• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1684-1690
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• 1995

A large time asymptotic solution for an unsteady heat conduction problem of a coated hot wire thermal conductivity measurement process was theoretically found. The solution revealed that the slope of wire temperature versus logarthmic time, which is used to evaluate the thermal conductivity, remains unchanged for large values of time even if a layer of coating is present on the hot wire. The significance of this result is that the thermal conductivity of an electrically conductive fluid can be measured with a coated hot wire using the same conversion relation as for a bare wire.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.154-161
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• 1984

A modified technique of the transient hot wire method to measure the thermal conductivity of fluid has been described in this paper. The thermal conductivity of fluid can be obtained by acquiring wire temperature as a function of time. Multiplication of the inverse slope of the temperature versus logarithm of time by an instrumental constant gives the thermal conductivity. The constant voltage was applied to Wheatstone bridge circuit. The wire temperature can be measured as a function of time precisely with the aid of the data acquisition system composed of a microprocessor and an analog-digital converter. The thermal conductivity of the electrically conducting fluid has been measured with the insulated hot wire coated by electrically non-conducting material. The effect of the coated insulation layer on the thermal conductivity has been examined, in which it is confirmed that the thermal conductivity of electrically conducting liquid can be determined by the transient coated hot wire method. Thermal conductivities of methanol, carbontetrachrolide, Freon-22 and glycerin have been measured at room temperature in the pressure from 0.1MPa to 35.1MPa. The experiment has been performed to compare the data from the bare and the coated wires, and the results are satisfactory.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.342-346
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• 2012

This work deals with the preparation of dense SiC based ceramics with high electrical conductivity without oxide sintering additives. SiC samples with different content of conductive Ti-NbC phase were hot pressed at $1850^{\circ}C$ for 1 h in Ar atmosphere under mechanical pressure of 30 MPa. The conductive phase is a mixture of Ti-NbC in weight ratio of Ti/NbC 1:4. Composite with 50% of conductive Ti-NbC phase showed the highest electrical conductivity of $30.6{\times}10^3\;S{\cdot}m^{-1}$, while the good mechanical properties of SiC matrix were preserved (fracture toughness 4.5 $MPa{\cdot}m^{1/2}$ and Vickers hardness 18.7 GPa). The obtained results show that use of NbC and Ti as sintering and also electrically conductive additives is appropriate for the preparation of SiC-based composite with sufficient electrical conductivity for electric discharge machining.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.25-26
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• 2003

Electrically conducting polymers such as polypyrrole(PPy) or poly(3,4-ethylene dioxythiophene)(PEDOT) were sequentially polymerized chemically and electrochemically on various kinds of woven fabrics, giving rise to the fabrics with high electrical conductivity. The specific volume resistivity of the fabric prepared in this study was extremely low as 0.2 $\Omega$-cm. We figured out the electrically conducting fabrics were practically useful for many applications such as an EMI shielding material, a flexible surface heating element or a strain sensor for large deformation.

• Korean Journal of Optics and Photonics
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• v.25 no.5
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• pp.279-285
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• 2014

We propose an electrically controllable terahertz wave modulator based on a metamaterial and vanadium dioxide ($VO_2$) thin film. A square loop shape is designed to play the roles of both a resonating metamaterial and a heater to electrically control the conductivity of $VO_2$. The transmission characteristics of the modulator were controlled by voltage. The transmission coefficient of the modulator was stably changed from 0.27 to 0.80 at 470 GHz according to the conductivity values of $VO_2$.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.288-291
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• 2002

The carbon fiber or glass fiber reinforced prepregs were manufactured using electrostatic flocking technology. The powder of high density polyethylene was used as a matrix. The base film of polyethylene was prepared using a fluidized bed of polyethylene powder under the high electric field. We obtained HDPE film with uniform thickness of minimum $80\mu\textrm{m}$. And the fibers were aligned on the molten HDPE film by the electroflocking process. The short fibers with 1mm were easily electrically charged and aligned under the high electric field. The carbon fibers with high conductivity were elasily electrically charged than the glass fibers with low conductivity. So lower electric field was needed for the carbon fibers.

• Journal of electromagnetic engineering and science
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• v.17 no.4
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• pp.228-232
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• 2017

The radiation properties and fabrication precautions of a 3D printed, electrically small folded spherical meander wire monopole antenna are investigated. The antenna is self-resonant and shows sufficiently high radiation efficiency at an electrical size ka of 0.4, with the radiation quality factor Q approaching the lower physical bound. In antenna fabrication, the possible structural deformation due to gravity is examined before the antenna frame is 3D-printed. The required conductivity is achieved by multiple manual paintings of a silver paste. The radiation efficiency and pattern show very good agreement with the computed expectations, whereas the resonant frequency deviates by 11.8%. The method to minimize such a fabrication error when using 3D printing technology for wire antennas is discussed.

• Journal of Biomedical Engineering Research
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• v.30 no.4
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• pp.279-287
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• 2009

Magnetic resonance electrical impedance tomography (MREIT) is a new medical imaging modality providing cross-sectional images of a conductivity distribution inside an electrically conducting object. MREIT has rapidly progressed in its theory, algorithm and experimental technique and now reached the stage of in vivo animal and human experiments. Conductivity image reconstructions in MREIT require various steps of carefully implemented numerical computations. To facilitate MREIT research, there is a pressing need for an MREIT software package with an efficient user interface. In this paper, we present an example of such a software, called CoReHA which stands for conductivity reconstructor using harmonic algorithms. It offers various computational tools including preprocessing of MREIT data, identification of boundary geometry, electrode modeling, meshing and implementation of the finite element method. Conductivity image reconstruction methods based on the harmonic $B_z$ algorithm are used to produce cross-sectional conductivity images. After summarizing basics of MREIT theory and experimental method, we describe technical details of each data processing task for conductivity image reconstructions. We pay attention to pitfalls and cautions in their numerical implementations. The presented software will be useful to researchers in the field of MREIT for simulation as well as experimental studies.

• Advances in nano research
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• v.15 no.4
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• pp.285-294
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• 2023

This study is aimed to investigate the electrically conductive properties of epoxy nanocomposites exposed to an acidic environment under various mechanical loads. For simultaneous assessment of the acidic environment and mechanical load on the electrical conductivity of the samples, the samples with and without carbon nanotubes were exposed to the acidic environment under three different loading conditions for 20 days. Then, the aged samples' strength and flexural stiffness degradation under crude oil and bending stress were measured using a three-point flexural test. The aged samples in the acidic environment and under 80 percent of their intact ultimate strength revealed a 9% and 26% reduction of their electrical conductivity for samples with and without CNTs, respectively. The presence of nanoparticles declined flexural stiffness by about 16.39%. Scanning electron microscopy (SEM) images of the specimen were used to evaluate the dispersion quality of CNTs. The results of this study can be exploited in constructing conductive composite electrodes to be used in petroleum environments such as crude oil electrostatic tanks.

• Fashion & Textile Research Journal
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• v.14 no.6
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• pp.1018-1023
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• 2012

Smartphone is integrated into the daily lives of all types of people not even young generation. A touch screen display is a primary input device of a smart phone, a tablet computer, etc. While there are many tough technologies in existence, resistive and capacitive are dominant and currently lead the touch screen panel industry. And a capacitive touch screen panel widely used in smart phones is coated with a material that stores electrical charges. In this study, we tried to manufacture gloves produced with electro-conducting leather as a tool to operate a touch panel screen. Therefore, electrically conductive materials, Polyaniline(PANI), Poly(3,4-ethylenedioxythiophene) (PEDOT), and Carbon nanotubes (CNT) were applied to the surface of leather to be used as a touching operator for capacitive touch screen panel. The leather samples were treated by simple painting method; firstly, they were painted with aqueous solution containing each of the electrically conductive materials and then dried. This cycle was repeated three times. Consequently, the treated leather samples showed electrical conductivity and reasonable working performance to the capacitive touch screen. And, PANI showed the best performance and highest electrical conductivity, and then PEDOT and, CNT in decreasing order. This is because the solubilities of PANI and PEDOT show higher than dispersibility of CNT. Thus, the concentration of conducting polymers was greater than that of CNT in the treating solutions.