• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1677-1683
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• 2015

To cope with exhaust gas regulation, Diesel engine applied to electronic control system. As it accurately regulated the injected fuel mass and the fuel efficiency and the output are increased but the noise and the vibration are decreased. In order to keep the performance of Electronic Diesel Control System, it is important to accurately control the fuel pressure. However, when the regulator of fuel pressure is not controlled properly, the failure phenomenons(starting failure, staring delay, accelerated failure, engine mismatch et al.) occur because the fuel pressure is not stabilize. In this study, effects on a fuel pressure, engine rotating speed according to the control rate of fuel-pressure regulator are investigated in order to analyzed the performance variation with failure of fuel-pressure regulator. As a result, when the control rate of a fuel-pressure regulator is 4%~6% lower than that of standard condition, the variation of engine's rpm and return fuel flow is increased, and the abnormal condition was occurred. Besides, it is possible to diagnose the failures on fuel-pressure regulator under these conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.8
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• pp.67-73
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• 2019

An ultra-high pressure treatment device is a device used for increasing the shelf life of food by sterilizing it by applying hydrostatic pressure to solid or liquid food. The ultrahigh pressure treatment system developed in this study is a pressure vessel with a processing capacity of 100 L and a maximum pressure of 700 MPa. Pressure vessels for ultrahigh-pressure processing equipment are manufactured using wire-winding techniques. The design formula for making ultra-high pressure vessels with wire windings is given in ASME Section VIII - Division 3. In this study, the ratio of the cylinder to the winding area that can be applied in a wire-winding application was analyzed using a finite element analysis. Furthermore, the relationship between the variation of the residual stress in the vessel and the ratio of the winding area due to the variation of the winding tension was analyzed, and a design guide applicable to the actual product design was developed. Finally, the design equation was modified by presenting the coefficients to correct the difference between the finite element analysis and the design equation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.120-129
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• 1991

This study refers to temporal variation of physical properties of tilled soil under natural rainfalls. Field measurements of porosity, average hydraulic conductivity and average capillary pressure head on a tilled soil were conducted by soil sampler and air-entry permeameter respectively at regular intervals after tillage. Temporal variation of these physical properties were analysed by cumulative rainfall energy since tillage. Field experiment was conducted on a sandy loam soil at Suwon durging April~July in 1989. The followings are a summary of this study results ; 1. Average porosity just after tillage was 0.548cm$^3$/cm$^3$. As cumulative rainfall energy were increased in 0.1070, 0.1755, 0.3849 J/cm$^2$, average porosity were decreased in 0.506, 0.4]95, 0.468m$^3$/cm$^3$ respectively. 2. Average hydraulic conductivity just after tillage was 45.42cm/hr. As cumulative rainfall energy were increased in 0.1755, 0.2466, 0.2978, 0.3849J/cm$^2$ average hydraulic conductivity were decreased in 15.34, 13.47, 9.58, 8.65cm/hr respectively. 3. As average porosity were decreased in 0.548, 0.506, 0.495, 0.468cm$^3$/cm$^3$ average capillary pressure head were increased in 6.1, 6.7, 6.9, 7.4cm respectively. 4. It was found that temporal variation of porosity, average hydraulic conductivity on a tilled soil might be expressed as a function of cumulative rainfall energy and average capillary pressure head might be expressed as a function of porosity. 5. The results of this study may be helpful to predict infiltration into a tilled soil more accurately by considering Temporal variation of physical properties of soil.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.124-132
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• 2004

A hydraulic system is difficult to keep the performance due to non-linearity, load pressure which changes according to working condition and system parameter variation, the requirement of control algorithm has been risen in order to satisfy them. An adaptive control is a control method which is suggested to achieve a control object though plant characteristics change. In spite of the case that plant characteristics and the degree of variation are difficult to grasp, adaptive control can keep the characteristics of closed-loop system regularly. In this study GMVAC(generalized minimum variance adaptive control) combined with output error feedback is proposed in order to solve problems of non-minimum phase, vibration and overshoot in initial response of the plant. The control performance according to the variation of characteristics of the plant is evaluated by changing the supply pressure only.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.3
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• pp.388-394
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• 2003

Hydraulic system is difficult to obtain a suitable performance due to the nonlinearity load pressure change and system parameter variation. The requirement of control a1gorithm has been complex in order to satisfy the performance. The adaptive control is a control method which is suggested to achieve the control object under the plant characteristics change. In spite of the case that plant characteristics and the degree of variation are difficult to grasp. the adaptive control could keep the characteristics of closed-loop system generally. In this study. a method of combined generalized minimum variance adaptive control (GMVAC) and output error feedback is proposed, in order to solve the problem of non-minimum phase of plant and the vibration and overshoot in initial response. The control performance according to the variation of characteristics of plant is evaluated by changing the supply pressure. The experimental results show the effectiveness of the proposed scheme.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.601-607
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• 2002

Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the stability of railway embankment and rainfall introducing the partial saturation concept of ground are defined to analyze the stability of embankment by rainfall. A pressure plate test is also peformed to obtain soil-water characteristic curve of unsaturated soils. Based on this curve, the variables in the shear strength function and permeability function are also defined. These functions are used fur the numerical model for evaluation of railway embankments under rainfall. As comparing the model and case studies, the variation of shear strength, the degree of saturation and pore-water pressure for railway embankment during rainfall can be predicted and the safety factor of railway embankment can be expressed as the function of rainfall amount namely rainfall index. Therefore, the research on safety factor on railway embankment considering train speed and rainfall infiltration with the variation of rainfall intensity and rainfall duration was carried out in this paper.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.789-795
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• 2008

Slope stability is affected by various factors. For safety management of slopes, monitoring systems have been widely constructed along railway lines. The representative data from the systems are variations of ground profile such like ground water level and pore water pressure etc. and direct displacement measured by ground clinometer and tension wire sensor. Slopes are mainly effected by rainfall and rainfall causes the decrease of factor of safety(FOS). Because FOS varies linearly by the variation of ground water level and pore pressure, it has a weak point that could not define the time and proper warning sign to secure the safety of the train. In this study, alternative of FOS such as reliability index and probability of failure is applied to slope stability analysis introducing the reliability concept. FOS, reliability index, probability of failure and velocity of probability of failure of the slopes by variation of ground water level are investigated for setting up the specification of safety management of slopes. By executing case study of a slope(ILLO-IMSUNGLI), it is showed to be applied to specification of safety management.

• Journal of Energy Engineering
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• v.18 no.3
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• pp.156-162
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• 2009

Cylinder-pressure based combustion analysis provides a mechanism through which a combustion researcher can understand the combustion process. This paper was to identify the most significant sources of cycle-to-cycle combustion variability in a spark ignition engine at idle. To analyse the cyclic variation in the test engine, the burn parameters are determined on a cycle-to-cycle basis through analysis of the engine pressure data. The burn rate analysis program was used in the analysis of the data. Burn parameters were used to determine the variations in the input parameter-i.e., fuel, air, residual mass, and so on.

• Tunnel and Underground Space
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• v.6 no.2
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• pp.101-121
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• 1996

The thermomechanical characteristics of rocks such as temperature dependency of strength and deformation were experimentally investigated using Iksan granite, Cheonan tonalite and Chung-ju dolomite for proper design and stability analysis of underground structures subjected to temperature changes. For the temperature below critical threshold temperature $T_c$, the variation of uniaxial compressive strength, Young's modulus, Brazilian tensile strength and cohesion with temperature were slightly different for each rock type, but these mechanical properties decreased at the temperatures above $T_c$ by the effect of thermal cracking. Tensile strength was most affected by $T_c$, and uniaxial compressive strength was least affected by $T_c$. To the temperature of 20$0^{\circ}C$ with the confining prressure to 150 kg/$\textrm{cm}^2$, failure limit on principal stress plane and failure envelope on $\sigma$-$\tau$ plane of Iksan granite were continuously lowered with increasing temperature but those of Cheonan tonalite and Chung-ju dolomite showed different characteristics depending on minor principal stress on principal stress plane and normal stress on $\sigma$-$\tau$ plane. The reason for this appeared to be the effect of rock characteristics and confining pressure. Young's modulus was also temperature and pressure dependent, but the variation of Young's modulus was about 10%, which was small compared to the variation of compressive strength. In general, Young's modulus increased with increasing confining pressure and increased or decreased with increasing temperature to 20$0^{\circ}C$ depending on the rock type.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.843-846
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• 2004

Cavity tone is generated due to the feedback between flow and acoustic wave. It is recognized that the period is determined by the time required for the flow convection in one direction, the time required for the acoustic propagation in the other direction and the time for phase shift depending on the flows and mode. Most of the phenomena have been investigated by experiments and a simple but fundamental theory. But the cause of the phase shift and the correctness of the theory have not been clearly explained so far. In this paper, the phenomena are calculated numerically to obtain detail information of flow and acoustic wave to explain the mechanism including the phase. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. The data are reduced using cross correlation function in space and time and cross spectral density function which has phase information. Abrupt change in pressure near corner in cavity is observed and is relate to phase variation. The time required for the feedback between the flow and acoustic wave is calculated after the numerical simulation f3r various modes. The periods based on the time calculated using the above method and direct observation from the acoustic waves generated and propagated in the numerical simulation are compared. It is found that no phase shift is required if we examine the time required carefully. Rossiter's formula for the cavity tone used for quick estimation needs to be modified far some modes.