• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.457-462
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• 2011

In this study, a simplified design procedure for friction dampers of a multi-story structure in order to reduce seismic response is proposed. To get insight for control effect of the structure with friction dampers is difficult, because of a nonlinear characteristic by a friction damper. Since a control force of a friction damper is influenced by coupling velocity between floors, adjoining modes are coupled. Thus structural response are derived by assuming steady-state response in resonance. As it is impossible that an exact solution is obtained for seismic load, first, a closed form solution can be achieved under harmonic vibration. Second, to convert a three-story building into a single-degree-of-freedom(SDOF) structure, modal analysis is performed. Third, an equivalent damping ratio is derived with utilizing closed form solution. And response reducing factor is proposed by it. Finally, friction force of a damper is designed for using response reducing factor, and then designed dampers are verified for seven seismic data. The nonlinear analysis results confirm the validity of the proposed procedure.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.55-59
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• 2008

In this paper, the linearity of Doherty amplifier has been improved by applying a compact slow-wave microstrip branch-line coupler on the output of Doherty amplifier. The proposed branch coupler has four microstrip high-low impedance resonant cells periodically placed inside the branch-line coupler to result in high slow-wave effect. The new coupler not only effectively reduces the occupied area to 30% of the conventional branch-line coupler at 1.8GHz, but also has high second harmonic suppression performance. We obtained the 3rd-order intermodulation distortion ($IMD_3$) of -31.16 dBc for CDMA applications with that of maintaining the constant power added efficiency (PAE). The IMD3 performance is improved as much as -7 dBc compared with a Doherty amplifier.

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.25-32
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• 2000

Comparisons are made between the first hyperpolarizability $\beta$ of pure N-(4-nitrophenyl)-(L)-prolinol (NPP) and poly (methyl metacrylate) (PMMA) or poly-p-(phenylene terephthalates) (PPT) with NPP side group determined with two different methods, electric-field-induced second-harmonic generation (EFISHG) and hyper-Rayleigh scattering (HRS) methods. Both techniques yield the same values within the experimental errors for pure NPP and NPP-PMMA in 1,1,2,2-tetrachloroethane solution. But the measured results of NPP-PPT polymer in 1,1,2,2-tetrachloroethane solution are showing that the first hyperpolarizability was enhanced with an enhencement of a factor 9.7 in EFISHG and a factor 2.4 in HRS relative to pure NPP. These results indicate that nonlinear optical chromophores organized as side groups of polymers with a rigid backbone contribute coherently to the secondorder nonlinear response of the polymer in the dc electric field as polar polymer chains. hains.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.1104-1111
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• 2014

The digital substations are being built based on the IEC 61850 network. The cooperation and protection of power system are becoming more intelligent and reliable in the environment of digital substation. This paper proposes a novel method to prevent the malfunction caused by the Transformer Magnetizing Inrush Current(TMIC) using the IEC 61850 based data sharing between the IEDs. To protect a main transformer, the current differential protection(87T) and over-current protection(50/51) are used generally. The 87T IED applies to the second harmonic blocking method to prevent the malfunction caused by the TMIC. However, the 50/51 IED may malfunction caused by the TMIC. To solve that problem, the proposed method uses a GOOSE inter-lock signal between two IEDs. The 87T IED transmits a blocking GOOSE signal to the 50/51 IED, when the TMIC is detected. The proposed method can make a cooperation of digital substation protection system more intelligent. To verify the performance of proposed method, this paper performs the real time test using the RTDS (Real Time Digital Simulator) test-bed. Using the RTDS, the power system transients are simulated, and the TMIC is generated. The performance of proposed method is verified in real-time using that actual current signals. The reaction of simulated power system responding to the operation of IEDs can be also confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1113-1118
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• 2011

In order to evaluate the characteristics of solid-solid contact interfaces, reflection or transmission techniques involving normal-incidence longitudinal waves are generally used. However, these normal-incidence techniques are of limited use in field applications such as in the inspection of welded parts. The oblique-incidence ultrasonic technique may be an alternative for overcoming these problems. However, in this technique, the mode conversion at the contact interfaces should be taken into account along with the normal and tangential interface stiffness. In this study, we have suggested a theoretical model for obliqueincidence ultrasonic waves at the contact interfaces and analyzed their reflection and transmission characteristics. Experimental results showed that the measured reflection coefficient and second harmonic wave agreed well with the suggested theoretical model. Consequently, the oblique-incidence technique can be a promising method for evaluating the characteristics of the contact interfaces.

• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.143-149
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• 2001

We performed the intracavity frequency-doubling of a tunable continuous-wave Ti:sapphire laser using a lithium triborate $(LiB_3O_5, LBO)$ crystal. For an efficient intracavity frequency-doubling, we measured the spectral and the angular bandwidth about the $\theta$-direction of LBO crystal. The measured values at a fundamental wavelength of 800 nm were 1.54 nm.cm and 3.8 mrad.cm, respectively. As a result of an intracavity frequency-doubling, we obtained the second-harmonic generation output power of 5.3 mW at 400 nm with the full width at half maximum(FWHM) of 0.089 nm from the fundamental output power of 185 mW at 800 nm. The frequency-doubled output was tuned from 397 nm to 403 nm.403 nm.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.61-67
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• 2011

The confocal laser scanning microscopy and two-photon microscopy was implemented based on a single laser source and an objective lens. We imaged and compared the morphology of identical sites of ex vivo human skin using both microscopes. The back-scattering emission from the sample provided the contrast for the confocal microscopy. The intrinsic autofluorescence and the second harmonic generation were used as the luminescence source for the two-photon microscopy. The wavelength of the Ti:Sapphire laser was tuned at 710 nm, which corresponds to the excitation peak of NADH and FAD in skin tissue. The various cell layers in the epidermis and the papillary dermis were clearly distinguished by both imaging modalities. The two-photon microscopy more clearly visualized the intercellular region and the nucleus of the cell compared to the confocal microscopy. The fibrous structures in the dermis were more clearly resolved by the confocal microscopy. Numerous cells in papillary dermal layer, as deep as $100\;{\mu}m$, were observed in both CLSM and two-photon microscopy. While most previous studies focused on fibrous structure imaging (collagen and elastin fiber) in the dermis, we demonstrated that the combined imaging with the CLSM and two-photon microscopy can be applied for the non-invasive study of the population, distribution and metabolism of papillary dermal cells in skin.

• Journal of the Daesoon Academy of Sciences
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• v.23
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• pp.109-152
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• 2014

This paper deals with the artistic expression of religious thought in terms of the uniqueness of different images and creativity. The relationship between religion and art is complicated but popular in modern society. Film becomes the icon of modern culture to enhance the knowledge of religious traditions. Among many Korean religious films, Kang Daejin's work, The Way of Peace (1984) contains the life and thought of Kang Jeungsan(1871-1909), the highest god of Daesoonjinrihoe. First, the film, The Way of Peace, pays attention to the legitimacy of succession from Kang Jeungsan to Cho Jeongsan(1895-1958). Korea was beset with trouble both at home and abroad. China, Japan, Russia, and the US had the colonial desire to conquer the lands of Korea and to explore natural resources. Though the people of Eastern Learning(東學) protested government and Japanese colonialists, Jeungsan applied the principle of non-violence to the world. In order to save all the living beings of the world, he reordered the universe and renewed the harmonic relationship of human beings and their spirit. Second, The Way of Peace proposed the soteriology of peace and change to audience regardless of seekers(道人) or not. Jeungsan transformed the closed society to the open society, changed divided religions to the transcendent truth(道). He empowered the marginalized people such as women, the lowly, the elderly, and the sick, who were oppressed in the Confucian society. And he redeemed the people from the disease by healing all diseases and correcting disorders. In conclusion, The Way of Peace is a good resource of religious education by which we can overcome the religious illiteracy. The knowledge of new religious movements and Daesoonjinrihoe is necessary for us to understand the diversity of human nature. In the near future, the new images of Jeungsan should be created through multi-media and cultural contents for the new generation.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.849-854
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• 2023

In this paper, a high-efficiency power amplifier was designed by applying the operating point Class J using LDMOS(laterally diffused metal oxide semiconductor) and optimizing the output matching circuit so that the second harmonic impedance becomes the reactance impedance. The designed power amplifier has a frequency of 108 ~ 110 MHz, Characteristics of PAE(power added efficiency) is 71.5% at P_SAT output (54.5 dBm), 55.5% at P_1dB output (51.5 dBm), and 24.38% at 45 dBm. The CSB(carrier with sideband) amplifier, which is the reference signal in the spatial modulation method, has an operating output of 45 dBm ~ 35 dBm, and linear SDM(sum in the depth of modulation) characteristics(40% ± 0.3%) were obtained. We measure the characteristics in amplitude modulation according to the bias operating point of the power amplifier for CSB and propose the optimal operating point to obtain linear modulation characteristics.

• Phonetics and Speech Sciences
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• v.12 no.1
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• pp.65-74
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• 2020

This study aims to compare the acoustic characteristics of vowel phonation in children with spastic and dyskinetic cerebral palsy (CP). Thirty-four children aged 4-12 years with CP participated in the study (spastic 26, dyskinetic 8). Voice samples for the acoustic analysis were extracted from a sustained vowel /a/. All acoustic measures were made using Praat. Group differences were compared by an independent t-test or Welch-Aspin test, if the equivalence assumption was not met. The results of this study are as follow. First, maximum phonation time(MPT) was significantly shorter for the dyskinetic CP than for the spastic CP. Second, shimmer percent was significantly increased in the dyskinetic CP than in the spastic CP. Lastly, there were no significant group differences in both the first formant and the second formant. These findings indicate that the dyskinetic CP has a poorer respiratory capacity and poorer laryngeal function than the spastic CP. On the other hand, both groups have a comparable ability to articulate the vowel /a/. The results of the present study help speech language pathologists identify the speech motor control ability of children with two types of CP (spastic and dyskinetic) and help to make an intervention plan associated with a specific type of CP.