• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.3
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• pp.13-24
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• 2013

Agriculture is affected directly by climate conditions and changes, and it is necessary to understand the impact of climate change on agricultural reservoirs which are the main water resources for paddy fields in Korea. This study aimed to evaluate the impact of climate change on the anti-drought capacity including water supply capability (WSC) and drought response ability (DRA) of agricultural reservoirs based on RCP (Representative Concentration Pathway) 4.5 and 8.5 scenarios of CanESM2 (The Second Generation Earth System Model) provided by CCCma (Canadian Center for Climate Modeling and Analysis). The WSC and DRA were estimated using frequency analysis and runs theory. The six reservoirs (Yooshin, Nogok, Kumsung, Songgok, Gapyung, Seoma) were selected considering geographical characteristics and design criteria of reservoir capacity. In case of Seoma reservoir, more than 10 year drought return period (DRP), the variation of the WSC was estimated larger than the others. In case of Yooshin reservior (2~5 DRP) DRC was decreased in 2025s under RCP8.5. These results could be utilized for agricultural reservoirs management and future design criteria considering climate change impacts on paddy irrigation.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.61-69
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• 2016

This study is the results related to the combustion instability phenomenon with respect to combustor length and thermal power as variables in dual swirling combustor configuration. Especially, the beating phenomena having the insensitive resonance frequency of relatively constant peaks are observed when the combustor lengths increase in a lower power regime. This beating phenomenon might be occurred due to the interacting behaviors of pilot and main burners with different periods. Therefore, such insensitive response seems to be a result of the beating phenomenon with interaction between the pilot and main flames even though the combustor lengths are increased.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.2
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• pp.19-27
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• 2001

All accurate and efficient antenna feed model is very important for computing GPR response using the FDTD method In literature, there are several feed models such as the equivalent network in angular-frequency domain, 1-D transmission-line cell， voltage boundary condition in time domain, etc. In this paper, theoretical relationship among the models is investigated. It is found that the above three models become equivalent when a short and lossless feed line can match with its connected transmitter receiver). In view of accuracy and efficiency of the simulation, the FDTD results according to the feed models arc compared with the measured data of the receiving responses for an actual GPR system.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.81-86
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• 2005

A vibration monitoring system for a small class of wind turbine (W/T) is established and operated. The monitoring system consists of monolithic integrated chip accelerometer for vibration monitoring, anemometers for wind data acquisition and auxiliary sensors for atmospheric data. Using the monitoring system, vibration response of a 6kW W/T generator is investigated. Acceleration data of the W/T tower under various operation condition is acquired in real time using LabVIEW and is remotely transferred from the test site to the laboratory in school by internet. Vibration state of the tower structure is diagnosed within the operating speed range. Resonance frequency range of the test model is investigated with the wind speed data of the test site.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.22-32
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• 2001

The numerical investigation of obliquely incident wave interactions with fully submerged dual buoy/porous-membrane floating breakwaters placed in parallel with spacing is studied based on linear potential theory and Darcy's law. The numerical solutions are obtained by using a discrete-membrane dynamic model and second-kind modified Bessel function distribution over the entire boundaries of fluid regions. First, numerical solutions for an idealized dual submerged system without buoys are obtained. Second, a more practical dual submerged system with membrane tension provided by buoys at its tops is investigated by the multi-domain boundary element method particularly devised for dual buoy/porous-membrane problems with gaps. The velocity potentials of wave motion are coupled with porous-membrane deformation, and solved simultaneously since the boundary condition on porous-membrane is not known in advance. The effects of varying permeability on membranes and wave characteristics are discussed for the optimum design parameters of systems previously studied. The inclusion of permeability on membrane eliminates the resonances that aggravate the breakwater performance. The system is highly efficient when waves generated by the buoys and membranes were mutually canceled and its energy at resonance frequency dissipates through fine pores on membranes.

• Korea Journal of Hospital Management
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• v.25 no.1
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• pp.58-72
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• 2020

Purposes: This study aims to investigate the determinants of change-oriented organizational citizenship behavior(CO-OCB) of hospital employees and test the mediating effect of the job satisfaction and organizational commitment on the CO-OCB. Methods: Data were collected from the self-administered questionnaire survey for hospital employees of ten hospitals located in five regions, including Seoul. Out of 1,100 questionnaires which were distributed through the administrative routes, a total of 617 copies were returned(response rate 56.1%) and analyzed by frequency analysis, t-tests, correlation analysis, multiple regression, and path analysis using SPSS 21.0 and AMOS 21.0. Findings: The study results revealed that the explanatory power(56.4%) of the model was most significantly increased by the variables of psychological attributes(R²-change 33,5%). Also, the variables of self-efficacy, followed by hope, the organizational climate for innovation, the psychological safety climate, team-member exchange, and leader-member exchange were found to have positive total effects on CO-OCB, through the mediating variables of job satisfaction and organizational commitment. Practical Implications: The study results imply that, in order to improve the CO-OCB of hospital employees, the administrators have to take the integrated approach considering the various domains of factors including the psychological attributes, job characteristics, interpersonal relations, and organizational climate simultaneously.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.379-380
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• 2008

Molecular Dynamics (MD) simulations have been used to model the dynamics of the charge-compensating sodium ions in the non-stoichiometric hollandite Nax$(Ti_{8-x}Cr_x)O_{16}$. These interstitial ions reside in 'tunnels' in the crystal structure and move under the forces of both the ions making up the cage structure and the many body interactions of the other sodium ions in the tunnel. The Velocity Autocorrelation Function (VAF) of the sodium ions is calculated for a range of temperature from 250K to 1000K and converted into the linear ac-conductivity and ac-susceptibility response via Fourier transformation. A peak is found in the conductivity around $6\times10^{12}$ Hz that has some of the character of a Poley absorption. Here it is shown to be due to an harmonically coupled site vibrations of the sodium atoms, which extend only over a limited range. At frequencies below the peak the conductivity tends towards a constant i.e. dc value corresponding to a constant flow of ions through the simulation cell. At high temperatures the conductivity due to this ion transport process behaves like a metal with an insulator to metal transition occurring around a specific temperature.

• The Journal of Information Technology
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• v.7 no.3
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• pp.1-10
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• 2004

Considerable efforts has been recently devoted to the determination of accurate channel models for the Power Line environment, both for the indoor and outdoor cases. The common denominator and limitation of the known and previously published models is the particular type of approach followed. In this paper is concerned with a power line channel modeling for the more fast and efficiently power line communication experiment. A capacitor load channel simulator is a essential equipment in the power line modem development for indoor network. We accomplished a channel modelling by the frequency response method about the total 224 capacitor load cases. On the basis of this measurement modeling it is here revealed that the PLC is a more deterministic media that commonly believed.

• Smart Structures and Systems
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• v.12 no.5
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• pp.523-545
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• 2013

Piezoelectric and dielectric behaviors of a piezoceramic patch adhesively centered on a carbon composite plate are identified using a robust multi-objective optimization procedure. For this purpose, the patch piezoelectric stress coupling and blocked dielectric constants are automatically evaluated for a wide frequency range and for the different identifiable behaviors. Latters' symmetry conditions are coded in the design plans serving for response surface methodology-based sensitivity analysis and meta-modeling. The identified constants result from the measured and computed open-circuit frequencies deviations minimization by a genetic algorithm that uses meta-model estimated frequencies. Present investigations show that the bonded piezoceramic patch has effective three-dimensional (3D) orthotropic piezoelectric and dielectric behaviors. Besides, the sensitivity analysis indicates that four constants, from eight, dominate the 3D orthotropic behavior, and that the analyses can be reduced to the electromechanically coupled modes only; therefore, in this case, and if only the dominated parameters are optimized while the others keep their nominal values, the resulting piezoelectric and dielectric behaviors are found to be transverse-isotropic. These results can help designing piezoceramics smart composites for various applications like noise, vibration, shape, and health control.

• Steel and Composite Structures
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• v.23 no.6
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• pp.657-668
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• 2017

In the most of previous studies, researchers have restricted their own studies to consider the effect of single walled carbon nanotubes as a reinforcement on the vibrational behavior of structures. In the present work, free vibration characteristics of functionally graded annular plates reinforced by multi-walled carbon nanotubes resting on Pasternak foundation are presented. The response of the elastic medium is formulated by the Winkler/Pasternak model. Modified Halpin-Tsai equation was used to evaluate the Young's modulus of the multi-walled carbon nanotube/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the multi-walled carbon nanotubes wt% range considered. The 2-D generalized differential quadrature method as an efficient and accurate numerical tool is used to discretize the equations of motion and to implement the various boundary conditions. The effects of two-parameter elastic foundation modulus, geometrical and material parameters together with the boundary conditions on the frequency parameters of the plates are investigated. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of annular plates.