• Carbon letters
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• v.14 no.1
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• pp.1-13
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• 2013

Carbon nanotubes (CNTs) are increasingly attracting scientific and industrial interest because of their outstanding characteristics, such as a high Young's modulus and tensile strength, low density, and excellent electrical and thermal properties. The incorporation of CNTs into polymer matrices greatly improves the electrical, thermal, and mechanical properties of the materials. Surface modification of CNTs can improve their processibility and dispersion within the composites. This paper aims to review the surface modification of CNTs, processing technologies, and mechanical and electrical properties of CNT-based epoxy composites.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.199-202
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• 2013

In order to study the effect of reactive diluents on the electrical insulation breakdown strength and mechanical properties of, a polyglycol and an aliphatic epoxy were individually introduced to an epoxy system. Reactive diluents were used in order to decrease the viscosity of the epoxy system; polyglycol acted as a flexibilizer and 1,4-butanediol diglycidyl ether (BDGE) acted as an aliphatic epoxy, which then acted as a chain extender after curing reaction. The ac electrical breakdown strength was estimated in sphere-to-sphere electrodes and the electrical breakdown strength was estimated by Weibull statistical analysis. The scale parameters of the electrical breakdown strengths for the epoxy resin, epoxy-polyglycol, and epoxy-BDGE were 45.0, 46.2, and 45.1 kV/mm, respectively. The flexural and tensile strengths for epoxy-BDGE were lower than those of the epoxy resin and those for epoxy-polyglycol were lower than those of the epoxy resin.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.426-428
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• 2015

The NGK suspension insulators are subjected in harsh environments in service above 40 years long time. The long term reliability of the insulators is required for both mechanical and electrical performances. This study describes some electrical performances according to KEPCO-standard. There was fail in electrical and mechanical performance test such as galvanizing, low-frequence wet flashover voltage, puncture and combine mechanical & electrical strength test. The NGK suspension insulators of 1968 were shown lower electrical and mechanical performance than those of 1979.

• Journal of Power Electronics
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• v.14 no.4
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• pp.722-732
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• 2014

The power-voltage (P-V) curve of photovoltaic (PV) arrays connected in parallel to bypass diodes would have several local maximum power points (LMPP) under partial shading conditions (PSC). Conventional maximum power point tracking (MPPT) methods fail to search for the global maximum power point (MPP) because the searched peak point may remain at the LMPP on the P-V curve under PSC. This study proposes an improved MPPT algorithm to ensure that PV arrays operate at global maximum power point (GMPP) under PSC. The proposed algorithm is based on a critical study and a series of observations of PV characteristics under PSC. Results show the regularity of voltage interval between LMPPs. The algorithm has the advantages of rapidly reaching GMPP, maintaining stability, and recovering GMPP quickly when the operating condition changes. Simulation and experimental results demonstrate the feasibility of the proposed algorithm.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.124-129
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• 2009

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.554-556
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• 2002

It has little possibility that cable and cable joint causes any problem in transmission system. But when cable fault occurs, the damage is very severe. There are weak points to have potential problem due to many cable joint especially in high voltage transmission line. In this study, we propose nobel method to detect PD in cable joints and show the effectiveness of the proposed method through experiment results.

• Transactions on Electrical and Electronic Materials
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• v.12 no.3
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• pp.98-101
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• 2011

A 10 nm nano-silica was introduced to a conventional 3 ${\mu}M$ micro-silica composite to develop an eco-friendly new electric insulation material for heavy electric equipment. Thermal and mechanical properties, such as glass transition temperature (Tg), dynamic mechanical analysis, tensile and flexural strength, were studied. The mechanical results were estimated by comparing scale and shape parameters in Weibull statistical analysis. The thermal and mechanical properties of conventional epoxy/micro-silica composite were improved by the addition of nano-silica. This was due to the increment of the compaction via the even dispersion of the nano-silica among the micro-silica particles.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.869-877
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• 2020

The power consumption in the low consistency (LC) refining is an important indicator for the optimal control of the process and it is composed of the net power and the no-load power. The refining efficiency and process characterization of LC refining are directly affected by power consumption. In this paper, the effect of pulp consistency and average fiber length on the power consumption and refining efficiency were studied through the LC refining trials conducted by an experimental disc refiner. It is found that the curve of power-gap clearance can be divided into constant power section, power reduction section, and power increase section. And the no-load power and the adjustable domain of loading applied by the refining plates will increase as the increase of pulp consistency, while the increase of net power is larger than that of no-load power which makes the increasing of refining efficiency. Meanwhile, the adjustable domain of loading applied by the refining plates can be slightly improved by increasing the average fiber length, but its effect on the no-load power in the LC refining process can be neglected. The study of power consumption in LC refining is of positive significance for the proper selection of pulp properties in LC refining, in-depth exploration of refining mechanism, and energy consumption reduction in refining.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.521-530
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• 2017

Improving the microstructure of NiO/YSZ is one of several approaches used to enhance the electrical and mechanical properties of an anode support in Solid Oxide Fuel Cells (SOFCs). The aim of the work reported in this paper was to predict the relationship between these microstructural changes and the resulting properties. To this end, modification of the anode microstructure was carried out using different sizes of Poly (Methyl Methacrylate) (PMMA) beads as a pore former. The electrical conductivity and mechanical strength of these samples were measured using four-probe DC, and three-point bend-test methods, respectively. Thermal etching followed by high resolution SEM imaging was performed for sintered samples to distinguish between the three phases (NiO, YSZ, and pores). Recently developed image analysis techniques were modified and used to calculate the porosity and the contiguity of different phases of the anode support. Image analysis results were verified by comparison with the porosity values determined from mercury porosimetry measurements. Contiguity of the three phases was then compared with data from electrical and mechanical measurements. A linear relationship was obtained between the contiguity data determined from image analysis, and the electrical and mechanical properties found experimentally. Based upon these relationships we can predict the electrical and mechanical properties of SOFC support from the SEM images.

• Journal of Power Electronics
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• v.19 no.3
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• pp.744-750
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• 2019

A new type of auto-rotary PM mechanical flux-varying PM machine (ARPMMFVPMM) is proposed in this paper, which can overcome the problem where the air-gap magnetic field of a PM machine is difficult to freely adjust. The topology structures of the machine and the mechanical flux-adjusting device are given. In addition, the operation principle of flux-adjusting is analyzed in detail. Furthermore, the deformation of a spring with the speed variation is obtained by virtual prototype technology. Electromagnetic characteristics including the flux distribution, air gap flux density, flux linkage, electromagnetic-magnetic-force (EMF), and flux weakening ability are computed by 2D finite element method (FEM). Results show that the machine has some advantages such as the good field control ability.