Search

In this paper, several Kaczmarz-type numerical methods for solving the matrix equation $AX=B$ and $XA=C$ are proposed, where the coefficient matrix $A$ may be full rank or rank deficient. These methods are iterative methods without matrix multiplication. Theoretically, the convergence of these methods is proved. The numerical results show that these methods are more efficient than iterative methods involving matrix multiplication for high-dimensional matrices., Comment: arXiv admin note: text overlap with arXiv:2305.16684

In this paper, we construct a class of nonlinear greedy average block Kaczmarz methods to solve nonlinear problems without computing the Moore-Penrose pseudoinverse. This kind of methods adopts the average technique of Gaussian Kaczmarz method and combines with the greedy strategy, which greatly reduces the amount of computation. The convergence analysis and numerical experiments of the proposed method are given. The numerical results show the effectiveness of the proposed methods.

A transient-liquid-phase (TLP) diffusion bonding method was employed to join ZrC–SiC ceramic and austenitic stainless steel by using Ti foil and various density Ni foam as interlayer. The Ti–Ni TLP contributed to a firm bonding between ceramic and foam interlayer while avoiding liquid infiltration in foam structure. The influence of holding time on the microstructure of the TLP reaction layer was investigated. The shear tests showed the joints with foam interlayer exhibited ductile failure mode and improved fracture work in comparison with the one with dense Ni interlayer. A maximum shear strength of 117.2 MPa was reached when the relative density of Ni foam was 0.57. The fracture behaviors of the joints during shear test were in-situ observed.

A three-dimensional network architecture of TiB whiskers were in situ synthesized in Al2O3/Ti6Al4V joints by using Ni–B coated Cu foam interlayer. Boron was extracted from Ni–B alloy at low braze temperature to form a thin flexible boride layer comprised by TiB and Ni3B nano-particles. Subsequently, a network structure of TiB whiskers was developed from the interlaced boride layers at high temperature. The underlying mechanisms were addressed based on microstructural evolution. The uncoordinated deformation of the network microstructure, stress adjustments and crack-deflection effects of TiB whiskers contributed to the high shear strength of joints.

Yb3+/Tm3+ co-doped LiNbO3 crystals were proposed to explore the temperature sensing characteristics of non-thermally coupled levels from Tm3+ ions. The prepared polycrystal is opaque and single crystal is transparent. Under 980 nm excitation, upconversion spectra were investigated at different temperatures changed from 323 K to 773 K. It is found the deep red (3F2,3 → 3H6) and blue (1G4 → 3H6) or red (1G4 → 3F4) emissions of Tm3+ ions exhibit opposite temperature dependent behaviors, so their temperature sensing characteristics are studied. The results indicate the temperature sensitivity is mainly affected by crystallinity of host material and concerned energy levels of FIR (fluorescence intensity ratio). As a consequence, the maximum relative sensitivity of about 0.7% K−1 is achieved based on the non-thermally coupled levels of Tm3+ ion in LiNbO3 crystals. The polycrystal reveals more excellent temperature sensing properties in low temperature, and single crystal is more suitable for high temperature application. Moreover, it is discovered the stability of FIR with different powers greatly depends on the concerned energy levels. This work may contribute a feasible and expansible way to further survey the sensitivity of optical temperature sensor and promote its applications.

Co modified fly ash (FA) prepared by wet impregnation method were investigated for gas-phase elemental mercury capture under air at 80 °C in this paper. X-ray fluorescence spectrometry (XRF), Brunauer-Emmett-Teller (BET), scanning electron micrographs (SEM), X-ray diffraction (XRD), thermogravimetric (TG) analysis and X-ray photoelectron spectroscopy (XPS) were employed to characterize the samples. Experimental results showed that the optimal Co loading was 9 wt%, which performed Hg0 removal efficiency of 76% in a laboratory packed-bed reactor at low temperature in the presence of O2. The high removal efficiency was mainly attributed to oxidation of Hg0 by the enrichment of well-dispersed Co3O4 on the surface of FA. However, higher Co loading resulted in the decrease of removal efficiency due to the decline of surface area and Co3O4 agglomeration. TG and XPS characterization indicated that Hg0 was oxidized by Co3O4 and some of the oxidized mercury formed recombination mercury oxide with Co3O4, which could either be existed stably at low temperature or be desorbed from the adsorbents at higher temperature. Finally, the possible adsorption mechanisms were proposed according to the observed phenomena.