• Atmosphere
• /
• v.25 no.1
• /
• pp.149-154
• /
• 2015

As an attempt to improve fog predictability at Incheon International Airport (IIA) we couple the 3D weather forecasting model currently operational in Korea Meteorological Administration (regional Unified Model, UM_RE) with a 1D turbulence model (PAFOG). The coupling is done by extracting the meteorological data from the 3D model and properly inserting them in the PAFOG model as initial conditions and external forcing. The initial conditions include surface temperature, 2 m temperature and dew point temperature, geostrophic wind at 850 hPa and vertical profiles of temperature and dew point temperature. Moisture and temperature advections are included as external forcing and updated every hr. To validate the performance of the coupled system, simulation results of the coupled system are compared to those of the 3D model alone for the 22 sea fog cases observed over the Yellow Sea. Three statistical indices, i.e., Root Mean Square Error (RMSE), linear correlation coefficient (R) and Critical Success Index (CSI), are examined, and they all indicate that the coupled system performs better than the 3D model alone. These are certainly promising results but more improvement is required before the coupled system can actually be used as an operational fog forecasting model. For the RMSE, R, and CSI values for the coupled system are still not good enough for operational fog forecast.

• Journal of Korea Technology Innovation Society
• /
• v.13 no.2
• /
• pp.231-251
• /
• 2010

The numbers of SCI paper or patent in science and technology are expected to be related with the number of researcher and knowledge stock (R&D stock, paper stock, patent stock). The results of the regression model showed that severe multicollinearity existed and errors were made in the estimation and testing of regression coefficients. To solve the problem of multicollinearity and estimate the effect of the independent variable properly, principal component regression model were applied for three cases with S&T knowledge production. The estimated principal component regression function was transformed into original independent variables to interpret properly its effect. The analysis indicated that the principal component regression model was useful to estimate the effect of the highly correlate production factors and showed that the number of researcher, R&D stock, paper or patent stock had all positive effect on the production of paper or patent.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.3
• /
• pp.805-812
• /
• 2014

This study investigates the impact of morphological change on the physical habitat simulation. For this, CCHE2D model is used for the hydraulic analysis including the morphological change, and the physical habitat suitability is assessed with habitat suitability curves. The model is applied to a 2.5km long reach downstream of the Goesan Dam, from Sujeon Bridge to Daesu Weir. Flow data of discharge and stage in July, 2006 are used in the computation. The numerical model is verified by means of comparison with the measured water surface elevation data, and the variation of the river bed is not verified in this study. Adult Zacco platypus is chosen for the dominant species. Physical habitat simulations result in composite habitat suitability and weighted usable area for drought, low, normal, and averaged-wet flows. The simulation results indicate that the composite suitability index increased at reaches right downstream of the Sujeon Bridge and around the bend. This also increased weighted usable area by 5.4-11.3%.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.2
• /
• pp.495-506
• /
• 2013

This study developed the Time-split Mixing Model (TMM) which can represent the pollutant mixing process on a three-dimensional open channel through constructing the conceptual model based on Taylor's assumption (1954) that the shear flow dispersion is the result of combination of shear advection and diffusion by turbulence. The developed model splits the 2-D mixing process into longitudinal mixing and transverse mixing, and it represents the 2-D advection-dispersion by the repetitive calculation of concentration separation by the vertical non-uniformity of flow velocity and then vertical mixing by turbulent diffusion sequentially. The simulation results indicated that the proposed model explains the effect of concentration overlapping by boundary walls, and the simulated concentration was in good agreement with the analytical solution of the 2-D advection-dispersion equation in Taylor period (Chatwin, 1970). The proposed model could explain the correlation between hydraulic factors and the dispersion coefficient to provide the physical insight about the dispersion behavior. The longitudinal dispersion coefficient calculated by the TMM varied with the mixing time unlike the constant value suggested by Elder (1959), whereas the transverse dispersion coefficient was similar with the coefficient evaluated by experiments of Sayre and Chang (1968), Fischer et al. (1979).

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1287-1292
• /
• 2007

Recently, the frequency of unexpecting heavy rains has been increased due to abnormal climate and extreme rainfall. There was a limit to analyze 1D or 2D stream flow that was applied simple momentum equation and fixed energy conservation. Therefore, hydrodynamics flow analysis in rivers has been needed 3D numerical analysis for correct stream flow interpretation. In this study, CFD model on FLOW-3D was applied to stream flow analysis, which solves three dimenson RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as ${\kappa}-{\varepsilon}$, RNG ${\kappa}-{\varepsilon}$ and LES. Those numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow distributions, water level pressure distributions and eddy flows around the piers at Jangwall bridge in urbarn stream.

• Korean journal of applied entomology
• /
• v.55 no.2
• /
• pp.119-128
• /
• 2016

This study was conducted to develop temperature-driven models for a population model of turnip aphid, Lipaphis erysimi: nymphal development rate models and apterious adult's oviposition (larviparous) model. Nymphal development and the longevity and fecundity of adults were examined on cabbage at six constant temperatures (10, 15, 20, 25, 30, $35{\pm}1^{\circ}C$, 16L:8D). L. erysimi nymphs did not survive at $10^{\circ}C$. Development time of nymphs increased with increasing temperature up to $30^{\circ}C$ and thereafter slightly decreased, ranging from 18.5 d at $15^{\circ}C$ to 5.9 d at $30^{\circ}C$. The lower threshold temperature and thermal constant were estimated as $7.9^{\circ}C$ and 126.3 degree days, respectively. The nonlinear model of Lactin 2 fitted well for the relationship between the development rate and temperature of small (1+2 instar), large (3+4 instar) and total nymph (all instars). The Weibull function provided a good fit for the distribution of development times of each stage. Temperature affected the longevity and fecundity of L. erysimi. Adult longevity decreased as the temperature increased and ranged from 24.4 d at $20^{\circ}C$ to 16.4 d at $30.0^{\circ}C$ with abnormal longevity 18.2 d at $15^{\circ}C$, which was used to estimate adult aging rate model for the calculation of adult physiological age. L. erysimi showed a maximum fecundity of 91.6 eggs per female at $20^{\circ}C$. In this study, we provided three temperature-dependent components for an oviposition model of L. erysimi: total fecundity, age-specific cumulative oviposition rate, and age-specific survival rate.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.947-956
• /
• 2013

In this study, WUA (Weighted Usable Area) was calculated to determine ecological flow at the confluence of Nakdong River and Gumho River by using River2D. To calibrate River2D, simulation results of River2D were compared with calibrated HEC-RAS simulation results and the optimum parameters were determined. After parameter calibration, WUA of Zacco platypus and Zacco temmincki which are dominant species in Nakdong River was calculated with changing upstream flowrate. From the result, WUA is changed according to flowrate and growth stage. In the flowrate-WUA/A graph, ecological flow can be determined as $33.3m^3/s{\sim}39.96m^3/s$ in Nakdong River and $3.6m^3/s{\sim}4.32m^3/s$ in Gumho River. After dredging for Four major rivers restoration project, WUA of Zacco platypus and Zacco temmincki were calculated by using the ecological flow. The results show that WUA after dredging are decreased when compared with undredged condition. WUA of Common carp is 2~3 times bigger than WUA of Zacco platypus and Zacco temmincki at the dredged condition in Nakdong River.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.21 no.2
• /
• pp.147-154
• /
• 2003

The close-range photogrammetry is a surveying technique the acquiring the 3D object from 2D geometric appearance shown in the image. Camera treatment is relatively so simple. Camera position refer to the object can be freely adjusted by locating the exposure station at any site. So it is used effectively on a small area or object for survey. In this study, using the digital camera which has capacity of keeping numerical value by itself and easy carrying, we analyze the positioning error according to various change of photographing condition. Also we try to find a effective method of acquiring basis data for 3D monitoring of high-accuracy in sub-pixel degree thorough digital close-range photogrammetry with bundle adjustment for local terrain model generation.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5B
• /
• pp.563-572
• /
• 2006

In designing the coastal structures, the accurate estimation of wave forces on them is very important. Recently, the empirical formulae such as Goda formula are widely used to estimate wave forces, as well as 2-D hydraulic and numerical model tests. But, sometimes, these estimation methods mentioned above seem to be unreasonable to predict 3-D structure of wave pressure on the coastal structures with 3-D plane arrangement in the real coastal area. Especially, in case of consideration of phase difference at harbor and seaward sides of the large-sized coastal structures like a composite breakwater, it is easily expected that the real wave pressures on each section of coastal structure have 3-D distribution. A new numerical model of 3-D Large Eddy Simulation, which is applicable to permeable structure, is developed to clarify the 3-D structure of wave pressures acting on coastal structure. The calculated wave forces on 3-D structure installed on the submerged breakwater show in good agreement with the measured values. In this study, the composite breakwater is adopted as a representative structure among the large-sized coastal structures and the 3-D structure of wave pressures on it is discussed in relation to the phase difference at harbor and seaward sides of it due to wave diffraction and transmitted wave through rubble mound.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.6
• /
• pp.558-567
• /
• 1997

Linear power amplifier modules with high-efficiency have been developed for PCS handy phone. These modules were designed using extracted large-signal models of MESFETs and harmonic balance simulation. The modules are intended for low-tier and high-tier at the operation frequency range of 1750 ~ 1780 MHz. For low-tier module, the output power and $IMD_3$ were 23.2 dBm and 31 dBc, respectively, at power-added efficiency of 34% with the supply drain bias of 3.6 V. For high-tier module, the output power and $IMD_3$ were 272.2 dBm and 31 dBc, respectively, at power-added efficiency of 33% with the supply drain bias of 4.2 V. These linear power amplifier modules are suitable for PCS handy phone.