• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.2
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• pp.119-123
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• 2014

In this study, four kinds of specimens of PE(polyethylene)-based insulating materials were prepared for selecting the optimum insulation materials in a wet environment. The specimens were tested by various methods, the anti tracking test, the transmittance test in the water vapor transmittance(WVT) and the abrasion resistive test, etc. The HDPE(high-density polyethylene) specimen was showed excellent property in the tracking resistance test and the lowest transmittance in water vapor transmittance test. In the abrasion resistive test, the LLDPE(linear low-density polyethylene) and MDPE(medium-density Polyethylene) were showed excellent mechanical properties. The value of cut-through resistance for MDPE and HDPE were superior to that for LLDPE and LDPE(low-density polyethylene).

• Journal of Forest and Environmental Science
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• v.30 no.1
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• pp.71-75
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• 2014

Forest roads failure is one of the most common problems caused by heavy rainfalls. This study investigated the characteristics on stabilization measures installed for cutting slopes failure of forest road resulted from heavy rainfalls. Three primary factors (slope length, slope gradient, soil type) affecting cutting slope failure were considered and stabilization measures were classified into two types (A type: wooden fence, vegetation sandbag, stone masonry; B type: wire cylinder, gabion, concrete retaining wall) through discriminant analysis based on their capacity of resistance to slope failure. Results showed that A type was mainly installed in such conditions as cut slope <8 m, cut slope gradient $30-40^{\circ}$ and soil type with soil while B type occurred in locational conditions as cut slope length >8 m, cut slope gradient < $30^{\circ}$ and > $30^{\circ}$, and soil type of gravelly soil and rock.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.109-116
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• 2000

The objective of this study is to measure rim surface adhesion and to calculate motion resistance produced by the adhesion acting on the rim section of a circular wheel under sticky soil condition. The mechanisms of generating motion resistance by the adhesion on a circular wheel were analyzed through wheel motion. Experiments were conducted in an indoor soil bin that contains loam soil. A circular steel wheel was used for experiments. A part of the wheel rim was cut off, and transducers which can measure normal and tangential forces were installed in this section. Calculated motion resistance at a part of the rim section was superposed for one wheel rotation as motion resistance produced by the rim surface adhesion. The motion resistance increased with increasing the dynamic load. Ratio of the motion resistance to total motion resistance measured by an axis transducer was about 23 to 46 % in this study.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.203-208
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• 2023

In this study, we propose a method to improve the precision of contact resistance measurement circuits using constant current method and voltage drop method, and implement a dashboard that monitors the measured data of contact resistance measurement systems through MQTT broker server. The contact resistance measurement system measures the resistance value and transmits the measured value to the MQTT broker server using wireless communications. This developed dashboard uses Node-RED and Node-RED-Dashboard to receive the resistance values of up to four contact resistance measurement systems and show them to user's monitor screen. Users can manage multiple measurement data using a single dashboard and easily interface with other devices through the MQTT broker server. Through the experimental results from real data measurements, the relative standard deviation about precision is improved to average 40.37% and maximum 64.73% respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.301-302
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• 2023

In this study, we aimed to identify changes in fire resistance according to the type of sleeves used for pipe penetrations and to examine their accreditation of fire resistance performance and use them as basic data. The test results of fire resistance according to the type of sleeve used in non-metallic pipe facilities showed that the temperature on the support side was higher for sleeves with higher thermal conductivity. For the temperature on the surface of the pipes, in the case of galvanized steel plates, steel pipes, and structures without sleeves, the highest temperature was observed after the expansion of the firestop material for 46 to 53 minutes and then decreased. PVC sleeves showed a steady increase in temperature until 53 minutes, after which the temperature did not increase further. In addition, for non-metallic pipes, the effect of the type of sleeve on fire resistance is considered to be insignificant because the lower part (heating direction of the furnace) under the support structure is cut off to block the heat during the two-hour fire resistance test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.235-240
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• 2002

In micro-EBM, it is well blown that RC circuit is suitable for discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, if very low, continuous (or normal) arc discharge occurs, then increases electrode wear and reduces machining speed remarkably. In this paper, RC circuit with transistor is used to micro-EDM. Experimental results show that RC circuit with transistor can cut off continuous (or normal) arc discharge effectively if duty factor and switching period of transistor are set up optimally. Through experiments with varying charge resistance, it can be known that RC circuit with transistor has about two times faster machining speed than that of RC circuit. Especially, it has prominent rise-effect of machining speed in low unit discharge energy, so that a high-quality and high-speed micro-EDM can be realized through RC circuit with transistor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.687-694
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• 2002

In order to replace the jacket material for URD power cables, the 6 kinds of polyethylene compounds were manufactured and evaluated. The characteristics of the compounds were investigated by water vapor transmission (WVT) test, thermal and mechanical test. In WVT test, all the polyethylene compounds showed the superior water resistance to conventional PVC. The molecular structure and density of polyethylene play an important role in WVT. Also, the polyethylene compounds showed the suitable characteristics in thermal and mechanical test. Especially, the linear polyethylene compounds showed the superior characteristics to LDPE ones. Due to the fillers in compounds, the abrasion resistance was decreased and the cut-through resistance was increased. From this study, it can be considered that the polyethylene compounds may be suitable to jacket material for URD power cables.

• Journal of Industrial Technology
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• v.18
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• pp.259-265
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• 1998

The molecular weights of surfactant SDS(M.W. 288) and SLS(M.W. 420) are smaller than the molecular weigh cut-off of cellulose acetate membrane used in this study. However, 20% of SDS and 67% of SLS were rejected by cellulose aectate membrane. The higher rejection rate of SLS than that of SDS is due to the longer hydrophobic chain and greater molecular weight. There was no resistance to permeation rate by membrane fouling. Most of permeation resistance was due to the concentration polarization. Permeation rate was declined with operating time and with increase in concentration of surfactant due to concentration polarization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.930-933
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• 2001

Titanium Alloys used in this experiment has an good corrosion resistance and specific strength, and is the new material developed for medical supplies living goods. In this study the rolled titanium alloy is done by annealing, solution heat-treatment and aging and then is worked by wire EDM. With changing the process conditions, the process properties of surface hardness, surface roughness, shape of process surface and the analysis of ingredients are measured through experiment repeating main cut and finish cut. It is confirmed to gain good measure values as increasing the number of processing of wire EDM. In this experiment the phenomena of processing is studied and the appropriate process condition is proposed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.58-63
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• 1996

A study is drawn up its result's tables and graphs by measuring tools(outside micrometer cylinder gauge and dial caliper gauge) on the difference of diameter volumes from before-discharge and after-discharge under 52 Kind's experimental condition by cupper and graphite electrode of CNC EDM. The EDM is attached with A.V.R. and memory scope for keep up accuracy and the fixed table of work piece is used in order to eliminate the noise by the internal resistance of it and forcing to eradicate the discharge liquid. It is analyzed cutting conditions to compare its wave value and pulse time.(Ton Toff) through voltage and current for decreasing working error.