This study presents three mathematical methods namely the polynomial stress function approach, the Fourier series form approach
and the approximated equations form approach for finding the stress distribution in a cantilever beam with rectangular cross
section loaded by a parabolically distributed load. By taking the stress function as a polynomial of the seventh degree, it
is attempted to find the coefficients either in complete or in full shape of the polynomial. In the Fourier series approach,
the load is discreted to unlimited series of harmonic loads and superposing resultant stresses is the affect of parabolically
distributed load on the beam. The resultant stresses are compared with some approximated stress formulas which have been provided
before. Finite element analysis are done for square, short, medium and long cantilever beams and the mathematical results
of stress distribution in five different height of the beam was compared with FEM results. It was found good results for τyy and τxy in all cross section of the beams and acceptable results for τxx only in y = 0. It is found that discreting loads to even a limit number of harmonic loads and superposing the resultant stresses can
give the distribution of τyy and τxy with the acceptable precision in medium and long cantilever beams with rectangular cross section. 相似文献
Multimedia Tools and Applications - Isolated hand sign language recognition from video is a challenging research area in computer vision. Some of the most important challenges in this area include... 相似文献
Inflammatory bowel diseases (IBDs) are immune-mediated, chronic relapsing diseases with a rising prevalence worldwide in both adult and pediatric populations. Treatment options for immune-mediated diseases, including IBDs, are traditional steroids, immunomodulators, and biologics, none of which are capable of inducing long-lasting remission in all patients. Dendritic cells (DCs) play a fundamental role in inducing tolerance and regulating T cells and their tolerogenic functions. Hence, modulation of intestinal mucosal immunity by DCs could provide a novel, additional tool for the treatment of IBD. Recent evidence indicates that probiotic bacteria might impact immunomodulation both in vitro and in vivo by regulating DCs’ maturation and producing tolerogenic DCs (tolDCs) which, in turn, might dampen inflammation. In this review, we will discuss this evidence and the mechanisms of action of probiotics and their metabolites in inducing tolDCs in IBDs and some conditions associated with them. 相似文献
In the first part of this series, a 3D straight line model was presented for the geometry of two-guide-bar warp-knitted fabrics. In this part, first, the variation of unit cell geometry under uniaxial tension in the range of elastic deformation is investigated. In the present study, the energy method and Castiglianos's theorem were used to derive the fabric's initial modulus. Energy terms which are considered in this study are extension, bending, and compression energies. Also, the friction phenomenon is taken into account by using frictional energy term. For this purpose, the loop of each bar is divided into eight elements. Free-body diagrams of elements are drawn to show the relative magnitude and direction of all forces acting upon an object in a given situation. After obtaining the force details, strain energy of each element is calculated. Finally, the initial modulus of warp-knitted fabrics is obtained. To verify the model, samples of tricot fabrics were produced and tested. Results showed that the generated model can predict precisely the initial modulus of aforementioned warp-knitted structures. 相似文献
Modified couple stress theory is a size-dependent theorem capturing the micro/nanoscale effects influencing the mechanical behaviors of the micro- and nanostructures. In this paper, it is applied to investigate the nonlinear vibration of carbon nanotubes under step DC voltage. The vibration, natural frequencies and dynamic pull-in characteristics of the carbon nanotubes are studied in detail. Moreover, the effects of various boundary conditions and geometries are scrutinized on the dynamic characteristics. The results reveal that application of this theory leads to the higher values of the natural frequencies and dynamic pull-in voltages. 相似文献
In this paper, we propose an efficient cascaded model for sign language recognition taking benefit from spatio-temporal hand-based information using deep learning approaches, especially Single Shot Detector (SSD), Convolutional Neural Network (CNN), and Long Short Term Memory (LSTM), from videos. Our simple yet efficient and accurate model includes two main parts: hand detection and sign recognition. Three types of spatial features, including hand features, Extra Spatial Hand Relation (ESHR) features, and Hand Pose (HP) features, have been fused in the model to feed to LSTM for temporal features extraction. We train SSD model for hand detection using some videos collected from five online sign dictionaries. Our model is evaluated on our proposed dataset (Rastgoo et al., Expert Syst Appl 150: 113336, 2020), including 10’000 sign videos for 100 Persian sign using 10 contributors in 10 different backgrounds, and isoGD dataset. Using the 5-fold cross-validation method, our model outperforms state-of-the-art alternatives in sign language recognition
We propose a multiscale approach to study the influence of carbon nanotubes’ agglomeration on the stability of hybrid nanocomposite plates. The hybrid nanocomposite consists of both macro- and nano-scale reinforcing fibers dispersed in a polymer matrix. The equivalent material properties are calculated by coupling the Eshelby-Mori-Tanaka model with the rule of mixture accounting for effects of CNTs inside the generated clusters. Furthermore, an energy based approach is implemented to obtain the governing equations of the problem utilizing a refined higher-order plate theorem. Subsequently, the derived equations are solved by Galerkin’s analytical method to predict the critical buckling load. The influence of various boundary conditions is studied as well. After validation, a set of numerical examples are presented to explain how each variant can affect the plate’s natural frequency. 相似文献
A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated circular plates made of functionally
grade material (FGM) is presented based on Kirchhoff’s-Love hypothesis with von-Karman type geometrical large nonlinear deformations.
To determine the initial stress state and pre-vibration deformations of the smart plate a nonlinear static problem is solved
followed by adding an incremental dynamic state to the pre-vibration state. The derived governing equations of the structure
are solved by exact series expansion method combined with perturbation approach. The material properties of the FGM core plate
are assumed to be graded in the thickness direction according to the power-law distribution in terms of the volume fractions
of the constituents. Control of the FGM plate’s nonlinear deflections and natural frequencies using high control voltages
is studied and their nonlinear effects are evaluated. Numerical results for FG plates with various mixture of ceramic and
metal are presented in dimensionless forms. In a parametric study the emphasis is placed on investigating the effect of varying
the applied actuator voltage as well as gradient index of FGM plate on vibration characteristics of the smart structure.
This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin
Farzad Ebrahimi received his B.S. and M.S. degree in Mechanical Engineering from University of Tehran, Iran. He is currently working on his
Ph.D. thesis under the title of “Vibration analysis of smart functionally graded plates” at Smart Materials and Structures
Lab in Faculty of Mechanical Engineering of the University of Tehran. His research interests include vibration analysis of
plates and shells, smart materials and structures and functionally graded materials. 相似文献
In this paper, a free vibration analysis of moderately thick circular functionally graded (FG) plate integrated with two thin
piezoelectric (PZT4) layers is presented based on Mindlin plate theory. The material properties of the FG core plate are assumed
to be graded in the thickness direction, while the distribution of electric potential field along the thickness of piezoelectric
layers is simulated by sinusoidal function. The differential equations of motion are solved analytically for two boundary
conditions of the plate: clamped edge and simply supported edge. The analytical solution is validated by comparing the obtained
resonant frequencies with those of an isotropic host plate. The emphasis is placed on investigating the effect of varying
the gradient index of FG plate on the free vibration characteristics of the structure. Good agreement between the results
of this paper and those of the finite element analyses validated the presented approach. 相似文献
Atherosclerosis is a major cause of human cardiovascular disease, which is the leading cause of mortality around the world. Various physiological and pathological processes are involved, including chronic inflammation, dysregulation of lipid metabolism, development of an environment characterized by oxidative stress and improper immune responses. Accordingly, the expansion of novel targets for the treatment of atherosclerosis is necessary. In this study, we focus on the role of foam cells in the development of atherosclerosis. The specific therapeutic goals associated with each stage in the formation of foam cells and the development of atherosclerosis will be considered. Processing and metabolism of cholesterol in the macrophage is one of the main steps in foam cell formation. Cholesterol processing involves lipid uptake, cholesterol esterification and cholesterol efflux, which ultimately leads to cholesterol equilibrium in the macrophage. Recently, many preclinical studies have appeared concerning the role of non-encoding RNAs in the formation of atherosclerotic lesions. Non-encoding RNAs, especially microRNAs, are considered regulators of lipid metabolism by affecting the expression of genes involved in the uptake (e.g., CD36 and LOX1) esterification (ACAT1) and efflux (ABCA1, ABCG1) of cholesterol. They are also able to regulate inflammatory pathways, produce cytokines and mediate foam cell apoptosis. We have reviewed important preclinical evidence of their therapeutic targeting in atherosclerosis, with a special focus on foam cell formation. 相似文献