• The KSFM Journal of Fluid Machinery
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• v.8 no.3 s.30
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• pp.42-47
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• 2005

Effects of a booster inducer on the suction performance of turbopumps are investigated in this paper. To see the effect of the booster inducer, suction performance tests are conducted with and without the booster inducer for three turbopumps. It is shown that the booster inducer can enhance the suction performance of turbopumps when the tip clearance of the main inducers are relatively large. Numerical analysis are also carried out to see the effects of the booster inducer on the performance of the main inducer. The booster inducer is shown to increase the static pressure at the inlet of the main inducer and prevent growing of inlet back flows which are believed to have deleterious effects on the suction performance of the inducer.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.37-43
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• 2004

Engine lubrication system is generally affected by vehicle driving conditions; acceleration, braking deceleration, and cornering. The oil supply system such as oil pan, baffle plate, and oil pick-up pipe should be optimized to cope with severe driving conditions. The main purpose of this paper is to understand the effect of the engine tilting angle on the oil supply system using engine tilting test rig. For the purpose, the oil pressure fluctuation and oil aeration in the main gallery are measured at various engine tilting angles. In addition, the oil flow is visualized by using transparent oil pan to investigate the cause of the formation of oil aeration. The test results show there is a strong correlation between the main gallery oil pressure fluctuation and oil aeration. It is also found that the visualization technique is helpful to stabilize the oil supply system at severe driving conditions.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.335-337
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• 2009

A scanning electron microscope(SEM) is a system that visualizes complex surface features. The resolution of SEM is affected by each of equipment components. In this study, we examined the effects of the four factors including the beam current, magnification, voltage and working distance. A statistical analysis was conducted to investigate the main and interaction effects. For a systematic characterization, a $2^4$ full factorial experiment was conducted. The $R^2$ of constructed statistical model was 88.9%. The main effect revealed that the current and working distance are dominant factors. Of the interactions, those between the current and voltage yielded the highest interaction. 3D plots generated from the model were used to explore various parameter effects.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.993-1000
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• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.552-557
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• 2004

Effects of a booster inducer on the suction performance of turbopumps are investigated in this paper. To see the effect of the booster inducer, suction performance tests are conducted with and without the booster inducer for three turbopumps. It is shown that the booster inducer can enhance the suction performance of turbopumps when the tip clearance of the main inducers are relatively large. Numerical analysis are also carried out to see the effects of the booster inducer on the performance of the main inducer. The booster inducer is shown to increase the static pressure at the inlet of the main inducer and prevent growing of inlet back flows which are believed to have deleterious effects on the suction performance of the inducer.

• Journal of Applied Reliability
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• v.17 no.3
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• pp.256-263
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• 2017

Purpose: This article provides the efficiency test results of conducting depot maintenance. Method: ANOVA (analysis of variance) and ANCOVA (analysis of covariance) tests are conducted using data obtained from Defense Logistics Integrated Information System (DELIIS). Results: The result shows that although the effect of the depot maintenance is significant, some parts do not follow the overall effect of the depot maintenance. In order to solve the problem we provide some suggestions to be improved. Conclusion: For improving the combat readiness condition of K-1 main battle tank, the maintenance policies and regulation must be revised for the parts of the weakness. In addition, the collection way of the operation and maintenance data must be redesigned.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.51-56
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• 2011

The various process parameters of thermal spray process affects on quality of Ni-based coatings. Thus, there is need to analyze the effect of process parameters on quality of Ni-based coatings. In this paper, the effects of process parameters on hardness and wear rate of Ni-based coatings were investigated using 4 design of experiments. First, the Ni-based coatings were fabricated according to $L_9(3^4)$ orthogonal array. The hardness tests and the wear tests were performed on the Ni-based coatings. The analysis of variance for the hardness and wear rate were carried out. As a results, the acetylene gas flow and the powder feed rate were identified as main factors effected on the hardness and the oxygen gas flow and the acetylene gas flow were identified as main factors effected on the wear rate. The full factorial experiments design with different levels was applied for investigation of effect of these main factors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.156-163
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• 2001

The experiment is conducted on the rapidly rotating incompressible flow within a confined cylinder using LDV(Laser Doppler Velocimetry). The configurations of interest are the flows between a rotating upper disk with a bar and a stationary lower disk enclosed within a cylinder. The flow is considered to be an axisymmetric undisturbed basic flow. The results show that the flow is strongly dependent on the radius and the shape of bar but is negligibly affected by the Reynolds number in turbulent flow. It is observed that in the lid-driven case the main forms near the wall as the Reynolds number increases. The thin bar causes the second axial flow due to the suction effect and the thick bar causes the main flow to be pulled toward the surface of the bar. The step bar shows the dual effect of the two. 1:2 tilt bar shows that the main flow distributes wider than the other cases in which interference occurs due step bar.

• Membrane Journal
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• v.28 no.1
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• pp.67-74
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• 2018

In the molecular dynamics study of polymeric membranes, it is very important to select the proper length of the polymer main chain because it requires a large number of constituent atoms and a long time to simulate the permeation behavior. In this study, we tried to investigate how the correlation between polymer main chain length and permeation behavior appears in actual molecular dynamics simulation results. Molecular dynamics were performed using the widely known commercial polymer Kapton(R) polyimide structure and the gas permeation behavior was simulated. The movement of the polymer main chain was not related to its length and the short main chain length did not act more actively. In addition, unlike the prediction that the end group of the polymer main chain is relatively easy to move, there are many cases where the atoms located at the middle of the polymer main chains have a higher movement than the atoms located at the end groups. Finally, permeabilities of the gas molecules was not affected by the length of the main chain and the end groups of the polymer, which indicates that the end effect should be carefully mentioned and followed by the verification process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.780-785
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• 2005

Vibration has been severly increased at the branch pipe of main steam header since the commercial operation of a nuclear power plant. Intense broad band disturbance flow at the discontinuous region such as elbow, valve or heather generates the acoustical pulsation which is propagated through the piping system. The pulsation becomes the source of low frequency vibration at piping system. If it coincide with natural frequency of the pipe system, excessive vibration is made. High level vibration due to the pressure pulsation related to high dynamic stress, and ultimately, to failure probability affects fatally the reliability and confidence of plant piping system. This paper discusses vibration effect for the branch pipe system due to acoustical pulsations by broad band disturbance flow at the large main steam header in 7nn nuclear power plant. The exciting sources and response or the piping system are investigated by using on site measurements and analytical approaches. It is identified that excessive vibration is caused by acoustical pulsations of 1.3Hz, 4.4Hz and 6.6Hz transferred from main steam header, which are coincided with fundamental natural frequencies of the piping structure. The energy absorbing restraints with additional stiffness were installed to reduce excessive vibration.