• Steel and Composite Structures
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• v.27 no.1
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• pp.95-108
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• 2018

A new composite reinforced method, namely self-compacting concrete filled circular CFRP-steel jacketing, was proposed in this paper. Experimental tests on eight RC square short columns reinforced with the new composite reinforced method and four RC square short columns reinforced with CFS jackets were conducted to investigate their eccentrically compressive behaviour. Nine reinforced columns were subjected to eccentrically compressive loading, while three reinforced columns were subjected to axial compressive loading as reference. The parameters investigated herein were the eccentricity of the compressive loading and the layer of CFRP. Subsequently, the failure mode, ultimate load, deformation and strain of these reinforced columns were discussed. Their failure modes included the excessive bending deformation, serious buckling of steel jackets, crush of concrete and fracture of CFRP. Moreover, these reinforced columns exhibited a ductile failure globally. Both the eccentricity of the compressive loading and the layer of CFRP had a significant effect on the eccentrically compressive behaviour of reinforced columns. Finally, formulae for the evaluation of the ultimate load of reinforced columns were proposed. The theoretical formulae based on the ultimate equilibrium theory provided an effective, acceptable and safe method for designers to calculate the ultimate load of reinforced columns under eccentrically compressive loading.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.165-166
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• 2014

The Composite waterproofing began to rise gradually 2000s in domestic. However, the sheet-membrane composite waterproofing method also acts as an abutment vulnerability that was a problem in a single method, and had the problem of damage to the formation of leakage paths. The existing non-overlap method, through vigorous research abutting sheet shall or could be developed to improve the seal performance of this method with the I-type joint coating material. Nevertheless, it has an integral top coat paint membrane and a sheet abutment limitation, damage to the upper membrane is damaged junction coating membranes has been generated. In this study, a method that has a layer of insulation on the joint bond breaker concept development, and to determine the physical properties with insulated joints to determine the breaking off of the upper joint is damaged coating membrane and tensile performance.

• Carbon letters
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• v.9 no.3
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• pp.210-217
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• 2008

Petroleum pitch and coke with wet mixture method or with dry mixture method were investigated to develop the composite anodic carbon material of high power lithium ion battery. Cokes coated with pitch were obtained by the heat treatment of mixture of cokes and pitch with different weight ratios at $800{\sim}1200^{\circ}C$. The charge and discharge characteristic of the consequent composite anodic carbon material assembled in batteries was tested. Cokes with wet mixture method have a smooth surface and their capacity changed little with changing temperature and content as compared to the cokes with dry mixture method. Although the reversible capacities showed different values by the anode manufacturing method, the composite anode with the mixture of 20 wt% of petroleum pitch and 80 wt% of coke showed the higher power capability and initial efficiency than the pitch based anode. However, the reversible capacity of the composite anode showed the reduced value as compared with the pitch based anode.

• Steel and Composite Structures
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• v.49 no.6
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• pp.701-711
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• 2023

In order to fully reflect variation characteristics of composite concrete dam health state, the monitoring data is applied to diagnose composite concrete dam health state. Composite concrete dam lesion development to wreckage is a precursor, and its health status can be judged. The monitoring data are generally non-linear and unsteady time series, which contain chaotic information that cannot be characterized. Thus, it could generate huge influence for the construction of monitoring models and the formulation of corresponding health diagnostic indicators. This multi-scale diagnosis process is from point to whole. Chaotic characteristics are often contained in the monitoring data. If chaotic characteristics could be extracted for reflecting concrete dam health state and the corresponding diagnostic indicators will be formulated, the theory and method of diagnosing concrete dam health state can be huge improved. Therefore, the chaotic characteristics of monitoring data are considered. And, the extracting method of the chaotic components is studied from monitoring data based on fuzzy dynamic cross-correlation factor method. Finally, a method is proposed for formulating composite concrete dam health state indicators. This method can effectively distinguish chaotic systems from deterministic systems and reflect the health state of concrete dam in service.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.403-408
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• 1998

The analytical model is developed in order to predict the nonlinear flexural responses of bonded and unbonded prestressed concrete beam which contains advanced composite materials. The block concept is used, which be regarded as an intermediate modeling method between the couple method with one block and the layered method with multiple sliced blocks in a section. The model can successfully predict the flexural behavior of variously reinforced prestressed concrete beams.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.48-51
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• 2002

This paper predicted the thermal conductivity of spun carbon/phenolic composites by the thermal resistance method. This method uses the analogy between the diffusion of heat and electrical charge. To verify the theoretical predictions, the thermal conductivity of spun carbon/phenolic composites was examined experimentally. The reported thermal conductivities of graphite/epoxy composite of a eight harness satin laminate was used of the comparison with the prediction values of the model and it was noticed that a good agreement has been found.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.135-140
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• 2000

A numerical method fur performance evaluation of LIPCA is proposed using a finite element method. Fully coupled formulations for piezo-electric material are introduced and eight-node incompatible element is used. After verifying the developed code, the behaviors of LIPCA and $THUNDER^{TM}$ are investigated.

• Steel and Composite Structures
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• v.34 no.3
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• pp.409-421
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• 2020

In the optimized structure sizing, the optimization methods are inserted in this context in order to obtain satisfactory solutions, which can provide more economical structures, besides allowing the consideration of the factors related to the environmental impacts in the structural design. This work proposes a mathematical model for the optimization of steel-concrete composite beams aiming to minimize the monetary cost and the environmental impact, using the Harmonic Search optimization method. Discrete variables were the dimensions of the steel profiles and the thickness of the collaborating slab of the composite steel-concrete beam. The proposed model was implemented in Fortran programming language and based on improvements in the structure of the optimization method proposed by Medeiros and Kripka (2017). To prove the effectiveness and applicability of the model, as well as the Harmonic Search method, analyzes were performed with different configurations of steel-concrete composite beams, in order to provide guidelines that make the use of these systems more streamlined. In general, the Harmonic Search optimization method has proved to be efficient in the search for the optimized solutions, as well as important considerations on the optimization of the monetary and environmental costs of steel-concrete composite beams were obtained from the developed examples.

• Steel and Composite Structures
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• v.29 no.3
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• pp.405-422
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• 2018

In this research, experimental tensile test and manufacturing of carbon nanotube reinforced composite beam (CNTRC) is presented. Also, bending, buckling, and vibration analysis of CNTRC based on various beam theories such as Euler-Bernoulli, Timoshenko and Reddy beams are considered. At first, the experimental tensile tests are carried out for CNTRC and composite beams in order to obtain mechanical properties and then using Hamilton's principle the governing equations of motion are derived for Euler Bernoulli, Timoshenko and Reddy theories. The results have a good agreement with the obtained results by similar researches and it is shown that adding just two percent of carbon nanotubes increases dimensionless fundamental frequency and critical buckling load as well as decreases transverse deflection of composite beams. Also, the influences of different manufacturing processes such as hand layup and industrial methods using vacuum pump on composite properties are investigated. In these composite beams, glass fibers used in an epoxy matrix and for producing CNTRC, CNTs are applied as reinforcement particles. Applying two percent of CNTs leads to increase the mechanical properties and increases natural frequencies and critical buckling load and decreases deflection. The obtained natural frequencies and critical buckling load by theoretical method are higher than other methods, because there are some inevitable errors in industrial and hand layup method. Also, the minimum deflection occurs for theoretical methods, in bending analysis. In this study, Young's and shear modulli as well as density are obtained by experimental test and have not been used from the results of other researches. Then the theoretical analysis such as bending, buckling and vibration are considered by using the obtained mechanical properties of this research.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.487-507
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• 1995

Composite resin repair requires strong bond strength between the new and old materials. The objective of the current study was to identify the optimal treatments for sufficient bond strengths. Bondings between same kinds of materials and cross bondings using chemical curing composites and light curing composites were tested. Surface treatments included the methods of sand-blasting, acid etching and coating of bonding agent. Seven kinds cases of combinations from three kinds of methods were experimented and compared with a control group of which surfaces were highly polished. Measurements of shear bond strength and observations of surface morphologic changes using a scanning electron microscope were done. Following conclusions were drawn : 1. The highest bond strength among composite resins were exhibited by the treatment of the sand-blasting and the coating of bonding agent. 2. Acid etched surfaces showed the lowest bond strength. Bond strengths obtained from experimental groups including acid etching were lower than those obtained from same kinds of experimental groups without acid etching. 3. Simple method of the coating of bonding agent produced the slightly increased bond strength on chemical curing composite and reduced bond strength on light curing composite. 4. Bonding surfaces of chemical curing composite resin showed slightly higher bond strengths than light curing composite resin, however significant differences were not confirmed statistically. 5. More significant irregular surfaces were created by sand-blasting method than acid etching method. 6. A principal component of fillers of both resins was silicon. Acid etching method produced the seperations and degradations of fillers, these were significant on light curing composite resins which containing barium fillers.