• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.491-493
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• 2013

This paper proposes a frequency-doubling optoelectronic oscillator employing a novel three-arm dual-output Mach-Zehnder modulator (MZM). One output of the MZM generates the fundamental-frequency signal which is recycled by the microwave optical fiber link for oscillation, and the other output can generate the frequency-doubled signal. Experiment was conducted using a commercial two-arm MZM, a phase modulator, and an optical fiber link of 89 meters in length. A 19-GHz frequency-doubled signal was successively obtained with fundamental signal suppression more than 36 dB.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.4041-4059
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• 2019

Key establishment method based on channel reciprocity for time division duplex (TDD) system has earned a vital consideration in the majority of recent research. While most of the cellular systems rely on frequency division duplex (FDD) systems, especially the 5G network, which is not characterized by the channel reciprocity feature. This paper realizes the generation of a group secret key for multi-terminals communicated through a wireless network in FDD mode, by utilizing the nature of the physical layer for the wireless links between them. I consider a new group key generation approach, which using bitwise XOR with a modified pairwise secret key generation approach not based on the channel reciprocity feature. Precisely, this multi-node secret key agreement technique designed for three wireless network topologies: 1) the triangle topology, 2) the multi-terminal star topology, and 3) the multi-node chain topology. Three multi-node secret key agreement protocols suggest for these wireless communication topologies in FDD mode, respectively. I determine the upper bound for the generation rate of the secret key shared among multi-node, for the three multi-terminals topologies, and give numerical cases to expose the achievement of my offered technique.

• Journal of Wellbeing Management and Applied Psychology
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• v.7 no.2
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• pp.13-21
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• 2024

Purpose: The purpose is to expand the role of local senior welfare centers as a place for intergenerational integration by analyzing the intergenerational awareness and satisfaction of participants in the intergenerational integration program. Research design, data and methodology: The empirical study conducted a survey on 205 participants (114 seniors, 91 teenagers) of the generation integration program being implemented at a senior welfare center located in Seoul. Results: Regarding the satisfaction of participants in the generation integration program, both the elderly and youth showed that the more contact they had between generations, the higher the satisfaction with participation. In the case of the elderly, the better the subjective health status, the older the respondent, and the lower the educational level, the higher the satisfaction, and the more frequently they met youth, the higher the satisfaction. On the other hand, the longer the youth participated in the program, the weaker their negative emotions toward the elderly, and the higher the degree of visits to grandparents, the higher their satisfaction with participation. Conclusions: The biggest determinant of satisfaction with the generational integration program at senior welfare centers is the intensity and frequency of contact between the elderly and youth generations.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.39-40
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• 2007

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2344-2347
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• 2007

To generate negative ion, a small dielectric barrier discharge (DBD) plasma reactor was used in this study and operated by high AC voltage. With increasing of voltage, we can get more negative ions. However unfortunately, if the input voltage is too high, it will also cause formation of ozone which is very harmful to human being health. So the work of finding out the best condition of Voltage and frequency was carried out firstly. After several times of measurement, operating at 20 kHz frequency is the best condition generating high ion concentration without ozone. For the purpose of finding out the best reactor structure, two types of surface dielectric barrier discharge (DBD) reactors were examined to produce negative oxygen ions at the conditions of 20 kHz frequency. The results indicated that the surface DBD reactor with several small tips showed better characteristics for generation of negative oxygen ions at the same condition.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.2
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• pp.103-110
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• 2020

Seismic qualification of instruments and devices mounted on electrical cabinets in a nuclear power plant is performed in this study by means of the in-cabinet response spectrum (ICRS). A simple method and two rigorous methods are proposed in the EPRI NP-7146-SL guidelines for generating the ICRS. The simple method of EPRI can give unrealistic spectra that are excessively conservative in many cases. In the past, the time domain analysis (TDA) methods have been mostly used to analyze a structure. However, the TDA requires the generation of an artificial earthquake input motion compatible to the target response spectrum. The process of generating an artificial earthquake may involve a great deal of uncertainty. In addition, many time history analyses should be performed to increase the accuracy of the results. This study developed a numerical analysis program for generating the ICRS by frequency domain analysis (FDA) method. The developed program was validated by the numerical study. The ICRS calculated by FDA thoroughly matched with those obtained from TDA. This study then confirms that the method it proposes can simply and efficiently generate the ICRS compared to the time domain method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.221-228
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• 1997

A strong combustion-driven sound from a surface burner made of a perforated metal fiber plate for premixed gas was investigated to clarify the physical mechanism of its generation. A simple model was developed for the acoustic power generation in terms of the heat transfer response function and the acoustic impedance of the burner. The acoustic impedance of the perforated metal fiber placed on the open exit was measured and the heat release response of the burner to the oscillating flow associated with the acoustic disturbance was expressed in terms of a response function. It was found that the power is generated by the heat release in response to the downstream particle velocity, in contrast to the upstream velocity in the case of the Rijke oscillation driven by a heater placed in the lower half of a columm with upstream flow. The measured frequencies of the oscillation were in agreement with the estimated resonance frequencies and their excitation was varied with the combustion conditions. For the same fuel rate, the excited frequency increases with the air ratio if it is low but decreases with the ratio if not so low. Such frequency characteristics were explained by assuming a heat release response function with a time constant and it was shown that the excited frequency decreases as the time constant increases.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.347-350
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• 2006

The high efficiency full-bridge LLC resonant converter using a contact-less transformer is proposed for the photovoltaic power generation system. For the series resonance with a series capacitor, the LLC resonant converter utilizes the leakage inductance and magnetizing inductance of a contact-less transformer. Unlike the conventional series resonant converter operated to the continuous resonant current at above resonance frequency, the proposed converter operates to the discontinuous resonant current at the narrow frequency control range below resonance frequency. Due to the discontinuous mode resonant current, the proposed converter can be achieved the zero voltage switching (ZVS) in the primary switches and the zero current switching (ZCS) in the secondary rectification diodes without any auxiliary circuit. In this paper, the experimental results of the proposed full-bridge LLC resonant converter using a contact-less transfonner are verified on the simulation based on the theoretical analysis and the 150W experimental prototype.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.278-284
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• 2004

A Second Harmonic Generation Frequency Resolved Optical Gating(SHG FROG) system was developed. Its performance test shows that it is capable of accurately measuring the temporal evolution of the electric field, both amplitude and phase, of femtosecond light pulses. For the retrieval of the temporal evolution of light pulses from their spectrograms obtained by using the FROG system, Principal Components Generalized Projection(PCGP) algorithm is used and in addition we used additional constraints of second-harmonic spectrum, marginals in frequency and time-delay of the spectrogram. Such modification of the software brings about significant improvement in speed and stability of the pulse retrieval process.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.233-239
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• 2007

As the Kyoto Protocol, which aims at reducing greenhouse gases in accordance to the UNFCCC, came into force, research on environment friendly energy resources has been a matter of concern worldwide. As a general power generation system, among renewable energy resources, that is interconnected and operated with power system, the wind turbine is emerging as an effective alternative. Since power capacity of the wind turbine has been steadily increasing and its relative importance is also increasing in total facility capacity, we cannot ignore its effect. Because controlling generation output in the wind turbine is not as easy as in the synchronous machine due to its facility characteristics and it generates irregular output fluctuations when interconnected with power system, system interconnection was difficult. But the effect of large capacity wind turbine on isolated power system like Jeju island is serious problem on the frequency stability. Accordingly, it is necessary to analyze the effects of wind turbine on system interconnection and assess the optimum capacity of wind turbine that satisfies the most important principle of stable power supply. This paper have analyzed the effects of wind turbine capacity increases on the system and suggested the method of the capacity to achieve its steady operation. And It is applied to the Jeju island.