The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1−xTbx)5Si1.72-Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (TC) of the compounds. The magnetic entropy change of (Gd1−xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|ΔSmax| = 2.24 J/(kg·K), TC = 198 K).
The hot deformation simulation of a ZK60 magnesium alloy at different temperatures from 373 to 673 K and different strain rates of 0.1, 0.01 and 0.002 s−1 was studied by using the Gleebe-1500 simulator. The plastic deformation behavior was measured and the deformation activation energy was calculated. The microstructures of ZK60 magnesium alloy with an addition of neodymium during the deformation process were observed by using Polyvar-MET optical microscope and Tecnai G2 20 TEM. The results show that the working hardening, the dynamic recovery and the dynamic recrystallization occur during the plastic deformation process at different temperatures and strain rates. The dynamic recrystallization starts when the temperature is over 473 K and the DRX grain size after hot deformation is only 5–10 μm. So the refined grains improve both the tensile strength and the elongation of alloys at room temperature. Neodymium is added into the alloy and a precipitate phase Mg12Nd that impedes the movement of dislocations is formed, which benefits to increasing mechanical properties of ZK60 magnesium alloy.
(PEO)8LiClO4-SiO2 composite polymer electrolytes(CPEs) were prepared by in-situ reaction, in which ethyl-orthosilicate (TEOS) was catalyzed by HCl and NH3·H2O, respectively. The ionic conductivity, the contact angle and the morphology of inorganic particles in the CPEs were investigated by AC impedance spectra, contact angle method and TEM. The conductivities of acid-catalyzed CPE and alkali-catalyzed CPE are 2.2×10−5 and 1.1×10−5 S/cm respectively at 30 °C. The results imply that the catalyst plays an important role in the structure of in-situ preparation of SiO2, and influences the surface energy and conductivity of CPE films directly. Meanwhile, the ionic conductivity is related to the surface energy.
Based on the microscopic phase-field dynamic model and the microelasticity theory, the coarsening behavior of L12 and DO22 phases in Ni75CrxAl25−x alloy was simulated. The results show that the initial irregular shaped, randomly distributed L12 and DO22 phases are gradually transformed into cuboidal shape with round corner, regularly aligned along directions [100] and [001], and highly preferential selected microstructure is formed during the later stage of precipitation. The elastic field produced by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics, and there is no linear relationship between the cube of the average size of precipitates and the aging time, which does not agree with the results predicted by the classical Lifshitz-Slyozov-Wagner. The coarsening processes of L12 and DO22 phases are retarded in elastically constrained system. In the concurrent system of L12 and DO22 phases, there are two types of coarsening modes: the migration of antiphase domain boundaries and the interphase Ostwald ripening.
ZnO thin films were prepared by direct current(DC) reactive magnetron sputtering under different oxygen partial pressures. And then the samples were annealed in vacuum at 450 °C. The effects of the oxygen partial pressures and the treatment of annealing in vacuum on the photoluminescence and the concentration of six intrinsic defects in ZnO thin films such as oxygen vacancy(VO), zinc vacancy(VZn), antisite oxygen(OZn), antisite zinc(ZnO), interstitial oxygen(Oi) and interstitial zinc(Zni) were studied. The results show that a green photoluminescence peak at 520 nm can be observed in all the samples, whose intensity increases with increasing oxygen partial pressure; for the sample annealed in vacuum, the intensity of the green peak increases as well. The green photoluminescence peak observed in ZnO may be attributed to zinc vacancy, which probably originates from transitions between electrons in the conduction band and zinc vacancy levels, or from transitions between electrons in zinc vacancy levels and up valence band.
Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h. Hardness tester, OM, XRD, SEM were used to investigate the mechanical properties and microstructures of the alloy. The results show that the hardness increases by 1–2 (HRC) and the compressive strength decreases slightly after cryogenic treatment. The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbide η-Fe2C. The decrease in compressive strength is caused by residual stress. The great amount of carbides, such as Cr7C3 and Fe2MoC, in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress. The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite. The cryogenic martensite is long and fine; while the non-cryogenic martensite is short and coarse. There is obvious surface relief of the cryogenic martensite transformation. It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly. The surface relief in the non-cryogenic martensite is wide and arranged in parallel, and the boundary of surface relief is not smooth. These characteristics may imply different growth ways of the two kinds of martensite.
In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% (mass fraction) Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AlN is formed after Mg3N2 is added. Both AlN and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AlN along (0001)Mg//(0001)AlN is 3.04%, which is very effective for heterogeneous nucleation.
A novel alkoxycarbonyl thiourea resin(ATR) was synthesized by monomer polymerization of oxydiethane-2,1-diyl dicarbonisothiocyanatidate and polyethylene polyamine, and characterized by FT-IR. The adsorption properties of ATR were investigated by batch test. The adsorption capacities for Au(III), Ag(I), Cu(II), Zn(II), Fe(III), Ca(II) and Mg(II) are 4.65, 0.40, 0.90, 0.86, 0.0080 and 0.016 mmol/g, respectively, when the adsorption condition is as follows: contact time 24 h, temperature 30 °C, initial concentration of Au(III) 5.08 mmol/L and that of other metals 0.10 mol/L, and concentration of acid 1.0 mol/L. The adsorption capacity for Au(III) increases with the increase of contact time, temperature and initial concentration of Au(III). The capacity after five adsorption-desorption cycles remains 90% that of the first time, and the separation factors of ATR for binary metal ion solutions are larger than 995, indicating that ATR is of good regeneration property and selectivity. XPS results show that the functional atoms of ATR supply electrons for Au and coordinate with Au during the adsorption.
With sol-gel method, nanometer La-Ti composite oxides were prepared. By means of atomic force microscope, the surface pattern, particle size distribution and specific surface area were studied. The newly prepared nanocrystals of La-Ti composite oxides were used as the catalysts to catalyze the dehydration of external compensated lactic acid to lactide. The lactide product was measured by polarimeter and micropolariscope. The results demonstrate that the ratio between D-lactide and L-lactide will not be equal to 1:1 if nanocrystals of La-Ti composite oxides are used as the catalysts, which implies, that nanocrystals of La-Ti composite oxides may be potential catalysts with a good selectivity.
A practical catalytic method to oxidize α-ionone with molecular oxygen using N-hydroxyphthalimide(NHPI) combined with acetylacetone cobatt(II) (Co(acac)2) was developed, and the probable catalytic mechanism was proposed. The influences of the reaction conditions on conversion of α-ionone and the selectivity of the major product (5-keto-α-ionone) were investigated, and the technical parameters for 5-keto-α-ionone were optimized. The results show that the primary product is 5-keto-α-ionone, and by-products include epoxy-α-ionone, as well as rearrangement products 4-keto-β-ionone and epoxy-β-ionone, which are characterized by infrared spectra, proton nuclear magnetic resonance spectra, mass spectra and elemental analysis. The selectivity of 5-keto-α-ionone and the conversion of α-ionone are 55.0% and 97.0%, respectively, when 30%(molar fraction) NHPI, 1.0%(molar fraction) Co(acac)2 and no solvent are employed under O2 pressure of 1.0 MPa and the reaction temperature of 65 °C for 11 h. The procedure shows good reproducibility in the parallel experiments.
Polyaniline(PAn) doped with multiple sulfonic acid system of dodecylbenzenesulfonic acid(DBSA) and sulfosalicylic acid(SSA) was synthesized by emulsion polymerization using ammonium persulfate(APS) as an oxidizing agent in the presence and the absence of a constant magnetic field(MF)of 0.8 T. The structure and properties of the PAn were characterized by X-ray diffractometer(XRD), thermogravimetric apparatus(TGA), FT-IR spectroscope(FT-IR) and four probe digital multimeter. The results indicate that, when the molar ratio of DBSA to SSA is 1/3, that of dopant to An is 3/2, that of APS to An is 4/5 in the synthesizing media, and the doping time is 3 h, the conductivity of the PAn synthesized in the presence of the MF of 0.8 T reaches 5.88 S/cm, which is higher than that of the PAn synthesized in the absence of the MF. The thermal stability, the crystallinity and the doping degree of the PAn synthesized in the presence of the MF are also improved. MF not only enhances the conductivity, but also reduces the doping time, the dosage of the dopant and the oxidizing agent when the conductivity reaches the maximum.
The initial efficiency is a very important criterion for carbon anode material of Li-ion battery. The relationship between initial efficiency and structure parameters of carbon anode material of Li-ion battery was investigated by an artificial intelligence approach called Random Forests using D10, D50, D90, BET specific surface area and TP density as inputs, initial efficiency as output. The results give good classification performance with 91% accuracy. The variable importance analysis results show the impact of 5 variables on the initial efficiency descends in the order of D90, TP density, BET specific surface area, D50 and D10; smaller D90 and larger TP density have positive impact on initial efficiency. The contribution of BET specific surface area on classification is only 18.74%, which indicates the shortcoming of BET specific surface area as a widely used parameter for initial efficiency evaluation.
High-pressure(HP) veins were extensively developed in western Tianshan high-pressure(HP) metamorphic belt. The HP vein and host-rocks were analyzed by electronic microprobe to trace the origin of vein-forming fluids. Analytical data show that the immediately adjacent host-rocks of the studied HP vein are eclogites and gradually turned into blueschist as the distance from the veins increases, which indicates that the vein-forming fluid was derived from adjacent host-rocks; the boundaries between the vein and the host-rocks are sharp, which indicates that the fracture of the host-rocks is brittle during the vein-forming process. It is suggested that this type of HP veins is precipitated from the liquid formed by the dehydration of the host-rocks during the prograde metamorphism from blueschist to eclogite facies, which results in hydrofracturing of the rocks and provides the space for the vein to precipitate. The width of the eclogite-facies host-rocks is usually 1–2 cm, which provides the direct evidence that the fluid flow is on centimeter-scale.
In the light of the localized progressive damage model, the evolution law of cohesive and frictional strength with irreversible strains was determined. Then, the location and the extent of the excavation disturbed zone in one deep rock engineering were predicted by using the strength evolution law. The theoretical result is close to the result of in-situ test. The strength evolution law excels the elastic-perfectly plastic model and elasto-brittle plastic model in which the cohesive and frictional strength are mobilized simultaneously. The results obtained indicate that the essential failure mechanism of the cracked rock can be described by the cohesion weakening and friction strengthening evolution law.
A method to forecast the over-excavation of underground opening by using the Bayes discriminant analysis(BDA) theory was presented. The Bayes discriminant analysis theory was introduced. Based on an engineering example, the factors influencing the over-excavation of underground opening were taken into account to build a forecast BDA model, and the prior information about over-excavation of underground opening was also taken into consideration. Five parameters influencing the over-excavation of opening, including 2 groups of joints, 1 group of layer surface, extension and space between structure faces were selected as geometric parameters. Engineering data in an underground opening were used as the training samples. The cross-validation method was introduced to verify the stability of BDA model and the ratio of mistake-discrimination was equal to zero after the BDA model was trained. Data in an underground engineering were used to test the discriminant ability of BDA model. The results show that five forecast results are identical with the actual situation and BDA can be used in practical engineering.
Elective culture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans in 9K medium modified with pyrrhotite was studied. Bioleaching of flotation concentrate of sphalerite by the selected bacteria was carried out. The results show that the microorganisms cultured by pyrrhotite are a mixture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, of which the capability to oxidize ferrous to ferric irons is enhanced by the high mass ratio of Fe to S in pyrrhotite. Three pyrrhotite samples were separated into various parts with corresponding S/Fe ratios by magnetic separation and were used to culture the elective bacteria as the substrate. The association of the cultures could provide a more rapid and complete oxidation of sphalerite than that of bacteria cultivated by conventional methods.
A heterotrophic acidothermophilic bacterial strain, YNTC-1, was isolated from an acidic hot spring in Tengchong, Yunan, China. YNTC-1 grows at pH value of 1.5–8.0 and temperature of 40–70 °C, with optimal pH and temperature at 3.0 and 55 °C, respectively. The cells of the strain are in shape of short rod, with 1.0–1.2 μm in length and 0.7–0.8 μm in diameter, and with distinct spores at both poles of each cell. The predominant fatty acids in cellular membrane of the strain are C18:1 θ7c. 16s rRNA gene analysis reveals that this strain is closely related to Alicyclobacillus sendaiensis, with over 99% sequence similarity. Based on phenotypic and genotypic analyses, YNTC-1 is identified as a member of A. sendaiensis. Considering some important morphological and biochemical differences between strain YNTC-1 and A. sendaiensis ATCC 27009T, YNTC-1 may be proposed to be a novel subspecies of A. sendaiensis. However, this viewpoint has to be confirmed by further studies. Co-bioleaching of pyrite and chalcopyrite with strain YN22, Sulfobacillus thermosulfidooxidans, shows that strain YNTC-1 has no evident influence on bioleaching rates of these two sulphide minerals.
The adsorption of Cu(II) and Cr(VI) on diaspore was studied with the help of X-ray diffraction analysis, BE measurement, zeta potential measurement and atomic adsorption spectrometry. The adsorption equilibrium almost reaches within 60 min. The adsorption isotherms of Cu(II) and Cr(VI) could be well described by the Langmuir equation. The adsorption capacities o Cu(II) and Cr(VI) are 1.944 and 1.292 mg/g, respectively. The adsorption percentage of Cr(II) increases with the increment solution pH, but the adsorption percentage of Cr(VI) decreases. This could be explained by zeta potential theoretical and electrostatic attraction between metal ions and diaspore surface.
The flocculation tests of four pure minerals (diaspore, kaolinite, illite, pyrophyllite) and bauxite ore were investigated by the sedimentation. The dispersion behavior of the four pure minerals shows a very good consistency with the variation of zeta potential. The concentrate with the mass ratio of Al2O3 to SiO2 (m(Al2O3)/m(SiO2)) 8.90 and the recovery of Al2O3 86.98% is obtained from bauxite ore (m(Al2O3)/m(SiO2)=5.68) in pH range of 9.5–10.0 by using sodium carbonate (5 kg/t) and sodium polyacrylate (7 g/t) as dispersant and flocculant respectively. Sodium carbonate acts as both pH modifier and favorable dispersant for aluminosilicates. The high performance of sodium polyacrylate on flocculation for diaspore is contributed to the carboxyl of sodium polyacrylate that interacts with active Al sites on diaspore by chemical absorption, and the hydrogen bond effects between hydroxyl group of macromolecule and surface Al-OH on diaspore to accelerate the sedimentation of diaspore.
The tensile strength, compressive strength and electrical resistivity of TiB2/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device, and the effects of carbon fibre content and carbon fibre length on tensile strength, compressive strength and electrical resistivity were investigated. The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre (length of 3 mm) content ranges from 0 to 4.0%; at the carbon fibre content of 1.5%, the tensile strength of coating reaches the maximum, 25.6 MPa. For the coating with carbon fibre content of 1.5%, the carbon fibre length has a great influence on tensile strength and compressive strength of coating; when the carbon fibre length is 6 mm, the tensile strength and compressive strength of coating reach the maximum, 27.6 MPa and 39.2 MPa, respectively. The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre, and the influence of carbon fibre length on electrical resistivity of coating at low temperature (30–200 °C) is more obvious than that at high temperature (960 °C).
In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 °C using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 °C in an argon atmosphere. X-ray diffractometry and scanning electron microscopy(SEM) were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the C space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4–3.0 μm. During the Li+ ion chemical intercalation, radical P2O74− disrupted into two PO43− ions in the presence of O2−, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.
Based on the working principle of vibratory excavation of hydraulic excavator, the expression of digging resistance changed with time under sine wave inspiritment was deduced; a comparison analysis was given after calculating the forces status of rock and soil under static load and vibratory load respectively by using MATLAB; and then RFPA-2D(rock failure process analysis code) was used to make comparison of simulation experiment on rock and soil failure process under static load and vibratory load. The results demonstrate that, compared with the normal excavation under the same situation, the digging resistance and the energy consumption can be reduced by respectively 30% and 60% at maximum, and that the working efficiency can be increased by 45% at maximum owing to vibratory excavation.
Based on characteristics of deep sea flexible mining system, a new pump-lockage ore transportation system was designed. According to Bernoulli equation and two-phase hydrodynamics theory, parameters of the new system were obtained and four ore transportation systems were analyzed. The results indicate that the pump head of 1 000 m mining system is 100–150 m and that of 5 000 m mining system is 660–750 m. In addition, based on similarity theory, a model of the new transportation system was made, which can simulate more than 5 000 m actual ore transportation system. So both theory and experiment prove that the new pump-lockage ore transportation system is an ideal design for deep sea flexible mining system.
A DMVOCC-MVDA (distributed multiversion optimistic concurrency control with multiversion dynamic adjustment) protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load (think time is 1s) the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.
A novel method was designed to solve reinforcement learning problems with artificial potential field. Firstly a reinforcement learning problem was transferred to a path planning problem by using artificial potential field(APF), which was a very appropriate method to model a reinforcement learning problem. Secondly, a new APF algorithm was proposed to overcome the local minimum problem in the potential field methods with a virtual water-flow concept. The performance of this new method was tested by a gridworld problem named as key and door maze. The experimental results show that within 45 trials, good and deterministic policies are found in almost all simulations. In comparison with WIERING’s HQ-learning system which needs 20 000 trials for stable solution, the proposed new method can obtain optimal and stable policy far more quickly than HQ-learning. Therefore, the new method is simple and effective to give an optimal solution to the reinforcement learning problem.
Based on the problem that the service entity only has the partial field of vision in the network environment, a trust evolvement method of the macro self-organization for Web service combination was proposed. In the method, the control rule of the trust degree in the Dempster-Shafer(D-S) rule was utilized based on the entity network interactive behavior, and a proportion trust control rule was put up. The control rule could make the Web service self-adaptively study so as to gradually form a proper trust connection with its cooperative entities and to improve the security performance of the whole system. The experimental results show that the historical successful experience is saved during the service combination alliance, and the method can greatly improve the reliability and success rate of Web service combination.
ABE-KONDOH-NAGANO, ABID, YANG-SHIH and LAUNDER-SHARMA low-Reynolds number turbulence models were applied to simulating unsteady turbulence flow around a square cylinder in different phases flow field and time-averaged unsteady flow field. Meanwhile, drag and lift coefficients of the four different low-Reynolds number turbulence models were analyzed. The simulated results of YANG-SHIH model are close to the large eddy simulation results and experimental results, and they are significantly better than those of ABE-KONDOH-NAGANO, ABID and LAUNDER-SHARMR models. The modification of the generation of turbulence kinetic energy is the key factor to a successful simulation for YANG-SHIH model, while the correction of the turbulence near the wall has minor influence on the simulation results. For ABE-KONDOH-NAGANO, ABID and LAUNDER-SHARMA models satisfactory simulation results cannot be obtained due to lack of the modification of the generation of turbulence kinetic energy. With the joint force of wall function and the turbulence models with the adoption of corrected swirl stream, flow around a square cylinder can be fully simulated with less grids by the near-wall.
The complete splitting process of steel fiber reinforced concrete (SFRC) at intermediate strain rate was studied by experiment. The basic information of a self-developed SFRC dynamic test system matching with Instron 1342 materials testing machine was given, and the experiment principle and the loading mode of cubic split specimen were introduced. During the experiment, 30 cubes of 150 mm×150 mm×150 mm and 36 cubes of 100 mm×100 mm×100 mm, designed and prepared according to C20 class SFRC with different volume fractions of steel fiber (0, 1%, 2%, 3%, 4%) were tested and analyzed. At the same time, the size effect of SFRC at intermediate strain rate was investigated. The experimental study indicates that SFRC size effect is not influenced by the loading speed or strain rate. When the steel fiber content increases from 0 to 4%, the splitting strength of SFRC increases from 100% to 261%, i.e. increasing by 161% compared with that of the common concrete. The loading rate increases from 1.33 kN/s to 80.00 kN/s, and the splitting tensile strength increases by 43.55%.