Calcium carbonate, which is widely employed as a filler added into the polymer matrix, has large numbers of applications owing to the excellent properties such as low cost, non-toxicity, high natural reserves and biocompatibility. Nevertheless, in order to obtain the good filling effect, calcium carbonate needs to be surface modified by organic molecules so as to enhance the dispersion and compatibility within the composites. This review paper systematically introduces the theory, methods, and applications progress of calcium carbonate with surface modification. Additionally, the key factors that affect the properties of the composites as well as the current difficulties and challenges are highlighted. The current research progress and potential application prospects of calcium carbonate in the fields of plastics, rubber, paper, medicine and environmental protection are discussed as well. Generally, this review can provide valuable reference for the modification and comprehensive utilization of calcium carbonate.

The recrystallization and texture evolution of cold-rolled FeCrAl−0.65Nb and FeCrAl−1.2Nb alloys thin-wall tubes annealed at 600–900 °C for 1–600 min were investigated. The microstructures were characterized by electron back scattering diffraction, electron probe micro-analyzer and transmission electron microscopy. The Vickers hardness and room temperature tensile properties were tested. The results showed that the hardness of fully recrystallized FeCrAl−1.2Nb alloy was higher and more likely to recrystallize than FeCrAl−0.65Nb alloy. The weak texture strength of annealing sample was obtained and the proportion of <111>//ND texture increased. The fine Laves phase distributed uniformly in FeCrAl−0.65Nb alloy had good pinning effect and inhibited recrystallization. Higher Nb content had little effects on tensile properties of thin-wall tube, and induced the formation of larger Laves phase. There was less fine Laves phase pinning in the large area adjacent to the blocky Laves phase, which resulted in easy recrystallization in FeCrAl−1.2Nb alloy.

A study on the low-cycle fatigue (LCF) behavior of K416B alloy was conducted at 650 °C. According to the results, the LCF behavior of K416B alloy at 650 °C is mainly manifested as elastic deformation and the fatigue life of the alloy is determined by the level of material strength. When tension-compression fatigue occurs, the deformation mechanism of the alloy is reflected in the form of dislocation slip, and the deformation dislocations are bowed out in the matrix by Orowan mechanism, which leads to a dislocation configuration similar to the Frawk-Reed source. At the late stage of low-cycle fatigue, the fatigue-induced cracks develop from the alloy surface. As fatigue test proceeds, it is possible for the cracks to continue development along the regions of eutectic and the bulk M₆C carbide due to stress concentration, thus causing the alloy to show cleavage fracture.

The effect of Li (2.0 wt%) addition on mechanical properties and ageing precipitation behavior of Al−3.0Mg−0.5Si was investigated by tensile test, dynamic elasticity modulus test, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images. The results show that the tensile strength of the Li-containing alloy can be significantly improved; however, the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture. The elasticity modulus of the Li-containing alloy increases by 11.6% compared with the base alloy. The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy, and δ′-Al₃Li phase becomes the main precipitates. Besides, β″-Mg₂Si and δ′-Al₃Li dual phases precipitation can be visibly observed at 170 °C ageing for 100 h, although the quantity of δ′-Al₃Li phase is more than β″-Mg₂Si phase. The width of the precipitate-free zone (PFZ) of the Li-containing alloy is much wider at the over-ageing state than the base alloy, which has a negative impact on the ductile and results in the decrease of elongation.

The effects of aging treatments on the tensile properties and compressive behavior of a thin-walled 6005 aluminum alloy tube were studied. Samples after three natural aging (NA) conditions were subsequently aged at 180 °C for 0.5–12.0 h artificial aging (AA). Tensile and compressive tests were performed after AA. The results show that for samples with the same NA, the longer the AA time is, the higher the strengths alloy owns, and at the same time the material shows a much lower elongation and faster process from plastic deformation to fracture. However, with NA prolonging, the alloy exhibits much better plastic deformation ability after AA, though its strength is decreased. The major cause of strength and plasticity variation induced by changing NA time is that the size of the main strengthening β″ precipitates is larger and the density is lower. This character is evaluated by the strain hardening exponent n. Compressive results show that the optimum energy absorption characteristics can be acquired at a moderate n (14<n<17). Large n (n⩾ 18) results in the fracture of tube during axial compression while low n (n⩽13) causes lower energy absorption.

The influence of pre-stretching on quench sensitive effect of high strength Al−Zn−Mg−Cu−Zr alloy AA 7085 sheet was investigated by tensile testing at room temperature, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The water-cooled and aged alloy exhibits higher strength than the air-cooled and aged alloy; 2.5% pre-stretching of tensile deformation exerts little effect on strength of water-cooled and aged alloy but increases that of air-cooled and aged one, and therefore the yield strength reduction rate due to slow quenching decreases from about 3.8 % to about 1.0 %, reducing quench sensitive effect. For the air-cooled alloy, pre-stretching increases the sizes of η′ strengthening precipitates but also increases their quantity and the ratio of diameter to thickness, resulting in enhanced strengthening and higher strength after aging. The reason has been discussed based on microstructure examination by TEM and DSC.

The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates, temperatures and strains were studied. The microstructure evolution was quantitatively characterized and analyzed, including recrystallization fraction, grain sizes, local misorientation, geometrically necessary dislocation and stored strain energy during hot deformation and subsequent heat treatment. The results show that the dislocation density and energy storage are linear with lnZ during hot deformation and subsequent heat treatment, indicating continuous recrystallization occurring in both processes. With higher lnZ, the dislocation density declines more sharply during subsequent heat treatment. When lnZ is less than 28, dislocation density becomes more stable with less reduction during subsequent heat treatment after hot deformation. As these dislocations distribute along low angle grain boundaries, the subgrain has good stability during subsequent heat treatment. The main recrystallization mechanism during hot deformation is continuous dynamic recrystallization, accompanied by geometric dynamic recrystallization at higher lnZ.

The microstructure, mechanical properties and stress corrosion cracking (SCC) of 7136 aluminum alloy under T6, T79 and T74 aging treatments were studied and the effects of microstructure on the mechanical properties and SCC were discussed. The results show that the ultimate tensile strength and yield strength of the aging 7136 alloys follow this sequence from high to low: T6>T79>pre-aging>T74. For 7136 Al alloy after T6 aging, the average diameter of the precipitates was (5.7±1.7) nm, and the diameter of 60.7% (number fraction) precipitates was 2–6 nm, leading to a good precipitation strengthening. The K_IC of T74-aging alloy is 38.2 MPa·m^1/2, which is 26.1% more than that of T6-aging alloy and 17.5% more than that of T79-aging alloy. The improved fracture toughness in T74-aging alloy is mainly due to the reduction of the strength difference between intragranular and grain boundary. The SCC resistance of the aging 7136 alloys follows this sequence from high to low: T79 > T74 > T6. After T79 aging, the discontinuous grain boundary precipitates and narrow precipitate free zones were obtained in 7136 alloy, which was beneficial to SCC resistance.

To recover zinc from electric arc furnace (EAF) dust, a process of primary normal pressure leaching and secondary alkaline pressure leaching is proposed. First, under the alkaline pressure leaching system, the experiment of pure zinc ferrite being reduced by iron powder was carried out. Under the optimal reduction conditions (i.e., temperature of 260 °C, NaOH concentration of 6 mol/L, liquid-to-solid ratio of 50 mL/g, and a 5-fold excess of iron powder), 89% of zinc was extracted. The iron in the reduced residue exists as a magnetite phase. Subsequently, the normal pressure leaching experiment was carried out with EAF dust as raw material, and 66% zinc was leached. The main phase of zinc in normal leaching residue was determined to be zinc ferrite. Then, the normal leaching residue was reduced by iron powder under the alkaline pressure leaching system, and 66.5% of zinc was extracted. After the two-stage leaching process, the leaching rate of zinc in EAF dust can achieve 88.7%. The alkaline pressure leaching solution can be returned as the normal pressure leaching solution, and the magnetite in the alkaline pressure leaching residue can be recovered by magnetic separation.

Zinc extraction from crude zinc oxide (CZO) is beneficial to the full utilization of secondary resources and environmental protection. In this paper, a systematic investigation was carried out to study the leaching behavior of CZO by using ammonia-ammonium carbonate solution. It was found that the maximum leaching rate of zinc from CZO dust was 95.7% under the conditions of [Zn]_T: [NH₃]_T: [CO₃²⁻] =1: 7.00: 1.75, liquid to solid ratio 5: 1, leaching temperature 30 °C and leaching time 60 min. Compared with pure zinc oxide (PZO) leaching, the CZO leaching required longer time and more leaching agents, which is caused by the Cd²⁺, Pb²⁺ and other metal cationic impurities in CZO. The metal cationic impurities dissolved in the leaching solution and combined with ammonium to form complexes, consuming leaching agents and affecting zinc leaching.

In this study, direct reduction-magnetic separation process was applied to enrich phosphorus and iron to prepare Fe-P crude alloy from a high phosphorus oolitic hematite ore (HPOH). The results show that at lower temperatures and with absence of any of additives, Fe cannot be effectively recovered because of the oolitic structure is not destroyed. In contrast, under the conditions of 15% Na₂SO₄ and reducing at 1050 °C for 120 min with a total C/Fe ratio (molar ratio) of 8.5, a final Fe-P alloy containing 92.40% Fe and 1.09% P can be obtained at an overall iron recovery of 95.43% and phosphorus recovery of 68.98%, respectively. This metallized Fe-P powder can be applied as the burden for production of weathering resistant steels. The developed process can provide an alternative for effective and green utilization of high phosphorus iron ore.

In order to solve the heat damages in deep mines, a cool-wall cooling technology and its working model are proposed based on the principles of heat absorption and insulation in this paper. During this process, the differential equation of thermal equilibrium for roadway control unit is built, and the heat adsorption control equation of cool-wall cooling system is derived by an integral method, so as to obtain the quantitative relationship among the heat absorption capacity of cooling system, the heat dissipating capacity of surrounding rock and air temperature change. Then, the heat absorption capacity required by air temperature less than the standard value for safety is figured out by section iterative method with the simultaneous solution of heat absorption control equation and the heat dissipation density equation of surrounding rock. Finally, the results show that as the air temperature at the inlet of roadway is 25 °C, the roadway wall is covered by heat-absorbing plate up to 39% of the area, as well as the cold water is injected into the heat-absorbing plate with a temperature of 20 ° C and a mass flow of 113.6 kg/s, the air flow temperature rise per kilometer in the roadway can be less than 3 °C.

By utilizing wave velocity imaging technology, the uniaxial multi-stage loading test was conducted on siltstone to attain wave velocity imagings during rock fracture. Based on the time series parameters of acoustic emissions (AE), joint response characteristics of the velocity field and AE during rock fracture were analyzed. Moreover, the localization effect of damage during rock fracture was explored by applying wave velocity imagings. The experimental result showed that the wave velocity imagings enable three-dimensional (3-D) visualization of the extent and spatial position of damage to the rock. A damaged zone has a low wave velocity and a zone where the low wave velocity is concentrated tends to correspond to a severely damaged zone. AE parameters and wave velocity imagings depict the changes in activity of cracks during rock fracture from temporal and spatial perspectives, respectively: the activity of cracks is strengthened, and the rate of AE events increases during rock fracture; correspondingly, the low-velocity zones are gradually aggregated and their area gradually increases. From the wave velocity imagings, the damaged zones in rock were divided into an initially damaged zone, a progressively damaged zone, and a fractured zone. During rock fracture, the progressively damaged zone and the fractured zone both develop around the initially damaged zone, showing a typical localization effect of the damage. By capturing the spatial development trends of the progressively damaged zone and fractured zone in wave velocity imagings, the development of microfractures can be predicted, exerting practical significance for determining the position of the main fracture.

The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment (AE: i. e., at the free surface) have been extensively investigated, yet they are rarely estimated in the quasi-vacuum environment (VE: i. e., far from free surface), which is of special importance in engineering practice. Several precise laboratory tests(i. e., split Hopkinson pressure bar test) on marble samples in both AE and VE were performed to investigate physical and dynamic mechanical behaviors of marble after heat treatment (25 °C to 900 °C) in AE and VE. The tests results demonstrate that related properties of marble could be divided into three different stages by corresponding critical temperatures of 300 °C and 600 °C, at which heat damage factors are 0.29 (0.30) and 0.88 (0.92) in VE (AE), respectively. The thermal damage developes more fully in AE than in VE. The thermal environment plays an important role, especially in Stage 3. Specifically, a conspicuous difference (greater than 20%) between AE and VE occurs in corresponding dynamic strength and the anti-deformation capacities of tested marble specimen. The influence of heat damage of rock is very important and valuable in engineering practice, particularly when the temperature is very high (greater than 600 °C).

In order to understand the influence of brittleness and confining stress on rock cuttability, the indentation tests were carried out by a conical pick on the four types of rocks. Then, the experimental results were utilized to take regression analysis. The eight sets of normalized regression models were established for reflecting the relationships of peak indentation force (PIF) and specific energy (SE) with brittleness index and uniaxial confining stress. The regression analyses present that these regression models have good prediction performance. The regressive results indicate that brittleness indices and uniaxial confining stress conditions have non-linear effects on the rock cuttability that is determined by PIF and SE. Finally, the multilayer perceptual neural network was used to measure the importance weights of brittleness index and uniaxial confining stress upon the influence for rock cuttability. The results indicate that the uniaxial confining stress is more significant than brittleness index for influencing the rock cuttability.

Dense captioning aims to simultaneously localize and describe regions-of-interest (RoIs) in images in natural language. Specifically, we identify three key problems: 1) dense and highly overlapping RoIs, making accurate localization of each target region challenging; 2) some visually ambiguous target regions which are hard to recognize each of them just by appearance; 3) an extremely deep image representation which is of central importance for visual recognition. To tackle these three challenges, we propose a novel end-to-end dense captioning framework consisting of a joint localization module, a contextual reasoning module and a deep convolutional neural network (CNN). We also evaluate five deep CNN structures to explore the benefits of each. Extensive experiments on visual genome (VG) dataset demonstrate the effectiveness of our approach, which compares favorably with the state-of-the-art methods.

Tight glutenite reservoirs are widely developed in Bohai Bay Basin, East China. They are mostly huge thick and rely on hydraulic fracturing treatment for commercial exploitation. To investigate the propagation behavior of hydraulic fractures in these glutenite reservoirs, the geological feature of reservoirs in Bohai Bay Basin is studied firstly, including the reservoir vertical distribution feature and the heterogeneous lithology. Then, hydraulic fracturing treatments in block Yan 222 are carried out and the fracturing processes are monitored by the microseismic system. Results show the hydraulic fractures generated in the reservoirs are mostly in X shape. The cause of X-shaped hydraulic fractures in this study is mainly ascribed to (I) the reservoir heterogeneity and (II) the stress shadow effect of two close hydraulic fractures propagating in the same orientation, which is confirmed by the following numerical simulation and related research in detail. This study can provide a reference for the research on the fracturing behavior of the deep thick glutenite reservoirs.

With the gradual depletion of available ore at shallow depth, deep mines have been widely operated around the world and therefore need a longer distance to transport the backfill to the underground stope. In this case, the determination of pressure drop is more important in the pipeline transportation system design. As the pilot loop systems require a large amount of capital and manual investment, even its results are reliable, there is an urgent need to find an alternative simple and cost-saving method to determine the pressure drop. Hence, laboratory L-pipe and a pilot-loop tests were employed to study the flow properties of cemented paste backfill cured at various solid and binder content. The results indicate that the L-pipe test presented a similar trend to the loop test, but the L-pipe was characterized by higher pressure drop values for various solid and cement contents. As cement content increased beyond 0%, the paste in the L-pipe showed a slighter difference in pressure drop evolution compared to the paste in the loop-pipe. These results suggest that the simple L-pipe is a workable substitute for semi-industrial loop tests and can provide guidance for designing practical CPB pipeline systems in deep mines.

In FLAC^3D, cable element or modified pile element can be used to build slope anchoring model. However, the difference between the two structural elements and their influence on the calculation results have not been studied in depth. In order to solve this problem, the Xiashu loess slope anchoring models based on cable element and modified pile element were constructed respectively. A variety of anchoring schemes were designed by orthogonal experiment method, and then they were brought into the model for calculation and the calculation results were analyzed by range analysis and variance analysis. The results show that the modified pile element can bear the bending moment and reflect the strain softening property of the grout. From the perspective of slope safety factor, the anchorage length and anchor bolt spacing are the main factors affecting the stability of the slope, and the anchorage angle is the secondary factor. The grout in cable element is assumed to be an elastic-perfectly plastic material, so the safety factor of the slope can be significantly increased by increasing the length of the anchor bolts. This will bring potential risks to the slope treatment project. Therefore, in the calculation of the slope anchoring model, the modified pile element is more suitable for simulating the anchor bolt.

In order to study the interaction between various fouling particles and ballast, a multi-layer and multi-scale discrete element model (DEM) including the sleeper, ballast bed and the surface layer of subgrade was developed. Two typical fouling particles, the hard particles (sand) and soft ones (coal fines), are considered. A support stiffness test of the ballast bed under various fouling conditions was conducted to calibrate the microscopic parameters of the contact model. With the model, the influence of fouling particles on the mechanical behavior and deformation of the ballast bed was analyzed from macro and micro perspectives. The results show that the increase in the strength of the fouling particles enlarges the stiffness of the ballast bed. Hard particles increase the uniformity coefficient of the contact force bond γ of ballast by 50.4%. Fouling particles increase the average stress in the subgrade, soft particles by 2 kPa and hard particles by 1 kPa. Hard particles can reduce the elasticity, plastic deformation and energy dissipation in the track structure. As the fouling particle changes from hard to soft, the proportion of the settlement in ballast bed increases to 40.5% and surface layer of swbgrade settlement decreases to 59.5%. Thus, the influence of fouling particles should be considered carefully in railway design and maintenance.

In the present work, uniaxial compressive tests were carried out on limestone-like samples containing two parallel open fissures or cement-infilled fissures with different geometries. Mechanical property and crack behavior of limestone-like samples with two parallel open fissures or cement-infilled fissures were affected by bridge inclination angle and fissure inclination angle. Four types of coalescence of rock bridge for samples containing open fissures or cement-infilled fissures were summarized and classified. The closure of tensile crack was observed in the samples with small fissure inclination angle. This is a new phenomenon which is not mentioned in previous studies. Test results show that the peak strength, crack initiation stress, and coalescence type are different between open fissures and cement-infilled fissures. The reason for this phenomenon is that grouting of cement can transfer stress and reduce stress concentration at the flaw tip and rock bridge area.

A method combining the pseudo-dynamic approach and discretization technique is carried out for computing the active earth pressure. Instead of using a presupposed failure mechanism, discretization technique is introduced to generate the potential failure surface, which is applicable to the case that soil strength parameters have spatial variability. For the purpose of analyzing the effect of earthquake, pseudo-dynamic approach is adopted to introduce the seismic forces, which can take into account the dynamic properties of seismic acceleration. A new type of micro-element is used to calculate the rate of work of external forces and the rate of internal energy dissipation. The analytical expression of seismic active earth pressure coefficient is deduced in the light of upper bound theorem and the corresponding upper bound solutions are obtained through numerical optimization. The method is validated by comparing the results of this paper with those reported in literatures. The parametric analysis is finally presented to further expound the effect of diverse parameters on active earth pressure under non-uniform soil.

Within the multi-barrier system for high-level waste disposal, the technological gap formed by combined buffer material block becomes the weak part of buffer layer. In this paper, Gaomiaozi bentonite buffer material with technological gap was studied, the heat transfer induced by liquid water flow and water vapor was embedded into the energy conservation equation. Based on the Barcelona basic model, the coupled thermo-hydro-mechanical model of unsaturated bentonite was established by analyzing the swelling process of bentonite block and the compression process of joint material. The China-Mock-up test was adopted to compare the numerical calculation results with the test results so as to verify the rationality of the proposed model. On this basis, the effect of joint self-healing on dry density, thermal conductivity and permeability coefficient of buffer material was further analyzed. The results show that, with bentonite hydrating and swelling, the joint material gradually increases in dry density, and exhibits comparatively uniform hydraulic and thermal conductivity properties as compacted bentonite block. As a result, the buffer material gradually shifts to homogenization due to the coordinated deformation.

Predicting the life of Ni-Cd battery for electric multiple units (EMU) can not only improve the safety and reliability of battery, but also reduce the operating costs of EMU. For this reason, a life prediction method based on linear Wiener process is proposed, which is suitable for both monotonic and non-monotonic degraded systems with accurate results. Firstly, a unary linear Wiener degradation model is established, and the parameters of the model are estimated by using the expectation-maximization algorithm (EM). With the established model, the remaining useful life (RUL) of Ni-Cd battery and its distribution are obtained. Then based on the unary Wiener process degradation model, the correlation between capacity and energy is analyzed through Copula function to build a binary linear Wiener degradation model, where its parameters are estimated using Markov Chain Monte Carlo (MCMC) method. Finally, according to the binary Wiener process model, the battery RUL and its distribution are acquired. The experimental results show that the binary linear Wiener degradation model based on capacity and energy possesses higher accuracy than the unary linear wiener process degradation model.

The stochastic resonance behavior of coupled stochastic resonance (SR) system with time-delay under mass and frequency fluctuations was studied. Firstly, the approximate system model of the time-delay system was obtained by the theory of small time-delay approximation. Then, the random average method and Shapiro-Loginov algorithm were used to calculate the output amplitude ratio of the two subsystems. The simulation analysis shows that increasing the time-delay and the input signal amplitude appropriately can improve the output response of the system. Finally, the system is applied to bearing fault diagnosis and compared with the stochastic resonance system with random mass and random frequency. The experimental results show that the coupled SR system taking into account the actual effect of time-delay and couple can more effectively extract the frequency of the fault signal, and thus realizing the diagnosis of the fault signal, which has important engineering application value.

The purpose of the research is to assess the sound absorption performance (SAP) of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit. For this purpose, the influences of structural parameters on the SAP of acoustic metamaterials were investigated by using experimental testing and a validated theoretical model. In addition, the sandwich structure was optimized by the genetic algorithm. The research shows that the panel thickness and micro-orifice diameter mainly affect the second resonant frequency and second peak sound absorption coefficient (SAC) of the structure. The unit cell size is found to influence the first and second resonant frequencies and two peaks of the SAC. An extremely low side-length of the honeycomb core decreases the SAP of the structure for low-frequency noise signals. Additionally, the sandwich structure presents a better SAP when the diameter of micro-orifices on the front micro-perforated panel (MPP) exceeds that of the back MPP. The sandwich structure shows better noise reduction performance after the optimization aiming at the noise frequency outside trains.