Search

Excessive vibration has always been a serious problem for conical shell structures, while the application of the graphene-based free-constrained layer (GFCL) based on carbon fiber-reinforced composite (CFRC) structure is a novel way to improve structural performance. An analytical model for vibration and dynamic characteristics of the GFCL-CFRC conical shell resting on the Winkler–Pasternak elastic foundation with arbitrary boundary conditions is constructed, and four types of GFCL porosity distribution and GFCL dispersion pattern are considered in this model. The multi-segment technique and virtual spring technique are utilized to simulate arbitrary boundary conditions. Then, the first-order shear deformation theory (FSDT) and Hamilton's principle are employed to obtain the motion equation of the GFCL-CFRC conical shell, and the motion equation of the GFCL-CFRC conical shell is solved by the Ritz method. In conclusion, the dispersion mode of GFCL, thickness ratio of GFCL, and fiber angle have influence on the dynamic performance. With a reasonable design, the dynamic performance of the GFCL-CFRC conical shell can be further improved. [ABSTRACT FROM AUTHOR]

A lumped parameter model is constructed to accurately predict the dynamic degradation characteristics of the fiber-reinforced composite sheet based on the thermal vibration measurement data. In the modeling process, a multiple-lumped-mass division technique is adopted along the longitudinal and width directions with consideration of thermal degradation on the connective stiffness and damping matrix. By solving the natural frequencies and vibration responses of the structure, a determination method for the key parameters of the model, such as the additional thermal stiffness matrix, the connective stiffness, and the damping coefficients, is proposed. In addition, the constructed model is verified by comparing the theoretical natural frequencies and vibration responses with the experimental results at different degradation time points and temperatures, and the calculation errors are within an acceptable range. Both the theoretical and experimental results reveal a gradual weakened downtrend of natural frequencies and a firstly increasing and then decreasing resonant response phenomenon. Also, some possible reasons for the above complex dynamic degradation phenomenon are provided. [ABSTRACT FROM AUTHOR]

A deeper understanding of the comparative advantage of emerging markets in agricultural export can be gained by analysing the spatial connections of emerging markets through the framework provided by the diamond model. The geographic economics factors are transformed to interconnections of emerging markets by a genetic algorithm based on Mahalanobis distances. The spatial effect of geographic economics factors on export competitiveness of agriculture is further identified by spatial modelling. The irrigated land area, competitive labour cost, foreign direct investment (F.D.I.), and export market opportunity are important to further develop the export competitiveness of the agriculture industry from emerging markets based on spatial modelling. Also there is a spatial disturbances effect in agricultural export of emerging markets based on transformed interconnections structured by geographic economic factors. A fuzzy cluster analysis is further performed, and the stationary solution of clusters in dynamic transition across market segments is analysed by a Markov Chain. It is further found that the distribution of emerging markets with a higher level of export competitiveness can be more concentrated in clusters with lower levels of proportion. The findings of this research can offer support to global managers in further understanding the spatial effect of geographic economics factors on export competitiveness of agriculture from emerging markets. [ABSTRACT FROM AUTHOR]