The rational design of polymer acceptors with strong and broad absorption is critical to improve photovoltaic performance. In this work, a new polymer acceptor PY9-T based on heptacyclic benzotriazole (Y9-C16) as a building block and thiophene unit as the linking unit was synthesized, which exhibited a low bandgap (1.37 eV) and a high extinction coefficient of the neat film (1.44×105 cm−1). When PY9-T was blended with the wide bandgap polymer donor PBDB-T, the all-polymer solar cells (APSCs) showed a high power conversion efficiency (PCE) of 10.45% with both high open circuit voltage of 0.881 V and short-circuit current density of 19.82 mA/cm2. In addition, APSCs based on PY9-T show good thermal stability, as evidenced by slight changes morphologies when annealed at 100 °C. These results suggest that Y9-C16 provides a new building block to develop efficient and stable polymer acceptors.
The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed (HCP) zirconium were investigated by molecular dynamics simulations, which were combined with experimental observation under high resolution transmission electron microscopy. The results show that externally applied loading first induced the HCP to body-centered cubic (BCC) phase transition in the Pitsch-Schrader (PS) orientation relationship (OR). Then, the face-centered cubic (FCC) structure transformed from the BCC phase in the Bain path. However, the HCP-to-BCC transition was incomplete at 100 K and 300 K, resulting in a prismatic-type OR between the FCC and original HCP phase. Additionally, at the temperature ranging from 100 K to 600 K, the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR, resulting in a basal-type relation between the newly generated HCP and FCC phases. A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%. Besides, the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity. This study reveals the deformation mechanisms in HCP-Zr at different temperatures, which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.
Hollow-structured Cu0.3Co2.7O4 microspheres have been synthesized by a simple one-pot template-free hydrothermal method with copper sulfate, cobalt acetate and ammonia as raw materials. The products were characterized by powder X-ray diffraction, energy dispersive X-ray analysis, selected area electron diffraction, high-resolution transmission electron microscopy, scanning electron microscopy and BET measurements. The research results show that the hollow Cu0.3Co2.7O4 microspheres consist of single-crystalline nanocubes with the diameter of about 20 nm. The formation mechanism of hollow Cu0.3Co2.7O4 microspheres is suggested as Ostwald ripening in a solid-solution-solid process, and Cu0.3Co2.7O4 microspheres are mesoporous containing two pore sizes of 3.3 and 5.9 nm. The as-prepared Cu0.3Co2.7O4 sensors have optimal gas responses to 50×10−6 mg/m3 C2H5OH at 190 °C.
To improve the adsorption performance and simplify uranium separation from aqueous media in post-treatment processes, a magnetic CoFe2O4@rGO composite was synthesized by microwave-hydrothermal method. The results of XRD, Raman, TEM/HRTEM, FTIR, BET and VSM characterization show that spinel-type cobalt ferrite CoFe2O4 nanoparticles ca. 13.4 nm in size are dispersedly anchored on the graphene sheet, and the saturation magnetization of the nanocomposite is 46.7 mA/(m2·g). The effects of different pH, initial concentration and other conditions on uranium adsorption capacity were investigated, and adsorption kinetics equations were fitted to determine the adsorption behaviour of uranium on CoFe2O4@rGO in simulated uranium-containing seawater. It was observed that the uranium adsorption capacity of CoFe2O4@rGO composite at pH=5 is 127.6 mg/g, which is 1.31 and 2.43 times that of rGO and pure CoFe2O4. The adsorption process conforms to Langmuir and quasi-second-order kinetic model. The excellent adsorption performance of CoFe2O4@rGO makes it potentially useful in the treatment of uranium-polluted water.
The almost completely dense copper was prepared by ultrafine copper powder prepared with both methods of electrolysis and novel water-gas atomization through cold isostatic pressing (CIP) and sintering under atmospheric hydrogen. Fine copper powder possesses the higher sintering driving force, thereby promoting shrinkage and densification during the sintering process. The grain size of sintered samples by electrolytic copper powder is smaller than that prepared by the atomized copper powder, and the twin crystals are particularly prone to forming in the former sintered microstructure due to the raw powder with low oxygen content and high residual stress originating from the CIP process. The relative density of samples by electrolytic and atomized powder at 1000 °C sintering temperature achieves 99.3% and 97.4%, respectively, significantly higher than that of the powder metallurgy copper parts reported in the literature. Correspondingly, the ultimate tensile strength and yield strength of samples by both kinds of copper powder are approximately similar, while the elongation of the sintered sample by the electrolytic powder (60%) is apparently higher than the atomized powder (44%). The superior performance of samples fabricated by electrolytic powder is inferred from the full density and low oxygen level for there is no cuprous oxide in the grain boundaries.
The texture evolution, twin crystallographic nature and grain orientation variation during the solution heat treatment process of the 304 stainless steel pipe were studied. It was found that after the solution heat treatment, the texture type clearly changed, and the texture strength was greatly increased. During the solution heat treatment process, grain boundaries migrated along the orientation available for grain growth, giving rise to abnormal growth of some grains through merging with the adjacent small grains. After the solution heat treatment, more <111>60° twins formed in the microstructures of the 304 stainless steel pipe, and the fraction of the twin boundaries showed a pronounced increase. Analysis of the twin crystallographic nature of the FCC crystals showed that four kinds of twin variants can be formed within austenite parent grains, and twelve kinds of misorientations can be formed between the austenite parent grains and the secondary twins.
Most of the materials used in engineered cementitious composite are fine in size to achieve ductile nature. Stone slurry powder (SSP) is an inert material obtained from stone industries as by-product which may cause hazardous impact on environment. In this research work, partial replacement of silica sand (SS) and fine sand (FS) by SSP with different contents (25% and 50% each) for making engineered cementitious composite has been explored. The performance was evaluated on the basis of strength, tensile strain, mid span deflection capacity, ultra-sonic pulse velocity and microstructure. Mechanical strength was found to be increased at 25% SSP in both replacements; whereas, strength decreased slightly at 50% replacement. Tensile strain, mid span deflection and quality of concrete were enhanced with increase in SSP content. Using SSP formed denser cementitious composite can help to save the natural resources and contribute in making green cementitious composite.
This work investigated the separation of potassium from sodium in alkaline solution using substituted phenol-based extradants. Superior potassium extraction was achieved with 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) than 4-sec-butyl-2-(α-methylbenzyl) phenol (BAMBP). The optimum conditions for the extraction were 1 mol/L t-BAMBP, 3:1 volumetric phase ratio (O/A), and two extraction stages. After cross-current extraction, the extraction ratio of potassium reached 90.8%. After scrubbing with deionised water at phase ratio of 4:1 and scrubbing stage of 4, a sodium scrubbing efficiency of 88.2% was obtained. After stripping using 1 mol/L H2SO4 at phase ratio of 3:1, the stripping efficiency of potassium reached 94.2%. The potassium/sodium (K/Na) concentration ratio increased 14.3 times from 0.15 in the feed solution to 2.3 in the stripping solution. The efficient separation of potassium from sodium in alkaline solution was achieved via solvent extraction with t-BAMBP.
To recover metal from copper slags, a new process involving two steps of oxidative desulfurization followed by smelting reduction was proposed in which one hazardous waste (waste cathode carbon) was used to treat another (copper slags). The waste cathode carbon is used not only as a reducing agent but also as a fluxing agent to decrease slag melting point. Upon holding for 60 min in air atmosphere first and then smelting with 14.4 wt% waste cathode carbon and 25 wt% CaO for 180 min in high purity Ar atmosphere at 1450 °C, the recovery rates of Cu and Fe reach 95.89% and 94.64%, respectively, and meanwhile greater than 90% of the fluoride from waste cathode carbon is transferred into the final slag as CaF2 and Ca2Si2F2O7, which makes the content of soluble F in the slag meet the national emission standard. Besides, the sulphur content in the obtained Fe-Cu alloy is low to 0.03 wt%.
The energy metabolism structure of microbial community plays an important role in the process of biohydrometallurgy. In this article, an artificial microbial community composed of three strains (Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum and Acidithiobacillus thiooxidans) was used to leach three kinds of chalcopyrites with different iron-sulfur ratios. After 36 d of leaching, the chalcopyrite with iron-sulfur ratio of about 1:1 achieved the highest copper extraction (69.62%). In the early stage, iron oxidizing bacteria predominated, and the expression of rus and rio was 8 times higher than that in the late stage. In the late stage, sulfur oxidizing bacteria predominated, and the expression of tetH and HdrAB was 4 times higher than that in the early stage. Furthermore, the three bioleaching systems above were added with elemental sulfur (3 g/L); the chalcopyrite with iron-sulfur ratio of about 2:1 achieved the highest copper extraction (80.63%). The results suggest that the energy metabolism structure of the microbial community could be changed by changing the iron-sulfur ratio during the leaching process for improving the leaching efficiency of chalcopyrite.
In this work, the bioleaching process of pyrite, chalcocite and covellite which were the main phase compositions for Zijin copper mineral was comprehensively studied. The influence parameters, such as leaching temperature, Fe3+ concentration, pH of solution and bacteria concentration were investigated. The leaching kinetics of the pyrite, chalcocite and covellite under the studied conditions was successfully modeled by an empirical diffusion-like equation, respectively. The apparent activity energy of pyrite leaching, chalcocite leaching (stage II) and covellite leaching was calculated to be 69.29, 65.02 and 84.97 kJ/mol, respectively.
Due to the influence of mining disturbance stress, it is of great significance to better understand the bearing characteristics of fully grouted bolts under different pull-out loading rates. For this purpose, a series of laboratory pull-out tests were conducted to comprehensively investigate the effects of different pull-out loading rates on the mechanical performance and failure characteristics of fully grouted bolts. The results show that the mechanical performance of the anchored specimen presents obvious loading rate dependence and shear enhancement characteristics. With the increase of the pull-out loading rates, the maximum pull-out load increases, the displacement and time corresponding to the maximum pull-out load decrease. The accumulated acoustic emission (AE) counts, AE energy and AE events all decrease with the increase of the pull-out loading rates. The AE peak frequency has obvious divisional distribution characteristics and the amplitude is mainly distributed between 50–80 dB. With the increase of the pull-out loading rates, the local strain of the anchoring interface increases and the failure of the anchoring interface transfers to the interior of the resin grout. The accumulated AE counts are used to evaluate the damage parameter of the anchoring interface during the whole pull-out process. The analytical results are in good agreement with the experimental results. The research results may provide guidance for the support design and performance monitoring of fully grouted bolts.
The wall surface roughness renders a significant impact on ventilation of roadways and cross-sectional wind speed distribution. Herein, the wall roughness (Ra) in the roadway has been defined theoretically. Moreover, three-center arched roadway models for different situations are established based on the normal distribution of roof roughness. The influence of inlet velocity, roof roughness and roadway height on wind speed distribution is systematically studied by using Fluent software. At Ra=0.1 m, the simulation results reveal that the wind speed is negatively related to the distance from the wall to the point where 80% of the central wind speed is reached (DA). Also, the wind speed distribution is significantly influenced by increasing the roof roughness. However, the wind speed distribution becomes asymmetric at Ra=0.2 m and 0.3 m. Furthermore, the low-speed area (v≤1 m/s) started to concentrate on the roof with the increase of roadway height. Overall, an Ra value of <0.1 m can reduce the influence of wall roughness on wind speed distribution of the roadway, which is suggested in practical applications.
In view of the mechanics characteristic of cemented tailings backfill (CTB) at early age, the separation Hopkinson pressure bar test device was used to explore the effects of curing age and impact energy. A total of 48 CTB samples with diameter of 50 mm and length of 25 mm were prepared with curing ages of 3, 5, 7 and 9 d. Impact tests under different impact energy (10, 20, 30 and 40 J) were carried out. The microstructure of CTB at different ages was analyzed by scanning electron microscopy (SEM). The results show that, the curing age mainly affects the mechanical properties and internal structure of early-age CTB. With increasing curing age, the mechanical properties of early-age CTB change from viscoelasticity to brittleness. The impact energy mainly affects the response of dynamic peak compressive strength to strain rate. Under low strain rate, the structure of CTB is broken, but still has bearing capacity, affecting the formation of later strength. It is concluded that the structural loses completely under the action of high strain rate. Therefore, the control of impact energy and the protection of curing age should be fully considered in actual production process.
Taking the raceway roundness error into account, mechanical characteristics of cross roller bearings (CRBs) were investigated. A static analysis model of CRBs considering the raceway roundness error was established. Based on this model, the rotational accuracy and load distribution of CRBs under constraints of geometry and external loads were derived. The fatigue life of CRBs with roundness error was calculated by applying Palmgren-Miner linear cumulative damage theory. The influence of inner and outer raceway roundness error on the performance of the CRBs, such as rotational accuracy, load distribution, and fatigue life, was studied through the analysis of examples. The results indicate that the influence of roundness error on the rotating inner raceway is more significant than that of roundness error on the nonrotating outer raceway. The roundness error on the rotating inner raceway always degrades the performance of CRBs. However, a proper roundness error on the nonrotating outer raceway can reduce the loads acting on the rollers and thus improve the fatigue life of CRBs. The effect of the roundness error amplitude on the bearing performance is ordinal, whereas the effect of the roundness order on the bearing performance is not in order.
The hybrid tracked vehicles(HTV) usually adopt series hybrid powertrain with extra steering mechanism, which has relatively low transmission efficiency and reduces the flexibility of structural arrangement. To overcome the disadvantages, a new kind of single-mode powertrain has been proposed. The power-split hybrid powertrain is composed of three planetary gear (PG) sets connected to one engine, left and right track outputs, and three motors. The proposed powertrain can realize steering while going forward by controlling the output torque on each side without extra steering mechanism or steering shaft. Due to the diversity of the connection way between components and planetary gear sets, a rapid configuration design approach is proposed for the design selection of HTV. The automated dynamic modelling method can show the one-to-one correspondence with the selected feasible groups by establishing two characteristic matrices, which is more simple than other researches. The analytically-based method is proposed to classify all possible connection designs into several groups to decrease the searching scope with improved design efficiency. Finally, the optimal control strategy is used to find the design with optimal fuel economy under typical condition of HTV. The case study is implemented by the proposed design approach which demonstrates better design performances compared with the existing series-hybrid HTV.
The double drum coal shearer is widely applied for the underground coal exploration in the mining industry. The vibration and noise control are significant factors for the stability design of the double drum coal shearer. In this paper, the vibration properties of a double drum coal shearer are firstly investigated. The horizontal, transverse and torsional vibrations of the motor body and the angle displacements of the rockers are taken into account. The walking units and the hydraulic units are modeled by the stiffness-damping systems. The nonlinear equation of motion of the double drum coal shearer is established by applying the Lagrange’s equation. The nonlinear vibration response of the system is calculated by using the Runge Kutta numerical method. The effects of the shearing loads, the equivalent damping and stiffness of the walking units, the inclination angels of the rockers and the equivalent damping and stiffness of the hydraulic units on the vibration properties of the system are discussed.
We consider an iterative phase synchronization scheme based on maximum a posteriori probability algorithm. In classical approaches, the phase noise estimation model considers one sample per symbol at the channel and receiver. However, information theoretic studies suggested use of more than one sample per symbol at the channel and receiver for achieving higher performance. In this article, a soft-information aided iterative receiver is derived, which uses off-the-shelf blocks for detection and demodulation by keeping the complexity of the receiver acceptable. We consider here two samples per symbols at the channel and receiver in a pragmatic paradigm. It is shown that phase noise estimation can be significantly improved at the expense of modest processing overhead. Simulation results are presented for low-density parity check coded quadrature amplitude modulations. Our results show a significant performance improvement for strong phase noise values compared to classical receiver approaches.
An experimental study and theoretical analysis were carried out to explore the ground-borne vibration generated by elevated high-speed railway in rock strata. Taking a typical rail line constructed on rock area in China as the research object, a set of field tests was performed on Rizhao-Lankao High-Speed Railway, the bridge and ground vibrations were measured as trains passed at 330–340 km/h, then the transferring law and spatial distribution under individual frequencies were investigated. The experiment results indicate that the bridge frequency spectrum exhibited relatively high-frequency vibration peaks caused by short-wavelength irregularity; ground vibration farther than 30 m away can be amplified with a higher frequency and numerous components. Furthermore, the wave propagation equation of a stratified rock strata was established based on direct-stiffness method to explore the vibration attenuation rules via frequency-domain analysis. It is found that the rock area has a weaker correlation between vibration transmissibility and frequency, thicker and harder rock strata loss their vibration attenuation capacity. It can be concluded that the high-speed railways induced vibration on rock strata shows a wide frequency band and large amplitude, the design of reducing vibration aimed at specific frequency is important according to next more detailed numerical study.
To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials (RCBMs) with dry- and wet-curing conditions, uniaxial compression and cyclic loading—unloading tests were carried out on rubber cement mortar (RCM). The mechanical properties of the uniaxial compression specimens cured at 95% (wet-curing) and 50% (dry-curing) relative humidities and cyclic loading—unloading specimens cured at wet-curing were analyzed. Under uniaxial compression, the peak stress loss ratio is higher for dry-curing than for wet-curing. The peak strain decreases with the increase of rubber content, and the peak strain increases with the decrease of curing humidity. Under cyclic loading—unloading, the variation trends of residual strain differences of the normal cement mortar and RCM at each cyclic level with the number of cycles are basically the same, but the failure modes are different. The analysis of the internal mesostructure by a scanning electron microscope (SEM) shows that initial damage is further enhanced by reducing curing humidity and adding rubber aggregate. The damage constitutive model based on strain equivalence principle and statistical theories was used to describe the uniaxial compression characteristics of RCM, and the law of mechanical damage evolution was predicted.
For the resource utilization of the solid waste coking sulfur paste and the improvement of performance of the asphalt mixture, a method for preparing modified asphalt mixture with coking sulfur paste modifier (CSPM) is herein proposed. Compared with the matrix asphalt mixture, the Marshall stability of the 30% CSPM modified asphalt mixture increased by 38.3%, the dynamic stability increased by nearly one time (reaching 1847.5 times/mm), the splitting strength ratio increased by 39.3% while the splitting tensile strength decreased by 11.7%. After curing, the performance of the CSPM modified asphalt mixture was further improved. The results show that CSPM improved the high temperature stability and water damage resistance of the asphalt mixture, and the low-temperature anti-cracking performance of that was slightly reduced. Chemical analysis of asphalt binders shows that a little sulfur reacted with asphalt to produce polysulfide compounds (R-Sx-R′), and a part of sulfur existed in the form of crystalline sulfur which was further increased after curing. The presence of crystalline sulfur as an inorganic filler is the key point for improving the high temperature stability and water resistance performance of modified asphalt mixture.
Combining fiber reinforced polymer (FRP) with seawater sea-sand concrete (SSC) can solve the shortage of river sand that will be used for marine engineering construction. The bond performance of BFRP bars and SSC specimens is researched by pull-out test in this paper. The effects of the parameters, such as bar type, bar diameter, concrete type and stirrup restraint, are considered. It is beneficial to the bonding performance by the reduction of bar diameter. The utilization of seawater sea-sand has a low influence on the bond properties of concrete. The bond strength of BFRP is slightly lower than the steel rebar, but the difference is relatively small. The failure mode of the specimen can be changed and the interfacial bond stress can be improved by stirrups restraint. The bond-slip curves of BFRP ribbed rebar include micro slip stage, slip stage, descent stage and residual stage. The bond stress shows the cycle attenuation pattern of sine in the residual stage. In addition, the bond-slip model of BFRP and SSC is obtained according to the experimental results and related literature, while the predicted curve is also consistent well with the measured curve.
Diesel soot subjected to high exhaust temperature suffers from thermal ageing, which is difficult to be removed by regeneration process. Based on the thermogravimetric (TG) analysis and images by high resolution transmission electron microscope (HRTEM), effects of thermal ageing temperature, ageing time and oxygen concentration on oxidation characteristic of soot are investigated. The activation energy of soot increases with the increase of ageing temperature and oxygen concentration. The activation energy increases rapidly when the ageing time is less than 45 min, and then it keeps in a value of 157 kJ/mol when the ageing time is between 45 and 60 min. Compared to the soot without thermal ageing, the shape of ageing soot particles presents shorter diameter and more regular circle by observing soot nanostructure. With the increase of ageing temperature, ageing time and oxygen concentration, the more stable structure of “shell and core” is shown in the basic carbon. The soot has an increased fringe length, decreased tortuosity and separation distance after thermal ageing process, which leads to the deepening of the disorder degree of soot nanostructures and reduction of soot oxidation activity. Consequently, the thermal ageing process should be avoided in order to optimize the active regeneration strategy.
Based on the collaborative exploitation of deep mineral resources and geothermal resources, the thermal accumulation process of cemented tailings backfill (CTB) was studied by numerical simulation. The effects of thermal accumulation time, slurry proportions and temperature conditions on the thermal accumulation of backfill are analyzed, the influence of the heat conduction between backfill and surrounding rock, the heat convection between backfill and airflow on thermal accumulation were compared simultaneously. The results show that the total thermal accumulation capacity increases by approximately 85% within 10–90 d. The influence of surrounding rock temperature and initial temperature on total thermal accumulation capacity is more significant and it is approximately 2 times of the influence of slurry proportions under the conditions of this study. It is clear that the rise of surrounding rock temperature and the decrease of initial temperature can improve the thermal accumulation capacity more effectively. Moreover, the heat conduction accounts for a considerable proportion in the process of thermal accumulation, the average heat conduction capacity is approximately 25 times of the heat convection capacity. This study can provide the theoretical basis and application reference for the optimization of thermal accumulation process of CTB in the exploitation of geothermal resources.
Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation. This paper introduced a computational model for analyzing probabilistic dynamic responses of three-dimensional (3D) coupled train-ballasted track-subgrade system (TBTSS), where the coupling effects of uncertain rail irregularities, stiffness and damping properties of ballast and subgrade layers were simultaneously considered. The number theoretical method (NTM) was employed to design discrete points for the multi-dimensional stochastic parameters. The time-histories of stochastic dynamic vibrations of the TBSS with systematically uncertain structural parameters were calculated accurately and efficiently by employing the probability density evolution method (PDEM). The model-predicted results were consistent with those by the Monte Carlo simulation method. A sensitivity study was performed to assess the relative importance of those uncertain structural parameters, based on which a case study was presented to explore the stochastic probability evolution mechanism of such train-ballasted track-subgrade system.