• Computers and Concrete
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• v.34 no.1
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• pp.63-77
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• 2024

In this research, we considered fractional order optimal control models for cancer, HIV treatment and glucose.These models are based on fractional order differential equations that describe the dynamics underlying the disease.It is formulated in term of left and right Caputo fractional derivative. Pontryagin's Maximum Principle is used as a necessary condition to find the optimal curve for the respective controls over fixed time period. The formulated problems are numerically solved using forward backward sweep method with generalized Euler scheme.

• Steel and Composite Structures
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• v.52 no.2
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• pp.183-197
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• 2024

Not all structural columns maintain a vertical orientation. Several contemporary building structures have inclined columns, introducing distinct challenges, particularly in buckling behavior. This study examines the buckling behavior of inclined, thin-walled steel bundled columns, differing from typical vertical columns. Using specimens with three tubes welded to plates linearly aligned at the top and triangularly at the bottom, tests indicated that buckling capacity increases with tube wall thickness and diameter but decreases with column height. Inclined tubes in bundled columns showed improved buckling resistance over vertical ones. Results were verified against standard steel design guidelines to assess their predictive accuracy.

• International Journal of Computer Science & Network Security
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• v.24 no.8
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• pp.105-118
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• 2024

The decision to integrate mobile cloud computing (MCC) in higher education without first defining suitable usage scenarios is a global issue as the usage of such services becomes extensive. Consequently, this study investigates the security determinants of the educational use of mobile cloud computing among universities students. This study proposes and develops a theoretical model by adopting and modifying the Protection Motivation Theory (PMT). The studys findings show that a significant amount of variance in MCC adoption was explained by the proposed model. MCC adoption intention was shown to be highly influenced by threat appraisal and coping appraisal factors. Perceived severity alone explains 37.8% of students "Intention" to adopt MCC applications, which indicates the student's perception of the degree of harm that would happen can hinder them from using MCC. It encompasses concerns about data security, privacy breaches, and academic integrity issues. Response cost, perceived vulnerability and response efficacy also have significant influence on students "intention" by 18.8%, 17.7%, and 6.7%, respectively.

• International Journal of Computer Science & Network Security
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• v.24 no.8
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• pp.135-138
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• 2024

The elementary stage is of great importance in establishing and supporting students during the beginning of their school life. Therefore, the current study aims to explore the Saudi teachers' perspectives about online learning and its effectiveness on some students' skills. The sample consisted of 250 male and female elementary teachers from different Saudi regions, and they responded to an online questionnaire consisting of both open and closed items to investigate their perspectives on online learning and face-to-face learning. The results showed a great perception and awareness among male and female teachers about the advantages and disadvantages of online learning. In addition, the results show that elementary teachers prefer face-to-face learning because it is the most stable and avoids many of the disadvantages mentioned for online learning. From this point of view, the study emphasizes the importance of integrating the two types of learning and directing teachers' professional development practices towards enhancing and developing their digital skills.

• Coupled systems mechanics
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• v.7 no.5
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• pp.627-634
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• 2018

Laser beam welding is more advantageous compared to conventional methods. Titanium/Aluminium dissimilar alloy thin sheet metals are difficult to weld due to large difference in melting point. The performance of the weldment depends upon interlayer formation and distribution of intermetallics. During welding, aluminium gets lost at the temperature below the melting point of titanium. Therefore, it is needed to improve a new metal joining techniques between these two alloys. The present work is carried for welding TI6AL4V and AA2024 alloy by using Nd:YAG Pulsed laser welding unit. The performance of the butt welded interlayer structures are discussed in detail using hardness test and SEM. Test results reveal that interlayer fracture is caused near aluminium side due to low strength at the weld joint.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.170-179
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• 2000

The objective of this study is to develop an analytical module for the prediction of burr formation during cutting process using the finite element method. This module is based on the rigid-plastic finite element method, ductile fracture criterion, fracture propagation technique and node separation criterion. The sequence of burr formation from burr initiation through end of burr formation is simulated and investigated by this module. The effect of material properties, such as AL6061-T6, AL2024-T4 and Copper, and cutting condition, such as rake angle and cutting depth, on burr formation is also discussed in this study. To validate this module the analysis results are compared with experimental ones.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.42-56
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• 1987

Fatigue Fracture behaviors of the TIG-welded aluminum alloys, such as Al 2024-T4, A1 5050-0 and Al 7075-T7 were investigated when a crack propagated from tensile residual stress region and compressive residual stress region. The experimental values were compared with the values expected by the Forman equation. The experimental results are summarized as the following: (1) In case of fatigue crack propagation from residual stress region, the values predicted by Forman equation were Found to exactly corresponded to the experimental values. (2) When the stress intensityfactors affected by compressive residual stress, Kres, were greater than the stress intensity factors by minimum applied stresses. Kmin, the Forman equation was found to be improper to be applied directly, but the equation appeared to be proper, if the stress ratio was modified to zero. (3) The experimental results confirmed that residual stress was relaxed by repeated tensile loading and the relaxing trend was greater in case of compressive residual stress than that of tensile residual stress.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.214-219
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• 1998

Analytic and experimental methods have been used for the characterization of flow behavior of semi-solid Al2024 alloy. Backward extrusion experimnet was chosen to avoid the crack on the unconstrained surface. The material constants for the flow stress by the upper bound technique that agreed with experimental results were determined. The various material constants obtained for al temperature range above the solidus temperature have been fitted and represented in the function of temperature and solid fraction. The obtained result has good agreement only in the high solid fraction.

• Journal of the Korean institute of surface engineering
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• v.25 no.2
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• pp.97-102
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• 1992

Transimission electron microscope(TEM)/ultramicrotomy were used to characterize the detailed surface morphology of 2024-T3 Al alloy surfaces prepared by various pretreatment process. It was found that, for good and superior initial adhesive strength and durability, chemically pretreated substrates appeared essential. The film morphology developed after CSA etching treatment, ass revealed by TEM, suggested the present of irregular cell pattern with finely separated whisker-like protrusion with was responsible for increase of bond strength.

• Bulletin of the Korean Mathematical Society
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• v.61 no.3
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• pp.717-734
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• 2024

Let R be a commutative ring with identity and m, n be positive integers. In this paper, we introduce the class of weakly (m, n)-prime ideals generalizing (m, n)-prime and weakly (m, n)-closed ideals. A proper ideal I of R is called weakly (m, n)-prime if for a, b ∈ R, 0 ≠ a^mb ∈ I implies either aⁿ ∈ I or b ∈ I. We justify several properties and characterizations of weakly (m, n)-prime ideals with many supporting examples. Furthermore, we investigate weakly (m, n)-prime ideals under various contexts of constructions such as direct products, localizations and homomorphic images. Finally, we discuss the behaviour of this class of ideals in idealization and amalgamated rings.