Similarity solutions for the mixed convection flow over a vertical plate with thermal radiation

The steady laminar boundary layer flow adjacent to a vertical plate with prescribed surface temperature immersed in an incompressible viscous fluid,where the effect of thermal radiation was taken into consideration,was investigated.The governing partial differential equations were transformed into a system of ordinary differential equations using similarity transformation,before being solved numerically by the shooting method.Both assisting and opposing buoyant flows were considered.It is found that dual...     

Effect of Co-polyester antistatic agent modified by carbon nanotubes on the properties of polypropylene fibers

Antistatic polymer fibers were investigated by using carbon nanotubes (CNTs) to enhance the antistatic ability of inner antistatic agents based on the mechanism of attracting moisture by polar radical groups. It is indicated that the antistatic ability of the fibers filled with composite antistatic agents that contain CNTs and organic antistatic agents was superior to that of the fibers filled either with pure organic antistatic agents or pure CNTs. The antistatic ability of the composite antistatic agent fabricated by an in situ process was superior to that of the composite antistatic agent fabricated by direct dispersing CNTs in the antistatic agent carrier. Moreover, the heat-treated CNTs could further enhance the antistatic effect compared with the initial CNTs. The antistatic effect is significantly influenced by the content of CNTs in the composite antistatic agent.     

Coupling of anionic wetting agents to dust of sulfide ores by dropping liquid method

By using the experimental approach of dropping liquid, the coupling of three anionic wetting agents with ten dust samples of sulfide ores was studied, and particularly the wetting effects of the wetting agents on the sulfide dust influenced by factors of agent concentration and sulfate additive in the wetting agent solutions were investigated. The results show that when the solution temperature is about 20℃, all the selected wetting agents are effective to most dust samples, but the effect is different. Wetting agents are more effective to the dust which is difficult to be wetted. Wetting agent solution with sodium sulfate can improve the wetting ability of sulfide dust. For sodium dodecyl benzene sulfonate, the suitable concentration of sodium sulfate is 1 - 2 mmol/L. The cost of wetting agents can be reduced because the sodium sulfate is much cheaper than many surfactants. Since the dust of sulfide ores is composed of various minerals and elements, the whole effect of depressing dust should be considered while innovating a wetting agent.     

Design and heat transfer analysis of a compound multi-layer insulations for use in high temperature cylinder thermal protection systems

Thermal protection systems are very essential for high temperature thermal conductivity measurement system to reduce the heat loss to environment at the range of 600–1800 K. A compound multi-layer insulations structure which composed of inner carbon fibrous materials and outer alternately arranged alumina fibrous materials and high reflectivity foils is proposed for use in high temperature cylinder thermal protection systems. A coupled conductive and radiation governing equations is presented for heat transfer analysis of the structure. The finite volume method and the discrete ordinate method are used to solve the governing equations. The optimization structure of the compound multi-layer insulations is investigated by considering the pressure of the gas, the density of the carbon fibrous materials, the density of the alumina fibrous materials, the number of reflective foil layers and the emissivity of reflective foils. The results show that the compound structure has the best thermal insulation performance when the pressure of the gas is below 0.01 k Pa, the density of carbon fibrous materials is 180 kg m~(-3), the density of alumina fibrous materials is 256 kg m~(-3) and the number of reflective foil layers is 39. In addition, the thermal insulation performance is much better when the emissivity of reflective foils is lower.     

Theory of intracavity-frequency-doubled solid-state four-level lasers

The spatial distributions of the pumping, the population inversion density, and the intracavity photon densities of the fundamental and the second harmonic are taken into account in the rate equations of the intracavity-frequency-doubled cw lasers. By normalizing the related parameters, it is shown that the general solution of these space-dependent rate equations is dependent upon three dimensionless parameters: the pump to laser-mode size ratio, the normalized pump level, and a parameter written as ηSHG, which is related to the ability of the nonlinear crystal to convert the fundamental to the second harmonic. By numerically solving these rate equations, a group of general curves are obtained to express the relations between the solution and the three dimensionless parameters. In addition, the optimal pump to laser-mode size ratio and the optimal ηSHG are determined. A comparison with the result obtained under the plane-wave approximation is also given.     

Experimental study on the infrared precursor characteristics of gas-bearing coal failure under loading

The stress and gas pressure in deep coal seams are very high, and instability and failure rapidly and intensely occur. It is important to study the infrared precursor characteristics of gas-bearing coal instability and failure. In this paper, a self-developed stress-gas coupling failure infrared experimental system was used to analyse the infrared radiation temperature(IRT) and infrared thermal image precursor characteristics of gas-free coal and gas-bearing coal. The changes in the areas of the infrared temperature anomalous precursor regions and the effect of the gas on the infrared precursors were examined. The results show that high-temperature anomalous precursors arise mainly when the gas-free coal fails under loading, whereas the gas-bearing coal has high-temperature and low-temperature anomalous precursors. The area of the high-temperature anomalous precursor is approximately 30%–40% under gasbearing coal unstable failure, which is lower than the 60%–70% of the gas-free coal. The area of the low-temperature abnormal precursor is approximately 3%–6%, which is higher than the 1%–2% of the gas-free coal. With increasing gas pressure, the area of the high-temperature anomalous precursor gradually decreases, and the area of the low-temperature anomalous precursor gradually increases. The highand low-temperature anomalous precursors of gas-bearing coal are mainly caused by gas desorption, volume expansion, and thermal friction. The presence of gas inhibits the increase in IRT on the coal surface and increases the difficulty of infrared radiation(IR) monitoring and early warning for gas-bearing coal.     

Method of lines for functionally gradient materials

The method of lines(MOL) for solving the problems of functionally gradient materials(FGMs) was studied. Navier‘s equations for FGMs were derived, and were semi-discretized into a system of ordinary differential equations(ODEs) defined on discrete lines with the finite difference. By solving the system of ODEs, the solutions to the problem can be obtained. An example of three-point bending was given to demonstrate the application of MOL for a crack problem in the FGM. The computational results show that the more accurate results can be obtained with less computational time and resources. The obvious difficulties of numerical method for crack problems in FGMs, such as the effect of material nonhomogeneity and the existence of high gradient stress and strain near a crack tip, can be overcome without additional consideration if this method is adopted.     

Research on the effect of the common flame retardant in reducing the flammability of the bitumen

The bituminous defect that the binder is flammable will bring road safety risk.Once it catches fires,large quantities of heat,smoke and poisonous gas are produced,released and spread quickly,which seriously hinder escape and rescue and harms heavily traffic safety.The common flame retardant system is used to modify the asphalt.Cone Calorimeter is adopted to evaluate the burning property of asphalt.The performance of the flame retardant is evaluated by limiting oxygen index and orthogonal design method.The paper analyzes the synergism of the asphalt and flame-retardant,and analyzes the effect of the flame on preventing the smoke to spread and demonstrates that the use of common flame retardants which is added into binder is good at reducing the flammability of the binder.This way can increase the safety of asphalt pavement when fire occurs in the tunnel.The study suggests that flame retardancy of asphalt can be evaluated by Limit Oxygen Index (LOI) and the flame retardancy property of asphalt has marked change according to the content of flame retardant.SB has perfect flame retardancy property,and ATH is better than MH in the effect of flame retardant.     

Constructal optimization of cylindrical heat sources with forced convection based on entransy dissipation rate minimization

Based on constructal theory and entransy theory,the optimal designs of constant-and variable-cross-sectional cylindrical heat sources are carried out by taking dimensionless equivalent resistance minimization as optimization objective.The effects of the cylindrical height,the cylindrical shape and the ratio of thermal conductivity of the fin to that of the heat source are analyzed.The results show that when the volume of the heat source is fixed,there exists an optimal ratio of the center-to-centre distance of the fin and the heat source to the cylinder radius which leads to the minimum dimensionless equivalent thermal resistance.With the increase in the height of the cylindrical heat source and the ratio of thermal conductivity,the minimum dimensionless equivalent thermal resistance decreases gradually.For the heat source model with inverted variable-cross-sectional cylinder,there exist an optimal ratio of the center-to-centre distance of the fin and the heat source to the cylinder radius and an optimal radius ratio of the smaller and bigger circles of the cylindrical fin which lead to a double minimum dimensionless equivalent thermal resistance.Therefore,the heat transfer performance of the cylindrical heat source is improved by adopting the cylindrical model with variable-cross-section.The optimal constructs of the cylindrical heat source based on the minimizations of dimensionless maximum thermal resistance and dimensionless equivalent thermal resistance are different.When the thermal security is ensured,the optimal construct of the cylindrical heat source based on minimum equivalent thermal resistance can provide a new alternative scheme for the practical design of heat source.The results obtained herein enrich the work of constructal theory and entransy theory in the optimal design field of the heat sources,and they can provide some guidelines for the designs of practical heat source systems.     

Semi-analytical solution for fully developed forced convection in metal-foam filled tube with uniform wall temperature

Fully developed flow and heat transfer in metal-foam filled tube with uniform wall temperature(UWT) is semi-analytically investigated based on the Brinkman–Darcy model and the two-equation model, in which the inertia term, axial conduction, and thermal dispersion are ignored. A two-dimensional numerical simulation that adopts the full governing equations is also conducted to analyze the effects of neglected terms on flow and thermal transport performance by comparing with the semi-analytical solution. The effects of the relevant parameters and thermal boundary conditions including UWT and uniform heat flux(UHF) on the heat transfer characteristics are discussed based on the semi-analytical solution. The results show that the inertia term has a significant effect on the prediction of pressure drop, but has a relatively mild effect on Nusselt number. The axial conduction has significant effect on the Nusselt number at lower Reynolds number, and the effects of thermal dispersion can be neglected when the thermal conductivity ratio between fluid and solid is remarkably smaller for air/metal foam as example(kf/ks3×10-3). The predicted Nusselt number of the semi-analytical solution is about 8% to 15% lower than that of the numerical solution with full model in the range of 4×10-5kf/ks3×10-3. Moreover, the temperature profile of solid is more sensitive to pore density and porosity than that of fluid under UWT condition. The Nusselt number under UWT is about 7% to 25% lower than that under UHF, and the difference is mainly determined by interfacial convection rather than solid conduction.     

Preparation and visible-light photocatalytic property of nanostructu- red Fe-doped TiO2 from titanium containing electric furnace molten slag

Nanostructured Fe-doped titanium dioxide was synthesized from titanium containing electric furnace molten slag （TCEFMS） by using an alkali fusion, followed by a hydrolyzation-acidolysis-cMcination route. The effects of Mkali/slag mass ratio, calcinating temperature, calcinating time, and water/slag mass ratio on the extraction efficiency and purity of products were systematically studied in this paper. It is indicated that the best extraction efficiency of nanostructured Fe- doped titanium dioxide is 99.35%, when the molten slag is calcinated at 700℃ for 1 h with the mass ratio of alkali/molten slag of 1.5：1. The influence of alkali/slag mass ratio on the photocatalytic activity of final products was evaluated by the photodegradation of methyl blue under visible light irradiation. A maximum photodegradation efficiency of 88.12% over 30 min was achieved under the optimum conditions.     

Martensitic transformation and magnetic properties of aged Ni-Fe-Ga-Ti shape memory alloy

This article reports the effect of ageing on the microstructure, martensitic transformation, magnetic properties, and mechanical properties of Ni51FelsGa27Ti4 shape memory alloy. There are five specimens of this alloy aged at 573 up to 973 K for 3 h per each. This range of ageing temperature greatly affects the microstructure of the alloy. As the ageing temperature increased from 573 up to 973 K, the microstructure of Ni51FelsGa27Ti4 alloy gradually changed from the entirely martensitic matrix at 573 K to the fully austenitic microstructure at 973 K. The volume fraction of precipi- tated Ni3Ti particles increased with the ageing temperature increasing from 573 to 773 K. Further increasing the ageing temperature to 973 K decreased the content of Ni3Ti in the microstructure. The martensitic transformation tempera- ture was decreased steadily by increasing the ageing temperature. The magnetization saturation, remnant magnetization, and coercivity increased with the ageing temperature increasing up to 773 K. A further increase in ageing temperature decreased these raagnetic properties. Moreover, the hardness values were gradually increased at first by increasing the ageing temperature to 773 K, and then dramatically decreased to the lowest value at 973 K.     

Interfacial intermetallic compound growth and shear strength of low-silver SnAgCuBiNi//Cu lead-free solder joints

The growth rule of the interfacial intermetallic compound （IMC） and the degradation of shear strength of Sn-0.SAg-0.5Cu-2.0Bi-0.05Ni （SACBN）/Cu solder joints were investigated in comparison with Sn-3.0Ag-0.5Cu （SAC305）/ Cu solder joints aging at 373, 403, and 438 K. The results show that （Cul-x,Nix）6Sn5 phase forms between the SACBN solder and Cu substrate during soldering. The interracial IMC thickens constantly with the aging time increasing, and the higher the aging temperature, the faster the IMC layer grows. Compared with the SAC305/Cu couple, the SACBN/Cu couple exhibits a lower layer growth coefficient. The activation energies of IMC growth for SACBN/Cu and SAC305/Cu couples are 111.70 and 82.35 kJ/mol, respectively. In general, the shear strength of aged solder joints declines continuously. However, SACBN/Cu solder joints exhibit a better shear strength than SAC305/Cu solder joints.     

Microstructural and mechanical properties of A1-4.5wt% Cu rein- forced with alumina nanoparticles by stir casting method

The microstructure and mechanical properties of A1-4.5wt% Cu Mloy reinforced with different volume fractions （1.5vo1%, 3vo1%, and 5vo1%） of alumina nanoparticles, fabricated using stir casting method, were investigated. CMculated amounts of alumina nanoparticles （about ~50 nm in size） were ball-milled with aluminum powders in a planetary ball mill for 5 h, and then the packets of milled powders were incorporated into molten Al-4.5wt% Cu alloy. Microstructural studies of the nanocomposites reveal a uniform distribution of alumina nanoparticles in the A1-4.5wt% Cu matrix. The results indicate an outstanding improvement in compression strength and hardness due to the effect of nanoparticle addition. The aging behavior of the composite is also evaluated, indicating that the addition of alumina nanoparticles can accelerate the aging process of the Mloy, resulting in higher peak hardness values.     

Recent developments on applications of sequential loop closing and diagonal dominance control schemes to industrial multivariable system

With a focus on an industrial multivariable system, two subsystems including the flow and the level outputs are analysed and controlled, which have applicability in both real and academic environments. In such a case, at first, each subsystem is distinctively represented by its model, since the outcomes point out that the chosen models have the same behavior as corresponding ones. Then, the industrial multivariable system and its presentation are achieved in line with the integration of these subsystems, since the interaction between them can not actually be ignored. To analyze the interaction presented, the Gershgorin bands need to be acquired, where the results are used to modify the system parameters to appropriate values. Subsequently, in the view of modeling results, the control concept in two different techniques including sequential loop closing control （SLCC） scheme and diagonal dominance control （DDC） schemes is proposed to implement on the system through the Profibus network, as long as the OPC （OLE for process control） server is utilized to communicate between the control schemes presented and the multivariable system. The real test scenarios are carried out and the corresponding outcomes in their present forms are acquired. In the same way, the proposed control schemes results are compared with each other, where the real consequences verify the validity of them in the field of the presented industrial multivariable system control.     

Thermodynamics and kinetics of alumina extraction from fly ash using an ammonium hydrogen sulfate roasting method

A novel method was developed for extracting alumina （Al2O3） from fly ash using an ammonium hydrogen sulfate （NH4HSO4） roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experi-mentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298-723 K range. Process op-timization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1：8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol;and the kinetic equation can be expressed as 1-（2/3）α-（1-α）2/3=0.0374t exp[-16627/（RT）], whereαis the extraction rate and t is the roasting temperature.     

Biodesulfurization of vanadium-bearing titanomagnetite concentrates and pH control of bioleaching solution

Vanadium-bearing titanomagnetite concentrates were desulfurized with Acidithiobacillus ferrooxidans （A. ferrooxidans）. The sulfur content of the concentrates was reduced from 0.69wt% to 0.14wt% after bioleaching for 15 d with a 10% pulp density at 30℃. Maintaining a stable pH value during biodesulfurization was critical because of high acid consumption, resulting from a combination of nonoxidative and oxidative dissolution of pyrrhotite in acid solution. It is discovered that the citric acid-disodium hydrogen phosphate buffer of pH 2.0 can control the solution pH value smoothly in the optimal range of 2.0-3.0 for A. ferrooxidans growth. Using the buffer in the volume fraction range of 5.0%-15.0% stimulates A. ferooxidans growth and improves the biodesulfurization efficiency. Compared with the buffer-free control case, the maximum increase of biodesulfurization rate is 29.7% using a 10.0vol% buffer. Bioleaching provides an alternative process for desulfurization of vanadium-bearing titanomagnetite ores.     

Preparation of CaO-Al2O3-SiO2 system glass from molten blast furnace slag

To use the potential heat of molten blast furnace slag completely, a CaO-Al2O3-SiO2 system glass （MSG） was prepared from the molten industrial slag. The corresponding method proposed in this study utilized both slag and its potential heat, improving the production rate and avoiding the environmental pollution. Using appropriate techniques, an MSG with uniform color and superior performances was produced. Based on the experimental results and phase diagram, the chemical composition of MSG by mass is obtained as follows：CaO 27%-33%, SiO2 42%-51%, Al2O3 11%-14%, MgO 6%-8%, and Na2O＋K2O 1%-4%. Thermodynamic processes of MSG preparation were analyzed, and the phases and microstructures of MSG were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that alkali metal oxides serve as the fluxes, calcium oxide serves as the stabilizer, and alumina reinforces the Si-O network. XRD and SEM analyses show that, the prepared MSG displays the glass-feature patterns, the melting process is more complete, and the melt viscosity is lowered with an increase in calcium oxide content;however, a continuous increase in slag content induces the crystalli-zation of glass, leading to the formation of glass subphase. The optimum content of molten slag in MSG is 67.37wt%. With respect to bend-ing strength and acid/alkali resistance, the performance of MSG is better than that of ordinary marble.     

Effect of some operational variables on bubble size in a pilot-scale mechanical flotation machine简

This work aims to provide a relationship of how the key operational variables of frother type and impeller speed affect the size of bubble （D32）. The study was performed using pilot-scale equipment （0.8 m^3） that is up to two orders of magnitude larger than equipment used for studies performed to date by others, and incorporated the key process variables of frother type and impeller speed. The results show that each frother family exhibits a unique CCC95-HLB relationship dependent on n （number of C-atoms in alkyl group） and m （number of propylene oxide group）. Empirical models were developed to predict CCC95 from HLB associated with other two parameters a and ft. The impeller speed-bubble size tests show that D32 is unaffected by increased impeller tip speed across the range of 4.6 to 9.2 m/s （representing the industrial operating range）, although D32 starts to increase below 4.6 m/s. The finding is valid for both coalescing and non-coalescing conditions. The results suggest that the bubble size and bubble size distribution （BSD） being created do not change with increasing impeller speed in the quiescent zone of the flotation.     

Feasibility of developing composite action between concrete and cold-formed steel beam

Cold-formed steel structures are steel structure products constructed from sheets or coils using cold rolling, press brake or bending brake method. These structures are extensively employed in building construction industry due to their light mass, ductility by economic cold forming operations, favorable strength-to-mass ratio and other factors. The utilization of cold formed steel sections with concrete as composite can hugely reduce the construction cost. However, the use of cold formed steel members in composite concrete beams has been very limited. A comprehensive review of developments in composite beam with cold formed steel sections was introduced. It was revealed that employing cold-formed steel channel section to replace reinforcement bars in conventional reinforced concrete beam results in a significant cost reduction without reducing strength capacity. The use of composite beam consisting of cold-formed steel open or close box and filled concrete could also reduce construction cost. Lighter composite girder for bridges with cold-formed steel of U section was introduced. Moreover, types of shear connectors to provide composite action between cold-formed steel beam and concrete slab were presented. However, further studies to investigate the effects of metal decking on the behavior of composite beam with cold-formed steel section and introduction of ductile shear connectors were recommended.