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Due to the distinct electromagnetic properties, double negative materials have bright application prospect in many areas in the future. The nickel (Ni)/polyphenylene sulfide (PPS) composites were prepared by hot pressing Ni and PPS powders mixture. Microstructures, dielectric properties, and magnetic performances of the resulted composites were studied in detail. Once Ni contents exceeded the percolation threshold, the conductive networks would form and the conduction mechanism would change from hopping conduction to metal-like conduction. Due to the plasma oscillation of the free electrons within the conductive networks, negative permittivity appeared. Interestingly, circuit loops in the connected Ni particles induced by external electric field resulted in a diamagnetic phenomenon under high frequency for the composite with ferromagnetic Ni particles.

Conductor–insulator composites have been extensive researched for high dielectric constant. Most of them concentrated on metal polymers or metal ceramics. Barium titanate–carbon fibers composites were prepared by using a solid state reaction process with carbon fibers contents ranging from7 vol% to 23 vol%. Due to the high-aspect-ratio of carbon fiber, it was easy to produce a conducting network at much lower volume fraction. FESEM images illustrated that the carbon fibers influenced the densification and microstructure of the ceramics. Besides, addition of carbon fibers led to increase in dielectric permittivity, also had effects on the dielectric loss and ac conductivity. The dielectric and conductivity properties as a function of carbon fibers volume fraction were explained by the percolation theory.

Al/Epoxy composites with different Al content were prepared by insulation coating process including high energy ball milling and hot press. The electrical properties and magnetic performance including ac conductivity, permittivity, reactance and permeability were investigated in detail. The frequency dispersions of ac conductivity followed the power law, indicating the hopping conduction behavior. The real part of permittivity for composites increased with higher Al content, which was attributed to the more interface between Al and epoxy. Besides, the real part of the relative permeability decreased with higher Al content in high frequency.

The dual metallic components, i.e., iron-aluminum particles were distributed in alumina matrix to fabricate lossy cermets. The electromagnetic parameters including ac conductivity, the complex permittivity and permeability were investigated. With the increase of filler fractions, the conductive carriers instead of the dipoles played a primary role in conductive and dielectric properties. Hopefully, the cermets composites could be promising candidates for electromagnetic wave attenuation and shielding.

The multi-walled carbon nanotube/alumina (MWCNTs/Al2O3) nanocomposites embedded with the shortened MWCNTs were prepared by pressureless sintering. The microstructure, conductive behavior and complex permittivity spectra of the composites were investigated. It was found that MWCNTs, which were shortened to low aspect ratio by the controllable acid and ultrasonic treatment, uniformly dispersed in the Al2O3 matrix. A unique dielectric resonance-induced negative permittivity behavior was observed in the composites with high MWCNTs content. The negative magnitude of permittivity was small (~-50) in the testing frequency. The dielectric loss peaks being accompanied by dielectric resonance moved to the higher frequency with increasing MWCNTs content. Those composites underwent a capacitive-inductive transition with increasing frequency and their conductive mechanism was hopping conduction. This work is beneficial to explore the generation mechanism of negative permittivity, and will greatly facilitate the practical application of metamaterials.

In this paper, Fe/SiO2 composites with different Fe content were prepared through pressureless sinter in weakly reductive atmosphere after high energy ball milling. The electrical properties including ac conductivity, permittivity were investigated in detail. The results showed that the frequency dispersions of ac conductivity follow the power law, indicating the hoping conduction behavior. The real part of permittivity for composites increased with higher Fe content, which was attributed to the more interface between Fe and SiO2. Besides, Debye-like dielectric relaxations were observed, and the Debye-like loss peak appeared blue shift as increasing the Fe content.

FeSiCr-epoxy composites consisting of different FeSiCr contents were prepared through the pressure molding after mixing by cryomilling at liquid nitrogen temperature. The electromagnetic properties including ac conductivity, permittivity, and permeability were investigated in detail. The results show that the frequency dispersions of ac conductivity followed the power law, indicating the hoping conduction behavior. The real permittivity of composites increased with the increase of FeSiCr contents, and the enhancement of permittivity may be attributed to the increase of the interface area between FeSiCr and epoxy, while Debye-like dielectric relaxations were observed, and the fitting analysis of Cole-Cole curve indicates a nonideal Debye relaxation. The frequency dispersions of permeability were also relaxation linetype, which is attributed to the domain wall displacement.

In this paper, C/SiO2 bulk composite was prepared via SiO2 microspheres’ self-assembly process combined with heat treatment. SEM and impedance analyzer was used to investigate the microstructure and high-frequency dielectric properties of the composites. The results show that SiO2 microspheres constituted the composite matrix, whose porosity was slightly higher than the densest hexagonal stacking. Sheet carbon distributed in pores formed by SiO2 microspheres. The real and imaginary parts of the dielectric constant of the composite material increased with the content of carbon, but decreased with the frequency. The permittivity of C/SiO2 composite could be adjusted by control the concentration of PVA solution.

The key for gel-casting is the preparation of ceramic aqueous slurries with excellent rheological properties. The effect of ammonium polyacrylate and pre-oxidation on rheological properties of Si3N4 slurries was investigated. The Si3N4 isoelectric point (IEP) is between 3 and 4 in premix solution and particle surface potential is maximum at pH between 9.5 and 10.5. PAA-NH4 of dispersant can obviously decrease the viscosity of Si3N4 slurries, and the optimal dosage is about 1.6wt% of Si3N4 powders. Meanwhile, the Si3N4 slurries exhibit pseudoplastic fluid with the characteristic of shear-thinning behavior. Due to the improvement of powder surface characteristic, the pre-oxidation significantly improve the rheological properties of the Si3N4 slurries.

The precursor nickel and manganese carbonates were synthesized by co-precipitation with sodium carbonate as precipitant, and then nickel and manganese oxides were gained after calcination. The phase and morphology of the synthesized product were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the electrochemical characterization was performed using cyclic voltammetry (CV), galvanostatic charge–discharge tests (GCD) and electrochemical impedance spectroscopy (EIS) in a 6mol/L KOH aqueous solution electrolyte. The result showed that the products were the mixture of nickel and manganese oxides and solid solution. nanoparticles and spherical particles were gained by controlling the molar ratio of nickel and manganese. All of the samples exhibited typical Faradic redox capacitance. The specific capacitance was different with the change of nickel and manganese molar ratio. The specific capacitance (Cs) reached 130F/g at 1A/g when the ratio was 2:1.

The precursor Ni (OH)2 was synthesized by a simple hydrothermal method with hexamethylenetetramine ((CH2)6N4) as precipitant and template, and then NiO was gained after calcination. The phase and morphology of the synthesized product were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the electrochemical capacitive characterization was performed using cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) in a 6mol/L KOH aqueous solution electrolyte. The result shows that spherical NiO without impurity was synthesized, the average diameter of the spheres is 5 um and these spheres were constructed by the interactive arrangement of many nanoflakes in three dimensions. This kind of NiO shows the typical electrochemical characteristics of pseudo capacitance with high specific capacity and excellent rate capability. The specific capacity can reach 515F/g at the current density of 1A/g

The microstructure and dielectric properties of the graphene–epoxy composites prepared by cryomilling at liquid nitrogen temperature were studied by SEM and RF impedance material analyzer. The result indicated that both the dielectric constant and conductivity of the composites increased with the increase of the graphene content. The value of the dielectric constant of the composite with about 8 wt % of graphene was as high as 200. Moreover, the frequency dispersion behaviors of the conductivity within a certain frequency range accorded with the Jonscher's power law demonstrating that the conductive mechanism is hopping conduction. The negative reactance decreased with the increase of the testing frequency which indicated a capacitive character

The precipitating behavior of δ phase in GH4169G alloy at 910°C was investigated and a novel process for achieving fine-grained GH4169G sheet with average grain size of ASTM13 was proposed. Globular δ phase precipitation precedes that of the plate-like δ phase, forming at grain boundary first and later in grain. After globular δ phase reaches a peak volume, it begins to transform into plate-like in grain boundary, and then the plate-like δ phase forms in grain in certain direction. The grain-fined process includes the following steps:(1) solution treated at a proper temperature, then air cooled; (2) soaked for δ phase precipitation; (3) cold rolled; (4) annealed for recrystallization. Microstructure analysis from optical microscopy (OM) and scanning electron microscopy (SEM) revealed that both plate-like and globular δ phase remarkably restrained the grain growth during annealing recrystallization. The optimum parameters for the grain refinement were determined finally.

In this paper, uniaxial compression testsfor GH4145 superalloywere conducted on Gleeble-3800 at room temperature and 60°C with strain rates ranging from 0.5s-1 to 10s-1. No cracks were observed in all the specimens deformed from 10% to 70%, indicating that the GH4145 superalloy possesses great ductility under room temperature. The flow stress of GH4145 superalloywas not sensitive to strain rate deformed around room temperature and it decreased slightly with the temperature increasing. Dynamic recovery during deformation will start to balance the effect of work hardening when the true strain was arisen up to 0.4. Good agreement between the calculated and simulated temperature and strain shows that calculation method is accurate enough for the prediction.

By using Chlorides (Cl-) as the tracer, the residence time distribution (RTD) method was applied to study the hydraulic characteristic influences of hydraulic retention time (HRT) on the opposite folded plate reactor and the plate baffle reactor under the condition of steady operation of both clear and sludge water. Under the condition of the same HRT, dead zone of opposite folded plate reactor was less than the one of flat plate reactor.

Hydrological exploration tests are designed and field data are acquired. By combination of theories and experiments, hydro geological condition and water filling factors of Mayingbao coal mine field are analyzed systematically aiming to ascertaining threatening degree of water hazard of the mine field and studying theory of mine water hazard prevention and control. According to coupling theory between GIS and AHP, models of “water abundance index” and “vulnerability index” are founded respectively. By methods of “three maps-double predictions” and “vulnerability index”, water inrush probability from roof and floor of chief exploitable coal seams in the mine field are evaluated quantitatively. Comprehensive regionalization of roof water filling probability and evaluation regionalization of floor water inrush vulnerability of the seams are formed. Based on above study, water inflow of first mining area is predicted and suggestion of water prevention and control for safety production is put forward. Nonlinear and multivariate theory in present geoscience research is improved because of the above results and the research provides necessary basic data for the mine designing, preliminary and feasibility research and subsequent safety production.

Freestanding ultralong (900 μm) aligned carbon nanotube (ACNT) films were studied as both an electrode material and a dry adhesive binder with the current collector in lithium ion batteries. Results revealed the formation of a solid electrolyte interface (SEI). The amazingly large initial discharge capacity (1836 mAh g-1) indicated that the ACNT electrode we utilized had great potential for the intercalation of Li ions resulted from extremely large surface area of ACNT films. And electrochemical performances also exhibited excellent cycling stability for this ACNT electrode because of the presence of SEI and the unique structure of the electrode itself.

Thermal conditioning (TC) can improve sludge mechanical dewaterability and drying performance, and produce solid fuel from sewage sludge with low-cost and harmlessness. This study investigates the influence of the TC on sludge combustion with thermogravemetric analysis of sewage sludge with/without TC. The experiments were carried out at a 150 mL/min air ambient with a heating rate of 10, 20, 30, 40, 50 °C/min. Tow integration approximation methods (Coats-Redfern and Flynn,-Wall-Ozawa) and a differential method (Kissinger method) were applied to study the kinetics. The Coats-Redfern method requires assuming the reaction’s kinetic mechanism. The calculated activation energy was lower than that from the Flynn-Wall-Ozawa and Kissinger, which were very close to each other. Among these methods, the Flynn-Wall-Ozawa can predict the energy required at every combustion stage, which therefore would be the best one to explore the combustion mechanism. The results show that the organic matters within sewage sludge are much more homogeneous after TC. The combustion of the thermal conditioning sludge (TCS) is much more stable with a 10% reduction in burnout time and a 9.94% reduction in combustion temperature range. The ignition temperature of the raw sludge keeps increasing from 188 to 224 °C with the heating rate, while that of the TCS is almost constant at 222-240 °C. The TC can improve the activation energy, which is about 144.52 and123.00 kJ/mol for the raw sludge (RS) and TCS. Considering the gaseous pollutant emissions, the TC can dramatically reduce NO emissions, which is decreased from 14.22 to 6.59 mg/g by the TC, representing a reduction of 50.7%. Therefore, the TC can promote the hydrolysis of macromolecular organics, which would improve the sludge combustion performance, and reduce the gaseous pollutant emissions from combustion.

With the STX-50 pneumatic-typed dynamic triaxial system, the undrained dynamic triaxial tests on the saturated cohesive soil are performed to study the dynamic strength properties. The changing process of the dynamic strength, backbone curve and the soil deformation of the cohesive soil under dynamic load are zoom analysis by stages to get their regularity. It is found that the stage change of the dynamic strength, backbone curve and the soil deformation all exist, which the stage I of the soil deformation has little damage, the stage III is not allowed, the stage II is determined by the importance of the concrete and the sensitive degree to the deformation. In order to analysis the deformation stability and stress stability of the formation in the effect of the dynamic load, provide qualitative and quantitative basis for the soil dynamic study.

Silica films prepared by the base catalyzed sol–gel process show poor mechanical property. In this study, silica anti-reflective films with good mechanical property have been prepared by the catalyzed sol–gel process with dimethyl formamide added as drying control chemical additives. The silica sol was first dip deposited onto substrate to form films on both sides of the substrate and then subjected to thermal treatment. After thermal treatment, the film was achieved due to the formation of porous structure in the resultant film as a result of decomposing tetraethylorthosilicate and dimethyl formamide. Nano-indenter measurement shows that the Young’s modulus and hardness of base catalyzed films are 10-20GPa and 0.25-0.55GPa, respectively. But the films added with dimethyl formamide are much better than those films derived from base-catalyzed silica sols, the Young’s modulus and hardness are 32-39GPa and 1.22-1.47GPa, respectively. The good mechanical properties make such films potential in both military and civil applications.

In order to study the effect of rock fracture distributions on stability of tunnel, the effect of joints with different strike dip, the size and density was considered by using probability and statistics method. Based on the Monte Carlo random simulation, the statistical network model of 2D jointed rockmass was established to describe and characterize jointed rock mass. On the basis of this, the numerical code RFPA2D is employed to analyze effect of fracture dip angle on the tunnel stability. Numerical results show that the fracture distribution has a little effect on tunnels failure mechanism and failure type of tunnel because the failure of tunnel in the jointed rockmass is similar to the one without joints and fissures. However with the change of the fracture dip angle, the loading capacity of the tunnel in the jointed rockmass varies accordingly.

DC/DC converters are known to exhibit bifurcations and chaos if switching actions are governed by feedback control. A dynamic controller based optimal control method is presented to control the chaos behavior and maximize the conversion efficiency of a zero-voltage-switching (ZVS) buck converter operating in continuous conduction mode (CCM). The simulation results show the effectiveness of the proposed scheme.

The combustion characteristics of textile dyeing sludge，sawdust and its blends at different proportions were studied by thermogravimetric analysis(TG-DTG) at different heating rates. The results showed that there existed four obviously temperature zones during the textile dyeing sludge combustion curves, which were corresponding to moisture's exhalation、two stages of devolatilizations and fixed carbon combustion. With the increasing of heating rates, the burning time was shorten and the combustion rate was faster of the textile dying sludge. DTG curve of the blends was more closed to that of the larger proportions. Comprehensive combustion characteristic index SN of the sludge-sawdust blends showed an uptrend, which demonstrated that higher volatility had better combustion characteristics.

The traditional intelligent tutoring system as a web-based education tools used for adaptive learning can’t solve the encountered question in time while the student is learning with the absence of nature language understanding system. In this paper, a web-based intelligent tutoring system is firstly introduced to solve the encountered question in real time. Secondly, a concept model representing the concept connotation, the extension and the relation between them is presented to support the nature language understanding system in order to extract the question’s meaning. Furthermore, a knowledge representation of verb and noun in impersonal mature domain is involved. Thirdly, the semantic processing arithmetic of the verb phase is given. Finally, the result of experiment and application of arithmetic are shown.

The combustion characteristics of the mixtures, which are made from different proportions of paper mill sludge and coal, were studied by the thermogravimetric analysis (TG-DTG) at different heating rates. The results showed that there were obviously three temperature zones in the paper mill sludge combustion curves, which is respectively corresponding to two devolatilization stages and a fixed carbon combustion stage. In these stages, the weight of sludge was lost promptly. When the proportions of sludge – coal blends were rather different, ignition point obviously shifted to the larger proportions, and DTG curve was more closed to the larger proportions. During the combustion process of the mixture, the paper mill sludge and the coal had basically maintained their own devolatilisation characteristics. And the comprehensive combustion characteristic index S of sludge-coal blend declined, demonstrating that higher volatility had better combustion characteristics. As the heating rate and the proportions of coal increasing, total weight loss rate increased, while burnout index Cbraised.

Aluminum films were deposited on glass substrate by electron beam heat evaporation, and porous alumina films with high transmittance were prepared by means of anodic oxidation under different anodizing conditions in oxalic acid solution or phosphoric acid solution respectively. Thus the morphology of these porous alumina films was characterized by different structural. he optical transmittance spectrum at normal incidence over the 300~1000nm spectra region were obtained by spectrophotometer, which shows, in visible and ultraviolet light region, the transmittance of porous alumina films prepared in oxalic acid solution is much better than that prepared in phosphoric acid solution. The SEM analysis results showed that the pores are circular and uniform in porous alumina prepared in oxalic acid but irregular and non-uniform in that prepared in phosphoric acid, which affected the surface roughness of alumina films.