• Computers and Concrete
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• v.8 no.1
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• pp.97-110
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• 2011

In this paper, FEM procedure is applied to the static and dynamic analyses of R/C structures. Simple R/C shell structure is solved by using FEM procedures and the experimental evaluations are performed to represent the applicability of FEM procedure to R/C structures. Also, R/C columns are analyzed numerically and experimentally. On the basis of these results, FEM procedures are applied to the R/C cooling tower structures assembled by huge R/C shell structure and a lot of discrete R/C columns. In this analysis, the parallel computing procedures are introduced into these analyses to reduce the computational effort. The dynamic performances of R/C cooling tower are also solved by the application of parallel computations as well. From the numerical analyses, the conventional FEM procedures combined with computational technologies enables us to design the huge R/C structures statically and dynamically.

• Proceeding of KASS Symposium
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• 2005.05a
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• pp.154-160
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• 2005

The present study is concerned with the application of dynamic relaxation method in the investigation of the large deflection behavior of spatial structures. The dynamic relaxation do not require the computation or formulation of any tangent stiffness matrix. The convergence to the solution is achieved by using only vectorial quantities and no stiffness matrix is required in its overall assembled form. In an effort to evaluate the merits of the methods, extensive numerical studies were carried out on a number of selected structural systems. The advantages of using dynamic relaxation methods, in tracing the post-buckling behavior of spatial structures, are demonstrated.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.354-354
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• 2010

Supramolecualr ordering has been actively studied due to it's possible applications to the fabrication processes of nano-electronic devices. Van der Waals interaction and hydrogen bonding are frequently studied mechanisms for various molecular structures based on non-uniform charge distributions. Halogen atoms in molecules can have electrostatic interactions with similar strength. Big halogen atoms have strong non-uniform charge distributions. To study molecular orderings formed by hydrogen and halogen interactions, we chose a molecular system containing oxygen, hydrogen, and bromine atoms, a bromo-quinone. A two-dimensional molecular network was studied on Au(111) using a low-temperature scanning tunneling microscope. Bromo-quinone molecules form self-assembled square grids having windmill structures. Their molecular orderings, chiral structures, and defects are explained in terms of hydrogen and halogen interactions.

• Journal of Photoscience
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• v.11 no.1
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• pp.1-6
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• 2004

Molecular assembling is one of the current interests in the field of bottom-up nanotechnology. Self-assembled monolayers of sulfur-containing molecules or supramolecular assemblies via surface sol-gel processes formed on conductive supports are chemically robust and can be easily fabricated without sophisticated instruments. We have fabricated various types of molecular assemblies consisting of donor-acceptor pairs on the surfaces of gold and indium-tin-oxide electrodes. Build-up of three-dimensional multi structures consisting of thiol dyes and gold nanoparticles also has been successful. These assemblies showed clear photocurrent responses in photoelectro-chemical cells. In this article, we will describe recent progress on photoelectric conversion using molecular assemblies especially focused on our research results.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.183-187
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• 2006

We present the effects of rapid thermal annealing (RTA) temperature on the structural and optical properties of self-assembled InAs quantum dot (QD) structures grown on GaAs substrates by molecular beam epitaxy (MBE). The photoluminescence (PL) measurements are performed in a closed-cycle refrigerator as a function of temperature for the unannealed and annealed samples. RTA at higher temperature results in the increase in island size, the corresponding decrease in the density of islands, and the redshift in the PL emission from the islands. The temperature dependence of the PL peak energy for the InAs QDs is well expressed by the Varshni equation. The thermal quenching activation energies for the samples unannealed and annealed at $600^{\circ}C$ are found to be $25{\pm}5meV$ and $47{\pm}5$ meV, respectively.

• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.423-437
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• 2013

Complex structures are usually assembled from several substructures with joints connecting them together. These joints have significant effects on the dynamic behavior of the assembled structure and must be accurately modeled. In structural analysis, these joints are often simplified by assuming ideal boundary conditions. However, the dynamic behavior predicted on the basis of the simplified model may have significant errors. This has prompted the researchers to include the effect of joint stiffness in the structural model and to estimate the stiffness parameters using inverse dynamics. In the present work, structural joints have been modeled as a pair of translational and rotational springs and frequency equation of the overall system has been developed using sub-structure synthesis. It is shown that using first few natural frequencies of the system, one can obtain a set of over-determined system of equations involving the unknown stiffness parameters. Method of multi-linear regression is then applied to obtain the best estimate of the unknown stiffness parameters. The estimation procedure has been developed for a two parameter joint stiffness matrix.

• Journal of Powder Materials
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• v.24 no.3
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• pp.229-234
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• 2017

We report on a simple and robust route to the spontaneous assembly of well-ordered magnetic nanoparticle superstructures by irreversible evaporation of a sessile single droplet of a mixture of a ferrofluid (FF) and a nonmagnetic fluid (NF). The resulting assembled superstructures are seen to form well-packed, vertically arranged columns with diameters of $5{\sim}0.7{\mu}m$, interparticle spacings of $9{\sim}2{\mu}m$, and heights of $1.3{\sim}3{\mu}m$ The assembled superstructures are strongly dependent on both the magnitude of magnetic field and the mixing ratio of the mixture. As the magnitude of the externally applied magnetic field and the mixing ratio of the mixture increase gradually, the size and interspacing of the magnetic nanoparticle aggregations decrease. Without an externally applied magnetic field, featureless patterns are observed for the ${\gamma}-Fe_3O_4$ nanoparticle aggregations. The proposed approach may lead to a versatile, cost-effective, fast, and scalable fabrication process based on the field-induced self-assembly of magnetic nanoparticles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.62-62
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• 2010

Photonic quasi-crystals(PQCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns. The multiple-exposing source is collimated laser beam and rotation, tilting system. The arrays of the PQCs exhibited variable lattice structures and shape the control of ratating angle ($\theta$), tilting angle ($\gamma$) and the exposure conditions. The used nanosphere size is upto the $1\;{\mu}m$. Images of prepared 2D PQCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the PQCs arrays of large area.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.243-243
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• 2012

Self-assembled monolayers (SAMs) prepared by aromatic thiols on gold surfaces have much larger potential for electronic device applications due to their electronic properties. In this study, the formation and structures of SAMs prepared by benzenethiol (BT), toluenethiol (TT), 2-fluorobenzenethiol (2-FBT), 3-fluorobenzenethiol (3-FBT), 4-fluorobenzenethiol (4-FBT), 4-chlorobenzenethiol (4-CBT), 4-fluorobenzenemethanethiol (4-FBMT), and 4-chlorobenzenemethanethiol (4-CBMT) on Au(111) were examined using scanning tunneling microscopy (STM) and Kelvin probe (KP) to explore the structure and electronic interface properties of eight differently substituted aromatic thiol SAMs on Au(111). And these values are compared with gas phase dipole moments computed by quantum chemical calculations for individual thiol molecules. It was revealed that all eight thiol-molecules form uniform SAMs on Au(111) at $75^{\circ}C$ compared to lower solution temperature by STM observation. The work function change obtained in the KP measurements and calculated molecular dipole moments have the linear relationship while the 4-FBMT and 4-CBMT deviate from this tendency.

• Steel and Composite Structures
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• v.24 no.4
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• pp.481-497
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• 2017

In this paper, full-scale loading tests were performed on a rectangular segmental tunnel lining, which was assembled by steel composite segments, to investigate its load-bearing structural behavior and failure mechanism. The tests were also used to confirm the composite effect by adding concrete inside to satisfy the required performance under severe loading conditions. The design of the tested rectangular segmental lining and the loading scheme are also described to better understand the bearing capacity of this composite lining structure. It is found that the structural ultimate bearing capacity is governed by the bond capacity between steel plates and the tunnel segment. The failure of the strengthened lining is the consequence of local failure of the bond at waist joints. This led to a fast decrease of the overall stiffness and eventually a loss of the structural integrity.