• Geomechanics and Engineering
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• v.18 no.1
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• pp.85-96
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• 2019

A free vibration analysis and wave propagation of triclinic and orthotropic plate has been presented in this work using an efficient quasi 3D shear deformation theory. The novelty of this paper is to introducing this theory to minimize the number of unknowns which is three; instead four in other researches, to studying bulk waves in anisotropic plates, other than it can model plates with great thickness ratio, also. Another advantage of this theory is to permits us to show the effect of both bending and shear components and this is carried out by dividing the transverse displacement into the bending and shear parts. Hamilton's equations are a very potent formulation of the equations of analytic mechanics; it is used for the development of wave propagation equations in the anisotropic plates. The analytical dispersion relationship of this type of plate is obtained by solving an eigenvalue problem. The accuracy of the present model is verified by confronting our results with those available in open literature for anisotropic plates. Moreover Numerical examples are given to show the effects of wave number and thickness on free vibration and wave propagation in anisotropic plates.

• Composites Research
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• v.31 no.6
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• pp.347-354
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• 2018

Shape memory polymer composites have been studied for deployable antennas in space because they have advantages of lightweight, large deformability, good processability, and low cost. In this research, shape memory polymer composites (SMPCs) were manufactured using carbon nanotubes (CNTs) as reinforcements and were used to fabricate SMPC antenna. The SMPCs were prepared by dispersing CNTs in the polymer matrix. Various dispersion methods were investigated to determine the most suitable one, focusing on the mechanical properties of SMPCs including their fracture behavior. The shape memory properties of SMPCs were measured and finally, the deployment behavior of the SMPC antenna was analyzed.

• Composites Research
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• v.33 no.6
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• pp.415-420
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• 2020

The interfacial properties in carbon fiber composites, which control the overall mechanical properties of the composites, are very important. Effective interface enhancement work is conducted on the modification of the carbon fiber surface with carbon nanotubes (CNTs). Nonetheless, most surface modifications methods do have their own drawbacks such as high temperatures with a range of 600~1000℃, which should be implemented for CNT growth on carbon fibers that can cause carbon fiber damages affecting deterioration of composites properties. This study includes the use of in-situ interfacial polymerization of polyamide 610/CNT to fabricate the carbon fiber composites. The process is very fast and continuous and can disperse CNTs with random orientation in the interface resulting in enhanced interfacial properties. Scanning electron microscopy was conducted to investigate the CNT dispersion and composites morphology, and the thermal stability of the composites was analyzed via thermogravimetric analysis. In addition, fiber pull-out tests were used to assess interfacial strength between fiber and matrix.

• Journal of Navigation and Port Research
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• v.44 no.6
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• pp.477-487
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• 2020

The inefficient operation of Busan New Port is due to container-terminal operators being dispersed in small groups, rather than being integrated. This dispersion increased following the reorganization of global shipping alliances in 2016 and causes unnecessary Inter-terminal Transportation(ITT) and ship delays. Studies of integrated operations for larger container terminals show that integration is not going well, however, due to the pre-emptive task that follows the integrated operation. Therefore, in this study, we divided the integrated operation into stages based on a simulated model of the container terminals in Busan New Port. The simulation took into account future increases in the ship's enlargement and terminal congestion, and the operational effects of each type of integrated operation were analyzed and evaluated.

• Advances in nano research
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• v.10 no.2
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• pp.151-163
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• 2021

The main target of this study is to investigate nonlinear transient responses of moving polymer nano-size plates fortified by means of Graphene Platelets (GPLs) and resting on a Winkler-Pasternak foundation under a transverse pressure force and a temperature variation. Two graphene spreading forms dispersed through the plate thickness are studied, and the Halpin-Tsai micro-mechanics model is used to obtain the effective Young's modulus. Furthermore, the rule of mixture is employed to calculate the effective mass density and Poisson's ratio. In accordance with the first order shear deformation and von Karman theory for nonlinear systems, the kinematic equations are derived, and then nonlocal strain gradient scheme is used to reflect the effects of nonlocal and strain gradient parameters on small-size objects. Afterwards, a combined approach, kinetic dynamic relaxation method accompanied by Newmark technique, is hired for solving the time-varying equation sets, and Fortran program is developed to generate the numerical results. The accuracy of the current model is verified by comparative studies with available results in the literature. Finally, a parametric study is carried out to explore the effects of GPL's weight fractions and dispersion patterns, edge conditions, softening and hardening factors, the temperature change, the velocity of moving nanoplate and elastic foundation stiffness on the dynamic response of the structure. The result illustrates that the effects of nonlocality and strain gradient parameters are more remarkable in the higher magnitudes of the nanoplate speed.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.3
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• pp.159-167
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• 2021

The need for biodegradable plastic continues to increase, improvement of physical properties is necessary for actual use in the market. In this study, composite film was produced by adding peroxide additives to bioplastic according to concentration to investigate changes in the melt index, elongation, morphology, and TGA of the composite film. The addition of peroxide compatibilizer showed superior elongation of film and TGA compared to those of control. The added amount of compatibilizer affected the extrusion process, and it was revealed that adding an appropriate amount of peroxidizer is important. Analysis of the composite film's morphology revealed a heterogeneous dispersion sequence due to different rates of crystallization depending on the resin, and surface physical properties were best in the group added with 4% peroxide. The results above showed that the test group added with 4% peroxide compatibilizer was superior in the production of composite biodegradable film.

• Composites Research
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• v.35 no.1
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• pp.47-51
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• 2022

In order to efficiently control the heat generation of electronic devices, many research has been conducted on thermally conductive composite materials. In this study, milled carbon fiber was dispersed in four solvent to investigate the relationship of carbon fiber alignment according to dispersion by solvents, and carbon fiberreinforced composite material(CFRP) was manufactured using vacuum filtration. To evaluate the arrangement of CFRP the arrangement of the prepared specimen was observed under an optical microscope, and thermal conductivity was measured by Laser Flash Analysis. The Through-plane thermal conductivity of CFRP using NMP and Ethanol was 10.79 W/mK and 10.57 W/mK respectively, which were improved by 218% and 209% compared to the In-plane thermal conductivity. The high viscosity of the solvent greatly affects the shear of the fluid, and it seemed to determine the alignment of the filler.

• Clinical and Experimental Reproductive Medicine
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• v.49 no.1
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• pp.40-48
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• 2022

Objective: As the associations of sperm DNA fragmentation with morphology have not been examined in detail, this study aimed to investigate the relationship between abnormalities of morphological details and DNA integrity in human sperm. Methods: In this cross-sectional study, men from infertile couples were enrolled at Hue Center for Reproductive Endocrinology and Infertility, Vietnam. Conventional semen parameters, including morphological details, were analyzed following the World Health Organization 2010 criteria. Sperm DNA fragmentation was evaluated using a sperm chromatin dispersion assay. The relationships and correlations between semen parameters, sperm morphology, and the type of halosperm and the DNA fragmentation index (DFI) were analyzed. Results: Among 130 men in infertile couples, statistically significant differences were not found in the sperm halo type between the normal and abnormal sperm morphology groups. The percentage of round-head spermatozoa was higher in the DFI >15% group (16.98%±12.50%) than in the DFI ≤15% group (13.13% ±8.82%), higher values for amorphous heads were found in the DFI >15% group, and lower values for tapered heads were observed in the DFI ≤15% group; however, these differences were not statistically significant. Small-halo sperm and the DFI were positively correlated with round-head sperm (r=0.243, p=0.005 and r=0.197, p=0.025, respectively). Conclusion: The rate of general sperm morphological abnormalities in semen analysis was not related to sperm DNA integrity. However, round sperm heads were closely associated with sperm DNA fragmentation.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.87-94
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• 2023

TMCP(Thermo Mechanical Control Process) steel was continuously cast (CC) by varying the argon gas flow rate and vacuum time in the Ruhrstahl Heraeus (RH) refining process. Using the CC specimens, the distribution of the inclusions and the mechanical properties were evaluated. A lot of oxides and Al-O type inclusions were observed. The average Vickers hardness did not show a constant, but showed dispersion in a certain range. The shape and scale parameters of the CC specimen with an argon gas flow rate of 160Nm³ and a vacuum time of 12 minutes was the best. Mechanical properties (tensile strength, yield strength and elongation) were consistent with the Weibull probability distribution analysis results. The impact resistance was the best for CC specimens with an argon flow rate of 140 Nm³ and a vacuum time of 12 minutes. Although the inclusions and mechanical properties of the CC specimens were evaluated according to the argon gas flow rate and vacuum time, these values were no significant difference.

• The Journal of Advanced Prosthodontics
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• v.15 no.4
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• pp.189-201
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• 2023

PURPOSE. The aim of this study was to investigate the mechanical properties of three-dimensional (3D) printed denture base resin incorporating microcapsules containing plant essential oils. MATERIALS AND METHODS. Denture base specimens containing up to 3% w/v essential oil microcapsule powders (MCPs), i.e., eucalyptus, geranium, lavender, menthol, and tea tree, in two resins (Detax and NextDent 3D+) were 3D printed using two printers (Asiga and NextDent 5100). The dispersion and interaction of the MCPs in the resin were assessed by SEM while the mechanical properties of the incorporated denture base including flexural strength (MPa), flexural modulus (MPa), Vickers hardness (VHN), and surface roughness (Ra) were also subsequently evaluated. Statistical analysis of any differences in mean values was determined using a two-way ANOVA with Tukey's post hoc testing (α = .05). RESULTS. The spherical shape of the MCPs was maintained during the mixing and polymerization/printing process. However, the Detax-Asiga group showed significant agglomeration of the MCPs even at the lowest MCP concentration levels (0.5% w/v). Overall, as the microcapsule concentration increased, the mean flexural strength decreased, though the menthol MCP groups remained compliant with the ISO standard. The flexural modulus and harness remained relatively unchanged, and the flexural modulus complied with the ISO standard regardless of the MCP concentration. Surface roughness increased with the addition of the MCPs but also remained below that required for clinical acceptance. CONCLUSION. Incorporation of microencapsulated plant essential oils into 3D printed denture base resin was successfully achieved. While incorporation negatively influenced flexural strength and surface roughness, little effect on flexural modulus and Vickers hardness was demonstrated.