• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.133-140
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• 2020

We discuss the method of a high precision range trigger and generation for a high range resolution radar. To verify the designed range resolution performance, we use test-equipments which can absolutely make a precision range shorter than the desined range resolution. The accuracy of generated range is proportional to the system reference clock. However, the system main processor is limited to input reference clocks and a higher available one is expensive in the conventional method. To solve this problem, we proposed that the range trigger and generation method using multi-phase-shiftings and integration. Through a experiment, we verified that the proposed method made problems which can be ocurred in the conventional method clear.

• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.35-47
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• 2001

This paper describes an efficient harmonic-CELP speech coder by taking advantages of harmonic and CELP coders into account. According to frame voicing decision, the proposed harmonic-CELP coder adopts the RP-VSELP coder as a fast CELP in case of an unvoiced frame, or an improved harmonic coder in case of a voiced frame. The proposed coder has main features as follows: simple pitch detection, fast harmonic estimation, variable dimension harmonic vector quantization, perceptual weighting reflecting frequency resolution, fast harmonic synthesis, naturalness control using band voicing, and multi-mode. These features make the proposed coder require very low complexity, compared with HVXC coder To demonstrate the performance of the proposed coder, a 2.4 kbps coder has been implemented and compared with reference coders. From results of informal listening tests, the proposed coder showed good quality while requiring low delay and complexity.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.132-140
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• 2001

A universal motor is a small dc series machine motor that is designed to operate from an ac machine. The characteristics of universal motors are high no-load and staring torque. Because of the high operating speed, the size of these motors for a given hp rating is typically smaller that other fractional hp ac machine, making it ideal for hand-held tools and appliances where weight, compactness, and speed are importance factors. A phase-angle control with AC drive system gains a high popularity due to their simple implementation, but contains the disadvantage of their poor input power factor, subharmonic current. Pulse width modulation control with DC drive systems increase the power factor as without delay phase angle. This paper analyzed the subharmonic characteristics of the phase angle control system that is controlled by zero voltage crossing similar to traditional method, and the dc chopper system that is used PWM.

• Journal of Biosystems Engineering
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• v.36 no.1
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• pp.15-22
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• 2011

An experimental variable rate nursery sprayer was developed to adjust application rates for canopy volume in real time. The sprayer consisted of two vertical booms integrated with ultrasonic sensors, and variable rate nozzles coupled with pulse width modulation (PMW) based solenoid valves. A custom-designed microcontroller instructed the sensors to detect canopy size and occurrence and then controlled nozzles to achieve variable application rates. A spray delivery system, which consisted of diaphragm pump, pressure regulator and 4-cycle gasoline engine, offered the spray discharge function. Spray delay time, time adjustment in spray trigger for the leading distance of the sensor, was measured with a high-speed camera, and it was from 50 to 140 ms earlier than the desired time (398 ms) at 3.2 km/h under indoor conditions. Consequently, the sprayer triggered 4.5 to 12.5 cm prior to detected targets. Duty cycles of the sprayer were from 20 to 34 ms for senor-to-canopy (STC) distance from 0.30 to 0.76 m. Outdoor test confirmed that the nozzles were triggered from 290 to 380 ms after detecting tree canopy at 3.2 km/h. The spray rate of the new sprayer was 58.4 to 85.2% of the constant application rate (935 L/ha). Spray coverage was collected at four areas of evergreen canopy by water sensitive papers (WSP), and ranged from 1.9 to 41.1% and 1.8 to 34.7% for variable and constant rate applications, respectively. One WSP area had significant (P < 0.05) difference in mean spray coverage between two application conditions.

• Atmosphere
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• v.18 no.2
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• pp.97-109
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• 2008

The aerosol characteristics in terms of 4 different cases (Asian dust, fog, clear sky and cloud) which had happened at Anmyeon Island in April 2006 were studied using various measurements such as the Micro Pulse Lidar (MPL), sunphotometer, $\beta$-ray $PM_{10}$ Analyzer, anemoscope and anemometer. In addition, synoptic charts, back trajectory analyses and satellite images were also used to help characterize the aerosol events. The aerosol optical properties were featured by the Aerosol Optical Depth (AOD) and ${\AA}ngstr\ddot{o}m$ exponent which were estimated by the sunphotometer. When Anmyeon Island was dominated by the Asian dust, the AOD was sharply increased as seven times as a yearly average of it (0.35). As compared with a yearly average of the ${\AA}ngstr\ddot{o}m$ exponent of 0.97, the ${\AA}ngstr\ddot{o}m$ exponent of a dust day was significantly low (0.099). In addition, $PM_{10}$ mass concentration showed an extremely high record. The maximum concentration reached $1790.5{\mu}gm^{-3}$ on 8 April 2006. The maximum mass concentration was shown with delay when the wind speed of $0ms^{-1}$ was observed. It was also found that a satellite image of the MODIS-RGB had a good agreement with the results of those measurements. It was shown that the MPL was able to describe effectively the vertical distribution of aerosol for all the cases. In particular, the MPL evidently captured the aerosol layer before the cloud observation. The aerosol layer was similarly described by the AOD. On a clear sky day, the AOD had not only a very low value (0.054) but also a feature of homogeneity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12B
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• pp.1236-1243
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• 2010

The perimeter defense system was created and its characteristics were evaluated. It was designed to utilize the fiber sensing device, namely OTDR(Optical Time Domain Reflectometer) which has been used for the maintenance of the optical communication network. An OTDR was constituted by a pulse laser with the nature of 1310nm, +15dBm for the observation of 400 meter optical fence. The high-speed 32-bit processor(S3C2440) has applied to MPU(Main Processor Unit) which helps to improve the performance of OTDR algorithms. Consequently, the maximum error was 0.84 meter on the performance test of the 10km monitoring and the pass criteria of ${\pm}1m$ satisfied in all the sections. The alarm delay time was under 3 sec after detecting the disorder. For the case of secondary trespassing after primary trespassing, the optical switch was installed in OTDR to monitor the secondary trespassing and to measure the multi-point detection. Therefore, this paper shows that the detections of secondary trespassing and multi-point is possible by means of optical switch.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2116-2118
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• 2000

In the technique of Q-switching, very fast electronically controlled optical shutters can be made by using the electro-optic effect in crystals or liquids. The driver for the Pockels cell must be a high-speed, high-voltage switch which also must deliver a sizeable current. Common switching techniques include the use of vacuum tubes, cold cathode tubes, thyratrons, SCRs, and avalanche transistors. Semiconductor devices such as SCRs, avalanche transistors, and MOSFETs have been successfully employed to drive Pockels cell Q-switch. In this study, a simple driver for the Pockels cell Q-switch was developed by using SCRs, pulse transformer and TTL ICs. The Pockels cell Q-switch which was operated by this driver was employed in pulsed Nd:YAG laser system to investigate the operating characteristics of this Q-switch. And we have investigated the output characteristics of this Q-switch as a function of the Q-switch delay time to Xe flashlamp current on.

• Korean Journal of Optics and Photonics
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• v.19 no.5
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• pp.370-375
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• 2008

High-speed high-resolution terahertz time-domain spectroscopy (THz-TDS) is demonstrated using the asynchronous-opticalsampling (AOS) method. A time-domain signal with a 10-ns time window is rapidly acquired by using two femtosecond lasers with slightly different repetition frequencies to generate and detect a terahertz pulse wave, without a mechanical delay stage. The spectrum obtained by the fast Fourier transformation (FFT) of the time-domain waveform has a frequency resolution of 100 MHz. The time resolution of our spectrometer is measured using the cross-correlation method to be 278 fs. A transmission spectrum of water vapor is measured and the absorption lines are analyzed in the frequency range from 0.1 to 1.2 THz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1051-1058
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• 2014

This paper presents a Electrical characteristics of the Memristor device using the PSPICE for circuit analysis. After making macro model of the Memristor device for circuit analysis, electric characteristics of the model such as time analysis, frequency and DC analysis according to the input voltage were performed by PSPICE simulation. Also, we made simple circuits of memristor series and parallel structure and analyzed the simulated SPICE results. Finally, we made a memristor-capacitor (M-C) circuit. charge and discharge characteristics were analyzed. In case of input pulse signal of 250 Hz, the Memristor-capacitor circuit showed delay time of 0.6ms, rising time of 0.58 ms and falling time of 1.6 ms.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.89-97
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• 2007

This paper describes a load simulator with power recovery capability, which is based on the voltage source converter-inverter set. The load simulator can save the electric energy that should be consumed to test the operation and performance of the power quality compensator and the power equipment. The load simulator consists of a converter-inverter set with a DSP controller for system control and PWM pulse generation. The converter operates as a universal load to model the linear load and the non-linear load, while the inverter feed the energy back to the power source with harmonic compensation. the performance of proposed load simulator was analyzed with scaled-model experiment, interconnected with the active power filter. The experimental results confirms that the proposed load simulator can be utilized to test the performance of active power filter.