Nonlinear vibration of rested Euler-Bernoulli beams on linear elastic foundation using Hamiltonian approach

In this paper, nonlinear vibration of Euler-Bernoulli beams resting on linear elastic foundation and subjected to the axial loads are studied analytically. Hamiltonian approach is new kind of analytical approaches are used to achieve the nonlinear frequency of the problem. The nonlinear vibration equation is also solved numerically using Runge-Kutta 4th technique. Comparison of Hamiltonian approach (HA) with Runge-Kutta 4th leads to highly accurate solutions using Hamiltonian approach

Extending the Root-Locus Method to Fractional-Order Systems

The well-known root-locus method is developed for special subset of linear time-invariant systems known as fractional-order systems. Transfer functions of these systems are rational functions with polynomials of rational powers of the Laplace variable s. Such systems are defined on a Riemann surface because of their multivalued nature. A set of rules for plotting the root loci on the first Riemann sheet is presented. The important features of the classical root-locus method such as asymptotes, roots condition on the real axis, and breakaway points are extended to fractional case. It is also shown that the proposed method can assess the closed-loop stability of fractional-order systems in the presence of a varying gain in the loop. Three illustrative examples are presented to confirm the effectiveness of the proposed algorithm

An evaluation of the effect of pulsed wave low-level laser therapy on the biomechanical properties of the vertebral body in two experimental osteoporosis rat models.

Osteoporosis (OP) increases vertebral fragility as a result of the biomechanical effects of diminished bone structure and composition. This study has aimed to assess the effects of pulsed wave low-level laser therapy (PW LLLT) on cancellous bone strength of an ovariectomized (OVX-d) experimental rat model and a glucocorticoid-induced OP (GIOP) experimental rat model. There were four OVX-d groups and four dexamethasone-treated groups. A group of healthy rats was used for baseline evaluations. The OVX-d rats were further subdivided into the following groups: control rats with OP, OVX-d rats that received alendronate, OVX-d rats treated with PW LLLT, and OVX-d rats treated with alendronate and PW LLLT. The remaining rats received dexamethasone and were divided into four groups: control, alendronate-treated rats, laser-treated rats, and laser-treated rats with concomitant administration of alendronate. PW LLLT (890 nm, 80 Hz, 0.972 J/cm(2)) was performed on the spinal processes of the T12, L1, L2, and L3 vertebras. We extracted the L1 vertebrae and submitted them to a mechanical compression test. Biomechanical test findings showed positive effects of the PW LLLT and alendronate administration on increasing bending stiffness and maximum force of the osteoporotic bones compared to the healthy group. However, laser treatment of OVA-d rats significantly increased stress high load compared to OVA-d control rats. PW LLLT preserved the cancellous (trabecular) bone of vertebra against the detrimental effects of OV-induced OP on bone strength in rats compared to control OV rats

Analysis of functionally graded rotating disks with variable thickness

Elastic solutions for axisymmetric rotating disks made of functionally graded material with variable thickness are presented. The material properties and disk thickness profile are assumed to be represented by two power-law distributions. In the case of hollow disk, based on the form of the power-law distribution for the mechanical properties of the constituent components and the thickness profile function, both analytical and semi-analytical solutions are given under free–free and fixed-free boundary conditions. For the solid disk, only semi-analytical solution is presented. The effects of the material grading index and the geometry of the disk on the stresses and displacements are investigated. It is found that a functionally graded rotating disk with parabolic or hyperbolic convergent thickness profile has smaller stresses and displacements compared with that of uniform thickness. It is seen that the maximum radial stress for the solid functionally graded disk with parabolic thickness profile is not at the centre like uniform thickness disk. Results of this paper suggest that a rotating functionally graded disk with parabolic concave or hyperbolic convergent thickness profile can be more efficient than the one with uniform thickness

On the Stress Analysis of Functionally Graded Gear Wheels with Variable Thickness

This paper presents the elastic solutions of the gear wheels made of functionally graded material (FGM) with variable thickness subjected to rotating loads. The material properties and wheel thickness profile are assumed to be represented by two power law distributions. Solid and hollow wheels are considered and the solutions for the stresses and displacements are given under appropriate boundary conditions. The solutions for FGM are compared with that of non-FGM, and for variable thickness and for uniform thickness. The effects of the material grading index, n, and the geometry of the wheel on the stress and displacement are investigated. It is found that a functionally graded wheel with parabolic and hyperbolic convergent thickness profile has smaller stresses and displacements compared with that with uniform thickness. The maximum radial stress for the solid functionally graded wheel with parabolic thickness profile was not at the center, whereas for solid wheel with uniform thickness, the maximum was at the center. The results obtained suggest that an FGM gear wheel with hyperbolic convergent and parabolic concave thickness profile is more suitable compared with that of uniform thickness

IMPROVEMENT OF LOADABILITY IN DISTRIBUTION SYSTEM USING GENETIC ALGORITHM

Abstract -Generally during recent decades due to development of power systems, the methods for delivering electrical energy to consumers, and because of voltage variations is a very important proble

Effect of Low-level Laser Therapy on Bone Defect Repair in Diabetic and Osteoporotic Rats using the Real-Time PCR Technique

Introduction: Bone formation is disturbed in type 1 diabetes followed by changes in the bone microstructure. The most important metabolic disorder in diabetes is osteoporosis, which is characterized by bone loss and bone structure degradation. This study aimed to determine the effect of lowpower laser on bone defect repair in the experimental model of diabetes and osteoporosis. Materials & Methods: A total of 30 fourmonth-old female Wistar rats weighing 190-220 g were selected and randomly divided into six groups, including 1: non-diabetic control (Co.), 2: non-diabetic laser (L.), 3: diabetic control (Co.D.), 4: diabetic laser (L.D.), 5: diabetic alendronate (A.D.), and 6: diabetic laser + alendronate (L.A.D.).Diabetes was induced in groups 3, 4, 5, and 6. All groups underwent ovariectomy and partial bone defect. In the laser group, a lowlevel laser (890nm, 80 Hz, 1/5J / cm 2) was radiated to 3 points at the defect location. Tibia bones were collected, and Real-time PCR was performed after a month. The data were analyzed using ANOVA. A p-value less than P<0.05 was considered statistically significant. Ethics code: 13237-91-1-1393- 10397 Findings: The t-test showed a significant decrease in tibia bone density in diabetic and osteoporotic rats, compared to the nondiabetic control group. Moreover, analysis of gene expression data (ANOVA, P<0.05) revealed a significant difference between the group of diabetic laser + alendronate and other groups in terms of Runx2 gene expression and Osteocalcin. Discussions & Conclusions: According to the findings, laser therapy combined with alendronate can accelerate the repair of partial bone defect in the experimental model of diabetes and osteoporosis. Keywords: Low-level laser, Osteoporosis, Partial bone defect, Real-time PCR, Type 1 diabete

ハチスカケ カシンダン セイリツショ ノ メノト ロウジョ カンケイ シリョウ ニツイテ

Osteoporosis is determined by decreased bone strength that increases the threat of fractures. The aim of this study was to evaluate the effects of pentoxifylline (PTX) and alendronate (ALN), on the stereological parameters, and gene expression in callus of fracture in an experimental rat model of ovariectomy-induced osteoporosis (OVX). The OVX was induced in 90 female rats. Fourteen weeks later, a complete fracture on the right femur was made. Rats were divided into five groups: 1) control: no treatment; 2) sham: received daily distilled water; 3) daily 3.00 mg kg-1 ALN subcutaneously (SC); 4) daily 200 mg kg-1 PTX (SC) and 5) daily PTX (SC) + ALN (same doses). The osteoclast count was significantly lower in all treatment groups, at 21 and 56 days post-surgery, compared to the control and sham groups. The PTX significantly increased total callus volume at 21 and 56 days post-surgery, compared to the other groups. The PTX+ALN treatment significantly increased both cortical bone volume on day 21, and osteocyte and osteoblast numbers on day 56, compared to the control and sham groups. It can be concluded that PTX and ALN have antiresorptive effects, in OVX rats. Also, PTX has increased the extracellular matrix on both 21 and 56 days after surgery, compared to the other groups. PTX+ALN elevated cortical bone volume on day 21, and osteocyte and osteoblast numbers compared to the control and sham groups on day 56. Keywords Fracture healing Osteoporosis Ovariectomy Real time PCR Stereolog