• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.20-31
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• 2014

This paper deals with the development of a realistic shape optimization of damaged columns that are subjected to conservative and non-conservative forces, using the Genetic Algorithm (GA). The analysis is based on the design of the most optimized shape of the column under the constraint of constant weight, considering the Static, Vibrational, and Flutter characteristics. Under the action of conservative and non-conservative longitudinal forces, an elastic column loses its stability. A numerical analysis based on FEM has been performed on a uniform damaged column, to compute the fundamental buckling load, vibration frequency, and flutter load, under various end restraints. An optimization search based on the Genetic Algorithm is then executed, to find the optimal shape design of the column. The optimized column references the one having the highest buckling load, highest vibration frequency, and highest flutter load, among all the possible shapes of the column, for a given volume. A comparison is then made between the values obtained for the optimized damaged column, and those obtained for the optimized undamaged column. The comparison reveals that the incorporation of damage in the column alters its optimal shape to only a certain extent. Also, the critical load and frequency values for the optimized damaged column are comparatively low, compared with those obtained for the optimized undamaged column. However, these results hold true only for moderate-intensity damage cases. For high intensity damage, the optimal shape may not remain the same, and may vary, according to the severity of damage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.17-26
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• 1990

A solution strategy for geometric non-linear analysis for the plane frame structures subjected to conservative and non-conservative forces is presented. By making efficient combination of the load incremental method and the displacement incremental method, this strategy can find postbuckling configuration such as snap-through and turning-back phenomena which cannot be easily found by the conventional load and displacement incrementation scheme. In the case of the analysis of the framed structure subjected to circulatory non-conservative forces, the total tangent stiffness matrix becomes unsymmetric and when calculating the incremental load and unbalanced load vector components, the direction change of the non-conservative forces is considered. Several example problems to demonstrate the feasibility of the present strategy, over ranges of deformation that are well beyond those likly to occur in practical framed structures, are given and discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.57-65
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• 1990

The finite element menthod for the investigation of the static and dynamic stability of the plane framed structures subjected to non-conservative forces is presented. By using the Hermitian polynomial as the shape function, the geometric stiffness matrix, the load correction stiffness matrix for non-conservative forces, and the matrix equation of internal and external damping are derived. Then, a matrix equation of the motion for the non-conservative system is formulated and the critical divergence and flutter loads are determined from this equation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.73-80
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• 2004

Mass matrix, elastic stiffness matrix, load correction stiffness matrix by circulatory non-conservative force, and Winkler and Pasternak foundation matrix of framed structure in 2-D are calculated for stability analysis of divergence or flutter system. Then, a matrix equation of the motion for the non-conservative system is formulated and numerical results are presented to demonstrate the effect of some parameters with using Newmark method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.351-363
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• 2004

Equation of motion of non conservative system considering mass matrix, elastic stiffness matrix, load correction stiffness matrix by circulatory force's direction change and Winkler and Pasternak foundation stiffness matrix is derived. Also stability analysis due to the divergence and flutter loads is performed. And the influence of internal and external damping coefficient on flutter load is investigated applying the quadratic eigen problem solution. Additionally the influence of non-conservative force's direction parameter, internal and external damping and Winkler and Pasternak foundation on the critical load of Beck's and Leipholz's and Hauger's columns are investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.11-22
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• 1990

An automatic incremental algorithm for geometric non-linear finite element analysis of the structures subjected to the conservative and non-conservative forces is presented. By making efficient combination of the load incremental method and the displacement incremental method, this scheme can trace various post-buckling equilibrium path such as snap-through and turning-back. Several numerical examples to demonstrate the feasibility of the present algorithm, over ranges of deformation that are well beyond those likely to occur in practical structures, are given and discussed.

• Restorative Dentistry and Endodontics
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• v.49 no.1
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• pp.4.1-4.9
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• 2024

Objectives: This study aims to correlate caries-causing microorganism load, lactic acid estimation, and blood groups to high caries risk in diabetic and non-diabetic individuals and low caries risk in healthy individuals. Materials and Methods: This study includes 30 participants divided into 3 groups: Group A, High-risk caries diabetic individuals; Group B, High-risk caries non-diabetic individuals; and Group C, Low-risk caries individuals. The medical condition, oral hygiene, and caries risk assessment (American Dental Association classification and International Caries Detection and Assessment System scoring) were documented. Each individual's 3 mL of saliva was analyzed for microbial load and lactic acid as follows: Part I: 2 mL for microbial quantity estimation using nutrient agar and blood agar medium, biochemical investigation, and carbohydrate fermentation tests; Part II: 0.5 mL for lactic acid estimation using spectrophotometric analysis. Among the selected individuals, blood group correlation was assessed. The χ² test, Kruskal-Wallis test, and post hoc analysis were done using Dunn's test (p < 0.05). Results: Group A had the highest microbial load and lactic acid concentration, followed by Groups B and C. The predominant bacteria were Lactobacilli (63.00 ± 15.49) and Streptococcus mutans (76.00 ± 13.90) in saliva. Blood Group B is prevalent in diabetic and non-diabetic high-risk caries patients but statistically insignificant. Conclusions: Diabetic individuals are more susceptible to dental caries due to high microbial loads and increased lactic acid production. These factors also lower the executing tendency of neutrophils, which accelerates microbial accumulation and increases the risk of caries in diabetic individuals.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.569.2-569
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• 2001

Flowable and microfill composites have been recommended for Class V cavities. But the use of flowable composites is controversial because of its physical properties. Objectives: The aim of this study was to evaluate the microleakage of 6 composites (2 hybrids, 2 microfills, and 2 flowable composites) with/without load cycling. Methods: Notch-shaped Class V cavities were prepared on buccal surfaces of 180 extracted human upper premolars and then divided into non-load cycling group(G1) and load cycling group(G2).(omitted)

• Structural Engineering and Mechanics
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• v.16 no.2
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• pp.195-217
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• 2003

This paper, which is an extension of a previous work by Viola et al. (2002), deals with the dynamic stability of beams under a triangularly distributed sub-tangential forces when the effect of an elastically restrained end is taken into account. The sub-tangential forces can be realised by a combination of axial and tangential follower forces, that are conservative and non-conservative forces, respectively. The studied beams become unstable in the form of either flutter or divergence, depending on the degree of non-conservativeness of the distributed sub-tangential forces and the stiffness of the elastically restrained end. A non-conservative parameter ${\alpha}$ is introduced to provide all possible combinations of these forces. Problems of this kind are usually, at least in the first approximation, reduced to the analysis of beams according to the Bernoulli-Euler theory if shear deformability and rotational inertia are negligible. The equation governing the system may be derived from the extended form of Hamilton's principle. The stability maps will be obtained from the eigenvalue analysis in order to define the divergence and flutter domain. The passage from divergence to flutter is associated with a noticeable lowering of the critical load. A number of particular cases can be immediately recovered.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.1-12
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• 2005

For a shear-deformable beam-column element subjected io non-conservative forces, equations of motion and a finite element formulation are presented applying extended Hamilton's principle. The influence of non-conservative force's direction parameter, internal and external damping forces, and shear deformation and rotary inertia effects on divergence and flutter loads of Beck's columns are intensively investigated based on element stiffness, damping and mass matrixes derived for the non-conservative system.