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In this study, the uniaxial compression and cyclic loading and unloading experiments were conducted on the non-water reactive foaming polyurethane (NRFP) grouting material with a density of 0.29 g/cm3, and the microstructure was characterized using scanning electron microscope (SEM) method. Based on the uniaxial compression and SEM characterization results and the elastic-brittle-plastic assumption, a compression softening bond (CSB) model describing the mechanical behavior of micro-foam walls under compression was proposed, and it was assigned to the particle units in a particle flow code (PFC) model simulating the NRFP sample. Results show that the NRFP grouting materials are porous mediums consisting of numerous micro-foams, and with the increasing density, the diameter of the micro-foams increases and the micro-foam walls become thicker. Under compression, the micro-foam walls crack, and the cracks are mainly perpendicular to the loading direction. The compressive stress–strain curve of the NRFP sample contains the linear increasing stage, yielding stage, yield plateau stage, and strain hardening stage, and the compressive strength and elastic modulus are 5.72 MPa and 83.2 MPa, respectively. Under the cyclic loading and unloading, when the number of cycles increases, the residual strain increases, and there is little difference between the modulus during the loading and unloading processes. The stress–strain curves of the PFC model under uniaxial compression and cyclic loading and unloading are consistent with the experimental ones, well indicating the feasibility of using the CSB model and PFC simulation method to study the mechanical properties of NRFP grouting materials. The failure of the contact elements in the simulation model causes the yielding of the sample. The yield deformation propagates almost perpendicular to the loading direction and is distributed in the material layer by layer, which ultimately results in the bulging deformation of the sample. This paper provides a new insight into the application of the discrete element numerical method in NRFP grouting materials.

Graphene oxide (GO) has been widely used to enhance the tensile/compressive strength of cement-based materials, whereas its shear reinforcing effect is still unknown. To verify the feasibility of GO as a shear reinforcement material, the shear reinforcing effect of GO on cement was experimentally investigated. The nanoscale Young’s modulus (E) of the GO-enhanced cement was measured with the peak force quantitative nanomechanical mapping method to clarify the enhancing mechanism. Results show that the addition of 0.02 and 0.04 wt% GO in cement could improve the shear strength by about 12 and 40%, respectively, which is mainly due to the enhanced cohesion, and at the nanoscale, the average E of the low-density hydration product increased by 1.6 and 13.2%, whereas that of high-density hydration product remains almost unchanged. There exist fewer nanoholes/cracks and unhydrated cement grains but more the high-density hydration product in GO-enhanced cement, implying a denser microstructure and higher hydration degree. GO can enhance the shear strength of cement because of its enhancing effects on the microstructure, nanoscale Young’s modulus of hydration products, as well as the hydration degree.

Two-component foaming polymer (TFPU) grouting material is increasingly used in civil engineering. Its compressive strength is key to achieving the desired enhancing effect. The constitutive model of TFPU grouting material is a theoretical basis to evaluate the strength performance, which, however, is not fully understood. Here the uniaxial compression experiment of TFPU samples of different densities (0.11–0.53 g·cm−3) was conducted. Based on the stress–strain curves, the damage evolution equation of each sample was obtained by function fitting, followed by the establishment of statistical damage constitutive model. The model was simplified to a universal function with density as the argument. Results show that the stress–strain curves contain the initial compression stage, linear elastic stage, yield stage, yield plateau stage, and strain hardening stage regardless of the varied density. The variation laws of the damage with strain conform to the form of first-order decay exponential function. The theoretical stress–strain curves are in good agreement with the experimental ones, indicating that the statistical damage constitutive model can well reflect the mechanical behavior of TFPU grouting material. With this constitutive model, the mechanical properties of TFPU grouting material can be obtained according to the density alone, which is more convenient for practical engineering applications.

The scaled boundary finite element method(SBFEM) is a semi-analysis method, combing the advantages of boundary element method and finite element method. However, in solving the quadruple corner-cut ridged elliptical(QCRE) waveguide, the traditional SBFEM employ the Lagrange polynomials as the basis functions which leads to the curved boundaries cannot be exactly represented and the continuity order across element is low. In this paper, a non-uniform rational B-spline (NURBS) enhanced SBFEM is firstly extended to solve the QCRE waveguide, which can exactly describe the curved boundaries, reduce the spatial dimensions by one and obtain analytically results in the radial direction. According to its symmetry, only a quarter of the ridged elliptical waveguide needs to be simulated and subdivided into several subdomains. The curved boundaries and straight boundaries of the subdomains are described and discretized by the NURBS and Lagrange basis functions, respectively. The side-face boundaries do not need to be discretized. Then, the NURBS enhanced SBFEM governing equation of the waveguide eigenvalue problem is derived based on the vibrational principle and scaled boundary coordinate transforming. Finally, a generalized eigenvalue equation respecting to the cut-off wave numbers is established by introducing the boundary dynamic stiffness and employing a continued fraction solution. Numerical results verify the high computational efficiency and accuracy of the NURBS enhanced SBFEM with exactly describing the curved boundaries. The influence of the corner-cut on the cut-off wave numbers of several modes and single-mode bandwidth are investigated in details.

Carbon nanomaterials, predominantly carbon nanofibers, carbon nanotubes, graphene, graphene nanoplates, graphene oxide and reduced graphene oxide, possess superior chemical, physical and mechanical properties. They have been successfully introduced into ordinary Portland cement to give enhancements in terms of mechanical properties, durability and electrical/thermal conductivity, and to modify the functional properties, converting conventional cement-based materials into stronger, smarter and more durable composites. This paper provides a comprehensive review of the properties of carbon nanomaterials, current developments and novel techniques in carbon nanomaterials enhanced cement-based composites (CN-CBCs). Further study of the applications of CN-CBCs at industrial scale is also discussed.

Multi-walled carbon nanotubes (MWCNTs) have been added in the plain cementitious materials to manufacture composites with the higher mechanical properties and smart behavior. The uniform distributions of MWCNTs is critical to obtain the desired enhancing effect, which, however, is challenged by the high ionic strength of the cement pore solution. Here, the effects of methylcellulose (MC) on stabilizing the dispersion of MWCNTs in the simulated cement pore solution and the viscosity of MWCNT suspensions werestudied. Further observations on the distributions of MWCNTs in the ternary cementitious composites were conducted. The results showed that MC forms a membranous envelope surrounding MWCNTs, which inhibits the adsorption of cations and maintains the steric repulsion between MWCNTs; thus, the stability of MWCNT dispersion in cement-based composites is improved. MC can also work as a viscosity adjuster that retards the Brownian mobility of MWCNTs, reducing their re-agglomerate within a period. MC with an addition ratio of 0.018 wt.% is suggested to achieve the optimum dispersion stabilizing effect. The findings here provide a way for stabilizing the other dispersed nano-additives in the cementitious composites.

OBJECTIVE To investigate the incidence of and risk factors for early cerebrospinal fluid (CSF) leak after anterior surgery for degenerative cervical myelopathy (DCM) and construct risk predictive models.METHODS Patients diagnosed with DCM and treated with anterior surgery from January 2007 to August 2018 were retrospectively selected. The basic data of preoperative and intraoperative records were extracted. Subsequently, we analyzed the relationship between early postoperative CSF leak and variables by performing restrictive cubic splines (RCS) for continuous variables and univariate and multivariate logistic regression for possible variables. The selected independent variables and covariates were modeled based on the Akaike information criterion (AIC). We generated receiver operating characteristic (ROC) curves and calibration curves to evaluate the nomogram. RESULTS Seventeen patients had CSF leak, with an incidence of 3.66%. There was a linear relationship between CSF leak and age (P=0.003) as well as bleeding loss (PCONCLUSIONS Older age, revision surgery, OPLL and more intraoperative blood loss were independent risk factors for early postoperative CSF leak. The predictive model can be used to guide the prevention of CSF leak in DCM patients.

In Analog-to-Digital Converter (ADC) spectrum measurement, the realization of coherent sampling is difficult to implement, which has always been one of the bottlenecks. When coherent sampling is not available, researchers have been looking for some precise methods to test high-resolution ADCs under non-coherent sampling conditions. This study introduces two algorithms to, respectively, resolve harmonic distortion and ADC amplitude clipping problems with non-coherent sampling based on the idea of replacement. In algorithm 1, in order to accurately depict a signal spectrogram with harmonics under non-coherent sampling, signal fundamental and harmonics are basically estimated twice, a rough estimate and a fine estimate to get accurate values, and then they are replaced by a coherent sampling spectrum. In algorithm 2, we first determine the sampling period, then propose a three-parameter approach to calculate parameters of clipped signal, analyze and correct the parameter error, and finally apply the corresponding idea signal to replace the clipped signal. This paper proves the two algorithms’ superiority through a lot of simulation results, such as 12-bit, 14-bit, and 16-bit ADC tests. Finally, we process the experiment on the ADC chip automatic test system to obtain 16-bit AD9268 spectrum data and verify the effectiveness of the two algorithms. The two algorithms correct the spectrum error caused by non-coherent sampling and clipping, ideally suitable for high-resolution ADCs.

The prominent dispersibility of graphene oxide (GO) and superior mechanical properties of multi-walled carbon nanotubes (MWCNTs) make them potential materials for reinforcing cementitious composites. The aims of this study were to investigate the effectiveness and mechanisms of GO/MWCNT admixtures on the impermeability of cementitious composites. Comparative tests concerning the transport properties between plain cement pastes and GO/MWCNT-OPC pastes at different water-to-cement (W/C) ratios were conducted in this study. Mercury intrusion porosimetry (MIP) tests were carried out to characterize the pore structures of the cement pastes, and the fractal dimensions were utilized to exploit the relationship between the pore structures and permeability-related properties. Power’s model, general effective media (GEM) theory, and scanning electron microscopy (SEM) images were used to illustrate the mechanism of pore structure enhancement. The results imply that mixing GO/MWCNTs into cementitious composites enhances the impermeability of hardened pastes, and the reinforcing efficiency rate in impermeability decreases linearly with the increment of W/C ratio. The fractal dimensions based on the MIP data characterized the pore structures and predicted the transport properties with considerable accuracy. Furthermore, the role of GO/MWCNTs as nucleating sites for hydration reaction and net-like distribution in the composites may explain the impermeability enhancement mechanism induced by the additional GO/MWCNTs. However, GO/MWCNTs tend to re-agglomerate due to the longer setting times at high W/C ratios and lead to a nonuniform distribution of hydration products, which is responsible for the incompetent reinforcing effects.

BACKGROUND: Long non-coding RNAs (lncRNAs) have recently been found to be vital regulators of various cancers, including colorectal cancer (CRC). It has been previously reported that the dysregulated expression of lncRNA Five prime to Xist (FTX) is involved in carcinogenesis. However, the role of lncRNA FTX in the progression of CRC is still unclear. METHODS: Fluorescence in situ hybridization (FISH) was used to detect the expression of lncRNA FTX and miR-214-5p in CRC tissues. Cell Counting Kit-8 assay, transwell assay, wound-healing assay, and proliferation assay were used to explore the function of lncRNA FTX in CRC cells. Quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and luciferase reporter assay were used to confirm the relationship between lncRNA FTX and miR-214-5p–jagged canonical Notch ligand 1 (JAG1). We further explored the role of lncRNA FTX in vivo using xenograft tumor assay. RESULTS: lncRNA FTX was found to be upregulated in CRC tissues by FISH. The downregulation of endogenous lncRNA FTX expression inhibited CRC cell proliferation, migration, and invasion. Mechanistically, lncRNA FTX sequestered miR-214-5p and thus released its repression on JAG1, driving the malignant progression of CRC. CONCLUSIONS: These findings give rise to a new perspective, the lncRNA FTX–miR-214-5p–JAG1 regulatory axis, in exploring the cancer-promoting mechanism of lncRNA FTX in CRC.

[Objective]To evaluate the long-term efficacy of Coflex interspinous process dynamic stabilization device in the treatment of lumbar spinal stenosis.[Methods]The clinical and imaging data of 73 patients undergoing Coflex interspinous process dynamic stabilization surgery from July 2008 to June 2012 were retrospectively analyzed. Clinical data include: visual analogue scale of pain (VAS), Owestry disability index(ODI) and Japanese Orthopedic Association Scores(JOA) of preoperation, 6 months after surgery, and last follow-up; complications; reoperation rates and incidence of adjacent segment degeneration(ASD). Imaging data including: lumbar range of motion(ROM), intervertebral space height(ISH) and intervertebral foramen height (IFH) of operative and adjacent segment at preoperative, 6 months after operation and the last follow-up.[Results]56 patients were followed up. The follow-up time was 107.6 ± 13.3 months, the operation time was 10.0 ± 3.1 minutes, the intraoperative blood loss was 153.9 ± 80.6 ml, and the hospitalization time was 10.2 ± 3.2 days. The VAS, ODI and JOA scores improved significantly after surgery. At 6 months after surgery and the last follow-up, ROM was significantly lower than that before surgery with statistical significance (P 0.05). The ROM of adjacent segments increased at 6 months and at the last follow-up compared with that before surgery, but the difference was not statistically significant (P > 0.05). At 6 months after surgery, ISH and IFH of implanted segment was significantly higher than that before surgery, and the difference was statistically significant (P

Microcapsules were constructed with starch sodium octenyl succinate (SSOS), β-cyclodextrin (β-CD), and pectin walls and peony seed oil cores. A rheological phenomenon occurred in which the emulsion initially behaved like a shear-thickening fluid and then a shear-thinning fluid within a shear range. The emulsion exhibited good stability under low amplitude stress; however, as amplitude increased the concentration of pectin played an important role in maintaining the stability of the emulsion system. The optimum embedding yield of peony seed oil (92.5%) was achieved with a ratio of 70% SSOS, 22.5% β-CD, and 7.5% pectin. This ratio produced 4.521 μm particles with the lowest surface-oil content (2.60%) and moisture content (1.76%). The peony seed oil microcapsules were spherical with smooth surfaces and a synchronous thermogravimetric analysis showed they possessed good thermal stability. Encapsulation increased the induction period to 5-7 times that of unencapsulated peony seed oil.

Wearable devices have now been widely used in the acquisition and measurement of heart sound signals with good effect. However, the wearable heart sound acquisition system (WHSAS) will face more noise compared with the traditional system, such as Gaussian white noise, powerline interference, colored noise, motion artifact noise, and lung sound noise, because users often wear these devices for running, walking, jumping or various strong noise occasions. In a strong noisy environment, WHSAS needs a high-precision segmentation algorithm. This paper proposes a segmentation algorithm based on Variational Mode Decomposition (VMD) and multi-wavelet. In the algorithm, various noises are layered and filtered out using VMD. The cleaner signal is fed into multi-wavelet to construct a time–frequency matrix. Then, the principal component analysis method is applied to reduce the dimension of the matrix. After extracting the high order Shannon envelope and Teager energy envelope of the heart sound, we accurately segment the signals. In this paper, the algorithm is verified through our developing WHSAS. The results demonstrate that the proposed algorithm can achieve high-precision segmentation of the heart sound under a mixed noise condition.

Polymer-modified cement mortar (PMCM) composite materials have drawn the attention of researchers worldwide because of their excellent capabilities such as crack resistance, durability, simple construction process, and cost-effectiveness. This paper investigates current research on the enhancement effect of adding polymers in ordinary cement mortar (OCM) composites. The main study areas include material fabrication, workability, mechanical properties, durability, microstructure, and application of PMCM composite materials. Literature research shows that the properties of OCM could be improved significantly with the variation of polymer types and concentrations in the composition of PMCM, making PMCM versatile in applications. Compared with OCM, PMCM has enhanced crack resistance, impermeability, and durability with the addition of polymers. Finally, this paper introduces the application of PMCM, and discusses the prospects and challenges of PMCM composite materials.

The mechanical properties of the roadbed rehabilitation polyurethane (PU) grouting materials subjected to different chemical corrosion are the theoretical basis for evaluating the long-term performance, which, however, is not clear yet. Here, the PU grouting materials with different densities were immersed in water, H2SO4, HCl, and NaOH solutions for different times, followed by the P-wave velocity tests and uniaxial compression tests. The influences of different corrosion environments on the damage and uniaxial compressive strength of PU samples were analyzed, and the statistical damage constitutive model under the coupling effects of chemical corrosion and the external load was established. Results show that the water brings little influence whereas both the acid and alkaline environments degrade the strength of PU grouting materials, and the longer the chemical corrosion time is, the greater the decrease in strength. The maximum declines in the yield strength of PU samples corroded by H2SO4, HCl, and NaOH solutions are about 32.8%, 31.3%, and 21.4%, respectively. The theoretical stress–strain curves based on the statistical damage constitutive model are in agreement with the experimental ones before yielding (with the average difference of 0.077–1.017 MPa), indicating the rationality of the theoretical model.

Plate shaped sandstones containing two fabricated circular holes that were filled with gypsum and high-strength concrete respectively were prepared for studying the effects of ligament length L ligament incline angle α, as well as filling modes on their strength properties and failure modes. The results show that the initial cracks can be categorized as wing crack, axial tensile crack and curved tensile crack. The failure modes of ligaments can be categorized as mode of single inclined crack, mode of single axial crack and mode of two parallel cracks. The final failure modes of all specimens can be categorized as the tension-shear mixed failure and shear failure. The strength of inclusions shows little influence on the final failure modes of specimens, while the failure modes vary with L and α. When α is a fixed value, the peak strength σ c and elastic modulus E c of tested specimens increase firstly with increasing L and reaches to the maximum value at L of 16 mm, then declines. When L is a fixed value, σ c declines firstly and then turns to increase as α increases to 75° from 45°, while E c increases linearly. The axial stress σ p performs the similar variation trends with those of σ c versus increasing L and α when ligaments fail.

The uniaxial compression experiments on the sandstone samples containing double fissures and a single circular hole were carried out by using electro-hydraulic servo universal testing machine to investigate the effect of rock bridge angle β and fissure angle α on mechanical properties and evolution characteristics of cracks. The results show that the peak strength, peak strain and elastic modulus of defected specimens decrease comparing with those for intact sample, and show a decreased trend firstly and then increase with β changing from 0° to 90°. The peak strength and elastic modulus achieve the minimum value as the rock bridge angle is 60°, while the peak strain reaches the minimum value with the rock bridge angle of 45°. The crack initiation of tested rock samples occurs firstly in stress concentration areas at tips of prefabricated fissures under uniaxial compression, and then propagates constantly and coalescences with the prefabricated hole. Some secondary cracks initiate and propagate as well until buckling failure happens. The rock bridge angle has a great influence on crack initiation, coalescence, final failure mode, crack initiation stress and transfixion stress. The peak strength varies significantly, while the elastic modulus and peak strain change slightly, and the failure modes are also different due to the influence of fissure angle. Keywords: Double fissures, A single circular hole, Strength characteristics, Crack propagation, Failure mode

In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures, fissures with different angles α were prefabricated in the plate sandstone samples, and the processed samples were then heated at 5 different temperatures. Indoor uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature, and the deformation, strength and failure characteristics of sandstone containing fissures. The results show that, with increasing temperature, the volume of sandstone increases gradually while the quality and density decrease gradually, and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 °C; the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25 °C and 400 °C. The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature, and the mechanical properties of sandstone show obvious deterioration after 400 °C. The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature; with increasing angle α of the fissure, the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical properties. When the temperature is 800 °C, the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously weakened. The failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including: tensile crack failure, tensile and shear cracks mixed failure, and shear crack failure. Tensile and shear crack mixed failure occur mainly at low temperatures and small angles; tensile crack failure occurs at high temperatures and large angles. Keywords: High temperature, Sandstone containing fissure, Strength characteristics, Deformation characteristics, Evolution law

In order to solve contact problems, ANSYS provides a variety of contact algorithms. However, there is no basis for how to select the contact algorithm when solving the contact problem in hydraulic structure engineering. Therefore, this paper introduces the basic concepts of contact algorithms briefly, such as penalty method, lagrange method, augmented lagrange method and L&P method, which are commonly used in ANSYS. Then, different examples are used to compare the four contact algorithms in terms of accuracy, convergence and efficiency. Finally, considering the accuracy, convergence and efficiency, it is suggested to adopt L&P method in hydraulic structure contact analysis.

Polyurethane (PU) is increasingly adopted as grouting materials in the non-excavation rehabilitation of infrastructures. The compressive strength of PU materials is the key to achieving a desirable grouting effect. However, the geometric sizes of PU samples in the uniaxial compression test are not specified yet, which makes the test results less universal. Here, PU samples with a square cross-section were prepared with different densities and geometric sizes. The micromorphology of the PU matrices was investigated via a scanning electron microscope (SEM). Uniaxial compression tests were conducted, and the effects of density, side length (l), and height to side length ratio (H/l) of the samples on the mechanical properties were analyzed. The results show that micro foams in PU matrices have average equivalent diameters and average eccentricities of 50–116 μm and 0.55–0.78, respectively. When the density increases, the foams become smaller and more sphere-like. Under the uniaxial load, until strain hardening occurs, both the varied density, l and H/l bring little influence on the variation laws of stress with the strain. The mechanical properties of PU grouting materials increase with the increased density following a power function. When l or H/l changes, the mechanical properties of low-density PU (≤0.30 g/cm3) are little affected while those of high-density PU vary significantly but irregularly. The larger PU samples may be weaker than the smaller ones but may also be stronger. Cubic PU samples with a side length of 40 or 50 mm are preferred for the uniaxial compression test.

As new building materials, polymers have gradually been used in infrastructure engineering applications such as civil engineering, water conservancy, and highway repair engineering. The shear behavior of the interface between polymer and bentonite plays an important role in the analysis of the interactions at the interface. This paper investigated the direct shear behavior of polymer-bentonite interface under various conditions. The shear stress, horizontal displacement, and failure mode were observed under four initial normal stresses, four values of the moisture content of bentonite, and three polymer densities by utilizing a large-scale multi-functional direct shear apparatus and a digital image correlation (DIC) system. The results show that the shear strength of polymer-bentonite interface is higher than that of the pure bentonite. An increase in either initial normal stress or polymer density improves the shear strength of polymer-bentonite interface, while a higher moisture content of bentonite reduces it. Moreover, the polymer-bentonite composite fails in the bentonite phase or at the interface between polymer and bentonite. Finally, the concepts of the equivalent angle of internal friction and the equivalent cohesion of the polymer-bentonite interface are proposed and applied to the analysis of the interaction between the polymer and bentonite.

Enzymatic degumming is an effective approach to produce nutritional, safe, and healthy refined oil. However, the high cost and low efficiency of phospholipase limit the application of enzymatic degumming. In this study, an 879 bp outer membrane phospholipase A (A1) (OM-PLA1) gene encoding 292 amino acid residues was isolated from the genome of Serratia marcescens. The recombinant OM-PLA1 profile of appropriately 33 KDa was expressed by the engineered Pichia pastoris GS115. The OM-PLA1 activity was 21.2 U/mL with the induction of 1 mM methanol for 72 h. The expression efficiencies of OM-PLA1 were 0.29 U/mL/h and 1.06 U/mL/OD600. A complex of magnetic graphene oxide (MGO) and OM-PLA1 (MGO-OM-PLA1) was prepared by immobilizing OM-PLA1 with graphene oxide-based Fe3O4 nanoparticles by cross-linking with glutaraldehyde. The content of phosphorus decreased to 5.1 mg/kg rapeseed oil from 55.6 mg/kg rapeseed oil with 0.02% MGO-OM-PLA1 (w/w) at 50°C for 4 h. MGO-OM-PLA1 retained 51.7% of the initial activity after 13 times of continuous recycling for the enzymatic degumming of rapeseed oil. This study provided an effective approach for the enzymatic degumming of crude vegetable oil by developing a novel phospholipase and improving the degumming technology.