• Journal of Biosystems Engineering
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• v.27 no.6
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• pp.491-500
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• 2002

This study was carried out to investigate experimentally the effect of the tire inflation pressure of a tractor on soil compaction and tractive performance. Two kinds of field experiments were conducted using an agricultural tractor. One experiment is concerned with the tractive performance of the tractor at the three levels of tire inflation pressure; 50kpa, 100kpa and 200kpa, and the other one is about the soil compaction at the four levels of tire inflation pressure; 50kpa, 100kpa, 150kpa and 200kpa, at three different numbers of passes; 1, 3 and 5 passes. From the results of the field experiment, it was found that decreasing the tire inflation pressure decreased the motion resistance of tractor and increased the tractive force and tractive efficiency. The tractive and working performance of the tractor could be improved by the reduction of tire inflation pressure. Increasing the inflation pressure and the number of passes increased the soil compaction. Rate of compaction increased rapidly at the first pass and declined at subsequent passes. To reduce the effect of soil compaction for the whole field, it is recommended that tractor should follow the rut of the first pass from the subsequent passes, and decrease the inflation pressure of the driving tires up to allowable minimum level.

• Journal of Wetlands Research
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• v.15 no.1
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• pp.91-103
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• 2013

In this Research, in order to improve problems of not enough technical validation and structural and hydraulic stability evaluation when nature-friendly revetment block is applied to field, hydraulic stability evaluation according to hydraulic behavior change of porosity soil block for vegetation reinforcement that secures ecological function was reviewed. By selecting object section, numerical analysis and hydraulic model experiments were performed; for numerical analysis, by using 1-dimensional numerical analysis model HEC-RAS and 2-dimensional numerical analysis RMA-2, one-dimensional(1D) and two-dimensional(2D) numerical analysis were performed; by applying Froude's similarity law, reduced-scale hydraulic model experiments according to vegetation existence were performed. In hydraulic model experiment, for validity of experiment result, the result of velocity and tractive force of reduced-scale hydraulic model experiments was converted to prototype so that it can be compared and reviewed under the same condition of one-dimensional(1D) and two-dimensional(2D) numerical analysis result; as a result, it was confirmed that comparatively united result appeared, and by comparing prototype-converted tractive force result with revetment's allowable tractive force coming from an existing research, block's hydraulic stability was suggested.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.4
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• pp.15-26
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• 2013

In recent years, river maintenance projects using natural methods have been continuously implemented in urban areas and methods emphasizing ecology are being developed and constructed in revetment areas. However, there is insufficient technical review on the hydraulic stability of those revetment methods during the event of flood. Therefore, a hydraulic analysis is necessary for the stream where revetments are applied. This study was conducted to develop an objective test method for the hydraulic stability of green revetment media. For this purpose, hydraulic model tests were performed for the green base materials for revetments. Tests were conducted using experimental devices for the hydraulic model which were installed to simulate the rapid current during the flood. Loss of soil by the hydraulic condition was compared and analyzed with that of dry green revetment media, and the evaluations were made on the corrosion resistance, tractive force, and contractile force. Test results showed that green revetment media had higher corrosion resistance in non-vegetation condition compared to dry green revetment media, and the loss of base materials by the rooting of vegetation showed significant reduction by the vegetation. In addition, results of the allowable tractive force of the base material indicated it is relatively stable in vegetation condition but scouring can occur in non-vegetation condition. Therefore, the development of vegetation in revetment areas is anticipated to be effective for the stability of revetment areas by reducing external forces interacting with the corrosion resistance and stream bank. The green revetment media in expected to contribute to the stability of revetment areas.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1643-1648
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• 2009

The braking system of train must posses the large baking effort in order to stop the train safety within the limited traveling distance. but, the excessive braking effort has been deteriorated the ride comfort due to high level of deceleration and jerk, and sometimes occurred the skid. because the applied braking force exceeds the allowable adhesive force. this skid causes not only to increase the a stopping distance but also to deteriorate the safety of train and damage the rall surface by wheel flat. In the present paper, braking force for disk brake of Tilting Train eXpress(TTX) was measured though on convention line test and the traction force was estimated by using the analytic model in skid condition. also, we have discussed the relationship between the bake force and traction force in starting condition.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.166-184
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• 1979

In order to prevent the water loss in the irrigation canal constructed on the sandy gravel layer or on the other highly permeable ground layer, lining has been practiced. Many studies have been done so far on the lining method to prevent the water loss in the irrigation canal and recently studies on the lining with plastic film or polyethylene film were also reported. However, the plastic film or polyethylene film has low strength and is liable to break, and water loss from pin hole caused by contacting with sand or gravel is highly predicted. This study was then conducted to find proper lining and buring method in canal construction of polypropylene mat after coated with vinyl, as one way to overcome the shortcoming frequently observed when plastic or usual polyehtylene film were used. Eventhough rather longer periods of experiments are needed to attain reliable and accurate results on the variation of durability, the durability of asphalt coated area, or on the damage due to freeze after burial or exposure of polypropylene mat, the experiemental results obtained during one year of period are summarized as follows: 1. The curvature at the area between canal bottom and side slope had increased stability and saved consruction cost. The relationship among the variation of curvature, the reduction of polypropylene mat and the reduced amount of soil cutting at each side slope was presented in Fig. 7 through 9. 2. The depth of covering material to protect polypropylene mat was desired to be over 30cm, considering the water depth, side slope, canal cleaning practices, traffic, or back pressure of irrigation period. 3. In order to increase the canal stability and to prevent slope erosion, sandy soil was required, to be placed under ground, and coarse gravel should cover the surface area of canal. 4. The studies on the stability of side slope in the canal should consider the passive area on the bottom and the slope should be about 1 to 2, considering the slope stability, allowable velocity and tractive force. 5. When compared with earth lining, the lining with polypropylene mat coated with vinyl was responsible to save 28% and 37% of canal lining cost, when the soil carrying distances were 500 and 700m. respectively. 6. The water interception was almost completely attained when the polypropylene mat coated with vinyl was used for lining. But further studies were assumed to be necessary for the use of asphalt since the strength of polypropylene mat connected with asphalt will vary with duration.