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The pavements are subjected to the moving vehicle, pore pressure and temperature loadings, the analytical solutions of thermo-hydro-mechanical response for the pavements are paid more attentions by the road engineers while the pavements are maintained. The analytical solutions of the multi-layered pavement model are derived by the novel DVP (duel variable and position) method in this paper. Starting with the basic equations of the pavement system, obeying Biot's dynamic poroelastic theory and generalized thermoelastic theory, the original problem is divided into two sub-systems and solved twice to avoid tangling two different loading frequencies. With the aid of moving coordinate and vector functions, the decomposition expressions of stress, displacement, temperature and pore pressure variations are deduced and propagated by using DVP method, and the transformed solutions are numerically inverted. In the numerical examples, the obtained solutions are firstly verified. Then the difference among the results of several pavement models are compared and analyzed. Finally, the effects of the surface temperature, moving load speed and interface conditions on the displacement, stress, and strain distributions are discussed by the solutions of thermo-hydro-mechanical pavement models in the numerical results.

The hydrodynamic erosion generated by the pumping action of the wheel load during rain and snow is the main cause of the semi-rigid base failure. Unfortunately, however, very few experimental methods and damage models can reasonably describe and predict the moisture damage performance of semi-rigid base materials under the pumping action. To address this issue, a hydrodynamic pressure erosion test was conducted firstly. Then, the compressive test was performed on the eroded specimens to evaluate the damage mechanism of semi-rigid base materials subjected to hydrodynamic erosion. Finally, a moisture-induced damage model that is applicable to the semi-rigid base materials was established by the concept of damage mechanics. The results indicated that the presented damage model encapsulates the complex behavior of the semi-rigid base materials under the hydrodynamic pressure and provides a more rational method for predicting the moisture damage performance of semi-rigid base materials.

Purpose This study aims to investigate the influence of surface texture distribution in respect to the procedure of pavement surface wear on friction performance. Design/methodology/approach The Weierstrass–Mandelbrot (W-M) equation is used to appropriate pavement surface profile. Through this approximation, artificial rough profiles by combining fractal parameters and conventional statistical parameters for different macro-texture are created to simulate the procedure of pavement surface wear. Those artificial profiles are then imported into discrete element model to calculate the interaction forces and friction coefficient between rolling tire and road. Furthermore, wavelet theory is used to decompose the profiles into different scales and explore the correlation between the profiles of each scale and pavement friction. Findings The influence of tire vertical displacement (TVD) on friction coefficient is greater than fractal dimension of road surface texture. When TVD decreases, the profiles can provide higher friction, but the rolling stability of tire is poor. The optimal fractal dimension of road surface is about 1.5 when considering friction performance. The pavement friction performance improves with wavelength from 0.4 to 6.4mm and decreases with wavelength from 12.8 to 51.2mm. Originality/value Artificial fractal curves are generated and analyzed by combining W-M function with traditional parameter, which can also be used to analyze the influence of texture distribution on other pavement performance. The preliminary research provides a potential approach for the evaluation of pavement friction performance. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0499/

This study explored the relationship between air voids and permeability, and investigated the correlation between air void type, coefficient of permeability, mechanical properties, and mois...

A convolutional neural network is proposed to feature the primary relationship between pavement surface texture and in-situ skid resistance measurement namely British Pendulum Test. The influence of texture collection interval was firstly analyzed. Then, effective contact textures were extracted. Finally, the sample size required for model training, which could serve as a reference for further texture-related research was addressed. Results indicated that textures with wavelengths above 2.40 mm is key for the wet friction. Textures below the cross section whose area is 0.6 times the nominal area do not contact the rubber. The sample size should be more than 100. The newly developed non-contact method shows high feasibility in predicting the skid resistance and effectively control the relative error within 14%.

The aim of this paper is to explore hot asphalt mixture (HMA) with potential cooling capacity through adding ceramsite. Ceramsite asphalt mixtures (CAM) are prepared by adding ceramsite to replace fine aggregate with different ratio. Marshall and pavement performance tests were performed to test the pavement performance of CAM. Indoor radiation and outdoor radiation tests are carried out to evaluate the thermal properties of CAM. Results indicate that the Marshall Stability and dynamic stability of CAM increase with the increasing ceramsite ratio from 0% to 60%. The retained MS and low temperature performance of CAM nearly do not change with ceramsite ratio, but the tensile strength ratio decreases with ceramsite ratio. However, all values of the tensile strength ratio are above the requirements of specification. In the aspect of the thermal properties of CAM, the addition of ceramsite can effectively reduce the thermal conductivity of asphalt mixtures. Also, ceramsite is helpful in reducing the temperature of pavement and enhancing the ability of heat resistance, and the optimal effect can reduce the bottom surface temperature about 2.6 °C when ceramsite ratio is 60%. Because of the improvement in the dynamic stability and the thermal conductivity, CAM can have a good rutting resistance and the recommended ceramsite ratio is 60%.

Gram-positive bacteria are responsible for a broad range of infectious diseases, and the emergency and wide spread of drug-resistant Gram-positive pathogens including MRSA and MRSE has caused great concern throughout the world. 4-Quinolones which are exemplified by fluoroquinolones are mainstays of chemotherapy against various bacterial infections including Gram-positive pathogen infections, and their value and role in the treatment of bacterial infections continues to expand. However, the resistance of Gram-positive organisms to 4-quinolones develops rapidly and spreads widely, making them more and more ineffective. To overcome the resistance and reduce the toxicity, numerous of 4-quinolone derivatives were synthesized and screened for their in vitro and in vivo activities against Gram-positive pathogens, and some of them exhibited excellent potency. This review aims to outlines the recent advances made towards the discovery of 4-quinolone-based derivatives as anti-Gram-positive pathogens agents and the critical aspects of design as well as the structure-activity relationship of these derivatives. The enriched SAR paves the way to the further rational development of 4-quinolones with a unique mechanism of action different from that of the currently used drugs to overcome the resistance, well-tolerated and low toxic profiles.

Water greatly affects the mechanical properties of cement bitumen emulsion mixture (CBEM). Its content is usually determined by the minimum voids content of CBEM. However, its effect on the...

This study focused on the interfacial transition zone (ITZ) between magnesium phosphate cement (MPC) paste and Portland cement paste (PCP). Multi-scale analyses were conducted to explore bonding characteristics and interfacial shear strengths of the ITZ with an innovative composite specimen. Meanwhile, ITZ was investigated by the Nano-indentation test, the scanning electron microscope (SEM), and the energy-dispersive spectrometer (EDS). Based on the damage mechanics and the interface kinematics formula, the viscous behavior and friction behavior were coupled together for the first time to develop the constitutive relation of the interface damage. A finite element (FE) model of MPC-PCP interface shear strength was developed and conducted to validate the proposed constitutive relation of the interface damage. Sensitivity analysis of repair size was predicted by the effect of different sizes on shear strength. The 7d shear strength of the repair interface reached 5.2 MPa, which indicates that MPC has good bonding with PCP. Investigated by SEM/EDS analysis, the cracks appeared at 10 μm away from PCP edge and the width at 6 h and 3d was around 3–5 μm. According to the nano-indentation test, the elastic modulus varied greatly in the ITZ and the lowest value located 10 μm away from the PCP side. Numerical results from FE models were found consistent with the experimental results, which validates the proposed constitutive relation of the interface damage.

For water robots in the intelligent operations meet to collision problems, a key collision avoidance algorithm based on VFH is developed, and the algorithm is improved and optimized, with a laser radar to launch the electromagnetic wave at a certain period Finally water robot controller was used to deal with data so as to analyze and process the data. Based on this, the histogram of obstacle vector field is established to judge the feasible and infeasible regions of the robot on water. Compared with the direction of the target destinations in feasible region corresponding weighting function is designed so as to determine the feasible area with smaller weight. the simulation by MATLAB to water robot position point for data analysis, Thus the simulation of water robot collision avoidance path diagram.

A new geopolymer prepared from a coal-based synthetic natural gas slag (CSNGS) and an alkali activator of potassium hydroxide (KOH) solution was studied. Firstly, the pozzolanic activity of CSNGS was evaluated. Then, the CSNGS geopolymers were produced under different conditions, and its compressive strength was also analyzed. Finally, XRD, FESEM/EDS, and FT-IR were carried out to investigate the microstructural properties and the reaction mechanism of CSNGS geopolymers. The findings showed that the CSNGS with a reasonable milling time exhibited high pozzolanic activity, and the composite pozzolanic activity index (CPAI) was the highest (CPAI = 92.2%) when the milling time was 45 min. Also, high heat curing temperature, long heat curing time and appropriate activator concentration were beneficial for the development of geopolymers strength. For CSNGS geopolymers, a maximum compressive strength of 27.8 MPa at 28 days was obtained. In addition, the XRD presented that the CSNGS geopolymers had an amorphous phase. The FESEM showed that a highly denser microstructure was formed by a number of geopolymeric gels attributing to the optimal synthesis conditions. The EDS analysis illustrated that the K-A-S-H gel was generated during the geopolymerization. The FT-IR suggested that the carbonization was easy to produce due to the excessive alkalinity. In general, it was feasible to fabricate geopolymers with the CSNGS and KOH solution.

Coal-based synthetic natural gas slag (CSNGS) is a by-product obtained from coal-based synthetic natural gas technology, and its output is increasing year by year. To divert CSNGS from hazardous waste stream to beneficial uses, the present study aims to propose a novel method by using the CSNGS as a raw material to fabricate the geoploymer under the alkali activation of sodium hydroxide solution. The effects of different factors such as water-solid ratio, activator concentration, raw material particle size, thermal curing temperature and duration on the strength of the CSNGS geopolymer were investigated by an orthogonal test. Microstructural features of the optimized CSNGS geopolymer were also evaluated via X-ray diffraction (XRD), field emission scanning electron microscope-energy dispersive spectrometer (FESEM/EDS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TG), mercury intrusion porosimetry (MIP) tests. The obtained results showed that the mechanical properties of geopolymers were mainly affected by the thermal curing temperature. When raising the curing temperature from 65 °C to 95 °C, more active components facilitated more reaction products (N-A-S-H), which led to a denser microstructure and changes in Si–O-T bonds, an increasing Si/Al ratio from 2.06 to 2.87, and a decreasing porosity with 29.2%. It was also found that the suitable range of the activator concentrations for CSNGS geopolymers were 6–9 mol/L. Also, the results of FT-IR and TG showed that significant carbonation could be produced when the activator concentration exceeded this range. For the CSNGS geopolymer, the 28 days compressive strength was 36.1 MPa at the optimal synthesis conditions. The findings of the study suggested that CSNGS can be used as a raw material for geopolymer cement manufacturing, which is beneficial for resource conservation, environmental protection, and cleaner production.

This paper deals with a review of the state-of-the-art performance investigations of green gas for grid (g3) gas, which is an emerging eco-friendly alternative insulation gas for sulfur hexafluoride (SF6) that will be used in gas-insulated power facilities for reducing environmental concerns. The required physical and chemical properties of insulation gas for high-voltage applications are discussed, including dielectric strength, arc-quenching capability, heat dissipation, boiling point, vapor pressure, compatibility, and environmental and safety requirements. Current studies and results on AC, DC, and lightning impulse breakdown voltage, as well as the partial discharge of g3 gas, are provided, which indicate an equivalent dielectric strength of g3 gas with SF6 after a proper design change or an increase in gas pressure. The switching bus-transfer current test, temperature rise test, and liquefaction temperature calculation also verify the possibility of replacing SF6 with g3 gas. In addition, the use of g3 gas significantly reduces theabovementioned environmental concerns in terms of global warming potential and atmosphere lifetime. In recent years, g3 gas-insulated power facilities, including switchgear, transmission line, circuit breaker, and transformer, have been commercially available in the electric power industry.

Different kinds of testing methods were used in recent studies to evaluate the moisture damage of a cement-treated base. However, these methods were based on the condition of static water, without considering the effect of dynamic water pressure and stress conditions in the pavement, which could not truly reflect the moisture damage process of the pavement base. This study presents details of a new method of evaluating the moisture damage of a cement-treated macadam under dynamic water pressure. Specimens with different curing times (7 d, 14 d, and 28 d) were scoured by means of a self-designed dynamic water scouring system, and the compressive strength was tested after scouring. The results show that most of the damage caused by scouring occurs in the early stage (less than 10 min), which accounts for more than 80 % of the total damage. Although the scouring damage continues in the later period (10∼40 min), the damage process is relatively slow. The results of the compressive test show that both the strength loss and strength loss rate of specimens at 28 d are much smaller than that of 14 d and 7 d. Results reveal that the curing time of the specimens has an essential influence on the scouring resistance.

Bacterial infections represent a significant health threat globally, and are responsible for the majority of hospital-acquired infections, leading to extensive mortality and burden on global healthcare systems. The second generation fluoroquinolone ciprofloxacin which exhibits excellent antimicrobial activity and pharmacokinetic properties as well as few side effects is introduced into clinical practice for the treatment of various bacterial infections for around 3 decades. The emergency and widely spread of drug-resistant pathogens making ciprofloxacin more and more ineffective, so it's imperative to develop novel antibacterials. Numerous of ciprofloxacin derivatives have been synthesized for seeking for new antibacterials, and some of them exhibited promising potency. This review aims to summarize the recent advances made towards the discovery of ciprofloxacin derivatives as antibacterial agents and the structure-activity relationship of these derivatives was also discussed.

The complex modulus (E*) is a fundamental material property extensively used for characterizing the viscoelastic behavior of asphalt concrete. In recent years, numerous micromechanics-based...

The main purpose of this study is to determine the effect of overlay on the crack propagation. In order to simplify the problem, a cement concrete pavement is modeled as an elastic plate on Winkler foundation. To derive the singular integral equations, the Fourier transform and dislocation density function are used. Lobatto-Chebyshev integration formula, as a numerical method, is used to solve the singular integral equations. The numerical solution of stress intensity factor at the crack tip is derived. In order to examine the effect of overlay for resisting crack propagation, numerical analyses are carried out for a cement concrete pavement with an embedded crack and a concrete pavement with an asphalt overlay. Results show the significant factors that influence the crack propagation.

The present study developed a new erosion test device, termed hydrodynamic pressure generator, for evaluating the moisture susceptibility of semi-rigid base materials. The hydrodynamic pressure generator was used to generate hydrodynamic loads at variable frequencies and pressures to erode the semi-rigid base materials, and a triaxial apparatus was used to provide confining and axial pressures to the specimens during erosion. After the erosion test, the uniaxial compression strength test was performed on the specimens. The results showed that the deformation process of the semi-rigid base materials under the long-term hydrodynamic erosion can be approximately divided into five stages. In addition, strong correlations were found between the air void and the compressive strength in the erosion test, suggesting that the air void could be used as a reliable indicator for evaluating the moisture susceptibility of the semi-rigid base materials. The results also revealed that the decrease of moisture resistance of semi-rigid base materials could be caused by the erosion of high hydrodynamic pressures, which largely depended on the confining pressure and the axial pressure conditions of the specimens. Because the newly proposed hydrodynamic erosion test allows the quantitative determination of the loss of the strength of specimen subjected to the hydrodynamic erosion and gives an insight into the design of improving moisture resistance for the semi-rigid base materials, it provides a promising approach to evaluating the moisture damage performance for semi-rigid base materials.

Iron tailings are a kind of industry waste generated during the ironmaking. Huge quantities of iron tailings caused many environmental problems. There is a strong demand for reducing the reserves of iron tailings. The primary of the study presented in this paper aims to explore the potential of applying iron tailings to cement concrete pavement to replace fine aggregates. The iron tailings concrete (ITC) is prepared and tested by performance tests to evaluate its mechanical properties (compressive strength, flexural strength and flexural modulus) and durability (abrasion resistance, water absorption, shrinkage ability and frost resistance). The results show that all the indexes can meet the requirement of rural low-grade cement concrete. This study provides a feasible way to solve the problem of excess iron tailings and a new way to reuse waste materials.

A hydrophobic polyacrylamide (HPAM) was synthesized by aqueous free-radical chain polymerization to understand the adsorption action of the polymer on the calcite during operating stimulation. The polymer was designed as acrylamide (AM)/2-acrylamide-2-methylpropanesulfonic acid (AMPS)/2-methacryloyloxyethyl 12-alkyl dimethyl ammonium bromide (MADA). The structure of the polymer was characterized by Fourier transform infrared spectroscopy. The adsorption properties of the polyacrylamide onto pure calcite was investigated. When we compared the ζ potentials of the calcite particles in the presence and absence of HPAM, the adsorbed amount was affected by different factors, and the adsorption behaviors were examined to determine the adsorption layer. The results of the ζ potential measurements indicated that the particles were negatively charged between pHs of 6 and 12, and the presence of HPAM did not reverse that. Equilibrium adsorption studies showed that the adsorbed amount was affected by the concentration of HPAM, liquid-to-solid ratio, calcite particle size, concentration of background ions, and temperature, which were related the adsorption behaviors of HPAM. Hydrogen bonds between HPAM and calcite were important because the adsorbed amount was significantly reduced when the hydrogen bonds were broken by urea. It is necessary to develop a more active reagent that can break the hydrogen bonds and improve the effect of hydraulic fracturing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45314.

The construction monitoring and control of a bridge is to monitor the structure stress, deformation and stability of a bridge in the construction process, and make the state of the structure optimal, ensure the bridge construction smooth and the final bridge in accordance with the design and specification requirements. Based on the supervision control of the cantilever construction of the continuous beam, this paper introduces the computation model of the continuous girder established by MIDAS/Civil; stress monitoring instrument selection, monitoring process and data processing; the elevation monitor for the top surface of the ridge and how to set pre-camber.

In our previous work, a hybrid shish kebab structure, with polyethylene (PE) crystal lamellae periodically decorated on the surface of an inorganic whisker (SMCW) and aligned approximately perpendicular to the long axis of the whisker, has been observed in the injection molded bar of PE/SMCW composites. To investigate the effect of the molecular weight of the PE matrix on the formation of the hybrid shish kebab structure and the corresponding physical properties of HDPE/SMCW composites, in this work, three types of PE with different molecular weights were used to prepare the composites. They were first melt blended and then subjected to dynamic packing injection molding (DPIM), in which the prolonged shear was exerted on the melt during the solidification stage. An obvious hybrid shish kebab (HSK) structure, with PE crystal lamellae closely packed on the surface of the SMCW, was found in the samples with a low molecular weight PE (LMW-PE) matrix and a medium molecular weight PE (MMW-PE) matrix. However, in samples with a high molecular weight PE (HMW-PE) matrix, an incomplete HSK structure with PE crystal lamellae loosely decorated on the surface of the SMCW was observed. Furthermore, DSC results indicated that SMCW served as a good nucleating agent only for the composite with a LMW-PE matrix and the nucleation efficiency decreased with increasing PE molecular weight. Correspondingly, the tensile strength of the PE/SMCW composites was significantly improved by adding SMCW for the samples with a LMW-PE or MMW-PE matrix. Especially for samples with a LMW-PE matrix, the tensile strength was remarkably enhanced by the presence of only 1 wt % SMCW. For the composites with a HMW-PE matrix, the addition of SMCW had almost no reinforcing effect on the composites. The molecular weight dependence of the formation of HSK and property enhancement was discussed on the basis of the chain mobility and crystallization capability of the PE matrix.

Water impairment is the main disease in current express highway, with various damage modes, which can be explained as follows: the structure material is repeatedly scoured by the water flow, then the aggregate and fine stuff are carried off to due to the dynamic water pressure generated in the pavement by the wheel-roads. Hence, the test apparatus(High-frequency & High-pressure Dynamic Water Pressure Generator, which can generate sinusoidal cyclic dynamic water pressure ,with peek value 1Mpa and frequency 0~25Hz)is developed to evaluate the road material dynamic pressure capacity. Combined with tri-axial test apparatus, it can study the mechanical performance of the road material under cyclic dynamic pore water pressure, and provide a new and effective method for the further study of the road material water impairment mechanism and tactics. This test apparatus is advanced in design, and can work properly with powerful function, believable data, and high precision. The study on the cement stability macadam specimen illustrates that: under the identical condition, the material strength decreases as the scouring frequency increases, while the plastic deformation increases with the scouring frequency.