• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.6
• /
• pp.376-379
• /
• 2016

In this paper, the efficiency improvement of the heterojunction with intrinsic thin layer (HIT) solar cells is obtained by optimization process of p-type a-SiC:H as emitter. The optoelectronic of p-type a-SiC:H layers including the optical band-gap and conductivity under the methane gas content variation is conducted in detail. A significant increase in the Jsc by $1mA/cm^2$ and Voc by 30 mV are attributed to enhanced photon-absorption due to broader band-gap of p-a-SiC:H and reduced band-offsets at p-side interface, respectively of HIT solar cells.

• Journal of Information Processing Systems
• /
• v.1 no.1 s.1
• /
• pp.102-106
• /
• 2005

As long as the effective contributions of satellite images in the continuous monitoring of the wide area and long range of time period, Landsat TM and Landsat ETM+ satellite images are surveyed. After quantization and classification of the deviations between TM and ETM+ images based on approved thresholds such as gains and biases or offsets, a correlation analysis method for the compared calibration is suggested in this paper. Four time points of raster data for 15 years of the highest group of land surface temperature and the lowest group of vegetation of the Kunsan city Chollabuk_do Korea located beneath the Yellow sea coast, are observed and analyzed their correlations for the change detection of urban land cover. This experiment based on proposed algorithm detected strong and proportional correlation relationship between the highest group of land surface temperature and the lowest group of vegetation index which exceeded R=(+)0.9478, so the proposed Correlation Analysis Model between the highest group of land surface temperature and the lowest group of vegetation index will be able to give proof an effective suitability to the land cover change detection and monitoring.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.306-309
• /
• 2005

This parer describes the tracking control simulation of 6-DOF shaking table with a bell crank structure, which converts the direction of reciprocating movements. For the Joint coordinate-based control which uses lengths of each actuator, the trajectory conversion process inverse kinematics is performed. Applying the Newton-Euler approach, the dynamic equation of the shaking table is derived. To cope with nonlinear problems, time-delay control(TDC) is considered, which has been noted for its exceptional robustness to parameter uncertainties and disturbance, in addition to steady-state accuracy and computational efficiency. If the nominal model is equal to the real system, joint coordinate-based control can be very efficient. However, manufacturing tolerances installation errors and link offsets contaminate the nominal values of the kinematic parameters used in the kinematic model of the shaking table. To compensate differences between the nominal model and the real system. the joint coordinate-based control using acceleration feedback in the Cartesian coordinate space is proposed.

• International Journal of Railway
• /
• v.2 no.1
• /
• pp.1-7
• /
• 2009

The development of structural solutions for high-speed or very high-speed tracks that minimize total life cycle costs of the system is a key issue to improve the operational profitability of new investments. In opposition to conventional ballasted tracks, slab track solutions can be a cost-effective solution, but only in the cases where the benefits due to the increase in track availability and the reduction of track maintenance offsets its much higher construction costs. In the cases where such investment is not feasible, it is worth to evaluate possible structural improvements to ballasted track that allow reducing its maintenance needs without increasing too much its construction costs. This paper evaluates the design requirements and the impact of improving conventional high-speed ballasted tracks by using a bituminous subballast layer. It is divided into two main parts: first the design requirements of the structural solutions with bituminous subballast and its possible benefits on high-speed track deterioration, and secondly the evaluation of the economic impact, in terms of construction costs, of using this structural solution material in future Spanish high-speed lines.

• Korean Journal of Breeding Science
• /
• v.40 no.4
• /
• pp.521-524
• /
• 2008

A new graft cactus (Chamaecereus silvestrii f. variegata) cultivars "Yellow Ttree" was developed at Cactus Research Institute, Gyeonggi-do A.R.E.S. in 2007. GC013001 and GC0110703 were crossed in 2005 and we got 42 seedlings from this combination. After pedigree selection in 2005, one cultivar were finally selected through the test of specific character in 2007 and named as "Yellow Ttree". "Yellow Ttree" has cylindrical shape of yellow color with 13~14 ribs. Formation of its offshoots is concentrated on the lower part of the plant. This cultivar is able to produce 13.9 offsets shoots per plant and its offshoots are hard.

• Coupled systems mechanics
• /
• v.7 no.6
• /
• pp.731-753
• /
• 2018

The recent seismic events have led to concerns on safety and vulnerability of Reinforced Concrete Moment Resisting Frame "RC-MRF" buildings. The seismic design demands are greatly dependent on the computational tools, the inherent assumptions and approximations introduced in the modeling process. Thus, it is essential to assess the relative importance of implementing different modeling approaches and investigate the computed response sensitivity to the corresponding modeling assumptions. Many parameters and assumptions are to be justified for generation effective and accurate structural models of RC-MRF buildings to simulate the lateral response and evaluate seismic design demands. So, the present study aims to develop reliable finite element model through many refinements in modeling the various structural components. The effect of finite element modeling assumptions, analysis methods and code provisions on seismic response demands for the structural design of RC-MRF buildings are investigated. where, a series of three-dimensional finite element models were created to study various approaches to quantitatively improve the accuracy of FE models of symmetric buildings located in active seismic zones. It is shown from results of the comparative analyses that the use of a calibrated frame model which was made up of line elements featuring rigid offsets manages to provide estimates that match best with estimates obtained from a much more rigorous modeling approach involving the use of shell elements.

• Ocean Systems Engineering
• /
• v.8 no.4
• /
• pp.441-459
• /
• 2018

A coupled dynamic analysis of a semisubmersible-type FOWT has been carried out in time domain under the combined action of irregular wave and turbulent wind represented respectively by JONSWAP spectrum and Kaimal spectrum. To account for the turbine-floater motion coupling in a more realistic way, the wind turbulence has been incorporated into the calculation of aerodynamic loads. The platform model was referred from the DeepCwind project and the turbine considered here was the NREL 5MW Baseline. To account for the operationality of the turbine, two different environmental conditions (operational and survival) have been considered and the aerodynamic effect of turbine-rotation on actual responses of the FOWT has been studied. Higher mean offsets in surge and pitch responses were obtained under the operational condition as compared to the survival condition. The mooring line tensions were also observed to be sensitive to the rotation of turbine due to the turbulence of wind and overestimated responses were found when the constant wind was considered in the analysis. Additionally, a special analysis case of sudden shutdown of the turbine has also been considered to study the swift modification of responses and tension in the mooring cables.

• Proceedings of the KIPE Conference
• /
• 2018.11a
• /
• pp.104-106
• /
• 2018

The harmonics and the DC offset in the grid can cause serious synchronization problems for grid connected inverters (GCIs) which leads not able to satisfy the IEEE 519 and p1547 standards in terms of phase and frequency variations. In order to guarantee the smooth and reliable synchronization of GCIs with the grid, Phase Locked Loop (PLL) is the crucial element. Typically, the performance of the PLL is assessed to limit the grid disturbances e.g. grid harmonics, DC Offset and voltage sag etc. To ensure the quality of GCI, the PLL should be precise in estimating the grid amplitude, frequency and phase. Therefore, in this paper a novel Robust PLL technique called Digital Lock-in Amplifier (DLA) PLL is proposed. The proposed PLL estimate the frequency variations and phase errors accurately even in the highly distorted grid voltage conditions like grid voltage harmonics, DC offsets and grid voltage sag. To verify the performance of proposed method, it is compared with other six conventional used PLLs (CCF PLL, SOGI PLL, SOGI LPF PLL, APF PLL, dqDSC PLL, MAF PLL). The comparison is done by simulations on MATLAB Simulink. Finally, the experimental results are verified with Single Phase GCI Prototype.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.39 no.5
• /
• pp.313-319
• /
• 2021

The national geodetic reference frame of Korea was adopted in 2003, which is referenced to ITRF (International Terrestrial Reference Frame) 2000 at the epoch of January 1, 2002. For precise positioning based on the satellites, it should be thoroughly maintained to the newest global reference frame. Other than plate tectonic motion, there are significant events or changes such as earthquakes, antenna replacement, PSD (Post-Seismic Deformation), seasonal variation etc. We processed three years of GNSS (Global Navigation Satellite System) data(60 NGII CORS stations, 51 IGS core stations) to produce daily solutions minimally constrained to ITRF. From the time series of daily solutions, the sites with unexpected discontinuity were identified to set up an event(mostly antenna replacement). The combined solution with minimum constraints was estimated along with the velocity, the offsets, and the periodic signals. The residuals show that the surrounding environment also affects the time series to a certain degree, thus it should be improved eventually. The transformation parameters to ITRF2014 were calculated with stability and consistency, which means the national geodetic reference frame is properly aligned to the global reference frame.

• Korean Journal of Remote Sensing
• /
• v.37 no.4
• /
• pp.789-802
• /
• 2021

Synthetic Aperture Radar (SAR) at C-band is an ideal remote sensing system for crop monitoring owing to its short wavelength, which interacts with the upper parts of the crop canopy. This study evaluated the potential of dual polarimetric Sentinel-1 at C-band for monitoring rice phenology. Rice phenological variations occur in a short period. Hence, the short revisit time of Sentinel-1 SAR system can facilitate the tracking of short-term temporal morphological variations in rice crop growth. The sensitivity of SAR backscattering coefficients, backscattering ratio, and polarimetric decomposition parameters on rice phenological stages were investigated through a time-series analysis of 33 Sentinel-1 Single Look Complex images collected from 10th April to 25th October 2020 in Gimhae, South Korea. Based on the observed temporal variations in SAR parameters, we could identify and distinguish the phenological stages of the Gimhae rice growth cycle. The backscattering coefficient in VH polarisation and polarimetric decomposition parameters showed high sensitivity to rice growth. However, amongst SAR parameters estimated in this study, the VH backscattering coefficient realistically identifies all phenological stages, and its temporal variation patterns are preserved in both Sentinel-1A (S1A) and Sentinel-1B (S1B). Polarimetric decomposition parameters exhibited some offsets in successive acquisitions from S1A and S1B. Further studies with data collected from various incidence angles are crucial to determine the impact of different incidence angles on polarimetric decomposition parameters in rice paddy fields.