• Journal of Korea Water Resources Association
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• v.39 no.12 s.173
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• pp.1013-1022
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• 2006

Urban flooding is usually caused by the surcharge of storm sewers. For this reason, previous studies on urban flooding are mainly concentrated on the simulation of urban drainage systems. However these approaches that find the pipes which have insufficient drainage capacity are very approximate and unreasonable ways in establishing both flood prevention and flood-loss reduction planning. In this study, a two-dimensional model linked the existing ILLUDAS model is developed to calculate the accurate and resonable solution about urban flood inundation and it is verified by using the simulation of July 2001 flood in Seoul. In the urban area with a small difference of ground elevations, the two-dimensional flood propagation phases must be considered to make a accurate analysis for inundated area and depth. The result of this study can be used to construct fundamental data for a flood control plan and establish a urban flood forecasting/warning system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.886-893
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• 2017

Recently, for detection of low-RCS targets, bistatic radar and multistatic radar have been widely employed. In this paper, we present the process of deriving the received signal modeling of the bistatic MIMO radar system and deals with the performance analysis of applying the bistatic signal to the ML arrival angle estimation algorithm. In case of the ML algorithm, as the number of the targets increases, azimuth search dimension for DOA estimation also increases, which implies that the ML algorithm for multiple targets is computationally very intensive. To solve this problem a closed-form expression of estimation error is presented for performance analysis of the algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.2939-2944
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• 2011

The performance and efficiency of a Molten Carbonate Fuel Cell system will improve with the aids of numerical simulations such as finite element analysis. For best simulation results, the virtual model must accurately reflect the actual model including the material properties. It is very difficult, however, to make a detailed numerical model of the stack that consists of hundreds of layers of unit cells composed of various materials like metal, ceramics, polymer, etc. Instead, a practical approach is to find a homogenized material property of the stack as a whole as an approximate replacement. In this paper, the compression ratio of a unit cell is introduced, and a new method is proposed to estimate the homogeneous material properties for both the active and the manifold regions of the stack under the assumption that the compressive deformation occurs only at the separators and matrices in the unit cells. The estimated properties are applied successfully to simulating an actual stack.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.4
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• pp.32-42
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• 2021

The printing process can have to print various colors with a limited capacity of printing facility such as ink containers that are needed cleaning to change color. In each container, cleaning time exists to assign corresponding inks, and it is considered as the setup cost required to reduce the increasing productivity. The existing manual method, which is based on the worker's experience or intuition, is difficult to respond to the diversification of color requirements, mathematical modeling and algorithms are suggested for efficient scheduling. In this study, we propose a new type of scheduling problem for the printing process. First, we suggest a mathematical model that optimizes the color assignment and scheduling. Although the suggested model guarantees global optimality, it needs a lot of computational time to solve. Thus, we decompose the original problem into sequencing orders and allocating ink problems. An approximate function is used to compute the job scheduling, and local search heuristic based on 2-opt algorithm is suggested for reducing computational time. In order to verify the effectiveness of our method, we compared the algorithms' performance. The results show that the suggested decomposition structure can find acceptable solutions within a reasonable time. Also, we present schematized results for field application.

• Structural Engineering and Mechanics
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• v.84 no.4
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• pp.437-452
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• 2022

For the first time, the higher-order shear and normal deformable plate theory (HOSNDPT) is used for the vibration and flutter analyses of the multilayer functionally graded graphene platelets reinforced composite (FG-GPLRC) plates under supersonic airflow. For modeling the supersonic airflow, the linear piston theory is adopted. In HOSNDPT, Legendre polynomials are used to approximate the components of the displacement field in the thickness direction. So, all stress and strain components are encountered. Either uniform or three kinds of non-uniform distribution of graphene platelets (GPLs) into polymer matrix are considered. The Young modulus of the FG-GPLRC plate is estimated by the modified Halpin-Tsai model, while the Poisson ratio and mass density are determined by the rule of mixtures. The Hamilton's principle is used to obtain the governing equations of motion and the associated boundary conditions of the plate. For solving the plate's equations of motion, the Galerkin approach is applied. A comparison for the natural frequencies obtained based on the present investigation and those of three-dimensional elasticity theory shows a very good agreement. The flutter boundaries for FG-GPLRC plates based on HOSNDPT are described and the effects of GPL distribution patterns, the geometrical parameters and the weight fraction of GPLs on the flutter frequencies and flutter aerodynamic pressure of the plate are studied in detail. The obtained results show that by increasing 0.5% of GPLs into polymer matrix, the flutter aerodynamic pressure increases approximately 117%, 145%, 166% and 196% for FG-O, FG-A, UD and FG-X distribution patterns, respectively.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.634-639
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• 2013

The aim of the study is to develop the 3D visualization of Building Information Model and integrated 4D model for optimization of resources in the construction project. This study discuss the process of methodology and creation of 4D model of the project and simulate it to monitor the workflow at the site. Different stages of the construction process and activities are generated by using Revit and MS Project. MS project has been used for creation of the schedules and these are linked with the Revit for 3D modeling. The time used as the fourth dimension and 4D model created by using Navisworks Time liner software. Narges shopping center is presented as a case study to realize the actual uses and benefits of Building Information Model (BIM). Narges shopping mall is located in Tehran, Iran. As a part of Hekmat master plan, Narges shopping center is an 11 stores building with a total area of 30000 Sq.m. This shopping and entertainment center is comprised of 150 retails and two multi-use public halls with a capacity of 400 persons each and underground parking with total 400 parking space. The main purpose of architecture was to create an urban public center along with its revolving, spiral like form and an ever changing continuous façade by means of different colors, materials, which is in harmony with the other building of the master plan. The approximate cost of the project is $17 million and duration of the project schedule is 30 months. The developed Building Information Model enabled us to identify the potential collisions or clashes between various structural and architectural systems. 4D model has been used for limiting the interaction between subcontractors installing the different systems so rework could be avoided and productivity maximized. It is also observed that the utility of BIM for construction stimulation and clash detection is the best suitable method. Clash detection before the implementation of work is highly recommended to avoid rework.

• International Journal of Computer Science & Network Security
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• v.23 no.12
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• pp.167-174
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• 2023

Electronic educational environments in the conditions of quarantine restrictions of COVID-19 have become a common phenomenon for the organization of distance educational activities. Under the conditions of Russian aggression, Ukrainian proof of their use is unique. The purpose of the article is to analyze the role of electronic educational environments in the process of training applicants for higher education in Ukraine in the realities of a large-scale war. General scientific methods (analysis, synthesis, deduction, and induction) and special pedagogical prognostic methods, modeling, and SWOT analysis methods were used. In the results, the general properties of the Internet educational platforms common in Ukraine, the peculiarities of using the Moodle and Prometheus platforms, and an approximate model of the electronic learning environment were discussed. The reasons for the popularity of Moodle among Ukrainian universities are analyzed, but vulnerable elements related to security are emphasized. It was also determined that the high cost of Prometheus software and less functionality made this learning environment less relevant. The conclusions state that the military actions drew the attention of universities in Ukraine to the formation of their own educational platforms. This is especially relevant for technical and military institutions of higher education.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.410-418
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• 2017

The stability of low-crested structure (LCS) and overtopping discharge over a seawall behind the LCS are influenced by the water level behind the structure. Hence, the experimental results can be distorted unless the increase of water level is known when two-dimensional experiment is carried out. In order to estimate increase of the mean water level behind the low-crested structure, this study applied a hybrid technique that combined results of two-dimensional model test and hydrodynamic numerical modeling based on the relationship between the water level and discharge. By using this technique, the mean water level increase and flow field can be obtained almost at the same time, which resolved the above problem considerably. In addition, this method can provide an approximate information about the outflow velocity from the openings of the structure, which is helpful for selecting appropriate planar configuration of the low-crested structure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.663-670
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• 2020

A study on mechanical property characterization and modeling technique was carried out to approximate the behaviour of structures with 2.5D C/SiC material. Several tensile tests were performed to analyze the behaviour characteristics of the 2.5D C/SiC material and elastic property was characterized by applying a mathematical homogenization and a modified rule of mixture. SiC matrix representing the elasto-plastic behavior approximates as a bilinear function. Then the equivalent yield strength and equivalent plastic stiffness were calculated by minimizing errors in experiment and approximation. RVE(Representative Volume Element)was defined from the fiber and matrix configuration of 2.5D C/SiC and a process of calculating the effective stiffness matrix by applying the modified rule of mixture to RVE was implemented in the ABAQUS User-defined subroutine. Finite element analysis was performed by applying the mechanical properties of fiber and matrix calculated based on the proposed process, and the results were in good agreement with the experimental results.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.6
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• pp.43-54
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• 2018

The accurate estimation of reference crop evapotranspiration ($ET_o$) is essential in irrigation water management to assess the time-dependent status of crop water use and irrigation scheduling. The importance of $ET_o$ has resulted in many direct and indirect methods to approximate its value and include pan evaporation, meteorological-based estimations, lysimetry, soil moisture depletion, and soil water balance equations. Artificial neural networks (ANNs) have been intensively implemented for process-based hydrologic modeling due to their superior performance using nonlinear modeling, pattern recognition, and classification. This study adapted two well-known ANN algorithms, Backpropagation neural network (BPNN) and Generalized regression neural network (GRNN), to evaluate their capability to accurately predict $ET_o$ using daily meteorological data. All data were obtained from two automated weather stations (Chupungryeong and Jangsu) located in the Yeongdong-gun (2002-2017) and Jangsu-gun (1988-2017), respectively. Daily $ET_o$ was calculated using the Penman-Monteith equation as the benchmark method. These calculated values of $ET_o$ and corresponding meteorological data were separated into training, validation and test datasets. The performance of each ANN algorithm was evaluated against $ET_o$ calculated from the benchmark method and multiple linear regression (MLR) model. The overall results showed that the BPNN algorithm performed best followed by the MLR and GRNN in a statistical sense and this could contribute to provide valuable information to farmers, water managers and policy makers for effective agricultural water governance.