• KCID journal
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• v.2 no.1
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• pp.57-64
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• 1995

현장 투수시험 방법 중에서 Borehole type의 Boutwell Permeameter와 Constant head bore-hole permeameter, 그리고 Porous probe type의 cone shaped porous probe(BAT Permeameter)에 대한 내용을 간단히 소개하였고, 각 측정법의 특징을 비교분석한 내용을 요약하면 (표-1)과 같으며, 기회가 있으면 Infiltrometer type와 Underdrain type에

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2009.10a
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• pp.196-199
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• 2009

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.717-719
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• 2013

• Development and Reproduction
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• v.1 no.2
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• pp.173-180
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• 1997

This study has been conducted to investigate the molting behavior and the effects of rearing temperature and day length on molting in the behavior and the effects of rearing temperature and day length on molting in the giant freshwater prawn, Macrobrachium rosenbergii reared in the laboratory. The results obtained were summarized as follow: 1. After pre-spawning molting, the protopodites of 1st, 2nd, 3rd, and 4th except 5th pleopod bore new breeding setae which conserve eggs in the brooding chamber and the basis of 3rd, 4th, and 5th pereiopods bore new breeding dresses which transport the ovulated eggs into the brooding chamber. 2. Adult females reared in 27.5-$29.4^{\circ}C$ molted 10-12 times per year at interval of 27-35 days, of which four or six moltings were common molting for growth and another four or five moltings were pre-spawning molting for spwaning and brooding. In winter season, pre-spawning molting did not happen to most of adult females in spite of the same temperature. 3. Duration of intermolt cycle was 31-38 days and 26-30 days at 25.3- $26.5^{\circ}C$ and 28.7- $30.4^{\circ}C$ of rearing temperature, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.209-216
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• 1999

In tunneling and road cuts by blasting, it is of the utmost importance that the remaining rock is of high quality in order to avoid rockfall, rockslides and excessive maintenance work. Therefore, numerous blasting techniques which make use of decoupled charge or shock wave superposition effect have been used to control overbrake. In this paper. some approximate method for the determination of blast load according to the charge condition was introduced at first and, instrumented tests were conducted in small scale transparent material to investigate the shape and amplitude of blast load around the bore hole. Compare to the fully coupled charge, low amplitude of blast load around the bore hole was observed in the decoupled charge and explosion gas pressure was important in the shape of blast load. Therefore, quasi-static behaviour of the crack pattern was shown due to low loading rate.

• Journal of Mechanical Science and Technology
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• v.14 no.9
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• pp.935-946
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• 2000

Elastic-plastic stress analysis has been performed to evaluate the fatigue life of an autofrettaged pressure vessel containing cross-bores subjected to pulsating internal pressure of 200 MPa. Finite element analyses were used to calculate the residual and operating stress distributions of the pressure vessel due to the autofrettage process and pulsating internal pressure, respectively. Theoretical stress concentration factors of 3.06, 2.58, and 2.64 were obtained at the cross-bore of the pressure vessel due to internal pressure, 50%, and 100% autofrettage loadings, respectively. Local stresses and local strains determined from the elastic-plastic finite element analysis were employed to calculate the failure location and fatigue life of the pressure vessel with radial cross-bores, incorporating the low-cycle fatigue properties of the pressure vessel steel and fatigue damage parameters. Increase in the amount of overstrain by autofrettage process moved the crack initiation location from the inner radius toward a mid-wall, and extended the crack initiation life. Predicted fatigue life of the fully autofrettaged pressure vessel with cross-bores increased about 50%, compared to the unautofrettaged pressure vessel. At the autofrettage level higher than 50%, the failure location and fatigue life of the pressure vessel were not significantly influenced by the autofrettage level.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.44-50
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• 2002

The connecting rod big-end bearing is one of the most heavily loaded components of the lubrication system of high-speed combustion engines. The supply oil flow has to pass to the main bearing and the rotating crankshaft before entering the connecting rod bearing. It is common knowledge that the centrifugal forces due to the crankshaft rotation influence the oil flow to connecting rod bearing through the oil supply bore, especially, when the oil supply system to the connecting rod bearing has a 180$^{\circ}$circumferential groove via a single drilling in the crankshaft. In this case, it should be confirmed that the groove oil pressure in the main bearing is sufficient to overcome these centrifugal forces. For the purpose, the dynamic oil pressure before entering oil supply bore to the connecting rod bearing was measured instead of averaged oil pressure in main gallery. Experimental test results show that the dynamic oil pressure in the oil groove was more useful than that of main gallery. And it was also found that the oil pressure fluctuation in the groove was sensitively affected by the reduction of the main bearing clearance.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.965-971
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• 2001

The objective of this study is to investigate the characteristics - microstructure, hardness, adhesive strength and friction coefficient - of the coatings with aging - treatment after optimizing internal- plasma spraying parameters for Al-30wt%Si powder as a basic research to manufacture the cylinder block bore for Al engine composed of Al-30wt%Si alloy on Al alloy, The optimum internal-plasma spraying parameters of Al-30wt%Si alloy are summarized as follows: voltage: 37.5V, current: 160A, working distance: 25mm, gun traverse speed: 4.5mm/s, rotating speed: 518m/min. The primary Si particles grew aggressively with increasing heat-treating temperature. The hardness of the as-sprayed coating was about Hv=275 but this value was abruptly decreased with increasing heat-treating temperature. And average friction coefficient of the coating was below 0.08 after heat treatment for 48h at $175^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1059-1063
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• 2010

Shimming is an important technique in development of nuclear magnetic resonance (NMR) magnets where image resolution is highly dependent on magnetic field homogeneity. Classically, shimming may be categorized into two types: 1) active shimming that incorporates with extra coils and precise tuning of their currents; and 2)passive shimming that incorporates with pieces of steel placed in a bore of a main magnet and their uniform magnetization under homogeneous external fields. Additional magnetic fields, produced by the coils and/or the steel sheets, compensate original magnetic field from the main magnet in such a way that the total field becomes more homogeneous. In this paper, we developed a passive shimming method based on linear programming optimization. Linear programming is well known to be highly efficient to find a global minimum in various linear problems. We firstly confirmed the linearity of magnetization of ferromagnetic pieces under a presence of external magnetic fields. Then, we adopted the linear programming to find optimized allocation of the steel pieces in the inner bore of a main magnet to improve field homogeneity.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.42-50
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• 2001

In this paper, the effects of scale formation in engine water jacket upon the thermal durability of engine itself and its component parts were studied. To understand the effect of quality of water, a full load engine endurance test for 50 hours was carried out with not-treated underground water. The followings were found through the tested engine inspection after the endurance test; 1-2 mm thick scale formation in the engine water jacket, valve seat wear, piston top land scuffing, piston pin stick, and cylinder bore scuffing in siamese area. In order to understand the causes of above test results, the heat rejection rate to coolant, the metal surface temperature of combustion chamber, and the oil and exhaust gas temperatures were measured and analyzed. The scale formed in the engine water jacket played a role as thermal insulator. The scale formed in the engine reduced the heat rejection rate to coolant and it caused to increase the metal surface temperature. The reduced heat rejection rate to coolant increased the heat rejection rate to oil and exhaust gas and increased the oil and exhaust gas temperature. Also, the reasons of valve seat wear, piston top land scuffing and cylinder bore scuffing, and piston pin stick quantitatively analyzed in this paper.