Measuring the internal stress of Al alloy forgings accurately is critical for controlling the deformation during the subsequent machine process. In this work, the crack compliance method was used to calculate the internal residual stress of Al-Cu high strength alloys, and the effect of various model parameters of crack compliance method on the calculated precision was studied by combining the numerical simulation and experimental method. The results show that the precision first increased and then decreased with increasing the crack range. The decreased precision when using a high crack range was due to the strain fluctuation during the machining process, and the optimized crack range was 71% of the thickness of forgings. Low orders of Legendre polynomial can result in residual stress curve more smooth, while high orders led to the occurrence of distortion. The Tikhonov regularization method effectively suppressed the distortion of residual stress caused by the fluctuation of strain data, which significantly improved the precision. In addition, the crack compliance method with optimized parameters was used to measure the residual stress of Al-Cu alloy with different quenching methods. The calculated results demonstrated that the distribution of residual stress was obtained accurately.

In the present study, the thermal, mechanical, and biological properties of xAg/Ti-30Ta (x=0, 0.41, 0.82 and 2.48 at%) shape memory alloys (SMAs) were investigated. The study was conducted using optical and scanning electron microscopy (SEM), X-ray diffractometry (XRD), compression test, and shape memory testing. The xAg/Ti-Ta was made using a powder metallurgy technique and microwave-sintering process. The results revealed that the addition of Ag has a significant effect on the pore size and shape, whereas the smallest pore size of 11 µm was found with the addition of 0.41 at% along with a relative density of 72%. The fracture stress and strain increased with the addition of Ag, reaching the minimum values around 0.41 at% Ag. Therefore, this composition showed the maximum stress and strain at fracture region. Moreover, 0.82 Ag/Ti-Ta shows more excellent corrosion resistance and biocompatibility than other percentages, obtaining almost the same behaviour of the pure Ti and Ti-6Al-4V alloys, which can be recommended for their promising and potential response for biomaterial applications.

The current work is an extension of the nonlocal elasticity theory to fractional order thermo-elasticity in semiconducting nanostructure medium with voids. The analysis is made on the reflection phenomena in context of three-phase-lag thermo-elastic model. It is observed that, four-coupled longitudinal waves and an independent shear vertical wave exist in the medium which is dispersive in nature. It is seen that longitudinal waves are damped, and shear wave is un-damped when angular frequency is less than the cut-off frequency. The voids, thermal and non-local parameter affect the dilatational waves whereas shear wave is only depending upon non-local parameter. It is found that reflection coefficients are affected by nonlocal and fractional order parameters. Reflection coefficients are calculated analytically and computed numerically for a material, silicon and discussed graphically in details. The results for local (classical) theory are obtained as a special case. The study may be useful in semiconductor nanostructure, geology and seismology in addition to semiconductor nanostructure devices.

Conductive polymer composites (CPCs) are widely used in the flexible strain sensors due to their simple fabrication process and controllable sensing properties. However, temperature has a significance impact on the strain sensing performance of CPCs. In this paper, the strain sensing characteristics of MWCNTs/PDMS composites under temperature loading were systematically studied. It was found that the sensitivity decreased with the increase of temperature and the phenomenon of shoulder peak also decreased. Based on the theory of polymer mechanics, it was found that temperature could affect the conductive network by changing the motion degree of PDMS molecular chain, resulting in the change of sensing characteristics. Finally, a mathematical model of the resistance against loading condition (strain and temperature), associated with the force-electrical equivalent relationship of composites, was established to discuss the experimental results as well as the sensing mechanism. The results presented in this paper was believed helpful for the further application of strain sensors in different temperature conditions.

Pencil hardness testing, electrochemical impedance spectroscopy, scanning electron microscopy, and scanning Kelvin probe microscopy were used to study the local corrosion characteristics of a graphene-oxide-modified inner coating. The effect of chloride concentration on the corrosion of the damaged inner coating was studied. The effects of chloride ions on damaged internal coatings and graphene-oxide-modified internal coatings were investigated. It was proposed to add graphene oxide into the epoxy coating to effectively inhibit the metal corrosion at the breakage. Because of the existence of graphene oxide(GO), the modified coating had a better physical property and had the effective infiltration of H₂O and Cl⁻ into the coating. The results showed that graphene oxide coatings can give X80 steel better corrosion resistance in sodium chloride solution.

Tricalcium silicate cement (TSC) has been widely used in dental materials because of its self-setting behavior, good bioactivity, biocompatibility, osteoinductivity, and antibacterial effect. Tricalcium silicate (C₃S) powder was prepared by Pechini technique with a calcining temperature of 1300 °C for 3 h. The influence of liquid/powder (L/P) rate on the setting time and the mechanical property of TSC was studied. Characterization methods including XRD, FTIR, SEM-EDS, TEM, and ICP-AES were utilized to study the properties of C₃S powder and its hydrated cement. The bioactivity and biocompatibility of the cement were investigated by soaking test and cell culture, respectively. The results show that the L/P rate plays an important role in the setting time and the compressive strength of TSC. The surface of TSC was covered by hydroxyapatite deposition during the immersion experiment and the cells attachment on the surface of TSC was well, which indicated that TSC has good bioactivity and biocompatibility. In addition, TSC has excellent antibacterial properties against Staphylococcus aureus. In conclusion, TSC is a promising candidate for root canal filling materials.

Applying spent lithium iron phosphate battery as raw material, valuable metals in spent lithium ion battery were effectively recovered through separation of active material, selective leaching, and stepwise chemical precipitation. Using stoichiometric Na₂S₂O₈ as an oxidant and adding low-concentration H₂SO₄ as a leaching agent was proposed. This route was totally different from the conventional methods of dissolving all of the elements into solution by using excess mineral acid. When experiments were done under optimal conditions (Na₂S₂O₈-to-Li molar ratio 0.45, 0.30 mol/L H₂SO₄, 60 °C, 1.5 h), leaching efficiencies of 97.53% for Li⁺, 1.39% for Fe³⁺, and 2.58% for PO₄³⁻ were recorded. FePO₄ was then recovered by a precipitation method from the leachate while maintaining the pH at 2.0. The mother liquor was concentrated and maintained at a temperature of approximately 100 °C, and then a saturated sodium carbonate solution was added to precipitate Li₂CO₃. The lithium recovery yield was close to 80%.

An innovative technology, nitric acid pressure leaching of limonitic laterite ores, was proposed by our research team. The HNO₃ regeneration is considerable significance for the improvement of the proposed technology and its commercial application, but it has not been systematically investigated. Herein, regenerating HNO₃ from Ca(NO₃)₂ solution with low-cost H₂SO₄, and simultaneous synthesis of fibrous CaSO₄·2H₂O by-products were studied. As a theoretical basis, the solubility of CaSO₄·2H₂O in HNO₃ medium is studied. It is concluded that the solubility of CaSO₄·2H₂O increases with increasing temperature or increasing HNO₃ concentration, which has considerable guiding significance for the subsequent experimental research and analysis. Then, the effects of various factors on the residual Ca²⁺ concentration of filtrate, the regenerated HNO₃ concentration and the morphology of synthesized products are investigated using ICP-AES and SEM. And the effect mechanism is also analyzed. The results indicate the regenerated HNO₃ concentration reaches 116 g/L with the residual Ca²⁺ concentration being 9.7 g/L at the optimum conditions. Moreover, fibrous CaSO₄·2H₂O by-products with high aspect ratios (length, 406.32 µm; diameter, 14.71 µm; aspect ratio, 27.62) can be simultaneously synthesized.

In this paper, sulfidation mechanism of cerussite in the presence of sulphur at high temperatures was investigated based on micro-flotation, X-ray powder diffractometry (XRD), electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The micro-flotation test results showed that flotation recovery of the treated cerussite increased to above 80% under a suitable flotation condition. It was found that the S/PbCO₃ mole ratio and pH obviously affected flotation recovery. XRD analysis results confirmed that the cerussite was decomposed into massicot and then was transformed into mainly PbS and PbO·PbSO₄ after sulfidation roasting. EPMA analysis results demonstrated that surface of the obtained massicot was smooth, but surface of the artificial galena was rough and even porous. Content of oxygen decreased, whereas content of sulphur increased with an increase in the S/PbCO₃ mole ratio. XPS analysis results revealed that various lead-bearing species, including mainly PbS, PbSO₄ and PbO·PbSO₄, were generated at the surface. Formation of PbS was advantageous to flotation of the treated cerussite. Based on these results, a reaction model of the cerussite sulfurized with sulphur was proposed.

The crystal structure, formation kinetics and micro-morphology of CaO·SiO₂ during high-temperature sintering process were studied in low-calcium system by XRD, FT-IR, Raman and SEM-EDS methods. When the molar ratio of CaCO₃ to SiO₂ is 1.0, β-2CaO·SiO₂ forms firstly during the heating process, and then CaO·SiO₂ is generated by the transformation reaction of pre-formed 2CaO·SiO₂ with SiO₂. 3CaO·SiO₂ and 3CaO·2SiO₂ do not form either in the heating or sintering process. Rising the sintering temperature and prolonging the holding time promote the phase transition of 2CaO·SiO₂ to CaO·SiO₂, resulting in the sintered products a small blue shift and broadening in Raman spectra. The content of CS can reach 97.4% when sintered at 1400 °C for 1 h. The formation kinetics of CaO·SiO₂ follows the second-order chemical reaction model, and the corresponding apparent activation energy and pre-exponential factor are 505.82 kJ/mol and 2.16×10¹⁴ s⁻¹ respectively.

The effects of cations stress of magnesium ion and sodium ion on the low-grade nickel sulfide ore oxidative leaching in simulated sulfuric acid solutions were investigated. This study was performed in two courses, including the effect of the cations on the valuable metals leaching efficiencies of the nickel ore and its influences on the electrochemical oxidation behavior of the nickel ore. The leaching results present that parts of magnesium-containing gangues and ferrous sulfide are preferentially dissolved into lixivium, and the leaching efficiencies of Ni and Cu decreased much related to the leached concentrations of Mg²⁺ increased. The results of electrochemical measurements show that the oxidation leaching of the low-grade nickel sulfide ore is controlled by the intermediates oxidative diffusion. Mg²⁺, as well as Na⁺, affects the transformations of the Fe³⁺/Fe²⁺ couple and sulfur-containing species, and those cations are apt to be attracted by the anions and directionally adhere to the negative active site of the metal sulfide surface, causing an increase in the electrochemical activities, which facilitates the electron transfer between the ore and leaching mediums. By comparative study of the role of Mg²⁺ and Na⁺, it is found that Mg²⁺ negatively affects the oxidative diffusion of the intermediates through promoting the generation of a compact film, which lowers the metals leached efficiencies, and the unfavorable effect of Na⁺ tends to be the coupled effect of the leached Mg²⁺ and Fe³⁺.

In this work, the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation. Three operating parameters of reflux classifier (RC) to pre-concentrate fine(0.023–0.15 mm) tailings of antimony oxide were optimized by response surface methodology (RSM) using a three-level Box-Behnken design (BBD). The parameters studied for the optimization were feeding speed, underflow, and ascending water speed. Second-order response functions were produced for the Sb grade and recovery rate of the concentrate. Taking advantage of the quadratic programming, when the factors of feeding, underflow and ascending water are respectively 225, 30 and 133 cm³/min, a better result can be achieved for the concentrate grade of 2.31% and recovery rate of 83.17%. At the same time, 70.48% of the tailings with the grade of 0.20% were discarded out of the feeding. The results indicated that the reflux classifier has a good performance in dealing with fine tailings of antimony oxide. Moreover, second-order polynomial equations, ANOVA, and three-dimensional surface plots were developed to evaluate the effects of each parameter on Sb grade and recovery rate of the concentrate.

Four sewage sludge (SS) feedstocks with distinct properties were converted into biochars by pyrolysis at 300–700 °C, in order to clarify the effects of the composition difference of SS feedstocks. The yields of biochars present a positive correlation with the contents of ash in SS. Notedly, the contents of organic matter (OM) in SS largely determine the quality of biochars. SS feedstocks with high content of OM are more likely to form stable biochars with higher aromaticity/carbonization degree, and the formed biochars possess higher calorific values. The contents of residual OM in biochars derived from SS feedstocks with low content of OM likely fail to meet the needs of soil improvement (10 wt.%). Most of heavy metals (HMs) existing in raw SS are remained in biochars after pyrolysis. The biochar produced from SS feedstocks with high content of HMs usually contains higher contents of HMs. Surprisingly, the leachability of HMs in biochars is all weakened to some extent compared to raw SS. In addition, the biochars show higher thermal stability and pH values, and P/K nutrients are enriched in biochars. The biochars prepared from four SS feedstocks exhibit different adsorption ability of methylene blue, especially at low dosage of biochar.

Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas. The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate precipitation (SICP) on reducing wind erosion risk of sandy soil. Field tests were carried out in Ulan Buh Desert, Ningxia Hui Autonomous Region, China. Results showed that the SICP method could significantly enhance the surface strength and wind erosion resistance of the topsoil. The optimal cementation solution (urea-CaCl₂) concentration and spraying volume, according to experiments conducted on sandy land, were 0.2 mol/L and 4 L/m², respectively. Under this condition, the CaCO₃ content was approximately 0.45%, the surface strength of sandy soil could reach 306.2 kPa, and the depth of wind erosion was approximately zero, after 30 d completion of SICP treatment. Soil surface strength declined with the increase of time, and long-term sand fixation effects of SICP treatment varied depending on topography. Whereas wind erosion in the top area of the windward slope was remarkable, sandy soils on the bottom area of the windward slope still maintained a relatively high level of surface strength and a low degree of wind erosion 12 month after SICP treatment. Scanning electron microscopy (SEM) tests with energy dispersive X-ray (EDX) confirmed the precipitation of CaCO₃ and its bridge effect. These findings suggested that the SICP method is a promising candidate to protect sandy soil from wind erosion in desert areas.

This paper proposes a novel method to predict the spur gear pair’s static transmission error based on the accuracy grade, in which manufacturing errors (MEs), assembly errors (AEs), tooth deflections (TDs) and profile modifications (PMs) are considered. For the prediction, a discrete gear model for generating the error tooth profile based on the ISO accuracy grade is presented. Then, the gear model and a tooth deflection model for calculating the tooth compliance on gear meshing are coupled with the transmission error model to make the prediction by checking the interference status between gear and pinion. The prediction method is validated by comparison with the experimental results from the literature, and a set of cases are simulated to study the effects of MEs, AEs, TDs and PMs on the static transmission error. In addition, the time-varying backlash caused by both MEs and AEs, and the contact ratio under load conditions are also investigated. The results show that the novel method can effectively predict the range of the static transmission error under different accuracy grades. The prediction results can provide references for the selection of gear design parameters and the optimization of transmission performance in the design stage of gear systems.

The thermal elastohydrodynamic lubrication characteristics of a modified gear system under a dynamic load were investigated, including the influence of the modification coefficient and vibrations. Based on the dynamic theory of gear systems, a six-degree-of-freedom tribo-dynamics model was established. Thermal elastohydrodynamic lubrication characteristics of a modified gear system under vibrations and a static load were analyzed. The results showed that the positive transmission gear system exhibited the better lubrication effect compared with other transmission types. A thick lubricating oil film could be formed, and the friction coefficient between the teeth and the oil film flash temperature was the smallest. As the modification coefficient increased, the lubrication condition was continuously improved, and the scuffing load capacity was enhanced. The increment of the modification coefficient increased the meshing stiffness of the gear system but reduced the stiffness of the oil film.

Maintaining temporal consistency of real-time data is important for cyber-physical systems. Most of the previous studies focus on uniprocessor systems. In this paper, the problem of temporal consistency maintenance on multiprocessor platforms with instance skipping was formulated based on the (m,k)-constrained model. A partitioned scheduling method SC-AD was proposed to solve the problem. SC-AD uses a derived sufficient schedulability condition to calculate the initial value of m for each sensor transaction. It then partitions the transactions among the processors in a balanced way. To further reduce the average relative invalid time of real-time data, SC-AD judiciously increases the values of m for transactions assigned to each processor. Experiment results show that SC-AD outperforms the baseline methods in terms of the average relative invalid time and the average valid ratio under different system workloads.

We have systematically investigated the feature, genetic model and distribution of calcareous insulating layers in marine strata of the I oil group in member 2 of Zhujiang formation (ZJ₂I oil formation), western Pearl River Mouth basin (PRMB) in the north of the South China Sea by using data such as cores, thin sections, X-ray diffraction of whole-rock, and calcite cement carbon and oxygen isotopes. The lithology of the calcareous insulating layers in the study area is mainly composed of the terrigenous clastic bioclastic limestone and a small amount of fine-grained calcareous sandstone. On this basis, two genetic models of calcareous insulating layers are established, including the evaporation seawater genetic model and shallow burial meteoric water genetic model. The calcareous insulating layers of the evaporation seawater genetic model developed in the foreshore subfacies, mainly at the top of the 1–1 strata and 1–3 strata. The calcareous insulating layers of the shallow burial meteoric water genetic model developed in the backshore subfacies, primarily in the 1–2 strata.

In order to study the distribution of shale gas reservoir in the Babaoshan Basin of Eastern Kunlun, the wide-field electromagnetic (WFEM) survey was carried out to obtain the spatial distribution characteristics of the underground electrical volume resistivity based on the delineation of the scope of the Babaoshan Basin by regional gravity data. The basic characteristics of the basement, basin framework, and extension, vertical change, burial depth of dark mud shale in this area were identified, and the electrical distribution of the Babaoshan mud shale horizon was revealed, which has been proved to be a good geological effect by drilling. The exploration results show that the WFEM has significant effects on the exploration of shale gas occurrence strata, which meets the needs of investigation and evaluation of multi-layered and large-scale shale gas, and plays a good demonstration role in the follow-up shale gas exploration.

Based on field observation, core description and well logging analysis, the tectonic-sedimentary framework of the Liangshan and Qixia Formations in the northwestern Sichuan Basin, China is deeply discussed. Two long-term sequence cycles were identified, denoted as LSC1 and LSC2, respectively. The sequence stratigraphic framework was established, suggesting the Liangshan Formation to be not isochronously deposited. Paleogeomorphy before deposition of LSC1 was reconstructed by the impression method. LSC1 was featured by thin, low-energy shoal deposits in the high topography, and thick inter-shoal sea and open sea deposits in the low topography. Meanwhile, paleogeomorphy before deposition of LSC2 was reconstructed using the residual thickness method, which was demonstrated to have primary high-energy, thick shoal deposits in the high topography, and thin inter-shoal and open sea deposits in the low topography. The results show that differential tectonic subsidence has already taken place during the Qixia Period, and thus the Dongwu Movement should occur earlier than previously expected. Meanwhile, pre-depositional paleogeomorphy has obvious controlling effects on the sequence stratigraphic filling and sedimentary facies distribution. Results of this study were expected to provide practical guidance to fine characterization of the sedimentary evolution process and prediction of high-quality reservoir distribution.

A step-by-step load was utilized to mimic the load history of the backfill column in the in-situ curing process. The inner damage of the specimen during curing and uniaxial compressive testing was monitored by electrical resistivity and ultrasonic equipment. Results show that: 1) Uniaxial compressive strength (UCS) and elastic modulus (EM) of the samples curing under pressure are higher than those of the control samples without pressure, ranging in ratio from 0.5% to 20.2% and 7.1% to 52.3%, respectively, and are influenced by the initial loading age (ILA) and stress strength ratio (SSR). The SSR during curing should not exceed 80%. 2) The earlier the ILA is, the higher the total strain becomes. The higher the SSR applies, the larger the total strain gets. The creep strain increases with the increase of SSR and can be described by Burger’s viscoelastic creep model. When SSR is less than 80%, the earlier the ILA is, the smaller the creep strain becomes after the last step-loading. 3) The stability of the early age backfill column under pressure can be monitored based on the change of ultrasonic pulse velocity (UPV) and electrical resistivity.

Based on the interface shear tests, the macro- and meso-mechanical behaviors of interaction between coral sand and different structure surfaces are studied, in which CCD camera is used to capture digital images to analyze the evolution of the interaction band and a particle analysis apparatus is applied to studying the distribution characteristics of particle morphology. This study proposes four-stage evolution process based on the shear stress-strain curve. During the shear process, coral sand particles slide and rotate within the interaction band, causing the changes in shear stress and vertical displacement. In addition, the effects of structure surface roughness on shear strength, volume change and particle breakage are illustrated that the greater the roughness of slabs is, the larger the shear stress is, the more obvious the contraction effect is and the more the particles break. Furthermore, the change in particle’s 3D morphology during the breakage will change not only their size but also other morphological characteristics with convergence and self-organization.

Based on the nonlinear Barton-Bandis (B–B) failure criterion, this study considers the system reliability of rock wedge stability under the pseudo-static seismic load. The failure probability (P_f) of the system is calculated based on the Monte–Carlo method when considering parameter correlation and variability. Parameter analysis and sensitivity analysis are carried out to explore the influence of parameters on reliability. The relationships among the failure probability, safety factor (F_s), and variation coefficient are explored, and then stability probability curves of the rock wedge under the pseudo-static seismic load are drawn. The results show that the parameter correlation of the B–B failure criterion has a significant influence on the failure probability, but correlation increases system reliability or decreases system reliability affected by other parameters. Under the pseudo-static seismic action, sliding on both planes is the main failure mode of wedge system. In addition, the parameters with relatively high sensitivity are two angles related to the joint dip. When the coefficient of variation is consistent, the probability of system failure is a function of the safety factor.

Thermogravimetric analysis and electrical resistivity were used to determine the hydration process of cement paste with rice husk ash (RHA) (0–15%) and water-cement ratio of 0.4 in this work. X-ray diffraction (XRD) method and scanning electron microscopy (SEM) were used to survey crystal composition and microstructures of specimens cured for 3 h, 1 d, 7 d and 28 d. Finally, electrical parameters (electrical resistance and AC impedance spectroscopy) of steel bars reinforced cement paste were investigated to study the effect of RHA on the corrosion resistance. Results showed that RHA could affect the cement hydration by hydration promotion and pozzolanic effect. The evaluation function for electrical resistivity and curing ages fitted well with linear increasing function. The addition of RHA higher than 5% demonstrated a decreasing role in the electrical resistivity of cement paste at earlier curing ages (3–7 d). Meanwhile, when at later curing ages (7–28 d) the result was the opposite. Moreover, RHA demonstrated positive effects on corrosion resistance of steel bars in cement paste.

Recycling end-of-life tire rubber as asphalt modifier is known as a sustainable paving technology with merits including enhanced pavement durability, waste tire consumption and noise reduction. However, the criticisms on the high construction emissions of asphalt rubber (AR) have limited its application. Warm mix asphalt (WMA) effectively reduces the mixing and compaction temperatures of conventional hot mix asphalt mixtures. The combination of AR and WMA, called warm asphalt rubber (WAR), is a promising paving material which achieves pavement sustainability from principles to practices. Many studies have demonstrated that WMA technologies work effectively with AR pavement in different ways, alleviating the concerns of potential higher emissions of AR by decreasing mixing and paving temperatures. A comprehensive literature review about WAR brings a better understanding of this promising paving technology. The findings of 165 publications were summarized in this review. It summarized the recent developments of WAR in various aspects, including rheological properties, mix design, mixture mechanical performance, field application, construction emission, and asphalt-rubber-WMA additive interaction. It is expected that this review is able to provide extensive information to explore further research development and application of WAR.

The connected and automated vehicles (CAVs) technologies provide more information to drivers in the car-following (CF) process. Unlike the human-driven vehicles (HVs), which only considers information in front, the CAVs circumstance allows them to obtain information in front and behind, enhancing vehicles perception ability. This paper proposes an intelligent back-looking distance driver model (IBDM) considering the desired distance of the following vehicle in homogeneous CAVs environment. Based on intelligent driver model (IDM), the IBDM integrates behind information of vehicles as a control term. The stability condition against a small perturbation is analyzed using linear stability theory in the homogeneous traffic flow. To validate the theoretical analysis, simulations are carried out on a single lane under the open boundary condition, and compared with the IDM not considering the following vehicle and the extended IDM considering the information of vehicle preceding and next preceding. Six scenarios are designed to evaluate the results under different disturbance strength, disturbance location, and initial platoon space distance. The results reveal that the IBDM has an advantage over IDM and the extended IDM in control of CAVs car-following process in maintaining string stability, and the stability improves by increasing the proportion of the new item.