• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.695-699
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• 2005

Propriety of PERT network for planning and management in large-scale systems was investigated. We also review the example of small and middle size system to compare the appropriateness of PERT analysis method. For comparing the appropriateness of PERT analysis method the calculation time, and the variances were estimated. Eventualy, we proposed the criteria of PERT analysis method for planning and management large-scale systems.

• Journal of Ocean Engineering and Technology
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• v.34 no.6
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• pp.387-393
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• 2020

Frictional resistance comprises more than 60% of the total resistance for most merchant ships. Active and passive devices have been used to reduce frictional resistance, but the most effective and practical device is an air lubrication system. Such systems have been applied in several ships, and their effects have been verified in sea trials. On the other hand, there are some differences between the results predicted in model tests and those measured in sea trials. In this study, numerical analyses were carried out for a model and a full-scale ship. A new extrapolation method was proposed to improve the estimation of the full-scale resistance of a ship with an air lubrication system. The volume of fluid (VOF) method was considered for the numerical models of the air layer. The numerical method was validated by comparing the experimental data on the air layer pattern and the total resistance.

• Steel and Composite Structures
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• v.39 no.5
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• pp.565-581
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• 2021

In this paper the buckling analysis of the nanoplate made of arbitrary bi-directional functionally graded (BDFG) materials with small scale effects are investigated. To study the small-scale effects on buckling load, the Eringen's nonlocal theory is applied. Employing the principle of minimum potential energy, the governing equations are obtained. Generalize differential quadrature method (GDQM) is used to solve the governing equations for various boundary conditions to obtain the buckling load of BDFG nanoplates. These models can degenerate into the classical models if the material length scale parameter is taken to be zero. Comparison between the results of GDQ method and other papers for buckling analysis of a simply supported rectangular nano FGM plate reveals the accuracy of GDQ method. At the end some numerical results are presented to study the effects of material length scale parameter, plate thickness, aspect ratio, Poisson's ratio boundary condition and side to thickness ratio on size dependent Frequency.

• ETRI Journal
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• v.45 no.6
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• pp.1035-1045
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• 2023

We propose a novel graphics processing unit (GPU) algorithm that can handle a large-scale 3D fast Fourier transform (i.e., 3D-FFT) problem whose data size is larger than the GPU's memory. A 1D FFT-based 3D-FFT computational approach is used to solve the limited device memory issue. Moreover, to reduce the communication overhead between the CPU and GPU, we propose a 3D data-transposition method that converts the target 1D vector into a contiguous memory layout and improves data transfer efficiency. The transposed data are communicated between the host and device memories efficiently through the pinned buffer and multiple streams. We apply our method to various large-scale benchmarks and compare its performance with the state-of-the-art multicore CPU FFT library (i.e., fastest Fourier transform in the West [FFTW]) and a prior GPU-based 3D-FFT algorithm. Our method achieves a higher performance (up to 2.89 times) than FFTW; it yields more performance gaps as the data size increases. The performance of the prior GPU algorithm decreases considerably in massive-scale problems, whereas our method's performance is stable.

• Journal of the Optical Society of Korea
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• v.19 no.4
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• pp.415-420
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• 2015

A novel method to measure the scale factor for the all-optical atomic spin inertial measurement device (ASIMD) is demonstrated in this paper. The method can realize the calibration of the scale factor by a self-consistent method with small errors in the quiescent state. At first, the matured IMU (inertial measurement unit) device was fixed on an optical platform together with the ASIMD, and it has been used to calibrate the scale factor for the ASIMD. The results show that there were some errors causing the inaccuracy of the experiment. By the comparative analysis of theory and experiment, the ASIMD was unable to keep pace with the IMU. Considering the characteristics of the ASIMD, the mismatch between the driven frequency of the optical platform and the bandwidth of the ASIMD was the major reason. An all-optical atomic spin magnetometer was set up at first. The sensitivity of the magnetometer is ultra-high, and it can be used to detect the magnetization of spin-polarized noble gas. The gyromagnetic ratio of the noble gas is a physical constant, and it has already been measured accurately. So a novel calibration method for scale factor based on the gyromagnetic ratio has been presented. The relevant theoretical analysis and experiments have been implemented. The results showed that the scale factor of the device was $7.272V/^{\circ}/s$ by multi-group experiments with the maximum error value 0.49%.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2011.05a
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• pp.19-20
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• 2011

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.4
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• pp.401-411
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• 2005

This study was conducted to develop a method to be able to estimate the vehicular emissions according to spatial scales-Seoul province, 25 counties and hundreds of grids $(1km{\times}1km)$. First, the emissions at each spatial scale was calculated by using the road network and the travel volume and speed of each link modeled by travel demand model (TDM). Second, the emission at each spatial scale was calculated on the basis of average speeds estimated by using three kinds of averaging method. These are called the provincial, volume-delay function (VDF) and zonal method, respectively. Third, three kinds of emissions and those by TDM are compared each other at three spatial scales. In Seoul (provincial scale), three kinds of emissions are less than those by TDM, but the differences of TDM from three speed averaging methods (SAMs) are small. The relative ratios of three SAMs to TDM are $88\~90\%\;in\;CO,\;99\~100\%\;in\;NOx,\;84\~85\%$ in VOCs. At county scale, NOx among three pollutants showed the highest correlation between TDM and three SAMs and the zonal method among three SAMs was proven to be the highest correlation with TDM. NOx showed the coefficients $(R^2)$ greater than 0.9 in all three SAMs but CO and VOC showed the coefficients $(R^2)$ greater than 0.9 in only zonal method. Slopes of co..elations of all pollutants showed the values close to '1' in zonal method. In the other two SAMs, slopes of NOx showed the values close to '1', but those of CO and VOC showed the values less than 0.85. At grid scale, correlations between TDM and three SAMs were not high. CO showed $0.68\~0.77\;in\;R^2s\;and\;58\~0.68$ in slopes. NOx showed $0.90\~0.94\;in\;R^2s\;and\;0.86\~0.94$ in slopes. VOC showed $0.56\~0.70\;in\;R^2s\;and\;0.48\~0.57$ in slopes. There are not high correlations between TDM and three SAMs in grid scale. This study showed that there is the most suitable method for calculating the average travel speed at each spatial scale and it is thought that the zonal method is more suitable than the VDF or provincial method.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.572-581
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• 2005

This research is conducted to develop predictable method of real scale nanofiltration treatability with small scale nanofiltration experiments. As a result of comparing calculated values with measured values, they are in a good agreement for the concentrations in filtered water and concentrated water. The results of that are not affected by change of system recovery from 20% to 95%. The proposed method is produced using constant recovery of elements, that is, no considering the pressure change. we can predict filtrated flux and contaminant concentrations with the method. The method has the following steps. (1) Calculate recovery of each element with water quality level after fixing recovery elements, (2) Predict system recovery with recovery of elements in 1, 2, 3, and 4 banks, (3) Run small scale nanofiltration experiments in predicted water quality and (4) Simulate large scale nanofiltration system for forecasting actual water quality. As the cost for nanofiltration pretest will reduced if we use the proposed method, it will be a promising method for introducing nanofiltration to supply safe drinking water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.9-16
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• 2018

Images with lower illumination from the light source or with dark regions due to shadows, etc., can improve subjective image quality by using retinex-based image enhancement schemes. The retinex theory is a method that recognizes the relative lightness of a scene, rather than recognizing the brightness of the scene. The way the human visual system recognizes a scene in a specific position can be in one of several methods: single-scale retinex, multi-scale retinex, and multi-scale retinex with color restoration (MSRCR). The proposed method is based on the MSRCR method, which includes a color restoration step, which consists of three phases. In the first phase, the existing MSRCR method is applied. In the second phase, the dynamic range of the MSRCR output is adjusted according to its histogram. In the last phase, the proposed method transforms the retinex output value into the display dynamic range using a logarithm transformation function considering human visual system characteristics. Experimental results show that the proposed algorithm effectively increases the subjective image quality, not only in dark images but also in images including both bright and dark areas. Especially in a low lightness image, the proposed algorithm showed higher performance improvement than the conventional approaches.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.3
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• pp.162-167
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• 2004

The scale model grounding systems to study the behavior of grounding system in uniform soils have been designed and fabricated. Constructional details and instrumentation have been discussed. To verify the accuracy of the results obtained from the experimental tests, they have been compared with computer calculation results. Also, in order to assess the effectiveness of bonding two grounding systems, grounding grid conductors which were downsized as a scale factor of 100:1 were analyzed by using the scale model method. A profile of GPR(Grounding Potential Rise) of each case was measured. The scale model grounding system presented in this paper can be valuable tool to analyze the ground potential profile and ground resistance of practical grounding system.