M-type strontium hexaferrite (SrFe12O19) particles had been prepared by a modified chemical co-precipitation route. Structural and magnetic properties were systematically investigated. Rietveld ...refinement of X-ray powder diffraction results showed that the sample was single-phase with the space group of P63/mmc and cell parameter values of a=5.8751 A and c=23.0395 A. The results of field-emission scanning electronic microscopy showed that the grains were regular hexagonal platelets with sizes from 2 to 4 mum. The composition determined by energy dispersive spectroscopy is the stoichiometry of SrFe12O19. The ferrimagnetic to paramagnetic transition was sharp with Curie temperature TC=737 K, which further confirmed that the samples were single phase. However, it was found that the coercivity, saturation magnetization and the squareness ratio of the synthesized SrFe12O19 samples were lower than the theoretical values, which could be explained by the multi-domain structure and the increase of the demagnetizing factor.
Hepatocellular carcinoma (HCC) often presents with multiple nodules within the liver, with limited effective interventions. The high genetic heterogeneity of HCC might be the major cause of treatment ...failure. We aimed to characterize genomic heterogeneity, infer clonal evolution, investigate RNA expression pattern and explore tumour immune microenvironment profile of multifocal HCC.
Whole-exome sequencing and RNA sequencing were carried out in 34 tumours and 6 adjacent normal liver tissue samples from 6 multifocal HCC patients. Protein expression of Ki67, AFP, P53, Survivin and CD8 was detected by immunohistochemistry. Fluorescence in situ hybridization was carried out to validate the amplification status of sorafenib-targeted genes.
We deciphered genomic and transcriptional heterogeneity among tumours in each multifocal HCC patient including mutational profiles, copy number alterations, tumour evolutionary trajectory and tumour immune microenvironment profiles. Of note, sorafenib-targeted alterations were identified in the trunk of phylogenetic tree in only one out of the six patients, which may explain the relative low treatment response rate to sorafenib in clinical practice. Moreover, we demonstrated RNA expression patterns and tumour immune microenvironment profiles of all nodules. We found that RNA expression pattern was associated with Edmondson–Steiner grading. Based on the differential expression of 66 reported immune markers, unsupervised hierarchical clustering analysis of 34 nodules identified immune subsets: one low expression cluster with seven nodules and one high expression cluster with 11 nodules. CD8+ T cells were more enriched in nodules of the high expression cluster.
Our study provided a detailed view of genomic and transcriptional heterogeneity, clonal evolution and immune infiltration of multifocal HCC. The heterogeneity of druggable targets and immune landscape might help interpret the clinical responsiveness to targeted drugs and immunotherapy for multifocal HCC patients.
► Effects of LSP on mechanical properties of stainless steel ANSI 304 are evaluated. ► LSP can clearly enhance the values of mechanical properties in the shocked region. ► Martensite transformation ...does not take place in the surface layer subjected to LSP. ► Enhancement mechanisms of LSP on mechanical property of stainless steel are revealed. ► The results can provide some insights on the surface modification of stainless steel.
The aim of this article is to address the effects of a single laser shock processing (LSP) impact on the nano-hardness, elastic modulus, residual stress and phase transformation of ANSI 304 austenitic stainless steel. Residual stress distribution of the LSP-shocked region is determined by X-ray diffraction (XRD) with sin
2
ψ method, and the micro-structural features in the near-surface layer are characterized by using cross-sectional optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). By comparing with the untreated samples, LSP can clearly improve nano-hardness, elastic modulus, and residual stress in the LSP-shocked region. The underlying enhancement mechanisms of LSP on nano-hardness, elastic modulus and residual stress of stainless steel ANSI 304 are also revealed. These studies may provide some important insights into surface modification for metal materials.
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► LSP can generate high-level compressive residual stresses and refine original grains. ► Massive LSP impacts can effectively prevent the SCC initiation of the U-bend sample. ► ...Mechanism of massive LSP impacts on SCC was also entirely revealed.
The effects of massive laser peening (LP) impacts on surface residual stress, micro-structure, and stress corrosion cracking (SCC) behaviour of U-bend samples were investigated by X-ray diffraction (XRD) technology, optical microscope (OM) and transmission electron microscope (TEM) observations. Two important factors to influence SCC initiation, residual stress and grain refinement, were discussed in detail by using different types of treatment processes. Results showed massive LP impacts can induce both deep compressive residual stress and refined grains in the surface layer of ANSI 304 stainless steel, and the corrosion mechanism of massive LP impacts on SCC was also analysed and revealed.
Abstract
Two-dimensional (2D) materials offer a prospect of membranes that combine negligible gas permeability with high proton conductivity and could outperform the existing proton exchange ...membranes used in various applications including fuel cells. Graphene oxide (GO), a well-known 2D material, facilitates rapid proton transport along its basal plane but proton conductivity across it remains unknown. It is also often presumed that individual GO monolayers contain a large density of nanoscale pinholes that lead to considerable gas leakage across the GO basal plane. Here we show that relatively large, micrometer-scale areas of monolayer GO are impermeable to gases, including helium, while exhibiting proton conductivity through the basal plane which is nearly two orders of magnitude higher than that of graphene. These findings provide insights into the key properties of GO and demonstrate that chemical functionalization of 2D crystals can be utilized to enhance their proton transparency without compromising gas impermeability.
► Weldments were done with laser shock processing impacts after cavitation erosion. ► Laser shock processing enhanced the erosion and corrosion resistance of weldments. ► Tensile residual stress and ...surface roughness decreased by laser shock processing. ► Microstructure was observed to explain the improvement by laser shock processing. ► Obvious passivation areas occurred with laser shock processing impacts.
Effects of laser shock processing (LSP) on electrochemical corrosion resistance of weldments after cavitation erosion were investigated by X-ray diffraction (XRD) technology, scanning electron microscope (SEM), roughness tester and optical microscope (OM). Some main factors to influence erosion and corrosion of weldments, residual stresses, surface roughness, grain refinements and slip, were discussed in detail. Results show that LSP impacts can induce compressive residual stresses, decrease surface roughness, refine grains and generate the slip. Thus, the erosion and corrosion resistance with LSP impacts is improved.
ABSTRACT
We have searched for weak fast radio burst (FRB) events using a data base containing 568 736 756 transient events detected using the Parkes radio telescope between 1997 and 2001. In order to ...classify these pulses, and to identify likely FRB candidates, we used a machine-learning algorithm based on ResNet. We identified 81 new candidate FRBs and provide details of their positions, event times, and dispersion measures. These events were detected in only one beam of the Parkes multibeam receiver. We used a relatively low S/N cut-off threshold when selecting these bursts and some have dispersion measures only slightly exceeding the expected Galactic contribution.
We therefore present these candidate FRBs as a guide for follow-up observations in the search for repeating FRBs.
•LSP can increase the wear resistance of TC11 under elevated temperature.•The test temperature and load have effect on tribological properties of TC11.•The wear mechanisms of TC11 are different under ...various sliding wear conditions.•The tribo-layers on the worn surface of the LSPed specimens are dense and uniform.
Titanium alloy is regarded as a high performance material which has wide application prospect in aerospace and medical field. However, their poor wear properties may lead to failures in early service stages. In this paper, the microstructure, micro-hardness and residual stress of TC11 alloy treated by laser shock peening (LSP) are investigated. The sliding wear experiments are performed to study the influence of various temperature and applied load on the wear behaviors of TC11 alloy with and without LSP. The results indicate that the LSPed specimen has a superior wear properties to that of as-received specimen under the same wear test conditions. The tribological properties are greatly dependent on wear testing temperature and applied load. For the specimens tested under 15 N, the variation trend of friction coefficient and wear rate reduces first (25–500 °C) and then increases (500–600 °C) with increasing the test temperature. When the sliding wear test conducted at 400 °C, the larger the applied load, the more the friction coefficient and wear rate. The prominent tribological performances of LSPed TC11 alloy is ascribed to the high compressive residual stress and grain refinement induced by LSP.
•Micro-dimple surface was subjected to laser shock peening with contacting foil.•Enclosure of micro cracks on bottom of micro dimple is found.•MLST+HCLSP treated sample reveals improved friction and ...wear performance.
The Ti6Al4V micro-dimple surfaces fabricated by a masked laser surface texturing (MLST) technique within water were subjected to soft contact laser shock peening (SCLSP) and hard contact laser shock peening (HCLSP). The effects of these two LSP methods on topography, micro-hardness and residual stress distribution were studied. The friction and wear performance under dry friction and oil lubrication were also studied. The enclosure of micro cracks in the micro-dimple bottom was observed when treated by SCLSP and HCLSP. The dry friction and wear test showed that the MLST+HCLSP surfaces had the best wear resistance performance. In the oil lubricated friction test, the occurrence of the hydrodynamic lubrication effect occurred on the micro-dimple surfaces. The MLST+HCLSP exhibited the best friction and wear resistance performance. These were due to the micro-hardness increase, the producing of compressive residual stress and the surface roughness reduction of as treated surfaces.
A class of high-order compact (HOC) exponential finite difference (FD) methods is proposed for solving one- and two-dimensional steady-state convection–diffusion problems. The newly proposed HOC ...exponential FD schemes have nonoscillation property and yield high accuracy approximation solution as well as are suitable for convection-dominated problems. The O(
h
4) compact exponential FD schemes developed for the one-dimensional (1D) problems produce diagonally dominant tri-diagonal system of equations which can be solved by applying the tridiagonal Thomas algorithm. For the two-dimensional (2D) problems, O(
h
4
+
k
4) compact exponential FD schemes are formulated on the nine-point 2D stencil and the line iterative approach with alternating direction implicit (ADI) procedure enables us to deal with diagonally dominant tridiagonal matrix equations which can be solved by application of the one-dimensional tridiagonal Thomas algorithm with a considerable saving in computing time. To validate the present HOC exponential FD methods, three linear and nonlinear problems, mostly with boundary or internal layers where sharp gradients may appear due to high Peclet or Reynolds numbers, are numerically solved. Comparisons are made between analytical solutions and numerical results for the currently proposed HOC exponential FD methods and some previously published HOC methods. The present HOC exponential FD methods produce excellent results for all test problems. It is shown that, besides including the excellent performances in computational accuracy, efficiency and stability, the present method has the advantage of better scale resolution. The method developed in this article is easy to implement and has been applied to obtain the numerical solutions of the lid driven cavity flow problem governed by the 2D incompressible Navier–Stokes equations using the stream function-vorticity formulation.
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