• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.82-88
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• 2008

This paper proposes a novel method of 2 dimensional shape display. Shape displays allow us to feel tile actual volume of the object, unlike conventional 2D visual displays of 3D objects. The proposed method employs a wireframe structure to present 2D or 3D objects. The wireframe is composed of small units driven by shape memory alloy (SMA) actuators. The drive unit is analogous to the agonist-antagonist system of animal musculoskeletal systems, where the SMA actuators serve as agonist and antagonist muscles. The force in the SMA actuator is controlled by electrical current. The drive unit is equipped with the locking mechanism so that it can sustain the external force exerted by the user as well as the own weight of the wireframe structure. By controlling the current into the SMA actuator and locking mechanism, we can control the angle of the drive unit. A chain of drive units enables presentation of 2 dimensional objects. 3 dimensional presentations are possible by collecting the chains of drive units.

• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1098-1103
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• 1994

Atomic force microscopy (AFM) images of two conducting layered transition-metal ditellurides, $TaTe_2$ and $Ta_{0.5}$$V_{0.5}$$Te_2$, were examined and their surface and bulk structural features were compared. All the measured unit cell parameters from AFM image were consistent and in complete agreement with the results of the X-ray diffraction. The microscopic structures of corrugated surface tellurium sheets were strongly affected by the modification of metal double zig-zag chains underneath Te surface. Large difference in the height amplitudes of AFM images in $TaTe_2$ and $Ta_{0.5}$$V_{0.5}$$Te_2$ phases was observed and this reflects large difference in the surface electron densities of two phases. On surface, the shorter intralayer Te…Te contacts in $TaTe_2$ induce more electron transfer from Te p-block bands to Ta d-block bands, thus electron density on surface observed in $TaTe_2$ is much lower than that of $Ta_{0.5}$$V_{0.5}$$Te_2$. However, in bulk, interlayer Te…Te contacts in V substituted phase are shorter than those in $TaTe_2$ phase, thus tellurium-to-metal electron transfer occurs more easily in $Ta_{0.5}$$V_{0.5}$$Te_2$ phase.

• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.623-627
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• 2000

Aggregation of hydrophobically end-capped poly(ethylene oxide)s: HEURs, denoted as $C_8$$EO_{380}$$C_8$, $C_12$$CO_{600}$$C_{12}$, and $C_{18}$$EO_{860}$$C_{18}$,are described using static fluorescence, dynamic light scattering, and atomic force microscope (AFM) techniques. The CAC (critical aggregation concentration) was determined by com-paring two fluorescent peaks which were influenced by the polarity of the probe dye molecules, pyrene. The aggregation occurs in concentrations higher than 10 g/L of $C_8$$EO_{380}$$C_8$ and the CAC decreases by increasing the side chain length. The dynamic light scattering experiment shows fast mode and slow mode decays, and both are diffusive. The fast mode does not depend on the concentration, but the slow mode shows concentration dependence influenced by the formation of an aggregated structure. The hydrophobic end groups effect more dominantly than the main chains for the formation of HEUR micelles. By increasing the concentration, the HEUR micelles change their structure from spheres to rodlike micelles, and finally make fused structures, which were visualized with atomic force microscopy.

• Journal of Ocean Engineering and Technology
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• v.37 no.3
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• pp.111-121
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• 2023

This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

• Macromolecular Research
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• v.11 no.6
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• pp.495-500
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• 2003

UV-induced graft polymerization of glycidyl methacrylate (GMA) to a polypropylene (PP) membrane was carried out in the vapor phase with benzophenone (BP) as a photoinitiator. Attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were utilized to characterize the copolymer. The degree of grafting increased with increasing reaction time, increased UV irradiation source intensity, and increased immersion concentration of the BP solution. The optimum synthetic condition for the PP-g-GMA membrane was obtained with a reaction time of 2 hrs, a UV irradiation source intensity of 450 W, and an immersion concentration of the BP solution of 0.5 mol/L. The pure water flux decreased upon increasing the degree of grafting and increasing the amount of diethylamino functional group introduced. The analysis of AFM and SEM images shows that the graft chains and diethylamino groups of PP-g-GMA grew on the PP membrane surface, resulting in a change in surface morphology.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.219-220
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• 2013

The phenomenology of liquid breakdown has been an area of interest for many years but is still not fully understood. Moreover, it was known that the behavior of magnetic nanoparticles in transformer oil could affect the dielectric breakdown voltage positively or negatively. In this study, we have imaged the magnetic nanoparticles in a transformer oil in-situ using an optical microscopic set-up and a microchannel according to the electric and magnetic fields applied. And we have calculated numerically dielectrophoresis and magnetophoresis forces, which must be the driving mechanisms to move magnetic nanoparticles in the fluid. It was found that when the electric field is applied the magnetic nanoparticles in the fluid experience an electrical force directed toward the place of maximum electric field strength. And when the external magnetic field is applied, the magnetic nanoparticles form long chains oriented along the direction of the field.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.341-341
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• 2006

Nanofishing enabled us to stretch a single polymer chain with picking it at its two modified termini using atomic force microscope (AFM). Stress-strain curves obtained to date had been the result on slow pulling events and therefore observed phenomena had been interpreted as quasi-static responses. In this study, we extended the capability of nanofishing to the phenomena far from equilibrium state by giving much faster pulling speeds. We could observe a momental increase entanglement and a successive stress relaxation.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.127-130
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• 2005

The early stage of the self assembly for octadecyltrichlorosilane (OTS)-based monolayers is investigated using atomic force microscopy (AFM). Height measurements using AFM prove that the island height of the monolayers gradually increases with increasing the island size, and is close to the limiting value (h = $\sim$25 $\AA$) after d = $\sim$600 nm in size. Since the theoretical length of a covalently bound OTS molecule is 26.2 Å, the limiting value of the island height means that the islands with d ${\geq}$ 600 nm consist of close-packed, fully extended chains. The heights for the islands with d < 600 nm are lower than the limiting value and decrease with decreasing the island sizes. This observation indicates that the OTS molecules in the small islands are less densely packed, and that the packing densities of the islands increase as the islands grow in size.

• Textile Coloration and Finishing
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• v.16 no.1
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• pp.59-64
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• 2004

As a simulation of solvent-assisted dyeing, the solvent effects on the structure of polyethylene terephthalate(PET) film treated by dimethylformamide(DMF) were investigated. The effects were evaluated by the atomic force microscopy(AFM) topographical changes and FT-IR spectrum analysis. PET films treated with DMF at $70^{\circ}C$ for several different treatment time(20, 40, and 60 min). AFM topography showed that, with increasing treatment time by DMF, PET surfaces became smooth due to the swelling phenomenon and the rigid structure changed into flexible state which was contributed to increase the surface area of PET films. FT-IR spectrum analysis showed that DMF and molecular chains of PET interacted each other via their polar carbonyl groups and that DMF also affected the out-of-plane bending vibration mode of phenyl ring of PET.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1554-1567
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• 2005

When multiple robotics systems with several sub-chains grasp a common object, the inherent force redundancy provides a chance of utilizing internal loading. Analysis of grasping space based internal loading is proposed in this work since this method facilitates understanding the physical meaning of internal loadings in some applications, as compared to usual operational space based approach. Investigation of the internal loading for a triple manipulator has been few as ,compared to a dual manipulator. In this paper, types of the internal loading for dual and triple manipulator systems are investigated by using the reduced row echelon method to analyze the null space of those systems. No internal loading condition is derived and several load distribution schemes are compared through simulation. Furthermore, it is shown that the proposed scheme based on grasping space is applicable to analysis of special cases such as three-fingered and three-legged robots having a point contact with the grasped object or ground.