• Journal of Gifted/Talented Education
• /
• v.11 no.3
• /
• pp.45-68
• /
• 2001

The Gifted need the constructivist loaming environments that reflect his or her cognitive and affective characteristics and needs to exert their potential fully. 'Structural Communication'was designed to encourage creative thinking in learners, allowing them to create an understanding of a topic, not simply memorize facts. It is considered in line with constructivist philosophy and cognitive paradigms. The major purpose of this study is to explore 'Web-Based Structural Communication'program to embody the collaborative loaming based on constructivism. It was applied on high school $2\times2$ matrix teaming for the gifted students. Recently developed computer technology, emerging network facilities, and internet enable us to extend the usefulness and efficiency of 'Structural Communication’Especially web provides not only the discussion environment that is free from space and time constraints and characteristics of leasers, but also the experiences of knowledge construction through the collaborative learning. Through the 'Web-based Structural Communication', the gifted will be able to argue, persuade and share their unique ideas and gradually elaborated ill-structured ideas. The gifted will escape from the tunnel vision of the early time and have multiple perspectives that are more objective and logical. As the result, the gifted are expected to acquire the effect of 'the Zone of Proximal Development'that Vygotsky advocated.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.37.2-37.2
• /
• 2010

Recently $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ has been consistently examined and investigated by scientists because of its high lithium storage capacity, which exceeds beyond the conventional theoretical capacity based on conventional chemical concepts. Consequently, $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ is considered as one of the most promising cathode candidates for next generation in Li rechargeable batteries. Yet the mechanism and the origin of the overcapacity have not been clarified. Previously, many authors have demonstrated simultaneous oxygen evolution during the first delithiation. However, it may only explain the high capacity of the first charge process, and not of the subsequent cycles. In this work, we report a clarified interpretation of the structural evolution of $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$, which is the key element in understanding its anomalously high capacity. We identify how the structural evolution of $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ occurs upon the electrochemical cycling through careful study of electrochemical profiles, ex-situ X-ray diffraction (XRD), HR-TEM, Raman spectroscopy, and first principles calculation. Moreover, we successfully separated the structural change at subsequent cycles (mainly cation rearrangement) from the first charge process (mainly oxygen evolution with Li extraction) by intentionally synthesizing sample with large particle size. Consequently, the intermediate states of structural evolution could be well resolved. All observations made through various tools lead to the result that spinel-like cation arrangement and lithium environment are created and embedded in layered framework during repeated electrochemical cycling.

• Structural Engineering and Mechanics
• /
• v.51 no.5
• /
• pp.755-771
• /
• 2014

Environmental changes, especially global climate change, are creating new challenges to the development of the Arctic regions, which have substantial energy resources. And attention to offshore structures has increased with oil and gas development. The structural impact response of an explosion-resistant profiled blast walls normally changes when it operates in low temperatures. The main objectives of this study are to investigate the structural response of blast walls in low temperature and suggest useful guidelines for understanding the characteristics of the structural impact response of blast walls subjected to hydrocarbon explosions in Arctic conditions. The target temperatures were based on the average summer temperature ($-20^{\circ}C$), the average winter temperature ($-40^{\circ}C$) and the coldest temperature recorded (approximately $-68^{\circ}C$) in the Arctic. The nonlinear finite element analysis was performed to design an explosion-resistant profiled blast wall for use in Arctic conditions based on the behaviour of material properties at low temperatures established by performing a tensile test. The conclusions and implications of the findings are discussed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.5
• /
• pp.3557-3566
• /
• 2015

In the case of elevated railway station in which railway is connected with superstructure of station, vibration and noise level is relatively higher than those of general structure type station due to structural characteristic which transmits vibration directly. Therefore, characteristic understanding of structural vibration and accompanying structure cause noise and establishment of reduction plan through the results are in need. Test and analysis are performed in this research to consider correlativity between structural vibration and accompanying structure cause noise when external forces are applied on standard slab and floating slab which is able to isolate vibration. By producing and loading on standard and floating slab, vibration and noise response are measured while simulation using numerical analysis, finite element method and SEA method is performed. The results about structural dynamic behavior of slab, correlativity between structural vibration and noise, reduction performance of floating slab is deduced through the analysis of tests.

• Structural Engineering and Mechanics
• /
• v.87 no.4
• /
• pp.317-332
• /
• 2023

Understanding and analysing the behaviour and response of historical structures in the face of climate changes and environmental conditions is of utmost significance for their preservation. There are several structural hazards associated with climate and hydrology changes in the region, including the settlement of piers, the rotation of piers, and temperature changes. The present study investigates the experimental and numerical structural behaviour of skewed and non-skewed Persian brick masonry barrel vaults under various conditions. The external loading conditions included pier rotation in five modes, settlement, and temperature variations in four states. Initially, the experiments extracted the mechanical properties of the scaled materials. Then, three semi-circular brick barrel vaults were tested with gravitational loads. The outcomes were used to develop and validate the finite element model. Following the development of the finite element model, numerical and parametric studies were conducted on the effect of the aforementioned structural hazards on the response of brick masonry barrel vaults with various Persian geometries (semi-circular, drop pointed, and four-centred), angles of skew (0, 15, 30, and 45 degrees), and dimensional ratios. According to the findings, the fragility of masonry materials makes historical structures susceptible to failure under different loading. A brick barrel vault fails in the presence of minor rotation and settlement of the piers. The four-centred geometric shape has the lowest performance among the seven Persian geometries; therefore, its health monitoring and retrofitting should be prioritised. In Isfahan, Iran, temperature variations, particularly during the warm seasons, cause critical conditions in such structures.

• Earthquakes and Structures
• /
• v.26 no.4
• /
• pp.311-326
• /
• 2024

Transmission tower structures are particularly susceptible to damage and even collapse under strong seismic ground motions. Conventional seismic analyses of transmission towers are usually performed by considering only ground motion uncertainty while ignoring structural uncertainty; consequently, the performance evaluation and failure prediction may be inaccurate. In this context, the present study numerically investigates the seismic responses and failure mechanism of transmission towers by considering multiple sources of uncertainty. To this end, an existing transmission tower is chosen, and the corresponding three-dimensional finite element model is created in ABAQUS software. Sensitivity analysis is carried out to identify the relative importance of the uncertain parameters in the seismic responses of transmission towers. The numerical results indicate that the impacts of the structural damping ratio, elastic modulus and yield strength on the seismic responses of the transmission tower are relatively large. Subsequently, a set of 20 uncertainty models are established based on random samples of various parameter combinations generated by the Latin hypercube sampling (LHS) method. An uncertainty analysis is performed for these uncertainty models to clarify the impacts of uncertain structural factors on the seismic responses and failure mechanism (ultimate bearing capacity and failure path). The numerical results show that structural uncertainty has a significant influence on the seismic responses and failure mechanism of transmission towers; different possible failure paths exist for the uncertainty models, whereas only one exists for the deterministic model, and the ultimate bearing capacity of transmission towers is more sensitive to the variation in material parameters than that in geometrical parameters. This research is expected to provide an in-depth understanding of the influence of structural uncertainty on the seismic demand assessment of transmission towers.

• Food Science and Biotechnology
• /
• v.17 no.3
• /
• pp.501-507
• /
• 2008

The quantitative structure-activity relationships (QSAR) study of antioxidative anthocyanidins and their glycosides were evaluated using 4 different assays of Trolox equivalent antioxidant capacity (TEAC), superoxide radical ($O_2^{{\cdot}-}$), hydrogen peroxide ($H_2O_2$), and peroxynitrite radical ($ONOO^-$) scavenging with TSAR software. Four models were developed with significant predictive values ($r^2$ and p value), which indicated that the antioxidant activities were mainly governed by the 3-dimensional structural energy (torsional energy), constitutional properties (the number of hydroxyl and methyl groups), and electrostatic properties (heat of formation, and dipole, quadrupole, and octupole components). This QSAR approach could contribute to a better understanding of structural properties of anthocyanidins and their glycosides that are responsible for their antioxidant activities. It might also be useful in predicting the antioxidant activities of other anthocyanins.

• International Journal of Concrete Structures and Materials
• /
• v.6 no.2
• /
• pp.111-121
• /
• 2012

The research presented in this paper analytically examines the fire performance of flat plate buildings. The modeling parameters for the mechanical and thermal properties of materials are calibrated from relevant test data to minimize the uncertainties involved in analysis. The calibrated models are then adopted to perform a nonlinear finite element simulation on a flat plate building subjected to fire. The analysis examines the characteristics of slab deflection, in-plane deformation, membrane force, bending moment redistribution, and slab rotational deformation near the supporting columns. The numerical simulation enables the understanding of structural performance of flat plate under elevated temperature and, more importantly, identifies the high risk of punching failure at slab-column connections that may trigger large-scale failure in flat plate structures.

• BMB Reports
• /
• v.49 no.12
• /
• pp.655-661
• /
• 2016

Polymer brush is a soft material unit tethered covalently on the surface of scaffolds. It can induce functional and structural modification of a substrate's properties. Such surface coating approach has attracted special attentions in the fields of stem cell biology, tissue engineering, and regenerative medicine due to facile fabrication, usability of various polymers, extracellular matrix (ECM)-like structural features, and in vivo stability. Here, we summarized polymer brush-based grafting approaches comparing self-assembled monolayer (SAM)-based coating method, in addition to physico-chemical characterization techniques for surfaces such as wettability, stiffness/elasticity, roughness, and chemical composition that can affect cell adhesion, differentiation, and proliferation. We also reviewed recent advancements in cell biological applications of polymer brushes by focusing on stem cell differentiation and 3D supports/implants for tissue formation. Understanding cell behaviors on polymer brushes in the scale of nanometer length can contribute to systematic understandings of cellular responses at the interface of polymers and scaffolds and their simultaneous effects on cell behaviors for promising platform designs.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.3
• /
• pp.141-146
• /
• 2017

We investigated configuration of metallic and insulating domains in $VO_2$ thin films, while spanning metal-insulator phase transition. Kelvin probe force microscopy, of which spatial resolution is less than 100 nm, enables us to measure local work function (WF) at the sample surface. The WF of $VO_2$ thin films decreased (increased) as increasing (decreasing) the sample temperature, during the phase transition. The higher and lower WF regions corresponded to the insulating and metallic domains, respectively. The metallic fraction, estimated from the WF maps, well explained the temperature-dependent resistivity based on the percolation model. The WF mapping also showed us how the structural defects affected the phase transition behaviors.