• Water for future
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• v.29 no.5
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• pp.173-184
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• 1996

In this study, a two-dimensional shallow-water equation was used to develop the mathematical model for computing water levels and flow distribution. In the discretization equations, based on the finite volume method (FVM), the third order Runge-Kutta method and the third order upwind scheme were introduced to handle the unsteady and vconvective terms in the governing equations. To determine the accuracy of the developed model, it was applied to the rectangular horizontal channel in a frictionless flow. The water depth and velocity obtained by the numerical model were found to agree closely with the exact solution. The model was also applied to the rectangular channel with both the symmetric and the non symmetric constriction. The velocity distribution of the flow and the propagation of the flood wave were simulated and the results well described the flow characteristics.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.315-323
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• 1998

$TiO_2$films of rutile and anatase phase have been prepared on silica glass substrates by the sol-gel method using $Ti(i-OC_3H_7)_4$. The effect of additives on the polymorph of $TiO_2$film has been examined in view of degree of crystallization. Third-order nonlinear optical properties of the both film have been investigated by the third harmonic generation method. The measured 3rd order nonlinear optical susceptibility of rutile and anatase thin films were about $1.4{\times}10^{-12}$ and $9.7{\times}10^{-13}$ esu, respectively.

• Human Ecology Research
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• v.58 no.2
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• pp.187-200
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• 2020

This study analyzes the teacher certification examination from 2014 to 2019. The research methods are summarized as follows. First, the questionnaire on tests conducted from 2014 to 2019 was divided into 'Teacher Eligibility Criteria', 'Assessment Area', and 'Evaluation Content Elements' for detailed analysis. Second, the examination for the 2019 school year from the 2014 school year compared the 2009 curriculum with the yearly question items in order to examine the correlation between the secondary school curriculum and test items. Third, this study examined the home economics department reflected in the curriculum of the five national universities. The results of the study are summarized as follows. First, according to the results of the questionnaire survey conducted from 2014 to 2019, the field of Home Economics education showed the highest rate of 25% or more in all years. Second, in order to examine the correlation between secondary school curriculum and Home Economics test items, this study compared the results of the 2014 - 2019 school year examination with the 2009 curriculum. Third, as a result of analyzing the curriculum of the five universities of the National College of Education, the basic courses were properly established at all colleges of education. As a result, the correlation was high overall, even within subcategories, the rate of exams was high only incertain attendants and the frequency of exams was low at some attendants.

• Journal of electromagnetic engineering and science
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• v.2 no.1
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• pp.22-27
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• 2002

This paper describes a SiGe HBT low noise amplifier (LNA) design for IMT-2000 mobile applications. This LNA is optimized for linearity in consideration of the out-of-band-termination capacitance. This LNA yields a noise figure of 1.2 dB, 16 dB gain, an input return loss of 11 dB, and an output return loss of 14.3 dB over the desired frequency range (2.11-2.17 GHz). When the RF input power is -2i dBm, the input third order intercept point (IIP3) of 8.415 dBm and the output third order intercept point (OIP3) of 24.415 dBm are achieved.

• Korean Journal of Health Education and Promotion
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• v.7 no.1
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• pp.72-82
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• 1990

The actual condition of drug abuse by some Juveniles in our country and effects of some elements on their drug abusing were observed providing basic materials for health education to juveniles to contribute to the health improvement of them and the reduction of the harmfulness of drug abuse. 1035 third school year students of some senior high schools in Seoul were subjected to the questionnaire survey. The results could be summarized as follows : 1. Among the twelve kinds of drug involved in the study, alcohol (72.0%), cigarette (44.2%), stimulants (23.9%), analgesics (7.9%) appeard abused in the order named. 2. As for the motives of using antitussives, 30.1% of students answered because of curiosity, then 28.8%, in order to get a calm condition, and then 16.4%, to get along with friends. 3. As the result from seeing how much each drug abuser is contact with his family, frends, school, social surroundings and himself, every abuser appeared having higher degree of discontentment with family, school, society and himself excepting friends. 4. And when analyzed the relationship between their misconducting and drug-abusing, a close relationship was shown : mere abusers among misconduct-experienced students, and more misconduct-experienced students among abusers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.149-153
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• 2005

A new method of power amplifier's linearity improvement using a Compact Microstrip Resonant Cell(CMRC) is proposed. It is found out that a CMRC at the input side gives better performance than that at the output. Tuning lines are used in the input and the output matching network to get the optimum performance. As a result, the 14.77 dB improvement fur the third-order IMD is obtained. And the size of the CMRC is only $17.1\times5.22mm$.

• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.98-104
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• 2009

An InGaP/GaAs MMIC LC VCO designed with Harmonic Noise Frequency Filtering(HNFF) technique is presented. In this VCO, internal inductance is found to lower the phase noise, based on an analytic understanding of phase noise. This VCO directly drives the on-chip double balanced mixer to convert RF carrier to IF frequency through local oscillator. Furthermore, final power performance is improved by output amplifier. This paper presents the design for a 1.721 GHz enhanced LC VCO, high power double balance mixer, and output amplifier that have been designed to optimize low phase noise and high output power. The presented asymmetric inductance tank(AIT) VCO exhibited a phase noise of -133.96 dBc/Hz at 1 MHz offset and a tuning range from 1.46 GHz to 1.721 GHz. In measurement, on-chip down-converter shows a third-order input intercept point(IIP3) of 12.55 dBm, a third-order output intercept point(OIP3) of 21.45 dBm, an RF return loss of -31 dB, and an IF return loss of -26 dB. The RF-IF isolation is -57 dB. Also, a conversion gain is 8.9 dB through output amplifier. The total on-chip down-converter is implanted in 2.56${\times}$1.07 mm$^2$ of chip area.

• Coupled systems mechanics
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• v.6 no.3
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• pp.251-272
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• 2017

In this paper, the thermo-mechanical vibration characteristics of functionally graded (FG) nanobeams subjected to three types of thermal loading including uniform, linear and non-linear temperature change are investigated in the framework of third-order shear deformation beam theory which captures both the microstructural and shear deformation effects without the need for any shear correction factors. Material properties of FG nanobeam are assumed to be temperature-dependent and vary gradually along the thickness according to the power-law form. Hence, applying a third-order shear deformation beam theory (TSDBT) with more rigorous kinetics of displacements to anticipate the behaviors of FG nanobeams is more appropriate than using other theories. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived through Hamilton's principle and they are solved applying analytical solution. The obtained results are compared with those predicted by the nonlocal Euler-Bernoulli beam theory and nonlocal Timoshenko beam theory and it is revealed that the proposed modeling can accurately predict the vibration responses of FG nanobeams. The obtained results are presented for the thermo-mechanical vibration analysis of the FG nanobeams such as the effects of material graduation, nonlocal parameter, mode number, slenderness ratio and thermal loading in detail. The present study is associated to aerospace, mechanical and nuclear engineering structures which are under thermal loads.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.473-480
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• 1994

We have applied nonlinear interferometry of coherent anti-Stokes Raman spectroscopy (CARS) to measure the nonresonant third order susceptibilities of various gases. For the experiment, we placed two gas cells serially and filled the first cell with argon as a calibration standard and the second cell with gases under test. The interference fringes of the CARS signals generated in the two gas cells were obtained by changing the thickness of the phase shifting unit which was made of BK-7 glass. The total effective nonresonant susceptibilities were determined from the measured amplitudes of the interference fringes of the CARS signals of the gases. The nonresonant susceptibilities were obtained by subtracting off resonant vibrational contributions from the total effective susceptibilities. The results of this work are compared with the published data and the overall uncertainty is estimated to be less than 5%. an 5%.

• Structural Engineering and Mechanics
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• v.64 no.5
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• pp.611-620
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• 2017

A new theory of weightless sagging planer elasto-flexible cables under point loads is developed earlier by the authors and used for predicting the nonlinear dynamic response of cable-suspended linear elastic beams. However, this theory is not valid for nonlinear elastic cracked concrete beams possessing different positive and negative flexural rigidity. In the present paper, the flexural response of simply supported cracked concrete beams suspended from cables by two hangers is presented. Following a procedure established earlier, rate-type constitutive equations and third order nonlinear differential equations of motion for the structures undergoing small elastic displacements are derived. Upon general quasi-static loading, negative nodal forces, moments and support reactions may be introduced in the cable-suspended concrete beams and linear modal frequencies may abruptly change. Subharmonic resonances are predicted under harmonic loading. Uncoupling of the nodal response is proposed as a more general criterion of crossover phenomenon. Significance of the bilinearity ratio of the concrete beam and elasto-configurational displacements of the cable for the structural response is brought out. The relevance of the proposed theory for the analysis and the design of the cable-suspended bridges is critically evaluated.