• Journal of Korean Society of Water and Wastewater
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• v.36 no.4
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• pp.219-228
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• 2022

In this study, we propose a flow velocity evaluation scheme based on pressure measurement in pressurized pipeline systems. Conservation of mass and momentum equations can be decomposed into mean and perturbation of pressure head and flowrate, which provide the pressure head and flowrate relationship between upstream and donwstream point in pressurized pipeline system. The inverse impedance formulations were derived to address measured pressure at downstream to evaluation of flow velocity or pressure at any point of system. The convolution of response function to pressure head in downstream valve provides the flow velocity response in any point of the simple pipeline system. Simulation comparison between traditional method of characteristics and the proposed method provide good agreements between two distinct approaches.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.165.1-165.1
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• 2003

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.940-947
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• 2022

Meta-heuristic algorithms have found their place in optimization problems. Henry gas solubility optimization (HGSO) is one of the newest population-based algorithms. This algorithm is inspired by Henry's law of physics. To evaluate the performance of a new algorithm, it must be used in various problems. On the other hand, the optimization of the proportional-integral-derivative (PID) gains for load-following of a nuclear power plant (NPP) is a good challenge to assess the performance of HGSO. Accordingly, the power control of a pressurized water reactor (PWR) is targeted, based on the point kinetics model with six groups of delayed-neutron precursors. In any optimization problem based on meta-heuristic algorithms, an efficient objective function is required. Therefore, the integral of the time-weighted square error (ITSE) performance index is utilized as the objective (cost) function of HGSO, which is constrained by a stability criterion in steady-state operations. A Lyapunov approach guarantees this stability. The results show that this method provides superior results compared to an empirically tuned PID controller with the least error. It also achieves good accuracy compared to an established GA-tuned PID controller.

• Tribology and Lubricants
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• v.6 no.1
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• pp.74-81
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• 1990

The threshold of instability for a rigid rotor supported in externally pressurized airlubricated circular or non-circular journal bearings of finite length is theoretically analyzed. The analysis is performed for a bearing having one feeding plane, no recess volume, which is assumed to be a line source, and is based on a first order perturbation of journal center motion about steady state position. And then linearized system dynamic analysis is carried out. Numerical results are given, showing the threshold of instability as a function of supply pressure ratio, feeding parameter and load. It is shown that the region that 2-lobe bearing is more stable than circular bearing exists and whirl ratio of 2-lobe bearing is less than that of the other types of bearing.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.6
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• pp.567-572
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• 2009

The underwater launch system using an ATP consists of five parts: compressor tank, proportional flow control servo valve, expulsion spool valve, air turbine pump, and discharge tube. The purpose of this study is to develop an underwater launch system using an ATP and to verify the validity of the system. The proportional flow control servo valve is modeled as a 2nd order transfer function. The projectile is ejected by pressurized water through the air turbine pump, which is controlled by expulsion valve. The mathematical model is derived to estimate the dynamic characteristics of the system, and the important design parameters are derived by using simulations. The computer simulation results show the dynamic characteristics and the possibility of control for underwater launch system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.309-316
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• 2004

A probabilistic structural integrity assessment is performed for a reactor pressure vessel under PTS(Pressurized Thermal Shock). A semi-elliptical finite axial crack is assumed to he in the beltline region(either base metal or weld meta)1 of the reactor vessel inside surface. The selected random variables are initial crack depth, neutron fluence on the vessel inside surface, copper, nickel, and phosphorus content of the vessel material, and RT/sub NDT/. The probabilities of crack initiation or vessel failure where the crack is propagated through vessel wall are calculated. The probabilities obtained with random crack size are compared to these obtained with deterministic us. Since the failure function cannot to explicitly by selected by selected random variables, Monte Carlo Simulation is applied to perform probabilistic analysis The influence of the amount of neutron fluence is also examined to assess the structural reliability for vessel life time.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.346-353
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• 2002

The steam generator feedwater flow rate in a nuclear power plant was estimated by means of artificial neural networks with the wavelet analysis for enhanced information extraction. The fouling of venturi meters, used for steam generator feedwater flow rate in pressurized water reactors, may result in unnecessary plant power derating. The backpropagation network was used to generate models of signals for a pressurized water reactor. Multiple-input single-output heteroassociative networks were used for evaluating the feedwater flow rate as a function of a set of related variables. The wavelet was used as a low pass filter eliminating the noise from the raw signals. The results have shown that possible fouling of venturi can be detected by neural networks, and the feedwater flow rate can be predicted as an alternative to existing methods. The research has also indicated that the decomposition of signals by wavelet transform is a powerful approach to signal analysis for denoising.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.28-34
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• 2006

A procedure of estimating failure probability is demonstrated for a pressurized pipe of CrMo steel used at $538^{\circ}C$. Probabilistic fracture mechanics were employed considering variations of pressure loading, material properties and geometry. Probability density functions of major material variables were determined by statistical analyses of implemented data obtained by previous experiments. Distributions of the major variables were reflected in Monte Carlo simulation and failure probability as a function of operating time was determined. The creep crack growth life assessed by conventional deterministic approach was shown to be conservative compared with those obtained by probabilistic one. Sensitivity analysis for each input variable was also conducted to understand the most influencing variables to the residual life analysis. Internal pressure, creep crack growth coefficient and creep coefficient were more sensitive to failure probability than other variables.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.234-239
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• 2004

A study on the probabilistic methodology for the estimation of the remaining life of Pressurized pipelines containing active corrosion defects is presented. This reliability assessment is earned out using extream value distribution of the corroded defects instead of already published failure perssure moded like NG18 or ASME B31G. The failure probability of pipelines depends on the number of corroded defects. and it could be calculated directly as the area exceeded a defined L V(Limited Value of corrosion depth). The remaining life of pressurized pipelines can also be estimated by the PDF of extream value distribution as calculating the exceeded area with a defined failure probability.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.546-552
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• 2009

Enzymatic ethanolysis of wheat germ oil with immobilized lipase was investigated for enhancing the function of wheat germ oil. Ethanolysis reactions were carried out in two different systems; non-pressurized and pressurized system. In non-pressurized system, the enzymatic ethanolysis was carried out in an erlenmeyer flask(25 ml) containing a mixture of wheat germ oil and 99.90% ethanol using 1~5 wt% immobilized lipase as Lipozyme TL-IM and Lipozyme RM-IM and the reaction mixtures were incubated at $40{\sim}70^{\circ}C$ with 120 rpm shaking. In pressurized system, the enzymatic ethanolysis was carried out at various condition; immobilized lipase concentration(2 wt%), reaction time(24 h), reaction temperature($40{\sim}60^{\circ}C$) and reaction pressure(75, 100, 150, 200 bars). The samples obtained from each fraction were analyzed by HPLC for analysing contents of monoglyceride, diglyceride, and triglyceride. The conversion of wheat germ oil relied on the reaction temperature and the concentration of immobilized lipase. The optimum condition of enzymatic ethanolysis in non-pressurized and pressurized systems was at $50^{\circ}C$ and 100 bar.