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The application of adhesively-bonded joints for strengthening of structures using iron-based shape memory alloys (Fe-SMAs) has recently emerged in construction. Fe-SMAs and the majority of structural adhesives exhibit a pronounced nonlinear material behavior, which may result in a favorable ductile failure mechanism. The development, however, of a mechanical model to predict the structural behavior of the joint is non-trivial due to the presence of nonlinearity in the adherent and adhesive. This study aims to propose a semi-analytical and semi-numerical model for describing the mechanical behavior of Fe-SMA-to-steel adhesively bonded joints. The developed model serves three main functions: (i) estimating the bond capacity for a given interfacial fracture energy, and vice versa; (ii) processing the bond–slip (τ−s) behavior directly from the load–displacement (F−Δ) curve, and vice versa; and (iii) delivering a numerical method to simulate the full-range mechanical behavior of the bonded joints, namely the behavior at different loading stages. The model is validated using the experimental testing of 26 Fe-SMA-to-steel lap-shear joints, as well as 24 further bonded joints subject to shear with different adherents (e.g., stainless steel strips and Nickel–Titanium SMA wires) and base materials (e.g., concrete and composite polymer). An experimental data processing protocol, on the basis of the experimentally measured force–displacement (F−Δ) behavior and the distributed displacement along the bond line (s−x) via the Digital Image Correlation (DIC) technique, is further proposed to assess the full-range behavior of bonded joints., Engineering Fracture Mechanics, 282, ISSN:0013-7944, ISSN:1873-7315

This work is the first systematic study on the static behavior of adhesively-bonded Fe-SMA-to-steel joints in applications adopting iron-based Shape Memory Alloys (SMAs). In order to provide a better understanding on the mechanical behavior of the adhesively bonded joint, an experimental campaign was established, involving 24 lap-shear tests in a displacement-controlled loading regime. The test series includes two types of Fe-SMAs (non-prestrained and prestrained), three types of adhesives (SikaDur 30, Araldite 2015, and SikaPower 1277), and three different thickness values (0.5, 1, and 2 mm) for the adhesive. A digital image correlation (DIC) technique was employed to measure the full-field displacement and strain, which were then used to infer the shear behavior. The mechanical behavior was analyzed on the basis of the experimentally derived load–displacement curves, the shear stress profiles along the bond line, and the bond–slip curves; three stages were observed during the loading process of a bonded joint: (i) a linear stage, (ii) a damage accumulation stage, and (iii) a debonding propagation stage. The test results indicate that a more ductile adhesive or a thicker adhesive layer possess a higher fracture energy, leading to a greater bond capacity. The results were also compared against those from lap-shear tests on carbon fiber reinforced polymer (CFRP) bonded joints. It is found that an Fe-SMA bond and a CFRP bond behave similarly when a linear adhesive is utilized; a nonlinear adhesive, however, results in significant mechanical differences between the two bonded joints, which merit individual analysis., Construction and Building Materials, 364, ISSN:0950-0618

TiO2/hectorite composite photocatalysts with different molar ratios of lithium, magnesium, and silicon were synthesized by a one-pot hydrothermal method. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherms, and ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS). When the molar ratio of lithium, magnesium, and silicon was 1.32:5.34:8 (TH-2), the composite showed the highest UV photocatalytic degradation of methylene blue (MB). The apparent rate constant of TH-2 was 0.04361 min−1, which was about 3.12 times that of EVONIK Degussa commercial TiO2 of AEROXIDE P25. The improvement of photocatalytic efficiency of the composite was mainly due to its high specific surface area, light trapping ability, and effective separation of electrons (e−) and holes (h+). At the same time, the F element of hectorite is beneficial to the formation of Ti3+ in TiO2, thus enhancing the photocatalytic activity. After five cycles, the removal rate of MB with TH-2 still reached 87.9%, indicating its excellent reusability.

Activating transcription factor 4 (ATF4) is a member of the basic leucine zipper (bZip) transcription factor family required for the terminal differentiation of osteoblasts. Despite its critical importance as one of the three main osteoblast differentiation transcription factors, regulators of osteoblast terminal maturation remain poorly defined. Here we report the identification of homologous pairing protein 2 (Hop2) as a dimerization partner of ATF4 in osteoblasts via the yeast two-hybrid system. Deletional mapping revealed that the Zip domain of Hop2 is necessary and sufficient to bind ATF4 and to enhance ATF4-dependent transcription. Ectopic Hop2 expression in preosteoblasts increased endogenous ATF4 protein content and accelerated osteoblast differentiation. Mice lacking Hop2 (Hop2-/- ) have a normal stature but exhibit an osteopenic phenotype similar to the one observed in Atf4-/- mice, albeit milder, which is associated with decreased Osteocalcin mRNA expression and reduced type I collagen synthesis. Compound heterozygous mice (Atf4+/- :Hop2+/- ) display identical skeletal defects to those found in Hop2-/- mice. These results indicate that Hop2 plays a previous unknown role as a determinant of osteoblast maturation via its regulation of ATF4 transcriptional activity. Our work for the first time reveals a function of Hop2 beyond its role in guiding the alignment of homologous chromosomes. © 2019 American Society for Bone and Mineral Research.

This paper investigates the fatigue repair of 15 central inclined cracked steel plates using different repair materials and prestress levels. Thirteen steel plates were repaired with three kinds of carbon fiber reinforced polymer (CFRP) and two kinds of adhesive in different configurations (single-sided, double-sided, non-prestressed and prestressed). Two unrepaired steel plates were used as the reference. Fatigue performance was evaluated using the fatigue life and the failure mode. It was found that when the tensile stiffness of distinct CFRP was identical, the fatigue lives of different specimens in the same configuration were alike regardless of the failure mode. Nevertheless, different CFRP and adhesives contributed strongly to the failure mode. Fatigue lives demonstrated that double-sided repair was more efficient than single-sided repair, while prestressed repair had the highest repair efficiency. When prestressed, higher prestress level led to greater fatigue life improvement. Besides, prestress levels measured from CFRP strain and steel plate strain were compared; the latter was found to be more consistent with the tested fatigue lives.

Previous experimental and numerical studies on central inclined cracked steel plates demonstrated that when the initial crack inclination angles range from 0° to 60°, fatigue lives are similar if the initial crack projection lengths on the direction perpendicular to the loading direction are the same. This is applicable to both unrepaired and repaired specimens. This numerical study extended the inclination angle range from 60° to 80° and was conducted on the stress intensity factor (SIF) and fatigue life of CFRP–repaired steel plates with inclined central cracks subjected to tensile fatigue loading. In the case of unrepaired specimens with a crack inclination angle of 0–70° and double-sided repaired specimens with a crack inclination angle of 0–60°, it was concluded that the crack projection length on the direction perpendicular to the loading axis is the main influence of fatigue life, even though the projection length is calculated from the crack length and inclination angle. Beyond these limits, there is an obvious increase of fatigue life as the crack inclination angle rises. To minimize the effect of mode II component of SIF on the crack tip, two tail slots perpendicular to the loading axis were induced in the front of the inclined crack tips. The tail slots caused the effective SIF to increase and this led to a reduction of fatigue life. However, the limits of the initial crack angle of fatigue life calculation did not change. The results of previous research were also compared to the findings of this study; they supported the conclusions to some extent.

The strengthening and repair of existing infrastructures, a large portion of which is comprised of steel structures, is essential for sustainable material use and energy resource management. Bonded strengthening using Carbon Fiber Reinforced Polymers (CFRPs) offers great potential toward a sustainable infrastructure management. In establishing CFRP retrofitting as a reliable solution for steel strengthening, a solid understanding of the mechanical behavior of the CFRP-to-steel bonded joints is essential. Given the variability in the evidence attained by experiments, in this study, we tackle this challenge from an uncertainty quantification perspective by proposing a model based on Polynomial Chaos Expansion (PCE) to predict the load capacity of the bonded joints. A stochastic bond–slip model, featuring a parsimonious representation with one deterministic coefficient and one probabilistic coefficient, is further proposed. A Monte-Carlo (MC) simulation is used to demonstrate the efficacy of the bond–slip model in predicting the mechanical behavior such as load–displacement behavior, shear stress profile, and effective bond length of strengthened specimens. Results are compared with existing deterministic models., Engineering Structures, 266, ISSN:0141-0296

Speech research should use relativized data in order to effectively eliminate differences caused by external factors such as gender and age, and the research results obtained will have universal significance. The T-value method is a method of relativization and normalization of pitch data proposed by Shi Feng. The core of the algorithm is to remove the specific unit of the fundamental frequency data to make it a dimensionless percentage ratio, which is convenient for statistical analysis. Pitch is the primary factor to determine the tone, and fundamental frequency is the physical quantity of pitch. Based on the T-value method, this study compiles a Matlab program to process the fundamental frequency data of more than 1500 samples extracted in the acoustic experiment at equal distances, and then calculates the five degree value to determine the tone value of Renbu dialect. In addition, the tone type and length of Renbu dialect are determined according to the mean value of fundamental frequency and duration. After statistical analysis, this study believes that there are 6 tone phonemes in Renbu dialect, with tone values of 53, 51, 44, 33, 231, and 224, which have a strong phoneme value in the Tibetan tone system and can assume independent semantic discrimination function under certain conditions.

Many studies exist on carbon fiber-reinforced polymer (CFRP) strengthening of cracked steel details (e.g., cracks in riveted or welded bridge connections). The majority of these studies us...

An experimental study was conducted on central-cracked steel plates with different crack inclination angles that had been repaired with carbon fiber reinforced polymer (CFRP) strand sheets. Initial cracks with five different inclined angles (0–60°) were artificially induced from a central hole of steel plates. All the cracks had the same projection length, running perpendicular to the loading axis. Crack lengths, crack trajectories, failure modes and the effects of different repair configurations were investigated, and fatigue crack propagation lives were compared. A typical adhesive failure mode, oblique compression failure in the adhesive layer, was observed. A conclusion was drawn that fatigue life was directly determined by the projection length, while the projection length was calculated from the initial crack length and inclination angle. The average fatigue life extension ratio of specimens with single-sided repairs was 1.44; that of specimens with double-sided repairs was 3.03.

In this paper, we report on the microstructural evolution and mechanical properties of a 5052 Al alloy processed by rotationally accelerated shot peening (RASP). A thick deformation layer of ∼2 mm was formed after the RASP process. Nano-sized grains, equiaxed subgrains, and elongated subgrains were observed along the depth of the deformation layer. Dislocation accumulation and dynamic recrystallization were found primarily responsible for the grain refinement process. An obvious microhardness gradient was observed for all of the samples with different RASP processing parameters, and the microhardness in the top surface of 50 m/s-5 min RASP-processed sample is twice that of its coarse-grained (CG) counterpart. The yield strengths of the RASP-processed 5052 Al alloy samples were 1.4–2.6 times that of CG counterparts, while retaining a decent ductility (25–84% that of CG). The superior properties imparted by the gradient structure are expected to expand the application of the 5052 Al alloy as a structural material.

An innovative fatigue strengthening solution for metallic structures that takes advantage of the shape memory effect of an iron-based shape memory alloy (Fe-SMA) and the bridging mechanism offered by the bonding technique has been proposed and examined. Fatigue tests on cracked steel plates with bonded carbon fiber-reinforced polymer (CFRP) and nonprestressed and prestressed Fe-SMA strips were conducted. The experimental results demonstrate that the bonded prestressed Fe-SMA strips are much more effective than CFRP strips, extending the fatigue crack growth life by a factor of 3.51. The proposed innovative solution is highly effective in retarding fatigue crack growth in metallic structures. ISSN:0142-1123 ISSN:1879-3452

This study aims to evaluate the repair performance of central-notched steel plates reinforced by the self-prestressing shape memory alloy carbon fiber reinforced polymer patching system (SMA/CFRP patch) through the numerical and theoretical study of the fatigue life after experimental fatigue life results were validated with the numerical method. These methods were used to determine the effectiveness of the reinforcing technique. Different widths of SMA/CFRP patches, elastic modulus of CFRP, prestress level, initial damage degree and crack type were considered as parameters that influenced the repair effectiveness. The outcomes showed that the increase in the Young’s modulus, prestress level and width could significantly improve the fatigue life of central-notched steel plates. The effect of the prestress level was more prominent with wider width. Good agreement with the test data revealed that numerical and theoretical methods could predict the fatigue life with reasonable accuracy, and the strengthening was more effective for edge-cracked specimens than central-cracked specimens.

Carbon fiber reinforced polymer (CFRP) repairing is an important approach to improve fatigue performance of cracked steel structures. Based on experiment and finite element method (FEM), the crack propagation and fatigue live of CFRP repaired steel plates with multi-holes were studied. The test results showed that the fatigue life of the steel plate could be reduced by the existence of multi-holes, and after being repaired with CFRP, the corresponding fatigue life was significantly improved. The multi-holes had a considerable effect on crack propagation trajectory and fatigue life, the main influencing factors were the number and location of the multi-holes. Further finite element analysis showed that the effect of the multi-holes on crack growth was mainly related to the change of the stress intensity factors ΔKI and ΔKII.

In this paper, the effects of carbon fiber reinforced polymer (CFRP) repairing on fatigue life improvement of center cracked steel plates was intensively studied. Generally, stress intensity factors (SIFs) were calculated using numerical approaches and employed to predict fatigue cycles via classical crack propagation models. We proposed a practical SIF formula based on thorough finite element (FE) analysis of 1254 CFRP-repaired specimens. The analyses were carried using Python Script in order to achieve a high FE modeling and calculating efficiency. A correction coefficient Fc, representing the CFRP repairing effect, was introduced in the formula to calculate SIFs at the crack tip. Thereafter, the formula were employed to predict the fatigue lives of CFRP repaired steel plates together with the Elber model. Good consistency was achieved with test results.

Scanning electron microscopy transmission Kikuchi diffraction is able to identify twins in nanocrystalline material, regardless of their crystallographic orientation. In this study, it was employed to characterize deformation twins in Cu/10 wt % Zn processed by high-pressure torsion. It was found that in 83% of grains containing twins, at least one twin intersects with a triple junction. This suggests that triple junctions could have promoted the nucleation of deformation twins. It should be cautioned that this technique might be unable to detect extremely small nanoscale twins thinner than its step size.

The survival rate of glioma patients is very low, and a lack of effective diagnostic techniques are available at present. The current study aimed to investigate the expression of p16 and Survivin and their association with proliferation and apoptosis in gliomas, as well as patient characteristics and prognosis. In total, 62 glioma specimens were surgically resected and pathologically confirmed at the Zhumadian Central Hospital (Zhumadian, China) between June 2008 and February 2014. Clinical data, including the gender and age of the patients, as well as the location, infiltration degree, size and pathological stage of the glioma, was collected. In order to evaluate the expression of p16 and Survivin in the gliomas, the Ki-67 labeling index was used to evaluate cell proliferation activity. The number of argyrophilic nucleolar organizer regions and the rate of cellular apoptosis was examined using the terminal deoxynucleotidyl transferase dUTP nick end labeling method. The results were analyzed using SPSS 14.0 statistical software. The positive rate of p16 gene expression in the gliomas was 46.77% (29 cases), and p16 gene expression was positively correlated with the differentiation status, tumor size and pre-operative symptoms. The positive rate of Survivin expression in the gliomas was 69.88% (58 cases), and Survivin expression was positively correlated with tumor size, differentiation status and clinical stage. The proliferation activity of the gliomas was enhanced with increasing p16 and Survivin expression, while apoptosis was inhibited. In conclusion, the overexpression of p16 and Survivin was closely associated with uncontrolled cell proliferation and the inhibition of apoptosis in gliomas. The combined analysis of the expression of p16 and Survivin in gliomas may provide guidance with respect to the clinical diagnosis, evaluation, treatment and prognosis of patients with glioma.