Experimental investigation on the flexural behavior of concrete reinforced by various types of steel fibers

The benefit of steel fiber on the mechanical behaviors of concrete has been well accepted. The flexural behavior of steel fiber reinforced concrete (SFRC) is complicated which depends on many factors, such as matrix properties, fiber material properties, fiber geometries, fiber volume contents, and interface properties. Thus, the investigations on the flexural behavior of SFRC are needed to be expanded. In this study, the effects of fiber type with varying shapes and aspect ratios on the flexural performance of SFRC were investigated. Five steel fibers were adopted in this study: milled fiber (M), corrugated fiber (C) and three hooked fibers with aspect radios of 45 (HA), 55 (HB), and 65 (HC). Two volume fractions (0.4% and 1.0%) of steel fiber and two compressive strengths (normal and high strengths) of matrix were considered. The load-deflection curves, energy absorption capacity and equivalent flexural strength were discussed. The results show that the flexural behavior of SFRC beams reinforced by 1.0% fibers is significantly higher than that of the beams reinforced by 0.4% fibers. Hooked fiber reinforced beams performed the best flexural load-deflection response compared to the beams reinforced by milled fiber and corrugated fiber reinforced, and exhibited an increasing trend of flexural performance as the fiber aspect ratio increased. The differences between specimens with different fibers for high strength matrix are more obvious compared to the normal strength matrix

Robust Amphiphobic Few-Layer Black Phosphorus Nanosheet with Improved Stability.

Few-layer black phosphorus (FL-BP) has been intensively studied due to its attractive properties and great potential in electronic and optoelectronic applications. However, the intrinsic instability of FL-BP greatly limits its practical application. In this study, the amphiphobic FL-BP is achieved by functionalization of 1 H ,1 H ,2 H ,2 H -perfluorooctyltrichlorosilane (PFDTS) on the surface of FL-BP. The obtained PFDTS coated FL-BP (FL-BP/PFDTS) demonstrates enhanced stability, which is not observed during significant degradation for 2 months in high moisture content environment (95% humidity). Particularly, attributing to the surface amphiphobicity, FL-BP/PFDTS exhibits strong surface water repellency in the presence of oleic acid (as the contaminant), while other passivation coating layers (such as hydrophilic or hydrophobic coating) become hydrophilicity under such conditions. Owing to this advantage, the obtained FL-BP/PFDTS demonstrates enhanced stability in high moisture content environment for 2 months, even though the surface is contaminated by oil liquid or other organic solvents (such as oleic acid, CH2Cl2, and N -methyl-2-pyrrolidone). The passivation of FL-BP by amphiphobic coating provides an effective approach for FL-BP stabilization toward future applications

Monitoring the Process of Endostar-Induced Tumor Vascular Normalization by Non-contrast Intravoxel Incoherent Motion Diffusion-Weighted MRI

Tumor vascular normalization has been proposed as a new concept in anti-tumor angiogenesis, and the normalization window is considered as an opportunity to increase the effect of chemoradiotherapy. However, there is still a lack of a non-invasive method for monitoring the process of tumor vascular normalization. Intravoxel incoherent motion diffusion-weighted magnetic resonance imaging (IVIM DW-MRI) is an emerging approach which can effectively assess microperfusion in tumors, without the need for exogenous contrast agents. However, its role in monitoring tumor vascular normalization still needs further study. In this study, we established a tumor vascular normalization model of CT26 colon-carcinoma-bearing mice by means of Endostar treatment. We then employed IVIM DW-MRI and immunofluorescence to detect the process of tumor vascular normalization at different times after treatment. We found that the D* values of the Endostar group were significantly higher than those of the control group on days 4, 6, 8, and 10 after treatment, and the f values of the Endostar group were significantly higher than those of the control group on days 6 and 8. Furthermore, we confirmed through analysis of histologic parameters that Endostar treatment induced the CT26 tumor vascular normalization window starting from day 4 after treatment, and this window lasted for 6 days. Moreover, we found that D* and f values were well correlated with pericyte coverage (r = 0.469 and 0.504, respectively; P < 0.001, both) and relative perfusion (r = 0.424 and 0.457, respectively; P < 0.001, both). Taken together, our findings suggest that IVIM DW-MRI has the potential to serve as a non-invasive approach for monitoring Endostar-induced tumor vascular normalization

Experimental study on the properties of corroded steel fibres

In this study, low carbon steel fibres were corroded to various corrosion degrees by cycling in 3.5% NaCl solution and 60 °C oven, and by applying a designed current density of 20 mA/cm2. Then the corrosion characters and corrosion degree on tensile strength of the two types of corroded steel fibres were investigated. It was found that the cycles induce pitting and the current induces relatively uniform corrosion. The results of tensile test show that the actual tensile strength of steel fibres was reduced in the case of pitting, while it was marginally affected by uniform corrosion. As the corrosion degree increased, both of the nominal tensile strength and elongation of the two types of corroded steel fibres decreased. In addition to weight loss, local section loss at the pits is the main reason for further degradation of the mechanical properties of steel fibres and gives a brittle failure

Bert-Based Chinese Medical Keyphrase Extraction Model Enhanced with External Features

Keyphrase extraction is a key natural language processing task and has widespread adoption in many information retrieval and text mining applications. In this paper, we construct nine Bert-based Chinese medical keyphrase extraction models enhanced with external features and present a thorough empirical evaluation to explore the impacts of feature types and feature fusion methods. The results show that encoding part-of-speech (POS) feature and lexicon feature generated from descriptive keyphrase metadata into the word embedding space improves the baseline Bert-SoftMax model for 4.82%, meaning that it’s beneficial to incorporate features into Chinese medical keyphrase extraction model. Furthermore, the results of the comparative evaluation experiments show that model performance is sensitive to both of feature types and feature fusion methods, so it’s advisable to consider these two factors when dealing with feature enhanced tasks. Our study also provides a feasible approach to employ metadata, aiming to help stakeholders of digital libraries to take full advantage of large quantities of metadata resources to boost the development of scholarly knowledge discovery.</p

Design and Implementation of Keyphrase Extraction Engine for Chinese Scientific Literature

Accurate keyphrases summarize the main topics, which are important for information retrieval and many other natural language processing tasks. In this paper, we construct a keyphrase extraction engine for Chinese scientific literature to assist researchers in improving the efficiency of scientific research. There are four key technical problems in the process of building the engine: how to select a keyphrase extraction algorithm, how to build a large-scale training set to achieve application-level performance, how to adjust and optimize the model to achieve better application results, and how to be conveniently invoked by researchers. Aiming at the above problems, we propose corresponding solutions. The engine is able to automatically recommend four to five keyphrases for the Chinese scientific abstracts given by the user, and the response speed is generally within 3 seconds. The keyphrase extraction engine for Chinese scientific literature is developed based on advanced deep learning algorithms, large-scale training set, and high-performance computing capacity, which might be an effective tool for researchers and publishers to quickly capture the key stating points of scientific text.</p

Calculation method of bond strength between rebar and steel fibre reinforced concrete

According to the significant deformation and crack propagation of steel fibre reinforced concrete (SFRC), the expression of hoop elongation for SFRC is established. Furthermore, the calculation method of bond strength between rebar and SFRC is proposed by the elasticity theory, fictitious crack theory and post-cracking softening model. The method is verified by the test results. The effects of relative cover thickness (ratio of concrete cover to rebar diameter), crack number and rebar diameter on the relative bond strength (ratio of bond strength to SFRC tensile strength) are analyzed. The results show that the relative bond strength of rebar embedded in SFRC is between plastic solution and partially elastic solution. Within 0.5% - 1.0% volumetric ratio of steel fibre, the relative bond strength increases with the increase of relative cover thickness and crack number, but reduces with the increase of rebar diameter. However, when the crack number is more than 5 or the rebar diameter is more than 32 mm, the variations of crack number and rebar diameter have insignificant effects on the relative bond strength

Atmospheric Optical Turbulence Characteristics over the Ocean Relevant to Astronomy and Atmospheric Physics

Due to the space and time constraints of turbulence measurement equipment and the experiment scene, it is difficult to obtain the atmosphere refractive index structure constant over the ocean. In this paper, the characteristics of atmospheric optical turbulence in offshore and open ocean conditions are summarized by analyzing the meteorological data obtained from two ocean atmospheric optical parameter field experiments. Because of the influence of land undersurface, the turbulence strength in offshore conditions is roughly the same as that on land and presents different characteristics in open ocean. Compared with the offshore area, the turbulence strength over the open ocean near-surface decreases during the day and increases at night, and the diurnal variation characteristics weaken. The turbulence strength profiles over the offshore area show different characteristics at different times, where the turbulence strength in the morning is higher than that in the evening. By retrieving the meteorological factors affecting the turbulence, it is found that the temperature gradient and wind shear are in good agreement with turbulence strength in both offshore and open ocean areas. Furthermore, the integrated parameters for astronomy and optical telecommunication are derived from profiles over the offshore and open ocean areas. It is of great significance to research the turbulent characteristics of ocean atmosphere for optical transmission and astronomical observations