• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.149-155
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• 1997

We have successfully grown colorless and transparent Rb-doped potassium niobate (KRN) single crystals using the top seeded solution growth(TSSG) technique. In our crystal growth experiments, the Rb doping concentrations within the melt range from 2-15 mol% relative to that of Nb$_2$O5. Atomic absorption measurements indicate that the Rb content in the KRN solid solution is rather low; the Rb segregation coefficient is found to be on the order of 0.05. It is believed that this is due to the relatively much larger Rb+ ionic radius compared to that of K+, rendering it more difficult for Rb to replace K in the KNbO$_3$(KN) host lattice. Preliminary single-pass second harmonic generation (SHG) experimental results indicate that there exists marginal improvement in the phase-matching temperature tolerance of KRN compared to that of pure Kn single crystals.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.230-231
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• 2003

$KNbO_3$is one of the best materials for efficient nonlinear frequency conversion, due to its large nonlinear optical coefficient ($d_{33}$ ＝ 20.6 pm／V), wide transparency range (0.4 ~ 5 $\mu$m) and freedom from photorefractive effects. Quasi-phase-matched second harmonic generation using periodically poled $KNbO_3$ (PPKN) crystals has been reported. Here we report on fabrication of PPKN and demonstration of a pulsed optical param etric oscillator (QPM OPO) pumped by an Nd：YAG laser. (omitted)

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.128-132
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• 2013

L-Arginine semi-oxalate (LASO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Photoluminescence studies confirm the violet fluorescence emission peak at 395 nm. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV-VIS-NIR spectrum. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. The solid state parameters such as plasma energy, Penn gap, Fermi energy and polarizability were calculated to analyze second harmonic generation (SHG). Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.607-612
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• 1996

A series of new NLO-active poly(4-nitrophenylallylamine) derivatives was synthesized by the nucleophilic substitution reaction of several substituted 4-nitrohalobenzenes and poly(allylamine hydrochloride). All polymers obtained were amorphous and their glass transition temperatures (Tg) were observed around 148-160 ℃. For each of these polymers, their specific Tg values were dependent on characteristic electronic structures. UV-visible absorption spectra showed maximum absorption intensity at 355-393 nm for π-π* transition of alkylaminonitrophenyl groups. The χ(2)value of poly(4-nitrophenylallylamine), as determined by the second harmonic generation at 1064 nm, for a thin polymer film poled at an elevated temperature, was 1.4x10-8esu. The third-order NLO properties of poly(4-nitrophenylallylamine) derivatives were evaluated through measurement of degenerate four-wave mixing technique and χ(3) coefficient in the range of 2.7~3.2x10-12 esu at 602 nm was found with 400 fs laser pulses.

• International Journal of Computer Science & Network Security
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• v.23 no.8
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• pp.40-48
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• 2023

Speech Emotions recognition has become the active research theme in speech processing and in applications based on human-machine interaction. In this work, our system is a two-stage approach, namely feature extraction and classification engine. Firstly, two sets of feature are investigated which are: the first one is extracting only 13 Mel-frequency Cepstral Coefficient (MFCC) from emotional speech samples and the second one is applying features fusions between the three features: Zero Crossing Rate (ZCR), Teager Energy Operator (TEO), and Harmonic to Noise Rate (HNR) and MFCC features. Secondly, we use two types of classification techniques which are: the Support Vector Machines (SVM) and the k-Nearest Neighbor (k-NN) to show the performance between them. Besides that, we investigate the importance of the recent advances in machine learning including the deep kernel learning. A large set of experiments are conducted on Surrey Audio-Visual Expressed Emotion (SAVEE) dataset for seven emotions. The results of our experiments showed given good accuracy compared with the previous studies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.5
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• pp.437-443
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• 2004

Aperture has been employed on the ground plane in the hairpin resonator. Aperture has been fabricated by etching the part of the ground effected coupling coefficient and then quality factor of hairpin resonator has been increased. When the hairpin oscillator using aperture has been compared with the conventional hairpin oscillator using microstrip, it has been improved the phase noise about 19 ㏈c @100 ㎑. As a result of PBG connecting to the output of the employing aperture hairpin oscillator, the second and third harmonics are suppressed. In this paper, oscillator has been designed and fabricated in operating 5.8 ㎓ band. The output power has been obtained 0,67 ㏈m and the second harmonic has been suppressed about -53,67 ㏈c.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.4
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• pp.251-257
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• 2015

In ultrasonic nonlinear parameter measurement using the fast Fourier transform(FFT) of tone-burst signals, the side lobe and leakage on spectrum because of finite time and non-periodicity of signals makes it difficult to measure the harmonic magnitudes accurately. The window function made it possible to resolve this problem. In this study, the effect of the Hanning and Turkey window functions on the experimental measurement of nonlinear parameters was analyzed. In addition, the effect of changes in tone burst signal number with changes in the window function on the experimental measurement was analyzed. The result for both window functions were similar and showed that they enabled reliable nonlinear parameter measurement. However, in order to restore original signal amplitude, the amplitude compensation coefficient should be considered for each window function. On a separate note, the larger number of tone bursts was advantageous for stable nonlinear parameter measurement, but this effect was more advantageous in the case of the Hanning window than the Tukey window.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.13 no.1
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• pp.28-32
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• 2002

Background and Objective : Classical singing students who have received in systematic voice training appeared distinctive voice characteristics compared to normal people who have not received in systematic voice training. The purpose of this study was to determine the correlation between acoustic parameters and Electroglottography(EGG) parameters in two groups(ordinary college students vs. classical singing students group). Materials and Methods : The 80 ordinary college students and 65 classical singing students participated in this study by utilizing Dr. speech program to obtain acoustic measurements and physiologic measurements simultaneously. The Pearson correlation coefficient was used to find the correlation between acoustic parameters and EGG parameters in two groups(ordinary college students group and classical singing students group). Results : The results of the study were as follows : First, there was no correlation between Jitter and EGG Jitter in ordinary college students group, but there was strong correlation between Jitter and EGG Jitter in classical singing students group. Second, there was no correlation between Shimmer and EGG Shimmer in ordinary college students group, but there was strong correlation between Shimmer and EGG Shimmer in classical singing students group. Third, there was no correlation between Harmonic to Noise Ratio(HNR) and EGG HNR in ordinary college students group, but there was strong correlation between HNR and EGG HNR in classical singing students group. Finally, there was no correlation between Normalized Noise Energy(NNE) and EGG NNE in two groups.

• Polymer(Korea)
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• v.25 no.6
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• pp.803-810
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• 2001

A nonlinear optical hyperbranched polyester (PE-Azo/Hyper) was synthesized from 4-[N,N-bis(hydroxyethyl)amino-4'-formyl] azobenzene and cyanoacetic acid by a Knoevenagel polycondensation using 4-(dimethylamino) pyridine as a base. The resulting polymer was soluble in polar aprotic solvents such as N,N-dimethylformamide and 1-methyl-2-pyrrolidinone and could be processed into optical quality films by spin coating. The molecular weight was determined to be $M_w$=61,800 ($M_W/M_n{=1.86}$) by gel permeation chromatography using polystyrene as a standard. No melting point was detected by differential scanning Calorimeter, indicating that this polymer presents an amorphous state. It shows a glass transition temperature of $121^{\circ}C$. The second-order nonlinear optical coefficient $d_{33}$ of the poled polymer determined by the second harmonic generation at 1064 nm was 25.4 pm/V.

• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.761-769
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• 2018

In this work, an optimization method of Friction Tuned Mass Damper (FTMD) parameters is presented. Friction tuned mass dampers (FTMD) are attached to mechanical structures to reduce their vibrations with dissipating the vibratory energy through friction between both bodies. In order to exploit the performances of FTMD, the determination of the optimum parameters is recommended. However, the presence of Coulomb's friction force requires the resolution of a non-linear stick-slip problem. First, this work aims at determining the responses of the vibratory system. The responses of the main mass and of the FTMD are determined analytically in the sticking and sliding phase using the equivalent damping method. Second, this work aims to optimize the FTMD parameters; the friction coefficient and the tuned frequency. The optimization formulation based on the Ricciardelli and Vickery method at the resonance frequencies, this method is reformulated for a system with a viscous damping. The inverse problem of finding the FTMD parameters given the magnitude of the force and the maximum acceptable displacement of the primary system is also considered; the optimization of parameters leads to conclude on the favorable FTMD giving significant vibration decrease, and to advance design recommendations.