• Advances in nano research
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• v.16 no.5
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• pp.509-519
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• 2024

In this study, the static analysis of carbon nanotube-reinforced composites (CNTRC) beams resting on a Winkler-Pasternak elastic foundation is presented. The developed theories account for higher-order variation of transverse shear strain through the depth of the beam and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. To study the effect of carbon nanotubes distribution in functionally graded (FG-CNT), we introduce in the equation of CNT volume fraction a new exponent equation. The SWCNTs are assumed to be aligned and distributed in the polymeric matrix with different patterns of reinforcement. The rule of mixture is used to describe the material properties of the CNTRC beams. The governing equations were derived by employing Hamilton's principle. The models presented in this work are numerically provided to verify the accuracy of the present theory. The analytical solutions are presented, and the obtained results are compared with the existing solutions to verify the validity of the developed theories. Many parameters are investigated, such as the Pasternak shear modulus parameter, the Winkler modulus parameter, the volume fraction, and the order of the exponent in the volume fraction equation. New results obtained from bending and stresses are presented and discussed in detail. From the obtained results, it became clear the influence of the exponential CNTs distribution and Winkler-Pasternak model improved the mechanical properties of the CNTRC beams.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.226-235
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• 2006

Populations of Zacco koreanus, distributed in four different tributaries of mid-upper reach Nakdong River were investigated to analyze a length-weight relation and von Bertalanffy's growth model. Fish sampling was conducted by common method (cast net and kick net) during March to October 2005. Fishes caught in the field were identified immediately, and then individuals of Zacco koreanus were preserved in 10% formalin to further measure their total length and weight in the laboratory. As the results of the equation based on length-weight relation, values of parameter b on the population of all tributaries were greater than 3.0 and the value on Bohyeon Stream was the maximum (3.26), indicating that the fish in the stream became more rotund as the length increases. In the mean time, we examined Brody growth constant (k) induced by the von Bertalanffy's growth model, and we found more steady state population in Wi (-0.18) and Byeongbo (-0.21) Streams than in fan (-0.38) and Bohyeon (-0.37) Streams. The findings would be used to assess local water environment on tributaries of the Nakdong River with understanding of ecological characteristics on the population of Zacco koreanus, as well as provide us fundamental information on domestic study of fish ecology.

• Korean Journal of Ecology and Environment
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• v.41 no.1
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• pp.43-53
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• 2008

This study was conducted to simulate storm hydrographs on a small forested watershed using TOPMODEL, which is a distributed hydrological model. The Myeongseong watershed, which is 58.3 ha in size, was selected to monitor rainfall and runoff data. The Monte Carlo simulation was also used to calibrate parameters of TOPMODEL. Six rainfall-runoff pairs collected at the watershed in the year 1997 were used for parameter calibration, and eight rainfall-runoff pairs collected during the period of $1998\sim1999$ were used for validation effort. The errors of runoff volume ranged from -2.74% to 1.81%, and an average value of model efficiency in terms of runoff volume was 0.92 for the calibration period. The average value of observed peak discharge was $0.324m^3\;s^{-1}$ for six rainfall-runoff pairs, while the prediction value was $0.295m^3\;s^{-1}$. The simulation errors of peak discharge varied according to rainfall characteristics and antecedent condition, within ranges of -27.65% to -1.13%. The model efficiency for the validation period was 0.92. For the validation period, observed peak discharges have an average value of $0.087m^3\;s^{-1}$ and average value of simulated peak discharge was $0.090m^3\;s^{-1}$. Observed and simulated values of time to peak for the calibration period were 18.3 hrs and 11.0 hrs, respectively, and 16.6 hrs and 13.5 hrs, respectively, for the validation period.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.529-536
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• 2013

The semi-distributed rainfall runoff model of SWAT is applied to the Seom-river experimental watershed. The simulations of various antecedent periods before the targeted simulation periods of 2002 to 2009 are not necessary despite of the slight appearance of corresponding changes in simulated total runoff. The simulated results of total runoff by using various numbers of soil layer maps have little differentiated nevertheless the slight changes in simulated results have been appeared. The 7 parameters of CANMX, $CN_2$, ESCO, GW_REVAP, SOL_ALB, SOL_AWC, and SOL_K greatly govern the rainfall runoff are confirmed and their sensitivity analyses have been carried out. The optimal parameters used in SWAT are derived by SUFI-2 of SWAT-CUP. The NS and $R^2$ are 0.99 and 0.98, respectively which is shown the good agreement between the observed and the simulated results. The uncertainty factors of P-factor and R-factor are 0.85 and 0.06, respectively which is also shown the high efficiency of the model. The high applicability is also shown with improving the RMSE in SWAT model simulation using the parameters estimated by SUFI-2 of SWAT-CUP.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.3
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• pp.129-141
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• 2023

Crop models have been used to predict yield under diverse environmental and cultivation conditions, which can be used to support decisions on the management of forage crop. Cultivar parameters are one of required inputs to crop models in order to represent genetic properties for a given forage cultivar. The objectives of this study were to compare calibration and ensemble approaches in order to minimize the uncertainty of crop yield estimates using the SIMPLE crop model. Cultivar parameters were calibrated using Log-likelihood (LL) and Generic Composite Similarity Measure (GCSM) as an objective function for Metropolis-Hastings (MH) algorithm. In total, 20 sets of cultivar parameters were generated for each method. Two types of ensemble approach. First type of ensemble approach was the average of model outputs (E_em), using individual parameters. The second ensemble approach was model output (E_pm) of cultivar parameter obtained by averaging given 20 sets of parameters. Comparison was done for each cultivar and for each error calculation methods. 'Jowoo' and 'Yeongwoo', which are forage rice cultivars used in Korea, were subject to the parameter calibration. Yield data were obtained from experiment fields at Suwon, Jeonju, Naju and I ksan. Data for 2013, 2014 and 2016 were used for parameter calibration. For validation, yield data reported from 2016 to 2018 at Suwon was used. Initial calibration indicated that genetic coefficients obtained by LL were distributed in a narrower range than coefficients obtained by GCSM. A two-sample t-test was performed to compare between different methods of ensemble approaches and no significant difference was found between them. Uncertainty of GCSM can be neutralized by adjusting the acceptance probability. The other ensemble method (E_pm) indicates that the uncertainty can be reduced with less computation using ensemble approach.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1235-1239
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• 2003

On the base of network frame and protocol system of Ethernet the networked sensing technology based on Ethernet is studied and the design principles of industrial Ethernet measurement of control system is put forward, and the general structure model is built in the paper. An eight-bit economical MCU scheme is proposed, and a general scheme of distributed intelligent networked measuring and control equipment based on TCP/IP is designed too. A compact TCP/IP protocol stack are successfully implemented in eight-bit MCU. With C51 program language, method of modularized programming is applied in soft design. The problem of in-system modifying measuring and control strategy of its system is solved successfully by assigning memory dynamically and saving parameter with EEPROM, and it makes the intelligent networked measurement and control system can explain and analyses control strategy from PC. Experiment result shows that, the research of intelligent networked measurement and control equipment and system base on TCP/IP is successful, with flexible network, convenient usage, and good commonality.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.9
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• pp.67-74
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• 2009

For the surge currents like lightning currents containing high frequency components and the abnormal currents having high frequencies which cause the EMI(Electromagnetic interference) problems for the electronic devices and communication instruments, the linear grounding electrodes have the significantly composite impedance characteristics which are dependent on the frequency of the applied current. The impedance of a grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode having the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertically and horizontally-buried grounding electrodes are calculated by using the distributed parameter circuit model. The propriety of the simulations has been confirmed by comparing the simulated results with the measured results.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.1-7
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• 2011

This paper proposes an enhanced noise robust algorithm for fault location on double-circuit transmission line for the case of single line-to-ground (SLG) fault, which uses distributed parameter line model that also considers the mutual coupling effect. The proposed algorithm requires the voltages and currents from single-terminal data only and does not require adjacent circuit current data. The fault distance can be simply determined by solving a second-order polynomial equation, which is achieved directly through the analysis of the circuit. The algorithm, which employs the faulted phase network and zero-sequence network with source impedance involved, effectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The proposed algorithm is tested using MATLAB/Simulink under different fault locations and shows high accuracy. The uncertainty of source impedance and the measurement errors are also included in the simulation and shows that the algorithm has high robustness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.1
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• pp.88-95
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• 2000

In this paper, an expansion-resonator type pulsation attenuator is proposed to absorb and attenuate flow an pressure ripple with high frequencies generated from hydraulic control systems. The basic principle of a pulsation attenuator proposed here is applied to propagation, reflection, absorption of pressure waves at the cross section of discontinuity and resonance in the pipeline. It has advantage of the compact size and high degree fo freedom for installation in hydraulic systems. The design scheme based on distributed parameter pipeline system with dissipative viscous compressible model is developed. To investigate the reduction of flow and pressure ripple with high frequencies produced by swash plate type axial piston pump, two kinds of attenuators are manufactured. It is experimently confirmed that the spectral intensity of flow and pressure ripple with high frequencies from the pump are reduced up to about 20$^{\circ}$~30dB by using attenuators proposed here. The calculated results were in good agreement with the measured values. From there sults of this study, it is shown that an expansion-resonator type pulsation attenuator is effective in a wide frequency ranges to attenuate the flow and pressure ripple from hydraulic components.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.230-244
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• 1996

We derive analytic expressions for the spontaneous emission spectrum (SES) of a multisection distributed feedback (DFB) structure device employing complex coupled gratings including the effects of both facets reflections. The multisection DFB structure device used in the analysis is a general model which allows the independent phase of a grating in each section, and the sections without gratings. The expressions are the same as those derived by makino and glinski in case the gratings are index coupled and the phase of a grating in each section, ${\varphi}_k$ is '0' which means the phase of gratings in the device is ocntinuous. The expressions for the SES of a phase-shift-controlled (PSC) DFB structure device using tunable devices are derived from the general expressions. The number of parametes of the expressions is reduced by using the parameter of effective phase shift defined by the sum of the phase shift in a PSC region and the difference of the phase of a grating in each active region. Equations showing the effect of both facets reflections and the effective phase shift on the SES are derived. The validaty of the equations is verified by computer simultions. Computer simulation results also show the possibility of evaluating the structure parametes of the device from its SES.