Accurate determination of natural frequencies and mode shapes of the rotating tapered Timoshenko beam is important in engineering practice. This paper re-examines the free vibration of rotating tapered Timoshenko beams using the technique of variational iteration, which is relatively new and is capable of providing accurate solutions for eigenvalue problems in a quite easy way. Natural frequencies and mode shapes for rotating tapered Timoshenko beams with linearly varying height as well as linearly varying height and width are investigated via two numerical examples, and solutions are compared with results published in literature where available. Since the method constitutes a numerical procedure, the convergence of solutions which is important for practical implementation is evaluated as well, where efficiency and accuracy of variational iteration method in solving high order eigenvalue problems are demonstrated.

Tapered beams constitute functionally graded materials that are widely used in various engineering fields. The vibrational characteristics of tapered beams made of axially varying functionally graded materials are investigated via variational iteration method. Natural frequencies and corresponding mode shapes of axially functionally graded tapered beams are examined, and calculated frequencies are compared with results provided by previous researchers using other approximate methods. The efficiency and accuracy of this technique are demonstrated. The effect of nonhomogeneous material distribution, taper ratio as well as boundary conditions on the dynamical behavior of axially functionally graded tapered beams is thoroughly investigated as well.

Small non-coding RNA RyhB is a key regulator of iron homeostasis in bacteria by sensing iron availability in the environment. Although RyhB is known to influence bacterial virulence by interacting with iron metabolism related regulators, its interaction with virulence genes, especially the Type III secretion system (T3SS), has not been reported. Here, we demonstrate that two RyhB paralogs of Salmonella enterica serovar Enteritidis upregulate Type III secretion system (T3SS) effectors, and consequently affect Salmonella invasion into intestinal epithelial cells. Specifically, we found that RyhB-1 modulate Salmonella response to stress condition of iron deficiency and hypoxia, and stress in simulated intestinal environment (SIE). Under SIE culture conditions, both RyhB-1 and RyhB-2 are drastically induced and directly upregulate the expression of T3SS effector gene sipA by interacting with its 5′ untranslated region (5′ UTR) via an incomplete base-pairing mechanism. In addition, the RyhB paralogs upregulate the expression of T3SS effector gene sopE. By regulating the invasion-related genes, RyhBs in turn affect the ability of S. Enteritidis to adhere to and invade into intestinal epithelial cells. Our findings provide evidence that RyhBs function as critical virulence factors by directly regulating virulence-related gene expression. Thus, inhibition of RyhBs may be a potential strategy to attenuate Salmonella.

Although flapwise bending vibration of rotating tapered beams has been extensively studied since the 1970s, most of these studies were based on approximations with varying degrees of accuracy and complexity. The flapwise bending vibration of rotating tapered beams is re-examined in this paper using the technique of variational iteration, which is relatively new and capable of providing accurate results for eigenvalue problems with good convergence. Natural frequencies and mode shapes of rotating beams are extracted for various rotational speeds and taper ratios, and solutions are compared with results published in the literature where available.

In this paper, the deformation behaviour of the large steel tank under uneven foundation settlement is investigated. The finite element model of the tank is firstly established, the finite element analysis of the large steel tank under the harmonic settlement conditions is carried out consequently, the influence of height-diameter ratio, diameter-thickness ratio and wind girder stiffness on the deformation behaviour of the tank top is studied. Based on the finite element results, regression equation for predicting maximum radial displacement of the tank is proposed. Furthermore, the accuracy of proposed solution is validated.