• Computers and Concrete
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• v.30 no.5
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• pp.357-367
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• 2022

In this paper, we propose an efficient control method that can be transformed into a general building control problem for building structure control using these reliability criteria. To facilitate the calculation of controller H∞, an efficient solution method based on Linear Matrix Inequality (LMI) is introduced, namely H∞-based LMI control. In addition, a self-tuning predictive grey fuzzy controller is proposed to solve the problem caused by wrong parameter selection to eliminates the effect of dynamic coupling between degrees of freedom (DOF) in Self-Tuning Fuzzy Controllers. We prove stability using Lyapunov's stability theorem. To check the applicability of the proposed method, the proposed controller is applied and the control characteristics are determined. The simulation assumes system uncertainty in the controller design and emphasizes the use of acceleration feedback as a practical consideration. Simulation results show that the performance of the proposed controller is impressive, stable, and consistent with the performance of LMI-based methods. Therefore, an effective control method is suitable for seismic reinforcement of civil buildings.

• Steel and Composite Structures
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• v.48 no.4
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• pp.475-483
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• 2023

In this paper, a new energy-efficient semi-active hybrid bulk damper is developed that is cost-effective for use in structural applications. In this work, the possibility of active and semi-active component configurations combined with suitable control algorithms, especially vibration control methods, is explored. The equations of motion for a container bridge equipped with an MDOF Mass Tuned Damper (M-TMD) system are established, and the combination of excitation, adhesion, and control effects are performed by a proprietary package and commercial custom submodel software. Systematic methods for the synthesis of structural components and active systems have been used in many applications because of the main interest in designing efficient devices and high-performance structural systems. A rational strategy can be established by properly controlling the master injection frequency parameter. Simulation results show that the multiscale model approach is achieved and meets accuracy with high computational efficiency. The M-TMD system can significantly improve the overall response of constrained structures by modestly reducing the critical stress amplitude of the frame. This design can be believed to build affordable, safe, environmentally friendly, resilient, sustainable infrastructure and transportation.

• Smart Structures and Systems
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• v.31 no.1
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• pp.69-78
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• 2023

The purpose of this paper is to develop a scalable grey predictive controller with unavoidable random delays. Grey prediction is proposed to solve problems caused by incorrect parameter selection and to eliminate the effects of dynamic coupling between degrees of freedom (DOFs) in nonlinear systems. To address the stability problem, this study develops an improved gray-predictive adaptive fuzzy controller, which can not only solve the implementation problem by determining the stability of the system, but also apply the Linear Matrix Inequality (LMI) law to calculate Fuzzy change parameters. Fuzzy logic controllers manipulate robotic systems to improve their control performance. The stability is proved using Lyapunov stability theorem. In this article, the authors compare different controllers and the proposed predictive controller can significantly reduce the vibration of offshore platforms while keeping the required control force within an ideal small range. This paper presents a robust fuzzy control design that uses a model-based approach to overcome the effects of modeling errors. To guarantee the asymptotic stability of large nonlinear systems with multiple lags, the stability criterion is derived from the direct Lyapunov method. Based on this criterion and a distributed control system, a set of model-based fuzzy controllers is synthesized to stabilize large-scale nonlinear systems with multiple delays.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.84-89
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• 2003

Fuzzy controller is one of the succeed controller used in the process control in case of model uncertainties. But it my be difficult to fuzzy controller to articulate the accumulated knowledge to encompass all circumstance. Hence, it is essential to provide a tuning capability. There are many parameters in fuzzy controller can be adapted, scale factor tuning of normalized fuzzy controller is one of the adaptation parameter. Two adaptation methods are implemented in this work on an experimental thermal process, which simulate heating process in liquefied petroleum gases (LPG) recovery process in one of petrochemical industries: Gradient decent (GD) adaptation method; supervisory fuzzy controller. A comparison between the two methods is discussed.

• The Journal of the Petrological Society of Korea
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• v.13 no.1
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• pp.16-33
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• 2004

By relating mineralogy, petrology and geochemistry to observed magnetic properties, an understanding of the geological factors that control magnetic signatures is obtained. Magnetic susceptibility measurements and geochemical analyses were carried out for 160 samples in the Jurassic to Cretaceous granitoids, which is distributed to Pocheon, Jipori, Geumsan, Namwon, Songnisan, Yongdam, Masan, Jindong, and Taebaeksan areas. The magnetic properties of igneous infusion in these granites reflect bulk rock composition, reduction-oxidation state, hydrothermal alteration which are controlled by tectonic setting, composition and history of the source region, depth of emplacement and nature of wall rocks.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.151-159
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• 2001

As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the ageing evaluation technique by the BI method. The four classes of the thermally aged 1Cr-!mo-0.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method within 5%. The IDE(Indentation Deformation Energy) of a BI technique as a new parameter for evaluating a degradation was suggested and the new IDE parameter clearly depicts the degradation degree.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.171-176
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• 2000

As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the aging evaluation technique by the BI method. The four classes of the thermally aged 1Cr-1Mo-0.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method. The IDE(Indentation Deformation Energy) of a BI technique as a new parameter for evaluating a degradation was suggested and the new IDE parameter clearly depicts the degradation degree.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.837-843
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• 1997

In oxidized polyethylene wax preparation, the effects of main parameters such as the property of used wax, oxidation time, oxidation temperature, air feed rates on the change of acid-numbers were investigated. The change in polymer property was also investigated. The results showed under given reaction conditions, the acid numbers with oxidation temperature increased upto $160^{\circ}C$, but at higher temperature, it decreased. The base resin which was lower molecular weight had higher acid number. The result showed molecular weight as a experimental parameter was more effective than density in oxidation experiment. In milder condition, free radical initiator was used for catalyst to get higher acid-numbers, which was successful in comparison to the non-catalyst system. Also the catalyst with longer half-life was efficient, in order of DCPO, HOPO and BPO.

• Elastomers and Composites
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• v.28 no.4
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• pp.267-273
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• 1993

A number of hydrophilic acrylic comonomers were incorporated into styrene-butadiene soap-free emulsion polymerization. It was found that reaction rate decreased according to : AN>AA>MMA>EA>IA>AAM>MA>HEMA. It was also observed that reaction rate increased with decreasing H-bonding factor contribution to the solubility parameter of the hydrophilic comonoer. The SBR latexes were very monodisperse with the particle size distribution of $1.03{\times}1.12$. Since growth rate is proportional to polymerization time, the difference in conversion rates between various comonomers was resulted from the particle number density of SBR latexes for the various hydrophilic comonomers. It was also found that the colloidal stability of the latexes was excellent because no external emulsifier was incorporated.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.5-10
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• 2002

For fitness-for-service evaluation of high temperature plant components with defects, crack growth life must be assessed properly as indicated in the recent draft of API 579 code. Type 308 stainless steel has been widely used as a field weld material in the petrochemical industry. In this study, creep crack data of type 308 stainless steel are collected and re-analyzed using $C_t$ as a characterizing fracture parameter. A unique da/dt versus $C_t$ relationship was obtained despite of difference of creep deformation constant of the reviewed materials and specimen geometry of the tested specimens. The obtained results can be employed for crack growth life assessment and fitness-for-service evaluation for the cracks in high temperature components. It is also argued that since the effect of creep properties and other material variability on the creep crack growth behavior would be minor the obtained model may be applied for most of the 308 stainless steels.