• International Journal of CAD/CAM
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• v.5 no.1
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• pp.19-27
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• 2005

As three-dimensional range scanners make large point clouds a more common initial representation of real world objects, a need arises for algorithms that can efficiently process point sets. In this paper, we present a method for extracting smooth surfaces from dense point clouds. Given an unorganized set of points in space as input, our algorithm first uses principal component analysis to estimate the surface variation at each point. After defining conditions for determining the geometric compatibility of a point and a surface, we examine the points in order of increasing surface variation to find points whose neighborhoods can be closely approximated by a single surface. These neighborhoods become seed regions for region growing. The region growing step clusters points that are geometrically compatible with the approximating surface and refines the surface as the region grows to obtain the best approximation of the largest number of points. When no more points can be added to a region, the algorithm stores the extracted surface. Our algorithm works quickly with little user interaction and requires a fraction of the memory needed for a standard mesh data structure. To demonstrate its usefulness, we show results on large point clouds acquired from real-world objects.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.427-437
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• 2018

Structural pounding is commonly observed phenomenon during major ground motion, which can cause both structural and architectural damages. To reduce the amount of damage from pounding, the best and effective way is to increase the separation distance. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. The aim of this research is to estimate probabilistic separation distance between adjacent structures by considering the variability in the system and uncertainties in the earthquakes characteristics through comprehensive numerical simulations. A large number of models were generated using a robust Monte-Carlo simulation. In total, 6.54 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results show that a gap size of 50%, 70% and 100% of the considered design code for the structural periods in the range of 0.1-0.5 s, leads to have the probability of pounding about 41.5%, 18% and 5.8%, respectively. Finally, based on the results, two equations are developed for probabilistic determination of needed structural separation distance.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.87-94
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• 2009

The objectives of this paper were to estimate cell based pollutant loadings for total maximum daily load (TMDL) programs and to evaluate the applicability of the agricultural nonpoint source (AGNPS) model for an intensive agricultural watershed in Korea. The model was calibrated and validated at a watershed of 384.8 ha of drainage area using the observed data from 1996 through 2000 in terms of runoff, suspended solid, total nitrogen, and total phosphorus on a hourly basis. Analysis of spatial variations of pollutant loadings for rainfall frequencies of various intensities and durations were conducted. In addition, the validated model was applied to estimated the TMDL removal efficiency for best management practices (BMPs) scenarios which were selected by taking into account the pollutant characteristics of the study watershed. The model can help to understand the problems and to find solutions through landuse changes and BMPs. Thus, the method used for this study was able to identify TMDL quantitatively as well as qualitatively for various sources pollution that are spatially dispersed. Also it provides an assessment of the impact of BMPs on the water bodies studied, allowing the TMDL programs to be complemented more effectively.

• Journal of Environmental Impact Assessment
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• v.23 no.2
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• pp.88-100
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• 2014

This study analyzed runoff characteristics of non-point sources pollutant and evaluated removal of pollution by BMP(Best Management Practice) using BASINS/WinHSPF model. Hourly meterological data including input data was provided from 2010 to 2011 year to run HSPF model in Miho stream watershed. As the results of calibration and validation of the model, the model could be successfully performed to simulate the flow and water quality parameters. The apprehensive area of non-point source pollution was chosen by non-point source pollution per area of a tributary to the Miho stream and applied constructed wetland in area chosen. Three scenarios were based on installation area of an constructed wetland and HSPF model would be applied to estimate the pollutant removals through the constructed wetland. The removal rates of pollutants through the constructed wetland were estimated with the runoff and water quality parameters by the comparisons of before and after the constructed wetland application.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.57-63
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• 2002

The construction market has a major impact on the overall United States economy. Recent statistics estimate the gross domestic product (GDP) of the U.S. construction industry at some $416.4{\$}$ billion dollars, representing approximately $4.5\%$ of the U.S. GDP. Because the business environment in construction is highly competitive, the participants in the industry must improve their performance and processes to survive. Hence, Benchmarking has been generating interest in the construction industry. This paper provides an overview of the CII Benchmarking and Metrics Program. Following some background and a descriptive discussion of the database, an abridged presentation of result of data analysis. The adoption of benchmarking in Korean construction industry can be another opportunity to improve Korean construction industry.

• Journal of Environmental Science International
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• v.13 no.7
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• pp.611-618
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• 2004

The Neural Network Models which mathematically interpret human thought processes were applied to resolve the uncertainty of model parameters and to increase the model's output for the streamflow forecast model. In order to test and verify the flood discharge forecast model eight flood events observed at Kumho station located on the midstream of Kumho river were chosen. Six events of them were used as test data and two events for verification. In order to make an analysis the Levengerg-Marquart method was used to estimate the best parameter for the Neural Network model. The structure of the model was composed of five types of models by varying the number of hidden layers and the number of nodes of hidden layers. Moreover, a logarithmic-sigmoid varying function was used in first and second hidden layers, and a linear function was used for the output. As a result of applying Neural Networks models for the five models, the N10-6model was considered suitable when there is one hidden layer, and the Nl0-9-5model when there are two hidden layers. In addition, when all the Neural Network models were reviewed, the Nl0-9-5model, which has two hidden layers, gave the most preferable results in an actual hydro-event.

• Structural Engineering and Mechanics
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• v.38 no.1
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• pp.1-25
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• 2011

A new nonlinear model was developed to evaluate the shear resistance of steel fiber-reinforced concrete beams (SFRCB) using linear genetic programming (LGP). The proposed model relates the shear strength to the geometrical and mechanical properties of SFRCB. The best model was selected after developing and controlling several models with different combinations of the influencing parameters. The models were developed using a comprehensive database containing 213 test results of SFRC beams without stirrups obtained through an extensive literature review. The database includes experimental results for normal and high-strength concrete beams. To verify the applicability of the proposed model, it was employed to estimate the shear strength of a part of test results that were not included in the modeling process. The external validation of the model was further verified using several statistical criteria recommended by researchers. The contributions of the parameters affecting the shear strength were evaluated through a sensitivity analysis. The results indicate that the LGP model gives precise estimates of the shear strength of SFRCB. The prediction performance of the model is significantly better than several solutions found in the literature. The LGP-based design equation is remarkably straightforward and useful for pre-design applications.

• Wind and Structures
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• v.21 no.2
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• pp.203-221
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• 2015

Wind speed is the most important parameter in the design and study of wind energy conversion systems. The weibull distribution is commonly used for wind energy analysis as it can represent the wind variations with an acceptable level of accuracy. In this study, the wind data for 11 cities in Iran have been analysed over a period of one year. The Goodness of fit test is used for testing data fit to weibull distribution. The results show that this data fit to weibull function very well. The scale and shape factors are two parameters of the weibull distribution that depend on the area under study. The kinds of numerical methods commonly used for estimating weibull parameters are reviewed. Their performance for the cities under study was compared according to root mean square and wind energy errors. The result of the study reveals the empirical, modified maximum likelihood estimate of wind speed with minimum error. Also, that the moment and modified maximum likelihood are the best methods for estimating the energy production of wind turbines.

• Journal of Construction Engineering and Project Management
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• v.4 no.3
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• pp.13-20
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• 2014

Estimating time and cost is an important mission in the early phase of a construction project, especially in feasibility study. It provides a foundation for making decision whether or not the project is performed on schedule and within budget. Thus, reliability of this estimate plays a key role in measuring the success of a project. This study was carried out to investigate the time-cost relationship in building construction projects in Bangladesh. The mathematical equation used in this study is based on Bromilow's equation. The research data were collected from sixty-three completed building projects through questionnaire survey. Type of clients, type of projects, and tender methods are the project characteristics considered in this study. The results of analysis indicated that the Bromilow's time-cost (BTC) models developed for each project characteristic are appropriate due to quite high coefficient of determination and relatively small mean percent errors. Among them, the forecasted model for time and cost according to tender methods is the best fit model. It is concluded that the BTC model could be applied in building construction project to predict its time and cost in Bangladesh. Four different regression models were also developed in this study. The results of BTC model between some selected countries were compared to gain the comprehensive view.

• Nuclear Engineering and Technology
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• v.44 no.7
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• pp.709-718
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• 2012

The pressurized water reactor APR1400 adopts DVI (Direct Vessel Injection) for the emergency cooling water in the upper downcomer annulus. The International Standard Problem number 50 (ISP-50) was launched with the aim to investigate thermal hydraulic phenomena during a 50% DVI line break scenario with best estimate codes making use of the experimental data available from the ATLAS facility located at KAERI. The present work describes the calculation results obtained for the ISP-50 using the RELAP5/MOD3.3 system code. The work aims at validation and assessment of the code to reproduce the observed phenomena and investigate about its limitations to predict complicated mixing phenomena between the subcooled emergency cooling water and the two-phase flow in the downcomer. The obtained results show that the overall trends of the main test variables are well reproduced by the calculations. In particular, the pressure in the primary system show excellent agreement with the experiment. The loop seal clearance phenomenon was observed in the calculation and it was found to have an important influence on the transient progression. Moreover, the collapsed water levels in the core are accurately reproduced in the simulations. However, the drop in the downcomer level before the activation of the DVI from safety injection tanks was underestimated due to multi-dimensional phenomena in the downcomer that are not properly captured by one-dimensional simulations.