• Journal of Elementary Mathematics Education in Korea
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• v.21 no.1
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• pp.73-92
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• 2017

A table as an effective arrangement tool of a set of data has not been focused on as a single research subject despite of the fact that the table has been clearly one of learning and teaching elements of national math curriculum for a long time. I hope this article gets to be a starting point for future studies of tables. For this, the Finland elementary mathematics textbooks which use tables so often for many various purpose are chosen and analysed. As a result, it confirms that tables can be practical tools for developing different mathematical ideas in mathematics textbooks. Its applicable area is not limited on statistics but numbers and operations, geometry, measurement, ratio and rate. In addition, some ideas of the outlook, the size and dimension of tables, and the context of datum and etc are induced from the Finland elementary mathematics textbooks.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.134-148
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• 2008

The state of in situ stress is an important factor in considering the suitability of a site as a geological repository for nuclear waste. In this study, three-dimensional distinct numerical analysis was conducted to investigate the effect of deformation zones on the state of stress in the Oskarshamn area, which is one of two candidate sites in Sweden. A discontinuum numerical model was constructed by explicitly representing the numerous deformation zones identified from site investigation and far-field tectonic stress was applied in the constructed model. The numerical model successfully captured the variation of measured stress often observed in the rock mass containing large-scale fractures, which shows that numerical analysis can be an effective tool in improving the understanding of the state of stresses. Discrepancies between measured and modelled stress are attributed to the inconsistent quality of measured stress, uncertainty in geological geometry. and input data for fractures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.889-897
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• 2014

This paper presents a method for finding an optimized result by using a genetic algorithm (GA) based on a PEMFC analysis result. The conventional analysis method designs fuel cells one-by-one, and each result is compared to obtain the best performance. Because the computational burden of the conventional analysis is enormous, the present optimization process provides an inefficient tool by automatically setting the boundary and material properties and mesh generation. As the change can be reflected automatically in the channel geometry with GA, the fuel cell analysis result with various sizes can be obtained easily. Therefore, the global maximum performance can be obtained through a GA optimization procedure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2183-2188
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• 2009

This paper describes an automatic mesh generation system for finite element analysis of three-dimensional cracks. It is consisting of fuzzy knowledge processing, bubble meshing and solid geometry modeler. This novel mesh generation process consists of three sub-processes: (a) definition of geometric model, i.e. analysis model, (b) generation of bubbles, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional crack structures. Bubble is generated if its distance from existing bubble points is similar to the bubble spacing function at the point. The bubble spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Practical performances of the present system are demonstrated through several mesh generations for 3D cracks.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.547-547
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• 2003

The aim of this study was to compare the effects of three Ni-Ti instruments on leaning ability by evaluating the volumetric and morphological changes in the apical 6mm of the root canals before and after preparation, using three-dimensionally reconstructed root canals of extracted human teeth. Forty-five teeth were used in this study. They were opened the chambers and removed the all pulp remnants ultrasonically. Subsequently, the canal wall was coated with silver paste and prepared using ProTaper, ProFile and GT rotary files according to the manufacturers instructions. Before and after root canal preparation, all the specimens were scanned with micro computed tomography and examined the differences in dentine volume removed, canal straightening, the proportion of the unchanged area and canal transportation. Quantitative analysis revealed that instrumentation increased in canal volume ranging between 0.081 and $1.866{\;}\textrm{mm}^3$. On average, the large apical preparation produced by ProTaper demonstrated smaller proportions of unchanged surface areas compared to the two other instruments in small canals. But in large canals like maxillary central incisor, the preparation of ProTaper instruments was not enough. ProTaper instrument was tended to increase more in canal volume as compared with the other two instruments but unchanged area was no significant difference. These results showed that three instruments had similar preparation ability and micro computed tomography in combination with the coated wall of root canal using silver paste is a nondestructive and valuable tool to study root canal geometry and changes after preparations in detail.

• Journal of Science and Technology Studies
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• v.3 no.2 s.6
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• pp.1-27
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• 2003

Complexity paradigm is a scientific amalgam that aims to unite a range of theoretical perspectives and research agendas across natural and social sciences. Proponents of complexity paradigm lay claims to an increasing number of areas of study, including artificial life, interpersonal networks, internal/international patterning of organizations, mapping of cyberspace, etc. All of those can be subsumed under the title, 'complexity turn.' Owing to the idea of open system, complexity paradigm has developed a number of new concepts/themes/perspectives that help to account for the complex mechanism of living and non-living creatures. A complex system comprises a number of properties such as disequilibrium, nonlinearity, dissipative structure, self-organization fractal geometry, autopoiesis, coevolution. Following a brief introduction to theoretical development, those properties are succinctly discussed. The complexity turn has provided a wealth of insights that enable to analyze system operations of any kind. It contributes a lot to illuminating the working of social system as well. The most remarkable attempt may be Niklas Luhmann's 'neofunctional system theory.' Merits and shortcomings of complexity paradigm were examined and its future prospect were assessed with the conclusion that complexity paradigm would continue to be useful both as effective transdisciplinary framework and powerful analytical tool.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.33-42
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• 2019

In this study, the channel and floodplain widths are indirectly measured for three different watersheds using satellite images to reflect the shape of Korean channels in the Soil and Water Assessment Tool (SWAT) model. For measuring the channel and floodplain widths, multiple satellite images were referred to ensure the widest width of certain points. In the single channel, the widths at the multiple points were measured. Based on the measured data, the regression equations were derived to estimate the channel and floodplain widths according to watershed areas. Applying these developed equations, this study evaluated the effect of the change of channel and floodplain widths on the SWAT simulation by comparing to the measured streamflow data. The developed equations estimated larger channel width and smaller floodplain compared with those calculated in the current SWAT model. As shown in the results, there was no considerable changes in the predicted streamflow using the current and developed equations. However, the flow velocity and channel depth calculated from the developed equations were smaller than those of the current equations. The differences were caused by the effect of different channel geometries used for calculating the hydraulic characteristics. The channel geometries also affected the water quality simulation in channels because the hydraulic characteristics calculated by the channel geometries are directly related to the water quality simulation. Therefore, application of the river cross-sectional regression equation reflecting the domestic stream shape is necessary for accurate water quantity / quality and water ecosystem simulation using hydrological model.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.221-230
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• 2019

In this paper, shear behavior of non-persistent joint surrounded in concrete and gypsum layers has been investigated using experimental test and numerical simulation. Two types of mixture were prepared for this study. The first type consists of water and gypsum that were mixed with a ratio of water/gypsum of 0.6. The second type of mixture, water, sand and cement were mixed with a ratio of 27%, 33% and 40% by weight. Shear behavior of a non-persistent joint embedded in these specimens is studied. Physical models consisting of two edge concrete layers with dimensions of 160 mm by 130 mm by 60 mm and one internal gypsum layer with the dimension of 16 mm by 13 mm by 6 mm were made. Two horizontal edge joints were embedded in concrete beams and one angled joint was created in gypsum layer. Several analyses with joints with angles of $0^{\circ}$, $30^{\circ}$, and $60^{\circ}$ degree were conducted. The central fault places in 3 different positions. Along the edge joints, 1.5 cm vertically far from the edge joint face and 3 cm vertically far from the edge joint face. All samples were tested in compression using a universal loading machine and the shear load was induced because of the specimen geometry. Concurrent with the experiments, the extended finite element method (XFEM) was employed to analyze the fracture processes occurring in a non-persistent joint embedded in concrete and gypsum layers using Abaqus, a finite element software platform. The failure pattern of non-persistent cracks (faults) was found to be affected mostly by the central crack and its configuration and the shear strength was found to be related to the failure pattern. Comparison between experimental and corresponding numerical results showed a great agreement. XFEM was found as a capable tool for investigating the fracturing mechanism of rock specimens with non-persistent joint.

• Journal of the Korean GEO-environmental Society
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• v.22 no.1
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• pp.5-12
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• 2021

Owing to economically efficient and easy installation, bucket foundation is a promising solution for offshore wind turbines. This paper aims at finding the behavior of suction caissons and soil surrounding the foundation by using three-dimensional finite element analysis. Under various loading conditions, a wide range of foundation geometries installed in dense and medium dense sandy soil was considered to evaluate ultimate horizontal load and overturning moment capacity. The results show that the rotation and displacement of the bucket due to monotonic loading are largely dependent on the foundation geometry, soil density and load eccentricity. Normalized diagrams and equations for the ultimate horizontal load and overturning moment capacities are presented that are useful tool for the preliminary design of such foundation type.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.928-934
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• 2009

Although the evolution and deployment of information technologies will undoubtedly play an important role in the current construction industry, many engineers are still unsure of the economic value of using these technologies. Especially for the planning of a construction project, a collaboration system to utilize the whole resources is a essential tool for the successful outcome. A detailed, authoritative, and readily accessible information model is needed to enable engineers to make cost-effective decisions among established and innovative plan alternatives. Most engineers rely on limited private experiences when they create solutions or design alternatives. Initial planning is crucial for the success of the construction project. Most construction projects are done through collaboration of engineers who have different specialized knowledge. Information technologies can dramatically enhance the performance of the collaboration. For the information delivery, we need a mediator between engineers. Object-based 3-D models are useful for the communication and decision assistance for the intelligent project design. In this paper, basic guidelines for the 3-D design according to different construction processes are suggested. Adequate interoperability of 3-D objects from any CAD system is essential for the collaboration. Basic architectures of geometry models and their information layer were established to enable interoperability for design checks, estimation and simulation. A typical international project for roadway was chosen for the pilot project. 3-D GIS model was created and bridge information models were created considering several requirements for planning and decision making of the project. From the pilot test, the integrated construction project planning using 3-D information models was discussed and several guidelines were suggested.