xNi/10NiO-NiFe2O4 (x=5, 10, 17) cermets and those doped with 1% BaO (mass fraction) were prepared by cold isostatic pressing at 200 MPa and sintering in nitrogen atmosphere at 1 473 K. The effects of BaO addition on relative density, microstructure and electric conductivity of cermets were investigated. The results show that relative densities of xNi/10NiO-NiFe2O4 cermets (x=5, 10, 17) doped with 1% BaO at 1 473 K in nitrogen atmosphere are increased by 0.49%, 1.45% and 2.99% compared with those of the undoped BaO cermets, respectively. Moreover, the electric conductivities (21.98, 28.37 and 50.10 S/cm) of xNi/10NiO-NiFe2O4 cermets (x=5, 10, 17) doped with 1% BaO at 1 233 K are improved compared with those (18.70, 22.79 and 39.58 S/cm) of xNi/10NiO-NiFe2O4 cermets (x=5, 10, 17), respectively. This indicates that perhaps the addition of BaO or formation of BaFe2O4 and Ba2Fe2O5 has an active effect on electric conductivities of xNi/10NiO-NiFe2O4 (x=5, 10, 17) cermets.
The auto-evolved ultrafine copper powders were synthesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray powder diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and laser size distribution analyzer (SL) respectively. The formation mechanisms of the powders and the efficiency of the elctrodeposition were discussed. The results show that the as-prepared powders are high-purity copper nanoparticles with the fcc structure taking a mixture of fishbone-like and irregular shapes. When the concentration of Cu2+ increases from 0.03 to 0.09 mol/L, the average size of copper particles increases from 0.92 to 1.80 µm, and current efficiency of electrodeposition linearly changes from 66.5% to 91.3%.
Vacuum brazing of SiO2 glass ceramic and TC4 alloy using a commercially available TiZrNiCu foil was investigated. The interfacial microstructure and the fractures were examined with an optical microscope (OM) and an S-4700 scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) and an electron probe X-ray microanalyzer (EPMA). The structure of joint interface was identified by XRD (JDX-3530M). Meanwhile, the fracture paths of the joints were comprehensively studied. The results show that processing parameters, especially the brazing temperature, have a significant effect on the microstructure and mechanical properties of joints. The typical interface structure is SiO2/Ti2O+Zr3Si2+Ti5Si3/(Ti,Zr)+Ti2O+TiZrNiCu/Ti(s.s)/TiZrNiCu+Ti(s.s)+Ti2(Cu,Ni)/TC4 from SiO2 glass ceramic to TC4 alloy side. Based on the mechanical property tests, the joints brazed at 880 °C for 5 min has the maximum shear strength of 23 MPa.
Co87Nb10Zr3, Co76Nb19Zr5, Co64Nb26Zr10 and Co64Nb16Zr20 amorphous films were deposited on noncrystalline glass substrates by DC unbalanced magnetron sputtering. The compositions of amorphous films were tailored in the light of the individual deposition rate of Co, Nb and Zr. The amorphous films with the anticipated composition were prepared by means of co-sputtering Co, Nb and Zr targets simultaneously. It is indicated that there is interaction among three targets during co-sputtering. The morphology and composition of the films were observed by SEM, AFM and EDS. The structure and magnetic property were measured by XRD and physical property measurement system (PPMS). The coercivity changes with the composition, varying from 240 to 1 600 A/m. After vacuum isothermal annealing at temperatures of 475, 500, 525 and 550 °C for 15 and 30 min, respectively, it is found that high Nb content is beneficial to improving thermal stability of amorphous films. The crystallized films have the mean grain size of 2–19 nm.
β-Sialon/ZrN bonded corundum composites were synthesized using fused white corundum, alumina micro powder, zircon and carbon black by nitridation reaction sintering process. Phase composition and microstructure of the synthesized composites were investigated by X-ray powder diffraction and scanning electronic microscope, and the formation process of the composites was discussed. The results show that the composites with different compositions can be obtained by controlling the heating temperature and contents of zircon and carbon black. The proper temperature to synthesize the composites is 1 773 K.
Chemical vapor deposition (CVD) of SiC from methyltrichlorosilane (MTS) was studied at two different molar ratios of H2 to MTS (n(H2)/n(MTS)). The total pressure was kept as 100 kPa and the temperature was varied from 850 to 1 100 °C at a total residence time of 1 s. Steady-state deposition rates as functions of reactor length and of temperature, investigated at different n(H2)/n(MTS) values, show that hydrogen exhibits strongly influences on the deposition rate. Especially, the deposition of Si co-deposit can be obtained in broader substrate length and at higher temperatures with increasing hydrogen partial pressure. Influence of hydrogen on the deposition process was also studied using gas phase composition and deposit composition analysis at various n(H2)/n(MTS). SEM micrographs directly show the variation of surface morphologies at various n(H2)/n(MTS). It can be found that the crystal grain of the deposit at 1 100 °C is better developed and the crystallization is also improved with increasing n(H2)/n(MTS).
To reduce defects caused by non-homogeneous metal flow in conventional extrusion, a die with guiding angle was designed to improve the metal flow behavior. The characteristic quantities such as the second invariant of the deviator stress J2 and Lode’s coefficient μ were employed for the division of deformation area. The results show that when the metal is extruded with the guiding angle, no metal flow interface forms at the container’s bottom, the dead zone completely disappears, the deformation types of the metal in the plastic deformation area change from three types to one type of tension, and the homogeneity of the deformation as well as metal flow are greatly improved. The non-homogeneous metal flow at the final stage of extrusion is improved, reducing the shrinkage hole at the axis end. The radial stress of the furthest point from the axis is transformed from tensile stress to compressive stress and the axial stress, and decreased from 70.8 to 34.8 MPa. Therefore, the surface cracks caused by additional stress are greatly reduced.
Iron(II) tetrasulfophthalocyanine (FeTSPc), as a novel mimetic enzyme of peroxidase, was used in the synthesis of a conducting polyaniline (PANI)/sodium dodecylsulfate (SDS) complex in SDS aqueous micellar solutions. The effects of pH, concentrations of aniline, SDS and H2O2, and reaction time on polymerization of aniline were studied in this case as shown by UV-Vis absorption spectroscopy. The results show that a wide range of pH (0.5–4.0) is required to produce the conducting PANI, and the optimal pH is 1.0 in SDS micelle. The optimal concentrations of aniline, SDS and H2O2 in feed, and reaction time in this case for the production of conducting PANI are respectively 10 mmol/L, 10 mmol/L, 25 mmol/L, and 15 h. FT-IR spectrum, elemental analysis, conductivity, cyclic voltammetry and thermogravimetric analysis confirm the thermal stability and electroactive form of PANI.
The flotation of kaolinite using a series of tertiary amines (N,N-dimethyl-dodecyl amine (DRN), N,N-diethyl-dodecyl amine (DEN), N,N-dipropyl-dodecyl amine (DPN) and N,N-dibenzyl-bodecyl amine (DBN)) was investigated. The results show that the maximum recoveries of kaolinite for DEN, DPN and DRN are 93%, 88% and 84%, respectively, but that of DBN is very low. On the basis of zeta potential and FT-IR spectra, the ionization of surface hydroxyl and isomorphic exchange of surface ions account for the charging mechanisms of kaolinite surface. The adsorption mechanism of tertiary amines on kaolinite surface is mainly electrostatic. The isoelectric point (IEP) of kaolinite increases from 3.4 to some more positive points after the interaction of kaolinite with the four tertiary amines. The FT-IR spectra of kaolinite change with the presence of some new sharp shapes belonging to the tertiary amines. The inductive electronic effects and space-steric effects of -CH3, -C2H5, -C3H7 and -C7H7 bonding to N atom result in different collecting power of the four tertiary amines.
In order to selectively separate chalcopyrite from pyrite, the effect of organic depressant lignosulfonate calcium (LSC) on the flotation separation of chalcopyrite from pyrite was investigated by flotation tests. The depression mechanism was studied by Fourier-transform-infrared (FTIR) analysis. The flotation tests of single mineral show that LSC can depress the flotation of pyrite in a certain pH range, but it has little effect on chalcopyrite flotation. Flotation separation of a mixture of chalcopyrite and pyrite can be completed to obtain a copper concentrate grade up to 24.73% with a recovery of 80.36%. IR analysis shows that LSC and butyl xanthate compete in absorption on pyrite surface, and there exists an LSC characteristic peak on pyrite surface. There is little adsorption of LSC on chalcopyrite.
The effects of Acidithiobacillus ferrooxidans (At. f) mutated with diethyl sulfate (DES) as a mutagen on the bioleaching of soluble phosphorus (P) from rock phosphate (RP) were investigated. The results show that the oxidative activity of At. f is greatly improved by 1.0% (volume fraction) of DES. Correspondingly, the highest leaching rate of soluble P is also obtained to be 14.9% by the At. f mutated, which is 85.8% higher than that of the adapted At. f without mutation. In addition, the SEM images are significantly performed that the corrosion of RP residue surfaces leached by 1.0% DES-induced At.f is much worse than that of leached by the adapted At. f. All the above indicate that the leaching efficiency of soluble P from RP with pyrite can be greatly improved by using DES-induced At. f to a certain extent.
The LiMn2O4/graphite battery was fabricated and its 3 C/10 V overcharge performance was studied. Spinel LiMn2O4 was synthesized by solid-state method and 325680-type size full battery was fabricated. The structure and morphology of the powders were characterized by XRD and SEM technique, respectively. The battery explodes after 3 C/10 V overcharged test, and surface temperature of the battery case arrives at 290 °C in 12 s after exploding. Black air is given out with blast. Carbon, MnO, and Li2CO3 are observed in the exploded powders. The cathode electrode remains spinel structure with 5.0 V charged. Cracks in the cathode electrode particles are detected with the increase of voltage by SEM technique. The 5.0 V charged electrode can decompose into Mn3O4 at 400 °C. It is demonstrated that the decomposition of 5.0 V charged electrode can be promoted and Mn4+ can be deoxidized to Mn2+ by carbon and electrolyte through the simulation of blast process.
Workability and mechanical properties of steel slag green concrete with different types of steel slag and different dosages of admixtures were investigated. The effectiveness of steel slag powder on suppressing alkali aggregate reaction (AAR) expansion was assessed using the method of ASTM C441 and accelerated test method. Experimental results show that mechanical properties can be improved further due to the synergistic effect and mutual activation when compound mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into concrete. In addition, about 50% decrease in expansion rate of mortar bars with mineral admixtures can be achieved in AAR tests. Mineral admixtures with steel slag powder as partial replacement for Portland cement in concrete is an effective means for controlling expansion due to AAR.
In order to reduce the “trial-mold” risk and cost, numerical simulation method was applied to micro injection molding weld line development investigation. The micro tensile specimen which has the size of 0.1 mm (depth)×0.4 mm (width)×12 mm(length) in test area was selected as the objective part, and polypropylene (PP) as the experimental material. Respectively with specific commercial software (Mold Flow®) and general computational fluid dynamic (CFD) software (Comsol® Multiphysics), the simulation experiments for development of weld line in micro injection molding process were executed and the real comparison experiments were also carried out. The results show that during micro injection molding process, the specific commercial software for normal injection molding process is not valid to describe the micro flow process, the shape of flow front in micro cavity flowing which is important in weld line developing study and the contact angle due to surface tension are not able to be simulated. In order to improve the simulation results for micro weld line development, the general CFD software, which is more flexible in user defining function, is applied. The results show better effects in describing micro fluid flow behavior. As a conclusion, as for weld line forming process, the numerical simulation method can give a characteristic analysis results for processing parameters optimizing in micro injection molding process; but for both kinds of softwares quantitative analysis cannot be obtained unless the boundary condition and micro fluid mathematic model are improved in the future.
The information integration method of semantic web based on agent ontology (SWAO method) was put forward aiming at the problems in current network environment, which integrates, analyzes and processes enormous web information and extracts answers on the basis of semantics. With SWAO method as the clue, the following technologies were studied: the method of concept extraction based on semantic term mining, agent ontology construction method on account of multi-points and the answer extraction in view of semantic inference. Meanwhile, the structural model of the question answering system applying ontology was presented, which adopts OWL language to describe domain knowledge from where QA system infers and extracts answers by Jena inference engine. In the system testing, the precision rate reaches 86%, and the recalling rate is 93%. The experimental results prove that it is feasible to use the method to develop a question answering system, which is valuable for further study in more depth.
Fault detection technique is introduced with similarity measure. The characteristics of conventional similarity measure based on fuzzy number are discussed. With the help of distance measure, similarity measure is constructed explicitly. The designed distance-based similarity measure is applicable to general fuzzy membership functions including non-convex fuzzy membership function, whereas fuzzy number-based similarity measure has limitation to calculate the similarity of general fuzzy membership functions. The applicability of the proposed similarity measure to general fuzzy membership structures is proven by identifying the definition. To decide fault detection of flight system, the experimental data (pitching moment coefficients and lift coefficients) are transformed into fuzzy membership functions. Distance-based similarity measure is applied to the obtained fuzzy membership functions, and similarity computation and analysis are obtained with the fault and normal operation coefficients.
The systematical and scalable frameworks were provided for estimating the blocking probabilities under asynchronous traffic in optical burst switching (OBS) nodes with limited wavelength conversion capability (LWCC). The relevant system architectures of limited range and limited number of wavelength converters (WCs) deployed by a share-per-fiber (SPF) mode were developed, and the novel theoretical analysis of node blocking probability was derived by combining the calculation of discouraged arrival rate in a birth-death process and two-dimensional Markov chain model of SPF. The simulation results on single node performance verify the accuracy and effectiveness of the analysis models. Under most scenarios, it is difficult to distinguish the plots generated by the analysis and simulation. As the conversion degree increases, the accuracy of the analysis model worsens slightly. However, the utmost error on burst loss probability is far less than one order of magnitude and hence, still allows for an accurate estimate. Some results are of actual significance to the construction of next-generation commercial OBS backbones.
A time-series similarity measurement method based on wavelet and matrix transform was proposed, and its anti-noise ability, sensitivity and accuracy were discussed. The time-series sequences were compressed into wavelet subspace, and sample feature vector and orthogonal basics of sample time-series sequences were obtained by K-L transform. Then the inner product transform was carried out to project analyzed time-series sequence into orthogonal basics to gain analyzed feature vectors. The similarity was calculated between sample feature vector and analyzed feature vector by the Euclid distance. Taking fault wave of power electronic devices for example, the experimental results show that the proposed method has low dimension of feature vector, the anti-noise ability of proposed method is 30 times as large as that of plain wavelet method, the sensitivity of proposed method is 1/3 as large as that of plain wavelet method, and the accuracy of proposed method is higher than that of the wavelet singular value decomposition method. The proposed method can be applied in similarity matching and indexing for lager time series databases.
In order to obtain a compact and exact representation of 2D range scans, UKF (unscented Kalman filter) and CDKF (central difference Kalman filter) were proposed for extracting the breakpoint of the laser data. Line extraction was performed in every continuous breakpoint region by detecting the optimal angle and the optimal distance in polar coordinates, and every breakpoint area was constructed with two points. As a proof to the method, an experiment was performed by a mobile robot equipped with one SICK laser rangefinder, and the results of UKF/CDKF in breakpoint detection and line extraction were compared with those of the EKF (extended Kalman filter). The results show that the exact geometry of the raw laser data of the environments can be obtained by segmented raw measurements (combining the proposed breakpoint detection approach with the line extraction method), and method UKF is the best one compared with CDKF and EKF.
According to the effective sampling of particles and the particles impoverishment caused by re-sampling in particle filter, an improved particle filtering algorithm based on observation inversion optimal sampling was proposed. Firstly, virtual observations were generated from the latest observation, and two sampling strategies were presented. Then, the previous time particles were sampled by utilizing the function inversion relationship between observation and system state. Finally, the current time particles were generated on the basis of the previous time particles and the system one-step state transition model. By the above method, sampling particles can make full use of the latest observation information and the priori modeling information, so that they further approximate the true state. The theoretical analysis and experimental results show that the new algorithm filtering accuracy and real-time outperform obviously the standard particle filter, the extended Kalman particle filter and the unscented particle filter.
Laboratory tests under different constraint conditions were carried out to obtain the soil-water retention curves (SWRCs) of highly-compacted confined/unconfined Gaomiaozi (GMZ) bentonite at 20, 40 and 80 °C, respectively. The effect of temperature on the soil-water characteristics of the highly-compacted GMZ bentonite was analyzed. The results show that the water retention capacity of the highly-compacted GMZ bentonite decreases as the temperature increases under unconfined and confined conditions. At a certain temperature, the constraint conditions have little influence on the water retention capacity of the compacted bentonite at high suction, but the water retention capacity of the confined specimen is lower than that of the unconfined specimen at low suction. Under unconfined conditions, the hysteretic behaviour of the compacted bentonite decreases with increasing temperature. At high suction (>4 MPa), the hysteretic behaviour of the unconfined bentonite tends to increase with the decrease of the suction. In summary, the hysteretic behaviour of the compacted bentonite is not significant.
Considering the delay effect of initial lining and revising the Winkler elastic foundation model, an analytical approach based on Pasternak elastic foundation beam theory for pipe roof reinforcement was put forward. With the example of a certain tunnel excavation, the comparison of the values of longitudinal strain of reinforcing pipe between field monitoring and analytical approach was made. The results indicate that Pasternak model, which considers a more realistic hypothesis in the elastic soil than Winkler model, gives more accurate calculation and agrees better with the result of field monitoring. The difference of calculation results between these two models is about 7%, and Pasternak model is proved to be a better way to study the reinforcement mechanism and improve design practice. The calculation results also reveal that the reinforcing pipes act as levers, which increases longitudinal load transfer to an unexcavated area, and consequently decreases deformation and increases face stability.
Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics (CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens, in most cases, takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at −10, 0 and 10 °C increase averagely by 9.09%, 6.63% and 17.83%, respectively, as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature, and when the temperature drops to a certain value, the improvement increases with falling temperature.
To establish bonding stress—slip constitutive model between bars and grout concrete, 13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding stress development of bars adhered to grout concrete was analyzed. The local bonding stress—slip curve was obtained. Based on the test results, a new bonding stress—slip constitutive model between bars and grout concrete was proposed. The results show that the maximum bonding stress is not influenced by the bar bond length, but it is strengthened when the splitting strength of grout concrete is increased. The model matches the experimental results well, and the regressing coefficient equals 1.7.
The temperature dependence on the reaction of desulfurization reagent CaCO3 and SO2 in O2/CO2 coal combustion was investigated by thermogravimetric analysis, X-ray diffraction measurement and pore structure analysis. The results show that the conversion of the reaction of CaCO3 and SO2 in air is higher at 500–1 100 °C and lower at 1 200 °C compared with that in O2/CO2 atmosphere. The conversion can be increased by increasing the concentration of SO2, which causes the inhibition of CaSO4 decomposition and shifting of the reaction equilibrium toward the products. XRD analysis of the product shows that the reaction mechanism of CaCO3 and SO2 differs with temperature in O2/CO2 atmosphere, i.e. CaCO3 directly reacts with SO2 at 500 °C and CaO from CaCO3 decomposition reacts with SO2 at 1 000 °C. The pore analysis of the products indicates that the maximum specific surface area of the products accounts for the highest conversion at 1 100 °C in O2/CO2 atmosphere. The results reveal that the effect of the atmosphere on the conversion is temperature dependence.
In order to investigate Joule heating power, a three-dimensional finite element model (FEM) was developed to predict Joule heating power in the channels of double-loop inductor. The simulated results were compared with experimental data from low load trials for a 400 kW inductor. The results, such as power factor and Joule heating power, show reasonable correlation with experimental data, and Joule heating rate reaches the maximum at the corners and the minimum at the centre of the cross-section area. With increasing relative permeability of iron core, length of coils, current frequency and resistivity of metal melt, the power factor and Joule heating power change. It is concluded that current frequency, the resistivity and length of the coil play a critical role in determining the power factor and Joule heating power, whereas relative permeability of the magnetic core shows no significant influence on them.
The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional (2D) finite element (FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement, horizontal displacement, pore water pressure, and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small, it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.
To investigate drivers’ lane-changing behavior under different information feedback strategies, a microscopic traffic simulation based on the cellular automaton model was made on the typical freeway with a regular lane and a high-occupancy one. A new dynamic tolling scheme in terms of the real-time traffic condition on the high-occupancy lane was further designed to enhance the whole freeway’s flow throughput. The results show that the mean velocity feedback strategy is generally more efficient than the travel time feedback strategy in correctly guiding drivers’ lane choice behavior. Specifically, the toll level, lane-changing rate and freeway’s throughput and congestion coefficient induced by the travel time feedback strategy oscillate with larger amplitude and longer period. In addition, the dynamic tolling scheme can make the high-occupancy lane less congested and maximize the freeway’s throughput when the regular-lane inflow rate is larger than 0.45.