• Smart Structures and Systems
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• v.8 no.1
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• pp.139-155
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• 2011

Polymeric thin-film assemblies whose bulk electrical conductivity and mechanical performance have been enhanced by single-walled carbon nanotubes are proposed for measuring strain and corrosion activity in metallic structural systems. Similar to the dermatological system found in animals, the proposed self-sensing thin-film assembly supports spatial strain and pH sensing via localized changes in electrical conductivity. Specifically, electrical impedance tomography (EIT) is used to create detailed mappings of film conductivity over its complete surface area using electrical measurements taken at the film boundary. While EIT is a powerful means of mapping the sensing skin's spatial response, it requires a data acquisition system capable of taking electrical impedance measurements on a large number of electrodes. A low-cost wireless impedance analyzer is proposed to fully automate EIT data acquisition. The key attribute of the device is a flexible sinusoidal waveform generator capable of generating regulated current signals with frequencies from near-DC to 20 MHz. Furthermore, a multiplexed sensing interface offers 32 addressable channels from which voltage measurements can be made. A wireless interface is included to eliminate the cumbersome wiring often required for data acquisition in a structure. The functionality of the wireless impedance analyzer is illustrated on an experimental setup with the system used for automated acquisition of electrical impedance measurements taken on the boundary of a bio-inspired sensing skin recently proposed for structural health monitoring.

• Journal of Powder Materials
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• v.23 no.3
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• pp.235-239
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• 2016

This study is performed to fabricate a Ti porous body by freeze drying process using titanium hydride ($TiH_2$) powder and camphene. Then, the Ti porous body is employed to synthesize carbon nanotubes (CNTs) using thermal catalytic chemical vapor deposition (CCVD) with Fe catalyst and methane ($CH_4$) gas to increase the specific surface area. The synthesized Ti porous body has $100{\mu}M$-sized macropores and $10-30{\mu}m$-sized micropores. The synthesized CNTs have random directions and are entangled with adjacent CNTs. The CNTs have a bamboo-like structure, and their average diameter is about 50 nm. The Fe nano-particles observed at the tip of the CNTs indicate that the tip growth model is applicable. The specific surface area of the CNT-coated Ti porous body is about 20 times larger than that of the raw Ti porous body. These CNT-coated Ti porous bodies are expected to be used as filters or catalyst supports.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.279-287
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• 2009

Fisher-Tropsch synthesis for the production of hydrocarbon from syngas was investigated on 20% cobalt-based catalysts (20% Co/HSA, 20% Co/Si-MMS), which were prepared by home-made supports with high surface areas such as high surface alumina (HSA) and silica mesopores molecular sieve (Si-MMS). In the gas phase reaction by syngas only, 20% Co/Si-MMS catalyst was shown in higher CO conversion and lower carbon dioxide formation than 20% Co/HSA, whereas the olefin selectivity was higher in 20% Co/HSA than in 20% Co/Si-MMS. In the effect of n-hexane added in syngas, the selectivities of $C_{5+}$ and olefin were increased by comparing the supercritical phase reaction with the gas phase reaction in addition to reduce unexpected methane and carbon dioxide.

• Composites Research
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• v.13 no.4
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• pp.33-41
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• 2000

In this research, the mathematical modeling of the formation of SiC layer on the activated carbon was studied to improve the durability and the oxidation resistance of catalyst supports. SiC layer on the activated carbon was formed by permeating SiC from dichlorodimethylsilane(DDS) into pores and depositing while the porous structure was kept. The best conditions of manufacturing the support were found by studying the characteristics of SiC/C which was modelled under various deposition conditions. Changes of the amount of deposition, the pore diameter, the surface area with time were obtained by simulating convection, diffusion and reaction in an isothermal reactor at a steady state. The uniform deposition in the pores of samples was obtained at a lower concentration of the reactant and a lower pressure. Additionally, it was observed that the pore diameter and the surface area have points of inflection at certain times of deposition, because deposition occurred on the inside surface of the pore at first and then on the outside surface of the particle.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.783-792
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• 2017

Carbon Fiber Reinforced Polymer (CFRP) laminates are used widely either for repairing or strengthening of existing structures. When CFRP laminates are used for strengthening of RC continuous T-beams in the Hogging Moment Zone (HMZ); above and around the intermediate supports, it is important to study the expected positions of the laminates across the width of the beam flange. Although, it is traditional to consider CFRP laminates added above the beam web, this is not practical since walls and columns are located in such positions in general. This paper examines the effect of changing the positions of CFRP laminates used for the strengthening of the hogging moment zone across the beam flange of two-span-T-section beams. The Finite Element (FE) Package ANSYS is used to create 3-D theoretical models needed for the study. It can be concluded that changing the position of CFRP strengthening across the beam flange, in the hogging moment zone, is effective upon the overall behavior. The best locations are either above the web or at the flange just beside the web, due to the presence of walls and/or columns.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.39.2-39.2
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• 2011

With the steady increase in the demand for flexible devices, mainly in display panels, researchers have focused on finding a novel material that have excellent electrical properties even when it is bended or stretched, along with superior mechanical and thermal properties. Graphene, a single-layered two-dimensional carbon lattice, has recently attracted tremendous research interest in this respect. However, the limitations in the growing method of graphene, mainly chemical vapor deposition on transition metal catalysts, has posed severe problems in terms of device integration, due to the laborious transfer process that may damage and contaminate the graphene layer. In addition, to lower the overall cost, a fabrication technique that supports low temperature and low vacuum is required, which is the main reason why solution-based process for graphene layer deposition has become the hot issue. Nonetheless, a direct deposition method of large area, few-layered, and uniform graphene layers has not been reported yet, along with a convenient method of patterning them. Here, we report an evaporation-induced technique for directly depositing few layers of graphene nanosheets with excellent uniformity and thickness controllability on any substrate. The printed graphene nanosheets can be patterned into desired shapes and structures, which can be directly applicable as flexible and transparent electrode. To illustrate such potential, the transport properties and resistivity of the deposited graphene layers have been investigated according to their thickness. The induced internal flow of the graphene solution during tis evaporation allows uniform deposition with which its thickness, and thus resistivity can be tuned by controlling the composition ratio of the solute and solvent.

• Nuclear Engineering and Technology
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• v.38 no.3
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• pp.201-210
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• 2006

This article presents a brief overview of an important area of neutron scattering: the general principles and techniques of elastic, quasielastic and inelastic scattering from a system composed predominately of incoherent scatterers. The methodology is then applied to the study of water, specifically when it is confined in nanometer-scale environments. The confined water exhibits uniquely anomalous properties in the supercooled state. It also nourishes biological functions, and supports essential chemical reactions in living systems. We focus on recent investigations of water encapsulated in nanoporous silica and carbon nanotubes, hydrated water in proteins and water or hydroxyl species incorporated in nanostructured minerals. Through these scientific examples, we demonstrate the advantages derived from the high sensitivity of incoherent neutron spectroscopy to hydrogen atom motions and hydrogen-bond dynamics, aided by rigorous data interpretation method using molecular dynamics simulations or theoretical modelling. This enables us to probe the inter-/intramolecular vibrations and relaxation/diffusion processes of water molecules in a complex environment.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.5
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• pp.393-405
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• 2017

This paper deals with the buckling strength of the skirt structure in the spherical LNG carriers. The spherical cargo tank systems consist of spherical tank, skirt, tank cover, pump tower, etc. The skirt supports the spherical cargo tank and is connected with ship hull structure. It is designed to act as a thermal brake between the tank and the hull structure by reducing the thermal conduction from the tank to the supporting structure. It is built up of three parts, upper aluminum part, middle stainless steel part and lower carbon steel part. The 150K spherical LNG carrier was designed and carried out the strength verification under Classification Societies Rule. The design loads due to acceleration, thermal distribution, self-weight and cargo weight were estimated considering requirements of the Class Rule and numerical simulation analyses. Based on the obtained design loads and experienced project data, the initial structure scantling was carried out. To verify the structural integrity, theoretical and numerical analyses were carried out and strength was evaluated aspect of buckling capacity. The results by LR and DNV design code are shown and discussed.

• Advances in concrete construction
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• v.9 no.6
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• pp.577-588
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• 2020

In this paper, vibration attributes of chiral double-walled carbon nanotubes (CNTs) based on nonlocal elastic shell model have been investigated. The impact of small scale is being perceived by establishing Flügge shell model. The wave propagation is engaged to frame the ruling equations as eigen value system. The influence of nonlocal parameter subjected to different end supports has been overtly examined. A suitable choice of material properties and nonlocal parameter been focused to analyze the vibration characteristics. The new set of inner and outer tubes radii investigated in detail against aspect ratio and length. The dominance of boundary conditions via nonlocal parameter is shown graphically. Whereas for lower aspect ratio the frequencies coincide but as it continues to expand the difference between all respective boundary conditions slightly tend to increase. The results generated furnish the evidence regarding applicability of nonlocal shell model and also verified by earlier published literature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.189-190
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• 2006

A patient table considering x-ray transparency, mechanical safety and compact multi-axis moving mechanism has been developed. The goal of medical imaging technology is to keep radiation exposure of patients during x-raying to a minimum. In order to obtain clear pictures at low dose, however, the x-ray table which supports the patient must be sufficiently permeable to radiation to allow good image resolution. The table top is made of low density foam for x-ray transparent effective area and structural aluminum plate to connect moving mechanism under the table, covered with thin carbon fiber. This sandwich construction is very rigid and lightweight, so the table top can handle relatively heavy load comparing to its cantilevered structure which is unavoidable as long as cooperate with C-arm radiography. To verify the design results finite element static analysis and experimental tests have been done. According to the verification the results well satisfy certification guide lines as a medical device.