• Journal of the Optical Society of Korea
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• v.19 no.3
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• pp.255-259
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• 2015

We have proposed and experimentally verified a pulse-width modulation (PWM) generator which directly generated a PWM signal in the optical domain. Output waveforms were clear at the repetition rate of 16 MHz; the duty cycle (DC) was from 14.7% to 72.1%; and the DC-control resolution was about 4.399%/dB. The PWM generator' operation principle is based on the injection-locking property of a single-mode Fabry-$P{\acute{e}}rot$ laser diode (SMFP-LD). The SMFP-LD, which has a self-locked mode wavelength at ${\lambda}_{PWM}$, was used to detect the power of the injection-locking signal (optical analog input). If the analog input power is high, the SMFP-LD is locked to the wavelength of the input signal ${\lambda}_a$ and there is no output after an optical bandpass filter (OBF). If the analog input power is low, the SMFP-LD is unlocked and there is output signal at ${\lambda}_{PWM}$ after the OBF. Thus, the SMFP-LD plus the OBF provide digital output for an analog input. The DC of the output PWM signal can be controlled by tuning the power of the analog input.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.3925-3934
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• 2023

The importance of fast neutron detection for nuclear safeguards purposes has increased due to its potential advantages such as reasonable cost and higher precision for larger sample masses of nuclear materials. Pulse-shape discrimination (PSD) is inevitably used to discriminate neutron- and gamma-ray- induced signals from organic scintillators of very high gamma sensitivity. The light output (LO) threshold corresponding to several MeV of recoiled proton energy could be necessary to achieve fine PSD performance. However, this leads to neutron count losses and possible distortion of results obtained by neutron multiplicity counting (NMC)-based nuclear material accountancy (NMA). Moreover, conventional PSD techniques are not effective for counting of neutrons in a high-gamma-ray environment, even under a sufficiently high LO threshold. In the present work, PSD performance (figure-of-merit, FOM) according to LO bands was confirmed using a conventional charge comparison method (CCM) and compared with results obtained by convolution neural network (CNN)-based PSD algorithms. Also, it was attempted, for the first time ever, to reject fake neutron signals from distorted PSD regions where neutron-induced signals are normally detected. The overall results indicated that higher neutron detection efficiency with better accuracy could be achieved via CNN-based PSD algorithms.

• Journal of Power Electronics
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• v.4 no.1
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• pp.56-63
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• 2004

A new driving circuit for the SPSS (Single-Pulse Soft-Switching) PFC converter is proposed. The switching device of a SPSS converter switches once in every half cycle of an AC commercial power source. Therefore, it can be solved many problems caused by the high frequency operation. The proposed SPSS converter achieves the soft-switching operation and the EMI noise can be reduced. The resonant capacitor voltage supplies to the resonant inductor even if the input AC voltage is the vicinity of zero cross voltage. Then, the power factor and input current waveform can be improved without delay time. A new driving circuit achieves the operation of SPSS converter by one switching drive circuit. The proposed converter can be satisfied the IEC standard sufficiently

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.2051-2054
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• 2004

This paper proposes a more accurate task level energy measurement technique for high speed microprocessors. The technique is based on the relationship of the amount of current consumed by the microprocessor and the pulse width of the power supply controller chip, employed in the synchronous buck DC-DC converter in the microprocessor's power supply. The accuracy of the measurement is accomplished by measuring variation in pulse width in each power supply cycle. The major advantage of this technique is that its accuracy does not depend on the operating frequency of the microprocessor. To prove the proposed technique, we implemented the measurement unit of the microprocessor energy meter using an FPGA chip operating at 50 MHz. Both static and dynamic load measurement are tested in order to obtain some behaviours. Moreover, various commercially available mainboards which employ synchronous buck regulators at 200 KHz switching frequency, were measured. The results agree with previous works with better accuracy at higher operating frequency.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.252-255
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• 2004

This paper presents a new technique to generate the 1-bit signal by decoding Pulse Width Modulation (PWM) signal to a binary file before programming onto the ROM. Since each PWM signal requires only 1-bit digital signal, PWM signal and other forms of digital signal related to multi-bit can be simply generated. The results demonstrate that using this new technique to generate the PWM signal can simplify the process and hardware complication. Moreover, the signal's data and frequency can be easily modified by programming the data onto the ROM and using the counter, respectively, which can reduce the size of the circuit and make the PCB easier.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.509-514
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• 2004

This paper introduces the modified slip energy recovery system in order to improve its power factor and to reduce harmonics of line current waveforms. Twelve pulse line commutated converter with the chopper type IGBT is applied where the chopper is applied across the DC terminal and the chopped DC is fed to the converter operating as an inverter and then passed through the wye-wye and delta-wye transformer circuit. This scheme leads to be able to adjust the speed of the motor by the duty cycle of the chopper operating in PWM mode. The fuzzy logic controller is also introduced to the modified slip energy recovery system for keeping the motor speed to be constant when the load varies. The experimental results in testing the 0.22 kW wound rotor induction motor from no-load condition to rated condition show the effectiveness of the proposed control scheme.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.591-599
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• 2001

The paper identifies a severe form of core saturation instability in an DC/AC interaction system. It then seeks solutions to the problem by HVDC control means. This is achieved by a proper design of the Voltage Dependent Current Order Limiter (VDCOL), the Current Regulator and Timing Pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained one with the use of uncharacteristic harmonic filter on the AC side. Robustness of all the options has been demonstrated through recovery performance of the DC link in response to both I-phase and 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

• Journal of Environmental Impact Assessment
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• v.21 no.3
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• pp.461-468
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• 2012

In general, long-term changes of ecological factors take a pulse form in which they interact with other factors and go through a repeated increasing and decreasing cycle. The coupling of the two approaches the grid model and the box model in ecological modeling can lead to an in-depth understanding of the environment. The study analyzes temporal variations of major storages with an energy system model that formulizes effectively the relationships among nutrients, phytoplankton, and zooplankton in the Yellow Sea and the East China Sea. An increase of light intensity and standing stock of nutrient increase the magnitude and frequency of pulsing. Also, an immense reduction of nutrient concentration can cause extinction of the pulsing and bring about a steady state. It is concluded that the nutrient loads in freshwater discharge from the Yangtze affect the cycles of major ecological components as well as water quality variables and play an important role in the marine ecosystem.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.973-975
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• 1992

The Acoustic Emission due to treeing progress in Crosslinked Polyethylene(XLPE) is studied by using the self developed automatic measuring system of acoustic emission. Tree progression and average pulse amplitude are almost in proportion to the rising of applied voltage but there is no proportionality relation between tree progression and pulse numbers. From now on, Skewness and kurtosis of average cycle, special property of $\phi$-a distribution characteristics can be confirmed as the useful parameters of treeing deterioration.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1401-1405
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• 2010

We have successfully demonstrated of metal-insulator-semiconductor (MIS) capacitors with $HfO_2$/p-Si structures. The $HfO_2$ film was grown at $200^{\circ}C$ on H-terminated Si wafer by atomic layer deposition (ALD) system. TEMAHf and $H_2O$ were used as the hafnium and oxygen sources. A cycle of the deposition process consisted of 0.1 s of TEMAHf pulse, 10 s of $N_2$ purge, 0.1 s of $H_2O$ pulse, and 60 s of $N_2$ purge. The 5 nm thick $HfO_2$ layer prepared on Si substrate by ALD exhibited excellent electrical properties, including low leakage currents, no mobile charges, and a good interface with Si.