A nonlocal strain gradient shell model incorporating surface effects for vibration analysis of functionally graded cylindrical nanoshells

In this pap er, a novel size-dep endent functionally graded (FG) cylindrical shell model is develop ed based on the nonlocal strain gradient theory in conjunction with the Gurtin-Murdoch surface elasticity theory . The new model containing a nonlocal parameter, a material length scale parameter, and several surface elastic constants can capture three typical typ es of size e ects simultaneously , which are the nonlocal stress ef- fect, the strain gradient e ect, and the surface energy e ects. With the help of Hamilton’s principle and rst-order shear deformation theory , the non-classical governing equations and related b oundary conditions are derived. By using the prop osed model, the free vibra- tion problem of FG cylindrical nanoshells with material prop erties varying continuously through the thickness according to a p ower-law distribution is analytically solved, and the closed-form solutions for natural frequencies under various b oundary conditions are obtained. After verifying the reliability of the prop osed model and analytical method by comparing the degenerated results with those available in the literature, the in uences of nonlocal parameter, material length scale parameter, p ower-law index, radius-to-thickness ratio, length-to-radius ratio, and surface e ects on the vibration characteristic of func- tionally graded cylindrical nanoshells are examined in detail.

Dynamic analysis of wind turbine tower structures in complex ocean environment

Studying and analyzing the dynamic behavior of offshore wind turbines are of great importance to ensure the safety and improve the efficiency of such expensive equipments.In this work,a tapered beam model is proposed to investigate the dynamic response of an offshore wind turbine tower on the monopile foundation assembled with rotating blades in the complex ocean environment.Several environment factors like wind,wave,current,and soil resistance are taken into account.The proposed model is ana-lytically solved with the Galerkin method.Based on the numerical results,the effects of various structure parameters including the taper angle,the height and thickness of the tower,the depth,and the diameter and the cement filler of the monopile on the funda-mental natural frequency of the wind turbine tower system are investigated in detail.It is found that the fundamental natural frequency decreases with the increase in the taper angle and the height and thickness of the tower,and increases with the increase in the diameter of the monopile.Moreover,filling cement into the monopile can effectively im-prove the fundamental natural frequency of the wind turbine tower system,but there is a critical value of the amount of cement maximizing the property of the monopile.This research may be helpful in the design and safety evaluation of offshore wind turbines.

Ginger extract enhances antioxidant ability and immunity of layers

This experiment was to investigate ginger extract on production performance,antioxidant ability and immunity of laying hens.A total of 600 Hy-Line brown laying hens aged at 25 wk old were randomly divided into 2 treatments,4 replicates per treatment,75 layers each replicate.The control group hens were fed a basal diet;the experimental group hens were fed basal diets with 0.1%ginger extract.The results were shown as follows:1)ginger extract significantly enhanced laying rates(P<0.05)and daily egg weight(P<0.05),substantially reduced the ratio of feed to egg(P<0.05)of the hens;2)ginger extract did not change the activities of glutathione peroxidase(GSH-PX)and total antioxidant capacity(TAOC)but significantly improved plasma superoxide dismutase(SOD)activity(P<0.05),reduced malondialdehyde(MDA)content(P<0.05)of the birds;3)ginger extract did not affect the contents of serum total protein(TP),albumin(ALB),globulin(GLB),but significantly increased lysozyme(LZM)activity(P<0.05);4)ginger extract also significantly reduced plasma prostaglandin E2(PGE2)content(P<0.05).This study shows that ginger extract not only can improve the birds’antioxidant capacity,enhance immune function,but also has a potential of reducing inflammatory response.