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When performing flutter analysis through the traditional methods, it is difficult to solve high-order strong nonlinear equations. For overcoming this difficulty, this paper establishes a double-parameter optimization model for searching the flutter critical wind speed and frequency. A new hybrid firefly algorithm called the quantum genetic firefly algorithm is presented to search the optimal solution to the optimization model. The proposed algorithm is the combination of the firefly algorithm and the quantum genetic algorithm. The results of the quantum genetic firefly algorithm are compared with the results shown by the firefly algorithm and quantum genetic algorithm. Numerical and experimental results of the proposed algorithm are competitive and in most cases are better than that of the firefly algorithm and quantum genetic algorithm.

According to the previous experimental research on bond-slip, select push-out test as experimental method research on bond-slip between cold-formed thin-walled steel and foam concrete. Through the observation of the specimens in the push-out test, combining with the natural bonding mechanism and influencing factors summarized the failure mode and its law of composite member. The reference and basis for the experimental research and theoretical analysis of it in the future are provided.

The new composite sandwich slab of the cold formed thin-walled steel and lightweight aggregate concrete is studied. The composite sandwich slab is a skeleton of cold formed thin-walled steel, cast-in-situ lightweight aggregate concrete, built-in benzene board as a sandwich layer. The composite sandwich slab has a light weight, seismic performance is good, and construction period is short of advantage, can effectively solve poor shortcomings of the steel structure fireproofing performance and corrosion resistance, and can effectively improve the whole and local stability of the steel structure. The composite sandwich slab bearing capacity of the cold formed thin-walled steel and lightweight aggregate concrete is analyzed using simple plastic theory. The deflection to consider interface slip of the composite slab is computed. The composite sandwich slab is tested statically; the failure mechanism of the slab is analyzed. The load-deflection curve, load-strain curve are obtained. The sandwich rate of the slab on the influence of the bearing capacity is analyzed using the finite element method, and theoretical with experimental results comparatively analyzed.

Membrane fouling mechanism in the vacuum membrane distillation (VMD) was studied both theoretically and experimentally by using ginseng crude extract aqueous solution as a model concentrate system. The concept of critical fouling operating conditions in VMD within which fouling is difficult to occur was introduced for the first time. By analyzing the forces acting on solute particles (microaggregates of biomacromolecules in the ginseng crude extracts solutions), three mathematical relations, namely the expressions of critical operating conditions, to distinguish between solutes depositing on membranes and those suspending in solutions, were derived. Then the effects of operating conditions including the cross-flow velocity, the feed temperature, and the vacuum degree on membrane flux were experimentally evaluated. The experimental results indicated that even under constant operating conditions, the membrane distillation flux could not maintain a stable level when one of following occurred: (1) the vacuum degree increased to its critical value, (2) the feed temperature increased to its critical value, or (3) the feed cross-flow velocity decreased to its critical value. The flux instability suggests that the critical flux had been exceeded and membrane fouling was taking place. These results confirmed the existence of critical fouling operating conditions in the VMD process.

Vacuum membrane distillation (VMD) was employed to concentrate Ginseng extracts aqueous solution. Polytetrafluoroethylene (PTFE) micro-porous plate membranes, with average pore size of 0.2 µm and thickness of 50 µm, were used inVMD process. The effects of operating temperature, vacuum pressure and feed concentration were investigated using a plate membrane module. Furthermore, scanning electron microscopy analysis technology was used to observe membrane fouling. The experimental results showed that both initial flux and flux decline were affected obviously by the selected operating variable, i.e. temperature, vacuum pressure and concentration. When the vapor pressure difference between two sides of membrane was small enough to certain value, the permeation flux in VMD concentration of Ginseng extracts aqueous solution can keep in a stability condition. In this case, the SEM image indicated that membrane fouling did not take place. There is a critical pressure difference which prevents membrane from fouling. On the other hand, high operating temperature and high vacuum tightness resulted in high pressure difference and hence high initial flux. But the permeation flux decreased quickly. And a fouling layer on membrane surface was observed. When increasing feed concentration, the initial flux reduced, and the flux declined more quickly.