• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.175-179
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• 1998

The insulation of cable which used for Ultra-High Voltage(UHV) underground power transmission requires excellent insulation capability for high voltage. The typical insulation materials are used XLPE, EPR, etc, but insulation efficiency of these is affected by void or alien substances, existed at the inside of insulators. In this paper, the partial discharge patterns of the defects within insulation cable are observed and analyzed. In this test, void, fiber and metal inclusions which possibly exist in cables, are simulated and investigated the patterns of partial discharges for each models Also the relations between calculated field strength and the insulation breakdown voltage. The experiment shows distinct partial discharge patterns in accordance with the kinds of defects within Insulation cable.

• Journal of the Optical Society of Korea
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• v.20 no.3
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• pp.396-400
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• 2016

Laser speckle patterns were used to monitor variations of thermal voltages of a cathode during a battery discharge. Discharge voltages measured with an oscilloscope were utilized as a figure of merit of thermal voltages in Zn metal. Using an optical imaging system, speckle patterns were taken for zinc metal surface over a time period of 3 minutes. Pixel sum distribution functions (PSDFs) were extracted from speckle patterns. Accumulated pixel sums quantified from PSDFs over an optimized grayscale range strongly correlated with discharge voltages. This suggested that dark matter or particles may have the capability of both absorbing and radiating thermal energies simultaneously. The black body-like properties were able to be validated by identifying coincidences with distinct features of a black body spectrum. The pixels belonging to the grayscale range were confirmed to represent dark matter of a speckle pattern. It was clear that dark matter was part of surface plasmon carriers. The proposed sensing system can be applied to monitor thermal energy variations in any material.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1144-1148
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• 2002

We prepared the polyaniline (Pani) film and powder by chemical polymerization and doping with different dopants and also investigated the capability of Li//polyaniline cells after assembling. The oxidation/reduction potentials and electrochemical reaction of Li//polyaniline cells were tested by cyclic voltammetry technique. The Li//Pani-HCl cells with 10% and 20% conductors show a little larger specific discharge capacities than that without conductor. The highest discharge capacity of almost 50 mAh/g at 100th cycle is also achieved. However, Li//Pani-LiPF6 with 20% conductor shows a remarkable performance of ~90 mAh/g at 100th cycle. This is feasible value for using as the positive electrode material of lithium ion secondary batteries. It is also proved that the powder type electrode of Pani is better to use than the film type one to improve the specific discharge capacity and its stability with cycle.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.1
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• pp.17-25
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• 1986

Discussions on this paper are related to the effects of organic materials to treeing phenomena of low density polyethylene. As additives, 11 kinds of organic compounds are selected by considering the respective features such as melting point, boiling point, electron affinity as well as molecular structure, and then the specimens of low density polyethylene are prepared by blending with 10wt% of the selected additives. For the comparison of effectiveness of treeing resistance and interpretation of the mechanism of compounds as treeing retardants, several investigations such as the tree acceleration test, the prestressed test and the measurement of internally occurred partial discharge are carried out. As the results, meta-Cresol is regard as the most effective retardant among those, and it is supposed that this aromatic compound to be comprised of radical having large electron affinity has strong capability to accept energetic electron to prevent or delay the growth of discharge streamer. Furthermore, by activating partial discharge at the wall of tree pit through the function of trapped electron at this material, the gas pressure in the pit is increased up to prevent the growth of streamer.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1491-1494
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• 2011

Lithium vanadium phosphate, $Li_3V_2(PO_4)_3$ was prepared by a simple solid state route. It was found that making a fine powder of $Li_3V_2(PO_4)_3$ by the mechanical milling is very effective for increasing the insertion/extraction of lithium from $Li_3V_2(PO_4)_3$ structure. In charge/discharge test, the ball-milled $Li_3V_2(PO_4)_3$ sample exhibited a higher initial discharge capacity of 174 mAh/g in the voltage range of 3.0-4.8 V, compared with pure $Li_3V_2(PO_4)_3$ sample (152 mAh/g). Furthermore, the ball-milled $Li_3V_2(PO_4)_3$ presented not only higher cycle retention rate after 50 cycles, but also better rate capability compared with pure sample in the whole region (0.1-7 C).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.139-144
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• 2006

A fabrication condition of the cathode electrode was optimized in a lithium secondary battery. The $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ powders were used as a cathode material. The $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$/Li cells were prepared with a certain formulation and their cycleability and rate-capability were evaluated. Optimum electrode composition simulated from the evaluated value was 86.3: 5.6: 8.1 in mass $\%$ of active material: binder: conducting material. Discharge capacity decreased markedly as the press ratio exceeded $30\%$ during preparation of the electrode. Discharge performance at a high current rate deteriorated abruptly as the electrode thickness was over $120{\mu}m$.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.465-480
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• 2003

The interception capabilities of storm water grate inlet were analyzed in this paper. The hydraulic model lot gutter flow was used to estimate the interception capability. With the consideration of width and length of road, gutter discharges were ranged of 4-15l/sec. The transverse slopes of gutter were selected 4, 7 and 10%. The longitudinal slopes were 0, 2, 5 and 7%. The four sizes of storm water grate inlet were used in this experiments ($30\times40cm,\;40\times50cm,\;40\times100cm,\;40\times150cm$). The total number of experimental cases were 240. As the transverse slopes of gutter increased, the interception capability also increased. As the flow width in gutter and the discharge were lower, the interception efficiencies increased and the longitudinal slopes of road increased, the interception efficiencies decreased. The empirical formula with the factors of total inflow discharge, the longitudinal slope and the transverse slope of gutter were derived. These equations could be used to estimate the intercepting discharge of grate inlet. The reasonable construction space of grate inlet for the road widths, the longitudinal slopes, the transverse slopes and the grate inlet sizes were suggested.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.294-299
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• 2001

Effects of the surface fluorination on the electrochemical charge-discharge properties of $Mg_2$Ni electrode in Ni-MH batteries fabricated by mechanical alloying were investigated. After 20h ball milling, Mg and Ni powder formed nanocrystalline $Mg_2$Ni. Discharge capacity of this alloy increased greatly at first one cycle, but due to the formation of Mg(OH)$_2$ passive layer, it showed a rapid degradation in alkaline solution within 10cyc1es. In case of 6N KOH +xN KF electrolyte (x = 0.5, 1, 2), a continuous and stable fluorinated layer formed by adding excess F$^{[-10]}$ ion, increased durability of $Mg_2$Ni electrode greatly and high rate discharge capability(90-100mAh/g). 2N KF addition led to the highest durability of all tested here. The reason of the improvement is due to thin MgF$_2$, which can prevent the $Mg_2$Ni electrode from forming Mg(OH)$_2$layer that is the main cause of degradation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.862-867
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• 2006

Bi-based nano-varistors and micro-varistors fabricated with each ZnO nano-powder and micro-powder were studied about characteristics on the surge capability in this study. ZnO nano-varistors were sintered in air at $1050^{\circ}C$ for 2 hr. The voltage-current and residual voltage properties of ZnO nano-varistor were compared with their of ZnO micrio-varistor. As a result of these properties, our ZnO nano-varistor has about 3 times at operating voltage as compared with conventional ZnO varistor fabricated with micro-powder and the residual voltage was 8.06 kV at nominal discharge current 101kA in the lighting impulse current test. And then the residual voltage rate 1.72 of our nano-varistor has had better performance than the 1.79 of micro-varistor because ZnO nano-varistor has shown much quick response property because of increasing effective cross-section area. Also, to analysis surge capability took thermal images for pyrexia temperature distribution with each of the varistors after operating varistors. Nano-varistor doesn't have shown local overheating and can confirm accurate temperature grade on the surface of its.

• Transactions of the Korean hydrogen and new energy society
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• v.6 no.1
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• pp.35-41
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• 1995

The MmNi-based alloy electrode was studied for use as a negative electrode in Ni-MH battery. Alloys with $MmNi_5-_xM_x$(M=Co,Al,Mn) composition were synthesized, and their electrode charateristics of activation rate, temperature dependence, electrode capacity and cycle life were investigated. With increasing Al content and decreasing Mn content in the alloys, the discharge capacity increased while the cycle life decreased. As x in $MmNi_5-_xM_x$ increased from 1.5 to 2.0, decreasing the Ni content, the discharge capacity, the low temperature property and the rate capability decreased. However its cycle life was improved. Increasing Co content resulted in a prolonged cycle life and decrease of high rate discharge capacity. It can be concluded that the most promising alloy in view of discharge capacity and cycle life is $MmNi_{3.5}Co_{0.7}Al_{0.5}Mn_{0.3}$.