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AbstractThe transient impact hypothesis was extended, and the oblique collision model was established by considering the tangential slip. In order to solve this problem, the oblique-impact equations for cam-follower were transformed into a linear complementarity problem. Impulsive control method was employed to control or anti-control the nonlinear responses. The simulation results show that the cam-follower system performs very complex nonlinear characteristics, such as period, quasi-period and chaos responses. Using the impulsive control method, the nonlinear responses of the cam-follower system can be controlled to P(n, n) and P(∞, n) or anti-controlled to chaos.

AbstractIn this study, the interactions among Eu(III), humic acid (HA) and γ-Al2O3as a function of pH and ionic strength were investigated by batch technique and extended X-ray absorption fine structure (EXAFS) analysis. For binary γ-Al2O3/Eu(III) systems, the pH-dependent and ionic strength-independent sorption behavior was indicative of an inner-sphere complexation mechanism. The EXAFS spectra analysis showed that Eu(III) sorption mechanisms at pH 5.0, 6.5 and 8.0 could be attributed to the formation of edge-shared and corner-shared surface complexes. In contrast, surface precipitation and/or surface polymerization tended to be the predominant sorption mechanism at pH 10.0. The spectra analysis results suggested no difference between the proportions of edge-shared and corner-shared complexes formed at different ionic strengths. For ternary γ-Al2O3/HA/Eu(III) systems, the sorption percentage of Eu(III) increased with increasing ionic strength. The EXAFS-derived structural parameters pointed to the formation of binary surface complexes (i.e., edge-shared mode and corner-shared mode) at low ionic strength and ligand-bridging ternary complexes at high ionic strength. In addition, the stoichiometry of ternary complexes showed a trend from 1:1 form (i.e., γ-Al2O3/L/Eu(III), L represents HA sites) to 1:2 form (i.e., γ-Al2O3/L2/Eu(III), L represents HA sites) with increasing ionic strength. The experimental findings in this study can provide an important theoretical basis for further predicting the fate of trivalent radionuclides in aquatic systems.

AbstractAcid–base titrations of magnetite/graphene oxide (M/GO) and Sr(II) adsorption onto M/GO were operated to investigate surface properties of M/GO and surface complexation bonding interactions between Sr(II) and M/GO. Experimental results showed that Sr(II) adsorption onto M/GO was facilitated by a high pH value and a low ionic strength. Modeling results exhaustively explained the changes of adsorption morphological at different pH and ionic strengths. Thermodynamic parameters (ΔH○, ΔS○, and ΔG○) calculated from the adsorption isotherms showed the adsorption of Sr(II) onto M/GO composite was an endothermic and spontaneous process. M/GO could be separated by magnetic separation from aqueous solution in large scale. The adsorption performance suggests M/GO could be a promising adsorbent material for the preconcentration and separation of radiostrontium from aqueous solution in radionuclide pollution cleanup.

The syntheses, structural characterizations and magnetic behaviors of three new complexes, 1-(3′,4′,5′-trifluorobenzyl)pyridinium [M(mnt)2]−[M = Ni (1), Pd (2) or Pt (3)], are reported. These complexes are isomorphous and their prominent structural character is that the [M(mnt)2]−anions form columnar stacks, in which the dimerization was observed. Complexes 2and 3are diamagnetic, while 1possesses an energy gap of 2474 K. For crystal 4, 1-(4′-fluorobenzyl)pyridinium [Ni(mnt)2] (its structure and magnetic susceptibility were briefly reported earlier), the magnetic behavior can be divided into two regimes, namely, weakly ferromagnetic coupling above 93 K and strongly antiferromagnetic coupling below 93 K. A transition occurs at 93 K which switches the magnetic exchange nature from ferromagnetic to antiferromagnetic. A sharp thermal abnormality with λ-shape, associated with the transition, appears from its heat capacity measurement to indicate that the transition is first order. The temperature dependences of the superlattice diffractions revealed the existence of the pretransitional phenomena up to at least 140 K. The unusual magnetic behavior of 4, such as the origin of the ferromagnetic interaction in the high temperature phase and what causes the spin transition, are discussed further.

The effect of the intensity of the magnetic field and the treatment time on the fracture toughness of graphene/epoxy composites is researched. Also, the mechanism of the effect of the magnetic field on the fracture toughness of graphene/epoxy composites and a method to improve the impact resistance is explored. Then, three-point bending tests are employed to characterize the fracture toughness of graphene/epoxy composite. The results show that the intervention of magnetic field could induce GNS to generated orientation arrangement, improving the fracture toughness of the graphene/epoxy composite. When the intensity of the magnetic field was increased, the growth rate of the fracture toughness slowed. However, when 2T magnetic was used to synthetically process the material, and when the processing time was less than 50 min, the fracture toughness of the composite material increased significantly.

The presence of periodical or nonperiodical impulses in vibration signals often indicates the occurrence of machine faults. This knowledge is applied to the fault diagnosis of such machines as engines, gearboxes, rolling element bearings, and so on. The development of an effective impulse detection technique is necessary and significant for evaluating the working condition of these machines, diagnosing their malfunctions, and keeping them running normally over prolong periods. With the aid of wavelet transforms, a wavelet-based envelope analysis method is proposed. In order to suppress any undesired information and highlight the features of interest, an improved soft threshold method has been designed so that the inspected signal is analyzed in a more exact way. Furthermore, an impulse detection technique is developed based on the aforementioned methods. The effectiveness of the proposed technique on the extraction of impulsive features of mechanical signals has been proved by both simulated and practical experiments.