• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.141-147
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• 2020

Single-layered grid space steel roof structure is an architectural system in which the structural ability of the nodal connection system greatly influences the stability of the entire structure. Many bolt connection systems have been suggested to enhance for better construct ability, but the structural behavior and maximum resistance of the connection system according to the size of bolt clearance play were difficult to identify. In particular, the identification of bending stiffness of the connection system is very important due to the characteristics of shell structures in which membrane stresses based on bending force effect significantly. To identify effective structural behavior and maximum bearing force, four representative nodal connection systems were selected and nonlinear numerical analysis were performed. The numerical analysis considering the size of the bolt clearance were performed to investigate structural behavior and maximum values of the bending force. In addition, the type of effective nodal connection system were evaluated. As a result, the connection system, which has two shear plane, represented high bending stiffness.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.76-83
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• 2010

Metallic sandwich panels with pyramidal truss structures are high-stiffness and high-strength materials with low weight. In particular, bulk structures have enough space for additional multi-functionalities. In this work, in order to fabricate 3-D structures efficiently, Layered Manufacturing Method (LMM) which was composed of three steps, including crimping process, stacking process and bonding process using rapid infrared brazing, was proposed. The joining time was drastically reduced by employing infrared brazing of which heating rate and cooling rate were faster than those of conventional furnace brazing. By controlling the initial cooling rate slowly, the bonding strength was improved up to the level of strength by conventional vacuum brazing. The observation of infrared brazed specimens by optical microscope and SEM showed no defect on the joining sections. The experiments of 1-layered pyramidal structures and 2-layered pyramidal structures subject to 3-point bending were conducted to determine structural advantages of multilayered structures. From the results, the multi-layered structure has superior mechanical properties to the single-layered structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.22-27
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• 1989

This paper presents a study of soil-structure interaction problems using infinite elements. The infinite elements are formulated for homogeneous and layered soil media, based on approximate expressions for three components of propagating waves, namely Rayleigh, compressive and shear waves. The integration scheme which was proposed for problems with single wave component by Zienkiewicz is expanded to the multi-wave problem. Verifications are carried out on rigid circular footings which are placed on and embedded in elastic half space. Numerical analysis is performed for a containment structure of a nuclear power plant subjected seismic excitation.

• Journal of Korean Association for Spatial Structures
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• v.19 no.2
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• pp.17-25
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• 2019

In this study, we propose a new scheme of nonlinear analysis for Incheon International Airport Terminal-2 which was opened on January of 2018 for the Olympic Winter Games of PyeongChang in South Korea. The terminal was built by a single layered irregular space frame. It has hard problems for nonlinear analysis geometrically, because of a limitation of personal computer's ability by the number of rigid joints in the roof. Therefore we attempt easier approach to be chosen a center part of the roof instead of the whole structure, and to substitute the other boundary parts as springs. The scheme shows some merits for saving memory and calculation time and so on.

• Computational Structural Engineering
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• v.2 no.3
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• pp.85-95
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• 1989

This paper presents a study of soil-structure interaction problems using infinite elements. The infinite elements are formulated for homogeneous and layered soil media, based on approximate expressions for three components of propagating waves, namely the Rayleigh, compressive and shear waves. The integration scheme which was proposed for problems with single wave component by waves. The integration scheme which was proposed for problems with single wave component by Zenkiewicz is expanded to the multi-waves problem. Verifications are carried out on rigid circular footings which are placed on and embedded in elastic half space. Numerical analysis is performed for a containment structure of a nuclear power plant subjected to a horizontal seismic excitation.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.59-71
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• 2012

Results of the analysis of the structural behavior of axially loaded nodes in freeform structure were not fully understood due to certain difficulties, including the application of various welding and bolting types. In this study, a node of single layered freeform structure was tested to determine its structural behavior when subjected to axial loads. The tests were classified into node ball tests to evaluate the center of the node subjected to cyclic and monotonic loading. The node part tests were also conducted to evaluate the whole node subjected to monotonic loading. The test showed that the node ball is safe with the tensile force, but the node ball needs to increase its strength with the node loaded compressive force due to the additional bending moment of the node ball's asymmetric form.

• Journal of Korean Association for Spatial Structures
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• v.12 no.4
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• pp.109-118
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• 2012

The large-space single-layer lattice dome is relatively simpler in terms of the arrangement of the various framework members and of the design of the junction than the multi-layered lattice dome, can reduce the numbers and quantity of the framework members, and has the merit of exposing the beauty of the framework as it stands. The single-layer lattice dome, however, requires a stability investigation of the whole structure itself, along with an analysis of the stress of the framework members, because an unstable phenomenon called "buckling" occurs when its weight reaches critical levels. Many researchers have systematically conducted researches on the stability evaluation of the single-layer lattice dome. No construction case of a single-layer lattice dome with a 300-m-long span, however, has yet been reported anywhere in the world. The large-space dome structure is difficult to erect due to the gigantic span and higher ceiling compared with other common buildings, and its construction cost is generally huge. The method of erecting a structure causes major differences in the construction cost and period. Therefore, many researchers have been conducting various researches on the method of erecting such structure. The step-up method developed by these authors can reduce the construction cost and period to a great extent compared with the other general methods, but the application of this method inevitably requires the development of system supports in the center section as well as pre-existing supports in the boundary sections. In this research, the safety during the construction of a single-layer lattice dome with 300-m-long span using pre-existing materials was examined in the aspect of structural strength, and the basic data required for manufacturing the supports in the application of the step-up method developed by these authors during the erection of the roof structure were obtained.

• Journal of Science of Art and Design
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• v.6
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• pp.267-287
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• 2004

The study of a new expression within Korean ink painting that meets the demands of the times has continued, resulting in various expressions with acrylics, handycoat, objects and installations, crossing over from traditional Korean painting techniques. A 'margin' was both a very important space and esthetical matter that expresses 'Ki', 'Distance', and 'Omission' in traditional sense when addressing Korean ink painting Its expression methods and concepts, however, have changed today. A 'margin' through Montage technique can be a significant example in understanding the expression methods of today's Korean ink painting. This is because the margins in Montage make the meaning of the work various and flourished and deeply construct the surface with a double-layered structure, instead of using a single layer. These 'margins' created by Montage are spaces where different images conflict, divide and continue with each other and where a reconciliation between different spaces is accomplished. Furthermore, they establish more vitality and truthfulness to life through both the images conflict and reconciliation. After the adoption of Post-modernism Art in Korean ink painting, the characteristics of the 'margin' in Montage style by the division of surface are an 'acceptant's participatory imaginative space'; where viewers fill the margins with their imaginations ; an 'abandoned space' ; where unnecessary parts are deleted for more live surface ; and a 'strategic space', where the work enriches the structure and contents of surface by using margins strategically.

• Korean Journal of Microbiology
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• v.17 no.1
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• pp.1-15
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• 1979

Mycoplasma pneumoniae strain CL-s attached to broth-covered surfaces was examined sequentially during growth from single cells for morphologic and ultrastructural changes using several different electron microscopic techniques. Changes in morphology revealed both round and spindle shapes and observation of cell transitions suggested some type of morphological cycle. The round to-ovoid cells observed in the early stages of growth appeared to be viable, and morphologically and ultrastructurally different from the spherical fors which were produced during the latter stage of growth. The spindle segments were detected appeared to be structurally the same as the terminal cored structure seen in thin sections and may be a growing point or an attachment site of the cell. A tubular structure was observed in the core of the terminal structure and a microtubule-like element appeared to bridge between some spindle segments. A matrix sunstance was observed around single cells as well in the intercellular space of the colonies prepared by critical point metrical triple-layered cytoplasmic mermbranes, surfaces, of which appeared to be structurally different each other, were observed in young cells, whereas symmetrical and thicker membranes were seen in older cells. Small bodies were found in 4d or older cultures and did not appear to contain any internal structures or an easily detectable unit membrane.

• Journal of Powder Materials
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• v.26 no.1
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• pp.49-57
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• 2019

Layered $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode materials single- and dual-doped by the rare-earth elements Ce and Nd are successfully fabricated by using a coprecipitation-assisted solid-phase method. For comparison purposes, non-doping pristine $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode material is also prepared using the same method. The crystal structure, morphology, and electrochemical performances are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, and electrochemical techniques. The XRD data demonstrates that all prepared samples maintain a typical ${\alpha}-NaFeO_2$-layered structure with the R-3m space group, and that the doped samples with Ce and/or Nd have lower cation mixing than that of pristine samples without doping. The results of SEM and EDS show that doped elements are uniformly distributed in all samples. The electrochemical performances of all doped samples are better than those of pristine samples without doping. In addition, the Ce/Nd dual-doped cathode material shows the best cycling performance and the least capacity loss. At a 10 C-rate, the electrodes of Ce/Nd dual-doped cathode material exhibit good capacity retention of 72.7, 58.5, and 45.2% after 100, 200, and 300 cycles, respectively, compared to those of pristine samples without doping (24.4, 11.1, and 8.0%).