Free vibration and stability of tapered Euler–Bernoulli beams made of axially functionally graded materials

AbstractThe free vibration and stability of axially functionally graded tapered Euler–Bernoulli beams are studied through solving the governing differential equations of motion. Observing the fact that the conventional differential transform method (DTM) does not necessarily converge to satisfactory results, a new approach based on DTM called differential transform element method (DTEM) is introduced which considerably improves the convergence rate of the method. In addition to DTEM, differential quadrature element method of lowest-order (DQEL) is used to solve the governing differential equation, as well. Carrying out several numerical examples, the competency of DQEL and DTEM in determination of free longitudinal and free transverse frequencies and critical buckling load of tapered Euler–Bernoulli beams made of axially functionally graded materials is verified

Static and free vibration of axially loaded functionally graded beams based on the first-order shear deformation theory

The first-order shear deformation beam theory for static and free vibration of axially loaded rectangular functionally graded beams is developed. In this theory, the improved transverse shear stiffness is derived from the in-plane stress and equilibrium equation and thus, associated shear correction factor is then obtained analytically. Equations of motion are derived from the Hamilton’s principle. Analytical solutions are presented for simply-supported functionally graded beams. The obtained results are compared with the existing solutions to verify the validity of the developed theory. Effects of the power-law index, material contrast and Poisson’s ratio on the displacements, natural frequencies, buckling loads and load–frequency curves as well as corresponding mode shapes are investigated

The possible role of heat shock protein-70 induction in collagen-induced arthritis in rats

Aim This study aimed to evaluate the possible role of heat shock protein-70 (HSP70) induction by 17-allylaminodemethoxygeldanamycin (17-AAG) in collagen-induced arthritis in rats. Material and methods Male Wistar rats were divided into five groups (n = 10/group) and were treated intraperitoneally twice a week for 4 weeks, namely normal control (saline), arthritis control (AR; saline), AR + 17-AAG, AR + methotrexate (MTX), and AR + 17-AAG + MTX. At the end of the treatments, arthritic score was determined and then the animals were sacrificed. Erythrocyte sedimentation rate (ESR), serum levels of HSP70, interleukin-17 (IL-17), tumor necrosis factor-alpha (TNF-α), rheumatic factor (RF), C-reactive protein (CRP), malondialdehyde (MDA), glutathione peroxidase (GPx), and matrix metalloproteinase-9 (MMP-9) were determined. Results In the AR group, all parameters increased significantly, except for GPx, which showed a pronounced decrease. The 17-AAG and/or MTX treatments significantly reduced arthritic score, ESR, IL-17, TNF-α, RF, CRP, MDA, and MMP-9 with significant increase in GPx compared to the AR group. The HSP70 level was significantly higher in the AR + 17-AAG and the AR + 17-AAG + MTX groups but significantly lower in the AR + MTX group as compared to the AR group. Also, it was significantly lower in the AR + MTX group as compared to the AR + 17-AAG group. Conclusion We concluded that HSP70 induction by 17-AAG attenuated the inflammatory process in a rheumatoid arthritis (RA) model induced by collagen, which suggested that HSP70 inducers can be promising agents in the treatment of RA

Crystal Plasticity Finite Element Simulation of Deformation and Fracture in Polycrystalline Microstructures

The mechanical response of metals and their alloys are governed by the deformation mechanisms in the underlying microstructure. High-fidelity modeling of deformation in metals requires development of proper constitutive laws at single crystal scale. Image-based crystal plasticity FE framework is regarded as one of the most powerful tools for deformation simulations, allowing the modelers to explicitly represent the elastic and plastic anisotropy of the material using physics-based laws in a computational domain which statistically represents the morphological and crystallographic properties of the microstructure. In this work, a thermodynamically-consistent coupled crystal plasticity-crack phase field framework is derived to model fracture prcoess in polycrystalline microstructures. The governing differential equations for the displacement and crack phase field are coupled via the Helmholtz free energy density (HFED). Using the volumetric-deviatoric decomposition of the elastic deformation gradient, a new HFED formulation is proposed which respects the unilateral damage conditions (tension-compression asymmetry of material response in the presence of cracks) and can be used for modeling fracture in anisotropic media under finite deformation conditions. Numerical modeling of fracture is computationally daunting, partly due to the frequent convergence issues and occurrence of instabilities. Recognizing that the instabilities take place due to an excess energy, three viscous stabilization methods are proposed in this work to dissipate this excess energy and effectively overcome the instabilities. Unlike arc-length methods, the viscous stabilization is applicable for rate-dependent constitutive models and its implementation into any existing FE code is straightforward. Crystal plasticity simulations of polycrystalline are generally carried out with linear tetrahedral elements due to their capability in conforming to complex geometries. These elements are known to suffer from volumetric locking in modeling (nearly-) incompressible materials, leading to numerical artifacts such as underestimation of displacements and overestimation of pressure levels. A modified F-bar-patch technique is developed in this work to alleviate volumetric locking in phase field modeling of ductile fracture. In the course of plastic deformation, the local strain rate experienced by different material points in the microstructure could be orders of magnitude different from the applied macroscopic strain rate. It is of paramount significance to develop a unified crystal plasticity law which could be applied for a wide range of strain rates. Using the dislocation glide mechanisms in \textit{hcp} metals, a unified flow rule is developed by combining the thermally-activated and drag-dominated processes. This unified law can be employed to model deformation over a wide range of strain rates and its explicit dependence of temperature makes it suitable for modeling high rate deformation of metals where adiabatic heating is significant

Energy regeneration from suspension dynamic modes and self-powered actuation

Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper concerns energy harvesting from vehicle suspension systems. The generated power associated with bounce, pitch and roll modes of vehicle dynamics is determined through analysis. The potential values of power generation from these three modes are calculated. Next, experiments are carried out using a vehicle with a four jack shaker rig to validate the analytical values of potential power harvest. For the considered vehicle, maximum theoretical power values of 1.1kW, 0.88kW and 0.97kW are associated with the bounce, pitch and roll modes, respectively, at 20 Hz excitation frequency and peak to peak displacement amplitude of 5 mm at each wheel, as applied by the shaker. The corresponding experimentally power values are 0.98kW, 0.74kW and 0.78kW. An experimental rig is also developed to study the behavior of regenerative actuators in generating electrical power from kinetic energy. This rig represents a quarter-vehicle suspension model where the viscous damper in the shock absorber system is replaced by a regenerative system. The rig is able to demonstrate the actual electrical power that can be harvested using a regenerative system. The concept of self-powered actuation using the harvested energy from suspension is discussed with regard to applications of self-powered vibration control. The effect of suspension energy regeneration on ride comfort and road handling is presented in conjunction with energy harvesting associated with random road excitations.Peer reviewedFinal Accepted Versio

An Efficient In Vitro Propagation Protocol of Cocoyam [Xanthosoma sagittifolium (L) Schott]

Sprouted corm sections of “South Dade” white cocoyam were potted and maintained in a greenhouse for 8 weeks. Shoot tips of 3–5 mm comprising the apical meristem with 4–6 leaf primordial, and approximately 0.5 mm of corm tissue at the base. These explants were treated to be used into the culture medium. A modified Gamborg's B5 mineral salts supplemented with 0.05 μM 1-naphthaleneacetic acid (NAA) were used throughout the study. Thidiazuron (TDZ) solution containing 0.01% dimethyl sulfoxide (DMSO) was used. Erlenmeyer flasks and test tubes were used for growing cultures. The effect of different media substrate, thidiazuron, and the interaction between TDZ and Benzylaminopurine (BAP) on cocoyam culture were tested. Results indicated that cocoyam can be successfully micropropagated in vitro through various procedures. All concentrations tested (5–20 μM BAP and 1–4 μM TDZ) produced more axillary shoots per shoot tip than the control without cytokinins. Greater proliferation rates were obtained through the use of 20 μM BAP and 2 μM TDZ, respectively, 12 weeks from initiation. Shoots produced with BAP were larger and more normal in appearance than those produced with TDZ, which were small, compressed, and stunted. The use of stationary liquid media is recommended for economic reasons

The New Perceptions on Life of Iranian Patients with Ankylosing Spondylitis: A Qualitative Study

Various studies suggest that ankylosing spondylitis (AS) as a chronic inflammatory disease with many disabilities can have impacts on different aspects of patients’ life. Despite many quantitative studies, only few qualitative studies have thus far been published on this subject. For the first time, the present study aims at gaining insight into the life experience of Iranian AS patients. We performed a content analysis through semi-structured interviews with twenty-eight patients diagnosed with AS, including three females and twenty-five males with an average age of 38.5 years, to gain insight into their experiences. Whatever the patients expressed was written and transcribed verbatim. Then, we did analysis of the results after each interview. The detailed information completely extracted from the interviews was classified as sub-themes and main themes. Three main themes were identified by the analysis: (i) “Always with pain” describing the effects were found in regard to pain on patients’ life, (ii) “The perceived limitation” describing many difficulties that people may face in the society as a result of their disease, and (iii) “Fearing the unknown future” which implies to both patients and their families have concerns about the future and what will happen. Our research findings in line with other qualitative studies showed that AS disease puts a heavy and intolerable burden on patients and their family. It seems that the experiences of people living with AS can be useful to meet challenges caused by the disease and it can enhance their coping with the disease

Free Vibration and Stability of Axially Functionally Graded Tapered Euler-Bernoulli Beams

Structural analysis of axially functionally graded tapered Euler-Bernoulli beams is studied using finite element method. A beam element is proposed which takes advantage of the shape functions of homogeneous uniform beam elements. The effects of varying cross-sectional dimensions and mechanical properties of the functionally graded material are included in the evaluation of structural matrices. This method could be used for beam elements with any distributions of mass density and modulus of elasticity with arbitrarily varying cross-sectional area. Assuming polynomial distributions of modulus of elasticity and mass density, the competency of the element is examined in stability analysis, free longitudinal vibration and free transverse vibration of double tapered beams with different boundary conditions and the convergence rate of the element is then investigated

Optimization of self-nanoemulsifying formulations for weakly basic lipophilic drugs: role of acidification and experimental design

Formulators face great challenges in adopting systematic approaches for designing self-nanoemulsifying formulations (SNEFs) for different drug categories. In this study, we aimed to build-up an advanced SNEF development framework for weakly basic lipophilic drugs, such as cinnarizine (CN). First, the influence of formulation acidification on CN solubility was investigated. Second, formulation self-emulsification in media with different pH was assessed. Experimentally designed phase diagrams were also utilized for advanced optimization of CN-SNEF. Finally, the optimized formulation was examined using cross polarizing light microscopy for the presence of liquid crystals. CN solubility was significantly enhanced upon external and internal acidification. Among the various fatty acids, oleic acid-based formulations showed superior self-emulsification in all the tested media. Surprisingly, formulation turbidity and droplet size significantly decreased upon equilibration with CN. The design was validated using oleic acid/Imwitor308/Cremophor El (25/25/50), which showed excellent self-nanoemulsification, 43-nm droplet size (for CN-equilibrated formulations), and 88 mg/g CN solubility. In contrast to CN-free formulations, CN-loaded SNEF presented lamellar liquid crystals upon 50% aqueous dilution. These findings confirmed that CN-SNEF efficiency was greatly enhanced upon drug incorporation. The adopted strategy offers fast and accurate development of SNEFs and could be extrapolated for other weakly basic lipophilic drugs

Extracellular small non-coding RNA contaminants in fetal bovine serum and serum-free media

In the research field of extracellular vesicles (EVs), the use of fetal bovine serum (FBS) depleted of EVs for in vitro studies is advocated to eliminate the confounding effects of media derived EVs. EV-depleted FBS may either be prepared by ultracentrifugation or purchased commercially. Nevertheless, these preparations do not guarantee an RNA-free FBS for in vitro use. In this study we address the RNA contamination issue, of small non-coding (nc)RNA in vesicular or non-vesicular fractions of FBS, ultracentrifugation EV-depleted FBS, commercial EV-depleted FBS, and in our recently developed filtration based EV-depleted FBS. Commercially available serum- and xeno-free defined media were also screened for small ncRNA contamination. Our small ncRNA sequencing data showed that all EV-depleted media and commercially available defined media contained small ncRNA contaminants. Out of the different FBS preparations studied, our ultrafiltration-based method for EV depletion performed the best in depleting miRNAs. Certain miRNAs such miR-122 and miR-203a proved difficult to remove completely and were found in all media. Compared to miRNAs, other small ncRNA (snRNA,Y RNA, snoRNA, and piRNA) were difficult to eliminate from all the studied media. Additionally, our tested defined media contained miRNAs and other small ncRNAs, albeit at a much lower level than in serum preparations. Our study showed that no media is free of small ncRNA contaminants. Therefore, in order to screen for baseline RNA contamination in culturing media, RNA sequencing data should be carefully controlled by adding a media sample as a control. This should be a mandatory step before performing cell culture experiments in order to eliminate the confounding effects of media.Peer reviewe