• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.26-35
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• 2010

The maximum output torque developed by the machine is dependent on the allowable current rating and maximum voltage that the inverter can supply to the machine. Therefore, to use the inverter capacity fully, it is desirable to use the control scheme considering the voltage and current limit condition, which can yield the maximum torque per ampere over the entire speed range. This controller is controlled speed and current using hybrid PI(HBPI) controller and estimation of speed using ANN. Also, this paper is proposed maximum torque control of induction motor using slip angular speed and current condition at widely speed range. The performance of the proposed induction motor drive with maximum torque control using HBPI controller is verified by analysis results at dynamic operation conditions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1990.04a
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• pp.44-49
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• 1990

This study is a seismic analysia of absorber rod in KMRR Reactivity Control Mechanism. The model being studied i8 two coaxial tubes (control absorber rod and flow tube) immersed in the water and partially coupled (overlap) by water Hap. The hydrodynamic mass effects by the water in each surrounding conditions are considered in the model. The natural frequencies, stresses and displacements of the system due to Safe Shutdown Earthquake are computed in the cases of in-phase modes and out-of-phase modes of two coaxial tubes. The results show that maximum stresses are well below the allowable limit and maximum displacements at the ends of both tubes in out-of-phase modes are so huck that the tubes contact each other in the overlap zone.

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.239-250
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• 2008

If there is a water flow with a range of temperature inside a pipe, the wanner water tends to float on top of the cooler water because it is lighter, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, such thermal stratification can play an important role in the aging of nuclear power plant piping because of the stress caused by the temperature difference and the cyclic temperature changes. This stress can limit the lifetime of the piping, even leading to penetrating cracks. Investigated in this study is the effect of thermal stratification on the structural integrity of the pressurizer surge line, which is reported to be one of the pipes most severely affected. Finite element models of the surge line are developed using several element types available in a general purpose structural analysis program and stress analyses are performed to determine the response characteristics for the various types of top-to-bottom temperature differentials due to thermal stratification. Fatigue analyses are also performed and an allowable environmental correction factor is suggested.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.147-147
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• 2003

This paper describes the finite element analysis(FEA) for the design of electromagnet for Control Element Drive Mechanism(CEDM) in System-integrated Modular Advanced Reactor(SMART) and compared with the lifting power characteristics of prototype electromagnet. A thermal analysis was performed for the electromagnet. A model for the thermal analysis of the electromagnet was developed and theoretical bases for the model were established. It is important that the temperature of the electromagnet windings be maintained within the allowable limit of the insulation. since the electromagnet of CEDM is always supplied with current during the reactor operation. So the thermal analysis of the winding insulation which is composed of polyimide and air were performed by finite element method. As a result, it is shown that the characteristics of prototype electromagnet have a good agreement with the results of FEA. The thermal properties obtained here will be used as input for the optimization analysis of the electromagnet.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.29-33
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• 2002

A procedure of free span and fatigue analysis of offshore pipelines was made per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were used to calculate the allowable span lengths. The screening criteria allow small amplitudes of vortex-induced vibration due to wave and current loading. However, the induced pipe stress is very small and usually below the limit stress of a typical S-N curve. A simplified method was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.1
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• pp.29-39
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• 1986

The purpose of this study is to develop an exhaust gas recirculation valve for reduction of the NOx emission of the gasoline engine. In this study the back pressure modulated(BPM) EGR system was developed and tested for the 1.6$\ell$ gasoline engine. By this system 50% of NOx emission was reduced at 7% EGR rate. Fuel consumption and CO emission were not affected by EGR but HC was increased up to the level of allowable limit. Overall operation was satisfactory. As a result of this study, the technics for developing EGR valve and adjusting the engine for EGR have been established.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.258-261
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• 2005

In this paper, experimental and numerical attempts are made fur application of powder metallurgy forming technology to making the cylinder block of a hydraulic pump of which height reaches nearly 70 mm and is ten times larger than the wall thickness. Leak tests with several compositions are carried out in order to find allowable powder composition to prevent leak under high pressure in service and CAE techniques are applied to finding proper process conditions. Through the research, the possibility of the powder formed cylinder block that is very competitive from the point of both cost and mass production has been shown, even though its thickness exceeds the recommended limit considering heterogeneous density distribution caused by the friction between a powder compact and dies.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.3
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• pp.19-25
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• 2019

The purpose of this study was to evaluate bending performance of concrete filled soldier pile for temporary retaining wall. Structural performance tests were conducted on total number of four specimens. Each specimen had a unique characteristics with combination of the following variables, existence of reinforcing bar and locations of reinforcing steel plates. The results of this study were as follows; concrete filled steel tubes with being reinforced bar and flange rather than non-bar showed better performance. Higher yield, tensile strength and sufficient plastic strain were archived and maximum moment observed in experiments exceeded theoretical maximum moment in both allowable stress design and limit state design at all specimens.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.2
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• pp.126-136
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• 2021

During operation of nuclear power plants, the fatigue assessment should be conducted repeatedly, considering changes of operating environments. For the case that cumulative usage factors (CUFs) may exceed the acceptance limit, flaw tolerance evaluation can be an alternative method to meet the regulatory requirements. In this respect, this paper analyzes the effects of the input variables for flaw tolerance evaluation based on ASME BPVC Section XI Appendix L. The reference analysis is performed for the example problem in NUREG/CR-6934. Then effects of the crack orientation, stress intensity factor solutions, thermal stress profiles, fatigue stress decomposition and fatigue crack growth curves are considered for the sensitivity analysis. The results show that the stress analysis considering the actual environment plays a crucial role in flaw tolerance evaluation.

• Journal of Korean Association for Spatial Structures
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• v.7 no.3 s.25
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• pp.79-86
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• 2007

Recently, as steel structures become higher and more long-spanned, construction of high-strength steels is increasing gradually. Application of high-strength steel can be possible to make a more light and economic steel structures by reducing thickness and space. To apply a high-strength steel to structure, criteria of high-strength steel for buckling is required. However, current specification is not sufficient for criteria of high-strength steels. In this paper, buckling behavior of high-strength steel truss columns with box sections is investigated by using three-dimensional elastic-plastic finite deformation analysis program. The criteria equation for allowable compressive stress of high-strength steel truss columns with box sections is proposed and confirmed the applicability. It is reasonable form analytical results that formulated equations after finding the upper limit of allowable axial direction compression stresses of high-strength steel truss columns. And new equation is suitable to buckling design of high-strength steel truss columns.