At the present, Portland cement-water glass double solution grouting materials have many problems, such as the instability of gelation time and of products, and poor groundwater-corrosion resistance performance, etc. A way to improve the performances of double solution grouting materials was studied by adding metakaolin into the systems. Based on the rapid gelation performance of Portland cement-water glass and the durability of alkali-activated salic cementitious materials, an ideal structural model of the novel anti-aqueous dispersion and anti-aqueous dissolution grouting material (AAGM) was established. Series of experiments were prepared to verify the Na+ solidification and water-corrosion resistance performance of the metakaolin-water glass double solution grouting materials which combined with cement. The results indicated that the compact structure of AAGM was composed of a dominant ingredient of (Na,Ca)-Si-Al-H zeolite gel and a minor part of C-S-H. Moreover, it was shown that the AAGM had hydrated product of low solubility and compact microstructure tested by Fourier transform infrared spectra (FTIR) and transmission electron microscopy (SEM), which proved the well anti-aqueous dispersion and anti-aqueous dissolution performance.
Besides the three main categories of bistable mechanisms such as latch-lock mechanisms, hinged multisegment mechanisms, and residual-compressive-stress buckled beams, a novel unsymmetrical bistable mechanism with a combined structure of permanent magnets and mechanical beams is proposed, and the bistability of such combined structure is analyzed based on the magnetic-charge model and material mechanics theory. The nonlinear combined force during snap-through procedure is calculated accurately, which is in accordance with that obtained by the experiments. The bistable characteristics such as the threshold snapping force, the traveling range, stable positions, and the elastic reaction force at the stable position can be adjusted freely by changing the magnet structure parameters and the relative distance among the three magnets. Finally, the dynamic response is analyzed theoretically and experimentally, which shows that the bistable structure has a good frequency distinguishing capacity for mechanical shock pulses.
A hypothesis of the electrical field distribution is presented for the physical model of the scanning probe tip with a conical body ending in a spherical apex. Based on this hypothesis, we deduced an analytical model to calculate the electrostatic force acting on the tip and analyzed the variation of the electrostatic force with the structural parameters of the tip. The simulating results are consistent with those by experiments and by the numerical methods of the equivalent charge distribution (ECD). The hypothesis is proved to be reasonable according to the above efforts.
Aim at the problem that there is an irregular data distribution when using multi-sensor to monitor machine conditions, a genetic clustering algorithm using geodesic distance metric (GCGD) is adopted to perform machine fault detection. In GCGD, a geodesic distance based proximity measure is employed replacing Euclidean distance that cannot correctly describe the relationship between data lying in a manifold, and GCGD determines partitioning of the feature vectors from a combinatorial optimization viewpoint. Fault detection experiments of inlet valve leakage in a two-stage reciprocating compressor reveal that GCGD achieves a better performance of fault detection than the K-means algorithm and a genetic algorithm based clustering technique.
The grinding wheel-profile is mostly formed by adjusting the angle of cylindrical profile model when regrinding gear hob with the large helix flute. Repeat trial cutting is needed with this method, which results in low efficiency. In order to improve the efficiency of processing, a mathematical model of grinding wheel profile was establish in according to forming principle of the rake face of gear hob and accurately calculate grinding wheel-profile. A automatic programming system of calculating grinding wheel-profile and automatically generate NC code is developed with the developing tool of VC++.
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