of transmitted clock and the transmitted clock is compared with local clock to generate a selection signal in the SW(selection window). This MS gets rid of the restriction of metastability by choosing a rising edge or a falling edge of local clock according to the value of selection signal. The simulation results show that the proposed MS operates correctly for all phase differences between a transmitted clock and a local clock.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.135-148
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• 2002

In this paper, a queue length calculation algorithm using image detectors has been proposed. The algorithm produces the queue length using a pair of image detectors installed both on upstream and on downstream of a corridor. In addition, a new framework for controlling the traffic signal system based on queue length has been presented. More specifically, the scheme of determining the cycle time and green split using the queue lengths has been proposed. To validate the results, a simulation study was conducted with a network environment. Results showed that the proposed method gave better operational performance than a traditional method. However, additional validation effort is necessary in order to apply the real traffic conditions.