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A novel simple two-unknown hyperbolic shear deformation theory for functionally graded beams
Mohamed Zidi,Mohammed Sid Ahmed Houari,Abdelouahed Tounsi,Aicha Bessaim,S. R. Mahmoud 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.2
In this article, a novel simple higher-order shear deformation theory for bending and free vibration analysis of functionally graded (FG) beams is proposed. The beauty of this theory relies on its 2-unknowns displacement field as the Euler- Bernoulli beam theory, which is even less than the Timoshenko beam theory. A shear correction factor is, therefore, not needed. Equations of motion are obtained via Hamilton‟s principle. Analytical solutions for the bending and free vibration analysis are given for simply supported beams. Efficacy of the proposed model is shown through illustrative examples for bending and dynamic of FG beams. The numerical results obtained are compared with those of other higher-order shear deformation beam theory results. The results obtained are found to be accurate.
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Institutional Quality and Public Debt Accumulation: An Empirical Analysis
Ben Ali Tarek,Zidi Ahmed 한국국제경제학회 2017 International Economic Journal Vol.31 No.3
The question of public debt management for both developed and developing economies has generated an enormous amount of political as well as academic interest. This study examines how governance affects public debt accumulation in the MENA countries during the 1996–2015 period. The six Worldwide Governance indicators (voice and accountability, political stability and the absence of violence/terrorism, government effectiveness, regulatory quality, rule of law and control of corruption) were used to measure the quality of governance in these countries. The results show that only three governance indicators support well the hypothesis that poor governance leads to higher accumulation of MENA public debt. Moreover, the estimates suggest a significant indirect impact of bad governance operating via decreased GDP growth. These findings have important implications for policy makers of these countries, which are currently facing major fiscal and external imbalances due to the high cost of war and terrorist attacks, low oil prices and a decline in trade. Sound public debt management represents an urgent task especially that public debt management problems often find their origins in the lack of attention paid by policymakers to the costs of bad governance and weak macroeconomic management.
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Imene Laoufi,Mohammed Ameur,Mohamed Zidi,El Abbes Adda Bedia,Abdelmoumen Anis Bousahla 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.4
Using the hyperbolic shear deformation plate model and including plate-foundation interaction (Winkler and Pasternak model), an analytical method in order to determine the deflection and stress distributions in simply supported rectangular functionally graded plates (FGP) subjected to a sinusoidal load, a temperature and moisture fields. The present theory exactly satisfies stress boundary conditions on the top and the bottom of the plate. No transversal shear correction factors are needed because a correct representation of the transversal shearing strain is given. Materials properties of the plate (elastic, thermal and moisture expansion coefficients) are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. Numerical examples are presented and discussed for verifying the accuracy of the present theory in predicting the bending response of FGM plates under sinusoidal load and a temperature field as well as moisture concentration. The effects of material properties, temperature, moisture, plate aspect ratio, side-to-thickness ratio, ratio of elastic coefficients (ceramic-metal) and three distributions for both temperature and moisture on deflections and stresses are investigated.
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Wang Ling,Bai Xinyang,Qiao Yuanjinzi,Si Lili,Yu Zidi,Ni Chenyang,Li Tianjiao,Guo Chengjin,Xiao Kai 한국식물생명공학회 2023 Plant biotechnology reports Vol.17 No.4
The members of the microRNA (miRNA) family exert essential roles in modulating plant growth and development as well as responses to diverse stresses, through negatively regulating their target genes at posttranscriptional or translational levels. In this study, we characterized taemiR9674a, a miRNA member in T. aestivum, in mediating plant responses to drought and salt stresses. Seven genes in total were predicted to act as the targets of tae-miR9674a via modulation of transcript cleavage. The transcripts of tae-miR9674a in roots and leaves were response to both stresses of drought and salt, displaying to be gradually upregulated following the progression of a 27-h regime of above stress treatments. The transgenic tobacco lines of tae-miR9674a exhibited modified growth traits under drought and salt treatments. Of these, the line with miRNA overexpression (i.e., Sen 1) improved drastically on plant biomass, leaf area, and root length, whereas that with its knockdown expression (Anti 1) significantly alleviated on above growth traits compared with wild type. The modified stress responses of tae-miR9674a were shown to be closely associated with the role of miRNA in regulating a suite of physiological parameters, of which Sen 1 displayed improved osmotic stress defensive-related traits, such as fastened stomata closing rate, increased leaf water retention capacity, enhanced osmolytes contents, and elevated antioxidant enzyme (AE) activities. The expression of NtP5CS1 involving proline biosynthesis and NtFeSOD, NtCAT1 and NtPOD4, the AE genes involved in modulating ROS homeostasis, was upregulated in Sen 1 upon drought and salt stresses, suggesting their involvement in miRNA-mediated plant drought and salt responses. Transcriptome analysis indicated that tae-miR9674a leads to modified expression of quantities of genes that functionally associate with GO terms “biological process”, “cellular component”, and “molecular function”, which are overrepresented by the biochemical pathways of phytohormones (i.e., ethylene and jasmonic acid), salt response, salt/drought osmotic stress response through abscisic acid-dependent pathway and reactive oxygen species (ROS) homeostasis. Our investigation suggested that tae-miR9674a is an essential mediator in plant osmotic stress tolerance by positively regulating osmotic stress acclimation, cellular ROS homeostasis, and related defensive processes.
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