• Steel and Composite Structures
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• v.44 no.2
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• pp.171-181
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• 2022

Functionally graded material (FGM) has been spotlighted as an advanced composite material due to its excellent thermo-mechanical performance. And the buckling of FGM resting on elastic foundations has been a challenging subject because its behavior is directly connected to the structural safety. In this context, this paper is concerned with a numerical buckling analysis of metal-ceramic FG plates resting on a two-parameter (Pasternak-type) elastic foundation. The buckling problem is formulated based on the neutral surface and the (1,1,0) hierarchical model, and it is numerically approximated by 2-D natural element method (NEM) which provides a high accuracy even for coarse grid. The derived eigenvalue equations are solved by employing Lanczos and Jacobi algorithms. The numerical results are compared with the reference solutions through the benchmark test, from which the reliability of present numerical method has been verified. Using the developed numerical method, the critical buckling loads of metal-ceramic FG plates are parametrically investigated with respect to the major design parameters.

• Steel and Composite Structures
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• v.52 no.2
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• pp.135-143
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• 2024

Once the foundation displacement of the transmission tower occurs, additional stress will be generated on the tower members, which will affect the seismic response of transmission tower-line systems (TTLSs). Furthermore, existing research has shown that the reciprocating slippage of joints needs to be considered in the seismic analysis. The hysteretic behavior of joints is obtained by model tests or numerical simulations, which leads to the low modeling efficiency of TTLSs. Therefore, this paper first utilized numerical simulation and model tests to construct a BP neural network for predicting the skeleton curve of joints, and then a numerical model for a TTLS considering the bolt slippage was established. Then, the seismic response of the TTLS under foundation displacement was studied, and the member stress changes and the failed member distribution of the tower were analyzed. The influence of foundation displacement on the seismic performance were discussed. The results showed that the trained BP neural network could accurately predict the hysteresis performance of joints. The slippage could offset part of the additional stress caused by foundation settlement and reduce the stress of some members when the TTLS with foundation settlement was under earthquakes. The failure members were mainly distributed at the diagonal members of the tower leg adjacent to the foundation settlement and that of the tower body. To accurately analyze the seismic performance of TTLSs, the influence of foundation displacement and the joint effect should be considered, and the BP neural network can be used to improve modeling efficiency.

• Journal of Multimedia Information System
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• v.1 no.2
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• pp.111-118
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• 2014

The Smart grid refers to the technology that enables efficient usage of electric power by collecting information concerning the power usage and power lines grafting information and communications technology to onto power grids. There are Zigbee, PLC or IEEE 802.11 WLAN MAC as a core technology of the Smart grid, but in this paper, the discussion is focused on the PLC. The PLC is the technology that carries out data communications using power lines and put into practical use in the field of lights or home appliances control recently but PLC-applied communications between electronic devices are rarely seen. For the reason that the PLC uses high-voltage power lines and has a disadvantage of experiencing higher data loss rate caused by the noises produced by going through transformers, the technology is yet to be used in many areas. Nevertheless, the PLC has been studied widely recently in respect that it's the low-cost communication solution for the Smart Metering [1]. Moreover, this technology is emerging as a novel data communication method and discussed as an important technology lately due to the developments of the Smart grid systems and Internet of things (IoT). Thus, in this paper, the results obtained from designing and performing implementation scenario for the PLC-based Smart grid home network system were compared and analyzed with that of IEEE 802.11 WLAN MAC (the foundation technology at Jeju Smart grid Test bed)-based Smart grid home network. Thus, in this paper, OPNET 14.5 PL8, OSI 7 layer, PLC router nodes and PLC nodes had been used for the designing and implementation simulations of both systems. Additionally, QoS was not considered in order to guarantee that all the traffics would not have the same processing priority.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.486-493
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• 2010

Recently, it has been a worldwide issue to develop offshore wind farm based on the past technical experiences of onshore wind turbine installation. In Korea, the government has the wind-energy to be a new-sustainable field of development to bring green-growth in near future and put political and fiscal efforts to support the academic and industrial technical development. Especially, there are much advancement for the fields of turbine, blade, bearing, grid connection, ETC. Correspondingly, technical needs do exist for the offshore foundation installation techniques in geotechnical point of view. Within few years, 2~5MW offshore wind turbines will be constructed at about 30m water depth and it is known that monopiles of D=4~6m are suitable types of foundation. In order to construct offshore wind-turbine foundation, technical developments for drilling machine, design manual, monitoring&maintenance technique are required. This paper presents technical issues with related to offshore wind farm and large diameter monopile in the point of renewable energy development.

• Coupled systems mechanics
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• v.11 no.4
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• pp.357-371
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• 2022

This paper presents a parametric study on the free vibration analysis of a functionally graded material (FGM) circular plate with non-uniform thickness resting on a variable Pasternak elastic foundation. The mechanical properties of the material vary in the transverse direction through the thickness of the plate according to the power-law distribution to represent the constituent components. The equation of motion of the circular plate has been carried out based on the classical plate theory (CPT), and the differential quadrature method (DQM) is employed to solve the governing equations as a semi-analytical method. The grid points are chosen based on Chebyshev-Gauss-Lobatto distribution to achieve acceptable convergence and better accuracy. The influence of geometric parameters, variable elastic foundation, and functionally graded variation for clamped and simply supported boundary conditions on the first three natural frequencies are investigated. Comparisons of results with similar studies in the literature have been presented and two-dimensional mode shapes for particular plates have been plotted to illustrate the effect of variable thickness profile.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.8
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• pp.189-199
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• 2017

The purpose of this study is to compare the grid usage that is common to Leonardo da Vinci and J.N.L. Durand in the process of designing the architectural plan. In the days when there was no proper measurement tool, auxiliary lines relied entirely on the architect's personal mindset and design convenience. Therefore, it is considered that studying the auxiliary lines drawn by the architects will be useful for studying the human perception system. Among auxiliary lines, the grid has been used by many architects. Leonardo da Vinci and J.N.L. Durand are famous. However, these two show a significant different grid usage. As auxiliary grid and space ares added the center of the Leonardo da Vinci grid continues to move, and the grid in his sketch is becoming a building space itself. So I call it 'conceptual grid'. In the case of J.N.L. Durand, the one center of the grid is always at the center of the drawing. That is, all the positions of the grid can be determined in phase around a common point, and all of the same specifications are assumed. The grid is a kind of filter. That's why his grid is a visual abstraction of the process of thinking. In this paper, I will call the grid of J.N.L. Durand as 'abstract grid'.

• Education of Primary School Mathematics
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• v.22 no.1
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• pp.13-27
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• 2019

The use of grid paper in elementary mathematics textbooks is used in numbers and calculations, figures and measurement areas. Among them, it is used most in the figure area. In spite of this utilization, it is necessary to supplement it because it is difficult to revise or supplement the trial and error that often occurs in the course of the course, as the process of using the textbook paper in the actual class. The use of grid paper in elementary mathematics textbooks is used in numbers and calculations, figures and measurement areas. Among them, it is used most in the figure area. In spite of this utilization, it is necessary to supplement it because it is difficult to revise or supplement the trial and error that often occurs in the course of the course, as the process of using the textbook paper in the actual class. In this study, we tried to find out the usability of grid paper boards which can be used more effectively than the grid paper among the teaching aids presented in the 'Development of teaching aids standards for math class' of Korea Foundation for the Advancement of Science & Creativity(2017). A questionnaire survey was conducted on the use of grid paper and grid paper board for teachers who actually use grid paper in elementary mathematics. As a result, we found out the achievement criteria of grid paper board utilization and investigated the study subject which is effective to use grid paper board. In particular, we have identified specific learning topics that are effective in each area and presented specific activities.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.3
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• pp.69-82
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• 2023

Representative meteorological data of the rural water district, which is the spatial unit of the study, was produced using the grid-based national standard RCP scenario rainfall data provided by the Korea Meteorological Administration. The retrospective reproducibility of the climate model scenario data was analyzed, and the change in climate characteristics in the water district unit for the future period was presented. Finally the data characteristics and differences of each meteorological element according to various spatial resolution conversion and post-processing methods were examined. As a main result, overall, the distribution of average precipitation and R95p of the grid data, has reasonable reproducibility compared to the ASOS observation, but the maximum daily rainfall tends to be distributed low nationwide. The number of rainfall days tends to be higher than the station-based observation, and this is because the grid data is generally calculated using the area average concept of representative rainfall data for each grid. In addition, in the case of coastal regions, there is a problem that administrative districts of islands and rural water districts do not match. and In the case of water districts that include mountainous areas, such as Jeju, there was a large difference in the results depending on whether or not high rainfall in the mountainous areas was reflected. The results of this study are expected to be used as foundation for selecting data processing methods when constructing future meteorological data for rural water districts for future agricutural water management plans and climate change vulnerability assessments.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.1
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• pp.1-7
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• 2018

Objective signs are everywhere that the stationary energy storage market is growing up quickly. The use of distributed resources such as solar photovoltaics and electric vehicles are expanding at a rapid pace, creating technical challenges for the distribution system that will require energy storage and a new generation of software to address. This paper is intended for distribution utility managers and executives and makes the following points: ${\bullet}$ Utility-integrated (as opposed to merely grid-connected) energy storage projects represent a distinct, new wave of industry growth that is just getting underway and is required to manage distributed energy resources moving forward. ${\bullet}$ Utilities and the energy storage industry have important roles to lower risk in adopting this technology - thereby enabling this wave of growth. ${\circ}$ The industry must focus on engineering energy storage for adoption at scale - including the creation and support of software open standards -both to drive down costs and to limit technology and supplier risk for utilities. ${\circ}$ Utilities need to take a program-based, rather than a project- based, approach to this resource to best balance cost and risk as they procure and implement energy storage. By working together to drive down costs and manage risk, utilities and their suppliers can lay the energy storage foundation for a new, more digital distributed electricity system.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.893-903
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• 2008

A method for predicting surface failures which occur during heavy rainfall on mountain slopes is proposed by using the digital land form model that is obtained by reading altitude on a topographical map at 10m grid point space. A depth of a potential failure layer is assumed at each grid point. In the layer, an infiltrated water movement from cell to cell is modeled in the study (cell is a square of the grid). Infiltrated ground water levels which show the three dimensional effects of a topographical factor in an area can be hourly calculated at every cell by the model. The safety factor of every cell is also calculated every hour by the infinite slope stability analysis method with the obtained infiltrated ground water level. Failure potential delineation is defined here as the time when the safety factor becomes less than unity under the assumptions that effective rainfall is 20mm/h and continues 20 hours.