Improved complete ensemble empirical mode decomposition with adaptive noise and composite multiscale permutation entropy for denoising blast vibration signal.

Monitoring the building blast vibration signal is an efficient way to determine the power of blast vibration hazards. Due to the harsh measurement environment, noise is inevitably introduced into the recorded signals. This research presents a denoising approach based on Improved complete ensemble empirical mode decomposition with adaptive noise(ICEEMDAN) and Composite Multiscale Permutation Entropy (CMPE). First, the noisy blast vibration signal is decomposed into different intrinsic mode functions using ICEEMDAN; then multiple intrinsic mode functions (IMFs) are separated into pure and noisy using CMPE, the noisy IMFs are denoised using wavelet thresholding; finally the blast wave is reconstructed using the pure and denoised mixed IMFs. The proposed approach was compared with four other approaches (CEEMDAN-CMPE, VMD-CMPE, SVMD-CMPE, and WST). The results indicate that the proposed approach has better performance and can be considered as an effective denoising method for building blast vibration signals.

Mineralogy and Geochemistry of Iron Tailings from Yeshan Iron Deposit, Southwest Jiangsu, China: Implications for Potential Utilization.

In this work, twenty-one core samples of tailings wastes were collected from Yeshan iron tailings pond in Jiangsu Province, China. The mineralogical-chemical properties of Yeshan iron ore tailings (IOTs) were investigated to explore potential utilization. Mineralogical investigations and mineral liberation analysis indicated that the iron tailings have complex texture and incomplete mineral liberation, suggesting further grinding can improve higher recovery. Yeshan IOTs accumulated much higher MgO originating from dolomite, therefore, it could be infeasible to utilize a large quantity of Yeshan IOTs as alternative raw meals for cement clinker or replace aggregates in concrete. 2D vertical distribution profiles created with the ordinary kriging method presented heterogeneous distributions of major elements, and the variation trends were inconsistent. The results obtained in this work provide insight for exploiting and reducing Yeshan IOTs.

Fluorapatite nanorod arrays with enamel-like bundle structure regulated by iron ions.

Pigmented rodent tooth enamel is mainly composed of parallel hydroxyapatite nanorods and a small amount of organic matrix. These hydroxyapatite nanorods tend to be carbonated and contain traces of iron, fluorine, and magnesium. The pigmented rodent tooth enamel which contains trace iron is stronger and more resistant to acid corrosion than unpigmented rodent enamel, which could provide inspiration for the preparation and synthesis of high performance and corrosion resistant artificial materials. However, the regulatory role and mechanical enhancement of iron ions in enamel growth are unclear. Here, we synthesized enamel-like fluorapatite nanorod arrays in vitro using a mineralization technique at room-temperature. To investigate the regulatory effect of iron ions on the fluorapatite nanorod arrays (FAP-Fe), the phosphate solution is slowly transfused dropwise in the calcium ion solution, and different concentrations of iron ions are added to the calcium ion solution in advance. We demonstrated that fluorapatite nanorod arrays (FAP) can be epitaxially grown from amorphous calcium phosphate nanoparticles and iron ions can improve the microstructure of FAP nanorod arrays and obtain the same enamel bundle structure as the natural enamel. Moreover, high concentration of iron ions can inhibit the crystallization of fluorapatite. The FAP-Fe nanorod arrays controlled by 0.02 mM Fe3+ have good mechanical properties. Their hardness is 1.34 ± 0.02 GPa and Young's modulus is 65.3 ± 0.4 GPa, respectively. This work is helpful to understand the role of trace elements in natural enamel in the regulation of enamel formation and to provide a theoretical foundation for the preparation of high strength artificial composites, which can play a greater role in the fields of biological alternative materials, anti-oil coating, oil/water separation, anti-bioadhesion and so on.

Theoretical study on structural and mechanical properties of Si-containing ternary transition metal nitrides M0.5Si0.5N (M = Ti, Zr, Hf).

Si-containing transition-metal nitrides Ti0.5Si0.5N, Zr0.5Si0.5N and Hf0.5Si0.5N with conventional rock salt B1 structure exhibit superior hardness, strength and oxidation resistance. However, the potential phases of the ternary systems at various pressures remain unexplored. In this work, we firstly studied the potential structures of Ti0.5Si0.5N, Zr0.5Si0.5N and Hf0.5Si0.5N in pressures of 0-100 GPa. A hexagonal phase with P63/mmc symmetry was uncovered and verified to be quenchable in the ambient conditions. The structural, mechanical and electronic properties were systematically studied and compared with the well-known ordered B1 structure. We surprisingly found that Ti0.5Si0.5N within this hexagonal phase displayed much improved ideal indentation shear strength from about 10 GPa for a B1 structure to 30 GPa. The estimated hardness based on the empirical formula is up to 38 GPa, greatly exceeding that of the B1 structure. By the detailed electronic analysis, the underlying atomic mechanism for the outstanding mechanical properties was also studied.

Cryogel-Templated Fabrication of n-Al/PVDF Superhydrophobic Energetic Films with Exceptional Underwater Ignition Performance.

The rapid heat loss and corrosion of nano-aluminum limits the energy performance of metastable intermolecular composites (MICs) in aquatic conditions. In this work, superhydrophobic n-Al/PVDF films were fabricated by the cryogel-templated method. The underwater ignition performance of the energetic films was investigated. The preparation process of energetic materials is relatively simple, and avoids excessively high temperatures, ensuring the safety of the entire experimental process. The surface of the n-Al/PVDF energetic film exhibits super-hydrophobicity. Because the aluminum nanoparticles are uniformly encased in the hydrophobic energetic binder, the film is more waterproof and anti-aging. Laser-induced underwater ignition experiments show that the superhydrophobic modification can effectively induce the ignition of energetic films underwater. The results suggest that the cryogel-templated method provides a feasible route for underwater applications of energetic materials, especially nanoenergetics-on-a-chip in underwater micro-scale energy-demanding systems.

Tensile Properties and Fracture Mechanism of Thermal Spraying Polyurea.

In this study, polyurea was experimentally tested under various spraying temperatures and pressures. The number of holes and the pore size produced after the tensile fracture of the polyurea were counted to illustrate the effect of the various spraying temperatures and pressures on the performance of the polyurea. The tensile characteristics of polyurea were greatly influenced by the spraying temperatures and pressures, according to the experimental findings and statistical analysis. The polyurea tensile performance was best when the spraying pressure was 17.25 MPa with a spraying temperature of 70 °C. The fracture mechanism was illustrated by the silver streaking phenomenon generated during the tensile stretching process. The fracture energy was absorbed by the fracture holes and pores during silver streaking, thus creating the huge gap in tensile properties.