• Journal of Korea Water Resources Association
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• v.38 no.6 s.155
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• pp.449-460
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• 2005

In this study, a WEP (Water and Energy transfer Processes) model was used to simulate the water cycle of the Dorimcheon catchment which suffers from the distorted water cycle as a typical urban catchment. Two different land uses in the past (i.e. 1975) and at present (i.e. 2000) were incorporated into the simulation to investigate the runoff characteristics resulting from the increase of the impervious ratio due to urbanization. The simulation results show that the concentration time is decreased and the peak discharge and the total runoff are increased by urbanization while the infiltration and baseflow are reduced. In addition, the effects of infiltration trenches and permeable pavements were also simulated to search for alternatives that can restore the distorted water cycle. The simulation results prove that the installation of both alternatives can restore the runoff characteristics to that prior to urbanization.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1271-1280
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• 2000

A sensor placement technique to identify structural parameter was developed. Experimental results must be acquired to identify unknown dynamic characteristics of a targeting structure for the comparison between analytical model and real structure. If the experimental environment was not equipped itself properly, it can be happened that some valuable information are distorted or ill-condition can be occurred. In this work the index to determine exciting points was derived from the criterion of maximizing parameter sensitivity matrix and that to choose measurement points was from that of preserving the invariant of sensitivity matrix. This idea was applied to a compressor hull structure to verify its performance. The result shows that the selection of measurement and excitation points using suggested criteria improve the ill-conditioning problem of inverse type problems such , as model updating.

• The Korean Journal of Financial Studies
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• v.3 no.1
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• pp.213-231
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• 1996

In this study we conduct a specification test of at-the-money option volatility. Results show that the implied volatility estimate recovered from the Black-Scholes European option pricing model is nearly indistinguishable from the implied volatility estimate obtained from the Barone-Adesi and Whaley's American option pricing model. This study also investigates whether the use of Black-Scholes implied volatility estimates in American put pricing model significantly affect the prediction the prediction of American put option prices. Results show that, at long as the possibility of early exercise is carefully controlled in calculation of implied volatilities prediction of American put prices is not significantly distorted. This suggests that at-the-money option implied volatility estimates are robust across option pricing model.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.76-84
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• 2012

This paper presents the measurement system of arrow's point of impact using laser scan camera and describes the image calibration method. The calibration process of distorted image is primarily divided into explicit and implicit method. Explicit method focuses on direct optical property using physical camera and its parameter adjustment functionality, while implicit method relies on a calibration plate which assumed relations between image pixels and target positions. To find the relations of image and target position in implicit method, we proposed the performance criteria based polynomial theorem model that overcome some limitations of conventional image calibration model such as over-fitting problem. The proposed method can be verified with 2D position of arrow that were taken by SICK Ranger-D50 laser scan camera.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.791-795
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• 2005

A simulation model is proposed to evaluate the effect of correlations between activity durations on the overall project duration. The proposed model incorporates NORTA, a recent developed statistical method, into the simulation process to allow arbitrarily specified marginal distributions for activity durations and any desired correlation structure. The generality is of practical value when systematic data is not available and planners have to rely on arbitrary experts' estimation, which may involve a mixed situation when some activity durations are continuously distributed whereas others are discrete outcomes. The proposed model is validated by showing that the correlation coefficients of the simulation results are close to the originally specified ones. The simulation results are compared to two conventional approaches: PERT and simulation without correlation. The comparisons illustrate that the proposed model can provide important management information, which would otherwise be distorted due to the neglect of the correlations between activity durations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.10
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• pp.911-919
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• 2013

Evaluation of the effect of radial distortion for a holographic stereogram demands conducting an experiment which comprises rendering of a 3D obejc, acquisition of perspective images, rearrangement of the acquired images for hogel images and quality assessment of the observing image reconstructed from the holographic stereogram. We propose numerical implementation of this evaluation by a specially developed algorithm for modeling of all required steps. The modeling is done by using a numerical model of an optical engine for generation of radially distorted hogel images at various degrees of distortion. The distorted images are used to form the holographic stereogram and to make the numerically reconstructed images from the holographic stereogram which are observed by an observer at desired location. The reconstructed images are compared by using PSNR.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1578-1586
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• 2016

A power quality improvement scheme for grid connected inverters, even in the presence of the disturbances in grid voltages due to harmonic distortions and three-phase imbalance, is presented for distributed generation (DG) power systems. The control objective is to force the inverter currents to follow their references with robustness even under external disturbances in grid voltages. The proposed scheme is realized by a disturbance observer (DOB) based current control scheme. Since the uncertainty in a system can be effectively canceled out using an estimated disturbance by the DOB, the resultant system behaves like a closed-loop system consisting of a disturbance-free nominal model. For experimental verification, a 2 kVA laboratory prototype of a grid connected inverter has been built using a digital signal processor (DSP) TMS320F28335. Through comparative simulations and experimental results under grid disturbances such as harmonic distortion and imbalance, the effectiveness of the proposed DOB based current control scheme is demonstrated.

• Nuclear Engineering and Technology
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• v.29 no.5
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• pp.385-392
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• 1997

The shape of TL glow curve is a useful indicator for assurance of correct reading of the personal dosimeter. Since the reading procedure of TLD is irreversible, however, an analytic remedy should be considered to procure reliable dosimetric information for the readings with irregular glow con shape. In this study, kinetic trapping parameters of CaSO$_4$ : Dy Teflon personal dosimeter(Teledyne PB-6A) were analyzed by Halperin and Braner's model for general-order kinetics. From these kinetic tapping parameters, we also developed a simple procedure to retrieve the dosimetric information from abnormally distorted glow curves. The computerized glow curve deconvolution(CGCD) fitting of the reference glow curve with kinetic parameters from this study yields relative errors of about 5% from the expected integral. It was also found that the glow curve remedial procedure developed could retrieve the distorted TL glow curves within ewer ranges of 1575. With the glow curve retrieval techniques, doses incurred by gamma radiation can now be successfully re-constructed for the CaSO$_4$ : Dy Teflon dosimeter resulting abnormal glow curves.

• Advances in aircraft and spacecraft science
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• v.2 no.4
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• pp.403-425
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• 2015

This work is focused on the definition and the analysis of both complete and incomplete similitudes for the dynamic responses of thin shells. Previous numerical and experimental investigations on both structural and structural-acoustic systems motivated this further analysis, mainly centred on the incomplete (distorted) similitudes. These similitudes and the associated scaling laws are defined by using the classical modal approach (CMA) and by invoking also the Energy Distribution Approach (EDA) in order to take into account both the cinematic and energetic items. The whole procedure is named SAMSARA: Similitude and Asymptotic Models for Structural-Acoustic Research and Applications. A brief summary of the procedure is herein given and the attention is paid to the analytical models of thin stiffened and unstiffened cylindrical shells. By using the well-known smeared model, the stiffened cylinder equations are used as general framework to analyse the possibility to define exact (replicas) or distorted similitudes (avatars). Despite the extreme simplicity of the proposed models, the results are really encouraging. The final aim is to define equivalent models to be used in laboratory measurements.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.305-312
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• 2018

This study was carried out to investigate euphausiid abundance in an acoustic survey from March 2010 to July 2010 to suggest reasonable usage and management of the euphausiid Euphausia pacifica in the coastal area of Guryongpo Pohang. The acoustic data were analyzed by the 2-frequency difference method and the distorted wave born approximation acoustical theoretical model, which is used for organisms of weak target strength with small scatter, such as euphausiid scatter, among other marine organisms. The distribution and monthly density of euphausiids were estimated in the survey area. The results show that the volume back scattering strength frequency difference for euphausiid was 13.91-7.6 dB, and their monthly averag density was $28.2g/m^2$.