Search

Introduction: In order to promote the comprehensive utilization of iron and steel solid waste, steel slag (SS), granulated blast furnace slag (GBFS), and flue gas desulfurization gypsum (FGDG) were used as raw materials to replace cement to prepare the full solid waste premixed solidified agent (PSA). Then PSA, iron ore tailings (IOTs), and water were mixed to prepare building foundation pit backfilling materials (BFPBM).Methods: Various tests were conducted to investigate the effects of SS fineness, SS content and mixing ratio of PSA on the properties of PFPBM, including mechanical property test, X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive spectrometry (EDS) and synthetic precipitation leaching procedure (SPLP). The stability of the BFPBM was tested and the hydration mechanism of the PSA was analyzed.Results: The results show that when the specific surface area (SSA) of SS is 457 m2ˑkg-1, the paste mass concentration (PMC) is 79%, the mixing ratio of PSA is 20%, and the mix proportion of PSA is SS: FGDG: GBFS = 58:10:32. In this case, water-reducing agent (WRA) accounting for 0.18% of the total amount of PSA is added. The 28d compressive strength of BFPBM is greater than 0.40 MPa with the maximum value of 6.22 MPa, and the mixture slump of BFPBM is greater than 215 mm, which meets the index requirements of Chinese National Standard T/CECS 1037-2022 Technical Standard for Backfilling Project by Using Premixed Fluidized Solidified Soil.Discussion: According to the mechanism study, the mineral phases of the PSA after hydration are: C2S, C3S, Ca (OH)2, ettringite (AFT), C-S-H gel, and RO phase. C2S, C3S, CaSO4 and other substances gradually disappeared with the hydration, while the content of AFt and C-S-H gel substances increased. BFPBM prepared from iron and steel waste has high strength and environmental friendliness, making it have good application prospects in foundation pit backfilling and mine filling.

Acoustic metamaterials are artificially structured materials exhibiting extraordinary acoustical properties unavailable in natural media. Currently, most of the acoustic metamaterials developed are passive. Although passive metamaterials are easy to fabricate with 3D printers, there are fundamental limitations associated with them. Firstly, the properties of all passive metamaterials cannot be changed after fabrication. Secondly, passive metamaterials typically employ resonant structures, which reduce the working bandwidth of the metamaterial. Moreover, the intense fields created by resonances usually mean that the energy dissipated in the material is considerably high. These limitations hinder the applicability of metamaterials because most applications require broadband acoustic signals. On the contrary, the active acoustic metamaterials have the potential to solve these problems by using embedded tunable electronics. However, the acoustic properties and functionality of most active metamaterial designs reported in the past are limited by the requirement that these metamaterials must be stable. To enforce stability, past designs have narrow bandwidth. This thesis demonstrates a novel design of active acoustic metamaterial based on Willis material concepts that eliminate the above limitations. Willis materials are complex media in which the unusual coupling between stress and particle velocity on one hand and linear momentum and strain, on the other hand, enable unique properties. In this work, we concentrate on creating stable yet broadband active acoustic metamaterials. We present the methodology and theory for designing Willis materials based on an active acoustic metamaterial architecture, in which Willis coupling parameters are allowed to vary independently. The proposed active acoustic metamaterial presented here is designed with three major improvements: broadband response; stable linear response; and modular design. After the design phase, we demonstrate the circuit schematic of the unit-cell for implementing such active Willis materials. Then we show the applications of the designed active metamaterial in the following order. Firstly, we show the acoustic non-reciprocity devices achieved from active Willis materials, and we also demonstrate the noise reduction ability of the designed non-reciprocity devices. Secondly, the application of designed metamaterial is extended to achieve acoustic anomalous reflectors. These applications are validated through experiments and numerical simulations. In addition, an experimental procedure to extract the effective material parameters from near-field measurements and to express material parameters in terms of acoustic polarizabilities are demonstrated to better understand the physics of the design. The material parameter retrieval method proposed earlier is analytical and only works the best for 1D scenarios, because the results from 2D measurements could be contaminated by diffraction and become inaccurate. For this reason, we extend the research on extracting the effective material parameters of small samples by applying machine learning methods. Since the scattered fields measured can be essentially presented as images, the machine learning method employs convolutional neural networks, which are good at associating image patterns to salient macroscopic material properties that determined these patterns. We demonstrate that convolutional neural networks (CNNs) can interpret the diffraction patterns and learn the mapping between the scattered fields and all the effective material parameters including mass density and stiffness tensors from a small set of numerical simulations. We show that the CNN-based methods provide insight into the dynamic behavior of matter including quantitative measures of the scattered fields sensitivity to each material property and how the sensitivity changes from material to material.

A Method was studied for determination of oxygen and nitrogen in Zr-based amorphous alloy by inert gas fusion-infrared absorption/thermal conductivity method, the optimum conditions were determined by experiments on the parameters such as crucible, sample weight and analysis power. When zirconium-based amorphous alloy is melted by heated crucible, the sample weight ranges between 0.07 g∼0.08 g, with analysis power is 6.0 KW; results will be stable and reliable. The relative standard deviation of the accuracy was between 1.13% and 3.47%, the relative standard deviation of the precision was between 0.67% and 4.92%. This method is quick and convenient, and the results are accurate and reliable, it can guarantee the quantitative determination of oxygen and nitrogen element in Zr-based amorphous alloy and guide the scientific research and production activities.