The pyrolysis of cyclohexane,methylcyclohexane,and ethylcyclohexane have been studied behind reflected shock waves at pressures of 5 and10 bar and at temperatures of 930-1550 K for 0.05%fuel diluted by Argon.A single-...The pyrolysis of cyclohexane,methylcyclohexane,and ethylcyclohexane have been studied behind reflected shock waves at pressures of 5 and10 bar and at temperatures of 930-1550 K for 0.05%fuel diluted by Argon.A single-pulse shock tube(SPST)is used to perform the pyrolysis experiments at reaction times varying from 1.65 to 1.74 ms.Major products are obtained and quantified using gas chromatography analysis.A flame ionization detector and a thermal conductivity detector are used for species identification and quantification.Kinetic modeling has been performed using several detailed and lumped chemical kinetic mechanisms.Differences in modeling results among the kinetic models are described.Reaction path analysis and sensitivity analysis are performed to determine the important reactions controlling fuel pyrolysis and their influence on the predicted concentrations of reactant and product species profiles.The present work provides new fundamental knowledge in understating pyrolysis characteristics of cyclohexane compounds and additional data set for detailed kinetic mechanism development.展开更多
For the thorough research on coal metamorphism impact on gas adsorption capacity, this paper collected and summarized parameters of experimental adsorption isotherms, coal maceral, proximate analysis and ultimate anal...For the thorough research on coal metamorphism impact on gas adsorption capacity, this paper collected and summarized parameters of experimental adsorption isotherms, coal maceral, proximate analysis and ultimate analysis obtained from National Engineering Research Center of Coal Gas Control and related literatures at home and abroad, systematically discussed the coal rank effect on its physicochemical properties and methane adsorption capacity, in which the coal rank was shown in Vitrinite reflectance, furthermore, obtained the Semi-quantitative relationship between physicochemical properties of coal and methane adsorption capacity.展开更多
Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend an...Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.展开更多
MgH_(2),TiH_(2),and ZrH_(2) are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years.To evaluate ignition sensitivity and explosion severit...MgH_(2),TiH_(2),and ZrH_(2) are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years.To evaluate ignition sensitivity and explosion severity,the Hartmann device and spherical pressure vessel were used to test ignition energy and explosion pressure,respectively.The results showed that the ignition sensitivity of ZrH_(2),TiH_(2) and MgH_(2) gradually increased.When the concentration of MgH_(2) is 83.0 g/m^(3) in Hartmann device,the ignition energy attained a minimum of 10.0 mJ.The explosion pressure of MgH_(2) were 1.44 times and 1.76 times that of TiH_(2) and ZrH_(2),respectively,and the explosion pressure rising rate were 3.97 times and 9.96 times that of TiH_(2) and ZrH_(2),respectively,through the spherical pressure vessel.It indicated that the reaction reactivity and reaction rate of MgH_(2) were higher than that of TiH_(2) and ZrH_(2).In addition,to conduct in edepth theoretical analysis of ignition sensitivity and explosion severity,gas production and combustion heat per unit mass of ZrH_(2),TiH_(2) and MgH_(2) were tested by mercury manometer and oxygen bomb calorimetry.The experimental results revealed that MgH_(2) had a relatively high gas production per unit mass(5.15 mL/g),while TiH_(2) and ZrH_(2) both had a gas production of less than 2.0 mL/g.Their thermal stability gradually increased,leading to a gradual increase in ignition energy.Furthermore,compared with theoretical combustion heat,the combustion ratio of MgH_(2),TiH_(2) and ZrH_(2) was more than 96.0%,with combustion heat value of 29.96,20.94 and 12.22 MJ/kg,respectively,which was consistent with the explosion pressure and explosion severity test results.展开更多
To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstruct...To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstructure,produced phases and damping capacities of the composites prepared with different particle size of B4C were characterized and analyzed.The results show that the reaction between B4C and Ti tends to be more complete when finer B_(4)C particle was used to prepare the composites.But the microstructure of the as-prepared composites is more homogenous when B4C and Ti have similar particle size.The strain-dependent damping capacities of(B_(4)C+Ti)/Mg composites improve gradually with the increase of strain amplitude,and composites prepared with coarser B4C particles tend to have higher damping capacities.The temperature-dependent damping capacities improve with increasing the measuring temperatures,and the kind of damping capacities of the composites prepared with 5mm B4C are inferior to those of coarser particles.The dominant damping mechanism for the strain-damping capacity is dislocation damping and plastic zone damping,while that for the temperature-damping capacity is interface damping or grain boundary damping.展开更多
Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitan...Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitant precursors as well as cumbrous multi-step hydrophobization process has often narrowed the field of applications. In this work, granular silica aerogel materials were synthesized by extracting Si O2 from recycled rich silicon coal gangue, followed by one-step hydrophobization and ambient pressure drying. Lightweight(about 0.16 g/cm3) and nanostructural aerogels were obtained through this route. They exhibit a 3D open porous microstructure with around 600 cm2/g surface area and 20 nm of the average pore diameter, thermal conductivity of 4-5 mm packed granules is 20-25 m W/(m·K), which was proved by both guarded hot plate and hot-wire transient methods. This study offers a new facile route for the synthesis of silica aerogel from recycled solid waste coal gangue and suggests a method, which may lead to a cost reduction in terms of industrial production.展开更多
Manganese was extracted from leaching low-grade manganese ore in sulfuric acid medium. The effects of granule diameter, leaching time, liquid/solid ratio (V/W) and the concentration of sulfuric acid were investigated ...Manganese was extracted from leaching low-grade manganese ore in sulfuric acid medium. The effects of granule diameter, leaching time, liquid/solid ratio (V/W) and the concentration of sulfuric acid were investigated through orthogonal and single factor experiments. The experimental results showed that the optimal leaching conditions are, size of 0.054mm, 120 minutes of reaction time, 3(V/W) of liquid/solid ratio and 30% of the concentration of sulfuric acid (g/g). Under those conditions, the leaching efficiency is 96.73%. The kinetics of the leaching process is in accordance with the characteristics of fractal reaction.展开更多
The sodium silicate, ferric chloride, ferrous sulfate, sodium chlorate and other common inorganic materials were used to synthesize two new poly silicate iron coagulants： Polysilicate Ferric Chloride （PFSiC） and Po...The sodium silicate, ferric chloride, ferrous sulfate, sodium chlorate and other common inorganic materials were used to synthesize two new poly silicate iron coagulants： Polysilicate Ferric Chloride （PFSiC） and Polymeric Ferric Silicate Sulfate （PFSiS）. Their coagulation effect on micro-polluted water was compared with the poly ferric choride （PFC） saled in the market. The results showed that turbidity, organic matter, total phosphorus, total nitrogen removal rate ofPFSiC, PFSiS coagulant were better than PFC on micro-polluted water treatment at the same dosage. The coagulation effect of PFSiC was the best. The surface morphology of three coagulants was observed by scanning electron microscopy （SEM）, and the coagulation mechanism was discussed preliminarily.展开更多
Structural and thermodynamic parameters of 56 oxygen-containing and 56 sulfur- containing organic compounds were computed at the B3LPY/6-311G＊＊ level using density functional theory （DFT） method. Furthermore,the d...Structural and thermodynamic parameters of 56 oxygen-containing and 56 sulfur- containing organic compounds were computed at the B3LPY/6-311G＊＊ level using density functional theory （DFT） method. Furthermore,the dependent equations between the experimental data of boiling points （Tb） and theoretical parameters were proposed with SPSS12.0 for windows software,whose correlation coefficients R2 are 0.933 and 0.945. These dependent equations were validated by cross-validation method （q2 are 0.923 and 0.929,respectively）. VIF （variance inflation factors） and t-value methods were also used to verify the significance and self-correlationship of each variable. Results indicate that our dependent equation exhibits good prediction ability,and molecular polarizability （α） is the main factor affecting the Tb of oxygen- and sulfur-containing organic compounds. To our interest,obvious dependence could also be found among the oxygen- and sulfur-containing organic compounds＇ experimental data of boiling points （Tb） with R^2 of 0.857.展开更多
The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It ...The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It is found that the chlorine substitution pattern strongly influences the thermodynamic properties of the compounds.The thermodynamic properties of congeners with the same number of chlorines also depend on the chlorine substitution pattern,especially for ortho-substituted congeners.PCXT congeners with one phenyl ring fully chlorinated are found to be the least stable among the analogues.The effect of the chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution(NPCS).The results show that the NPCS model may be used to predict the thermodynamic properties for all 135 PCXT congeners. In addition,the values of molar heat capacities at constant pressure(cp,m)from 200 to 1000 K for PCXT congeners are calculated,and the temperature dependence relation of this parameter is obtained using the least-squares method.展开更多
Organophosphorus flame retardants(OPFRs) are gradually replacing brominated flame retardants(BFRs), which are widely used in the world. The increasing output of OPFRs and the increasing detection of OPFRs in environme...Organophosphorus flame retardants(OPFRs) are gradually replacing brominated flame retardants(BFRs), which are widely used in the world. The increasing output of OPFRs and the increasing detection of OPFRs in environmental media have attracted wide attention of scholars at home and abroad. OPFRs are generally semi-volatile, easy to enter the environment and accumulate in organisms,causing potential hazards to the environment and human health. In this paper, the pollution status and toxic effects of OPFRs in aquatic environment were introduced,and the research progress of human health risk caused by them was summarized.The existing problems were pointed out, and the future research was prospected. In the future, the analytical methods of various environmental and biological media should be improved, and comprehensive and in-depth environmental investigation and ecological and health risk assessment should be carried out. Attention should be paid to the effects of combined pollution on organisms and the study of biological acceptability.展开更多
Waste pyrolysis technology as a new method of waste treatment induces more and more attention. Waste pyrolysis technology is not on- ly good for garbage reduction, but also can restrain the generation of dioxin, reach...Waste pyrolysis technology as a new method of waste treatment induces more and more attention. Waste pyrolysis technology is not on- ly good for garbage reduction, but also can restrain the generation of dioxin, reaching the target for harmless decrement. We introduced technique process, development situations at home and abroad, existing problems and improvement measures of waste pyrolytic technology.展开更多
Polymer bonded explosives(PBXs)have high energy density,excellent mechanical properties and better thermal stability.In this study,droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres...Polymer bonded explosives(PBXs)have high energy density,excellent mechanical properties and better thermal stability.In this study,droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres.The effects of different binder types and binder concentrations on the morphology of the microspheres were studied,and results proved that NC/GAP(1:4)provides particles a regular spherical morphology and good dispersion.Subsequently,the influence of the concentration of the dispersed phase and the flow rate of the continuous phase on the particle size distribution of the microspheres was fully studied.The microspheres had narrow particle size distribution and high spherical shape.Under optimized process conditions,HMX/TATB microspheres were prepared and compared with the physical mixtures.The X-ray diffraction,differential scanning calorimetry,flow properties,bulk density,and mechanical sensitivity of the samples were also studied.Results showed that the crystal form of the microspheres remains unchanged,and the binder maintains good compatibility with explosives.In addition,the fluidity,bulk density,real density and safety performance of the microspheres are remarkably better than the physical mixture.This study provides a new method for preparing PBX with narrow particle size distribution,high spherical shape,excellent dispersion and high bulk density.展开更多
In order to theoretically study the growth morphology of dihydroxylammonium 5,5’-bistetrazole-1,1’-dio late(TKX-50)crystal in different solvent systems,crystal–solvent models were established,and then molecular dyn...In order to theoretically study the growth morphology of dihydroxylammonium 5,5’-bistetrazole-1,1’-dio late(TKX-50)crystal in different solvent systems,crystal–solvent models were established,and then molecular dynamics(MD)methods were adopted as a means to simulate particle motion.Modified attachment energy(MAE)model was employed to calculate the growth morphology of TKX-50.The simulation results demonstrate that COMPASS force field and RESP charge are suitable for molecular dynamics simulation of TKX-50.The morphologically dominant growth surfaces of TKX-50 in vacuum are(020),(011),(11–1),(100)and(120),respectively.In water(H_(2)O)and N,N-dimethylformamide(DMF)solvents,the(11–1)face is the largest in the habit face,the growth rate of(020)face becomes faster.With the increase of temperature,the aspect ratios of TKX-50 crystal in DMF solvent increase,and the areas of the(120)faces decrease.In ethylene glycol/H_(2)O mixed solvent system with volume ratio of 1/1,aspect ratio of TKX-50 is relatively small.In formic acid/H_(2)O mixed solvents with different volume ratios(1/4,1/3,1/2,1/1 and 2/1),aspect ratio of TKX-50 is relatively small when volume ratio is 1/2.展开更多
Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conser...Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies.In this study,an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different confluence flows on the erosion process of ephemeral gullies.Results showed that when the confluence flow was larger,the effect of geocell was more evident,and the protection against ephemeral gully erosion was stronger.When the confluence flow rates were 0.6,1.8,2.4,and 3.0 m^(3)/h,ephemeral gully erosion decreased by 37.84%,26.09%,21.40%,and 35.45%.When the confluence flow rates were 2.4 and 3.0 m^(3)/h,the average sediment yield rate of the ephemeral gully was close to 2.14 kg/(m^(2)•min),and the protective effect of ephemeral gully erosion was enhanced.When the flow rate was higher,the surface fracture of the ephemeral gully was more serious.With an increase in confluence flow rate,the ratio of erosion to deposition increased gradually,the erosion area of ephemeral gullies was expanded,and erosion depth changed minimally.In conclusion,geocell measures changed erosion patterns by altering the rill erosion/deposition ratio,converting erosion from rill erosion to sheet erosion.展开更多
The impact of 500 kV transmission lines of Anqing power plant across the lake wetland reserve along the Yangtze River on the safety of the ecosystem was taken as the researched object.The power frequency electric fiel...The impact of 500 kV transmission lines of Anqing power plant across the lake wetland reserve along the Yangtze River on the safety of the ecosystem was taken as the researched object.The power frequency electric field intensity(PFEFI),power frequency magnetic field intensity(PFMFI),radio interference,construction noise,vegetation destruction and the influence on water quality were investigated and monitored,and the influences of PFEFI,PFMFI,radio interference and construction noise on wild animals,especially the habitats and migration of birds were mainly researched.The direct and indirect influences on the surrounding environment as well as plants and animals in sensitive areas were analyzed and predicted.The results firstly showed there existed a 182 400m^3 stereo-space(PFEFI>4kV/m)which made flying birds unsafe under the lowest height 11 mof the lines,which fills the gap in the research of this field.Finally,some operational protection countermeasures were put forward at the current technical level to achieve the win-win goal of economic development and natural protection.展开更多
Silica( SiO_2) based aerogel/xerogel materials have been received ever-growing attentions for versatile applications. However,the widespread applications are narrowed by the inert properties,fragile and brittle nature...Silica( SiO_2) based aerogel/xerogel materials have been received ever-growing attentions for versatile applications. However,the widespread applications are narrowed by the inert properties,fragile and brittle natureof silica materials and cumbersome preparation processes. In this paper,titania( TiO_2) was introduced into SiO_2 matrix to form photocatalytic hybrid gels. The TiO_2/SiO_2 composites were then reinforced by the impregnation of various fibrillary reinforcements,such as glass,mullite mineral and ceramic fibers. The properties of the composites were studied systematically in terms of fiberstability,microstructure,chemical interaction and thermal conductivity. The final xerogel composites displayed improved monolithic geometry,satisfied thermal conductivity(0. 09-0. 25 W·m^(-1)·K^(-1)) and optimized photocatalytic performance(85% removal of model pollutant of methyl orange( Mo)),which could be expected to be a feasible route to multi-functional building facades in the future.展开更多
The capacity factors （k＇） of fourteen types ofhalogenated thiophenols in different phases of methanol-water eluent were determined by reversed phased high-performance liquid chromatography （RP-HPLC） and the relat...The capacity factors （k＇） of fourteen types ofhalogenated thiophenols in different phases of methanol-water eluent were determined by reversed phased high-performance liquid chromatography （RP-HPLC） and the relationships between the logarithm of capacity factor lgK＇ and methanol ratio ψ were analyzed. A fair linear relationship is found between lgK＇ and ψ, and the correlation coefficients R2 of the constructed linear equations are all greater than 0.990. Relationship between the chromatographic data lgKw＇ when extrapolated to pure water and n-octanol/water partition coefficient lgKow obtained by the group contribution method has shown a good linear correlation with R2= 0.956. The structure parameters of fourteen halogenated thiophenols were calculated by using DFT, and the correlation equation of lgKw＇ and structure parameters was obtained by using SPSS, lgKw＇ = -0.409 ＋ 0.039a and R2 = 0.981, meaning that lgKw＇ is mainly determined by the polarizability α.展开更多
We analyzed the compositions and basic properties of agricultural and forest biomass carbon,and used the pot method to study the influence of such element on the remediation of contaminated soils and growth of crops.R...We analyzed the compositions and basic properties of agricultural and forest biomass carbon,and used the pot method to study the influence of such element on the remediation of contaminated soils and growth of crops.Results show that agricultural and forest biomass carbon contains various nutrients that are necessary for crop growth,high specific surface area,and pore structure development.Cotton stalk charcoal can reduce bioavailability of Cadmium(Cd) in soil.Under mild Cd pollution,soil treated with cotton stalk charcoal adsorbs Cd at a rapid rate.With increasing extent of Cd pollution,Cd adsorption rate gradually slows down and Cd adsorption amount gradually increases.In soil treated with cotton stalk charcoal,the amount of Cd accumulated in the edible portions and roots of Brassica chinensis significantly decrease.The Cd mass fraction of the edible portions and roots are reduced by 49.43%- 68.29%,64.14%- 77.66% respectively.Appropriately adding carbon cotton stalks increases crop biomass.At a certain range,increasing cotton stalk charcoal also promotes the absorption of major nutrients in Brassica chinensis.展开更多
The effluent quality from a secondary clarifier in an activated sludge process depends on the performance in the secondary clarifier at great extent. Several models have been developed based on the Kynch solid flux th...The effluent quality from a secondary clarifier in an activated sludge process depends on the performance in the secondary clarifier at great extent. Several models have been developed based on the Kynch solid flux theory to improve the clarifier performance at last decades. This paper proposed a model which is established according to the basis sedimentation process of the secondary clarifier and Kynch flux theory for a clarifier with feedwell in upper of tank and the diffusion effective are combined into the model, which benefts the further improvement of the model and makes the solutions fit to the measurement data in secondary clarifier,展开更多
文摘The pyrolysis of cyclohexane,methylcyclohexane,and ethylcyclohexane have been studied behind reflected shock waves at pressures of 5 and10 bar and at temperatures of 930-1550 K for 0.05%fuel diluted by Argon.A single-pulse shock tube(SPST)is used to perform the pyrolysis experiments at reaction times varying from 1.65 to 1.74 ms.Major products are obtained and quantified using gas chromatography analysis.A flame ionization detector and a thermal conductivity detector are used for species identification and quantification.Kinetic modeling has been performed using several detailed and lumped chemical kinetic mechanisms.Differences in modeling results among the kinetic models are described.Reaction path analysis and sensitivity analysis are performed to determine the important reactions controlling fuel pyrolysis and their influence on the predicted concentrations of reactant and product species profiles.The present work provides new fundamental knowledge in understating pyrolysis characteristics of cyclohexane compounds and additional data set for detailed kinetic mechanism development.
文摘For the thorough research on coal metamorphism impact on gas adsorption capacity, this paper collected and summarized parameters of experimental adsorption isotherms, coal maceral, proximate analysis and ultimate analysis obtained from National Engineering Research Center of Coal Gas Control and related literatures at home and abroad, systematically discussed the coal rank effect on its physicochemical properties and methane adsorption capacity, in which the coal rank was shown in Vitrinite reflectance, furthermore, obtained the Semi-quantitative relationship between physicochemical properties of coal and methane adsorption capacity.
基金supported by the National Natural Science Foundation of China(Grant No.51709021)the Open Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2016491111)
文摘Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.
基金This work was greatly supported by the Natural Science Foundation of China(11802272)the Open Research Fund Program of Science and Technology on Aerospace Chemical Power Laboratory(STACPL220181B01).
文摘MgH_(2),TiH_(2),and ZrH_(2) are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years.To evaluate ignition sensitivity and explosion severity,the Hartmann device and spherical pressure vessel were used to test ignition energy and explosion pressure,respectively.The results showed that the ignition sensitivity of ZrH_(2),TiH_(2) and MgH_(2) gradually increased.When the concentration of MgH_(2) is 83.0 g/m^(3) in Hartmann device,the ignition energy attained a minimum of 10.0 mJ.The explosion pressure of MgH_(2) were 1.44 times and 1.76 times that of TiH_(2) and ZrH_(2),respectively,and the explosion pressure rising rate were 3.97 times and 9.96 times that of TiH_(2) and ZrH_(2),respectively,through the spherical pressure vessel.It indicated that the reaction reactivity and reaction rate of MgH_(2) were higher than that of TiH_(2) and ZrH_(2).In addition,to conduct in edepth theoretical analysis of ignition sensitivity and explosion severity,gas production and combustion heat per unit mass of ZrH_(2),TiH_(2) and MgH_(2) were tested by mercury manometer and oxygen bomb calorimetry.The experimental results revealed that MgH_(2) had a relatively high gas production per unit mass(5.15 mL/g),while TiH_(2) and ZrH_(2) both had a gas production of less than 2.0 mL/g.Their thermal stability gradually increased,leading to a gradual increase in ignition energy.Furthermore,compared with theoretical combustion heat,the combustion ratio of MgH_(2),TiH_(2) and ZrH_(2) was more than 96.0%,with combustion heat value of 29.96,20.94 and 12.22 MJ/kg,respectively,which was consistent with the explosion pressure and explosion severity test results.
基金Project(51901095)supported by the National Natural Science Foundation of China。
文摘To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstructure,produced phases and damping capacities of the composites prepared with different particle size of B4C were characterized and analyzed.The results show that the reaction between B4C and Ti tends to be more complete when finer B_(4)C particle was used to prepare the composites.But the microstructure of the as-prepared composites is more homogenous when B4C and Ti have similar particle size.The strain-dependent damping capacities of(B_(4)C+Ti)/Mg composites improve gradually with the increase of strain amplitude,and composites prepared with coarser B4C particles tend to have higher damping capacities.The temperature-dependent damping capacities improve with increasing the measuring temperatures,and the kind of damping capacities of the composites prepared with 5mm B4C are inferior to those of coarser particles.The dominant damping mechanism for the strain-damping capacity is dislocation damping and plastic zone damping,while that for the temperature-damping capacity is interface damping or grain boundary damping.
基金Funded by the National Natural Science Foundation of China(Nos.51308079,51408073 and 51278073)
文摘Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitant precursors as well as cumbrous multi-step hydrophobization process has often narrowed the field of applications. In this work, granular silica aerogel materials were synthesized by extracting Si O2 from recycled rich silicon coal gangue, followed by one-step hydrophobization and ambient pressure drying. Lightweight(about 0.16 g/cm3) and nanostructural aerogels were obtained through this route. They exhibit a 3D open porous microstructure with around 600 cm2/g surface area and 20 nm of the average pore diameter, thermal conductivity of 4-5 mm packed granules is 20-25 m W/(m·K), which was proved by both guarded hot plate and hot-wire transient methods. This study offers a new facile route for the synthesis of silica aerogel from recycled solid waste coal gangue and suggests a method, which may lead to a cost reduction in terms of industrial production.
基金financially supported jointly by the Bureau of Land Resources and Housing Management of Chongqing (Scientific &Technologic Program in 2011)Post graduates’Science & Innovation Fund of Chongqing University (Project No. CDJXS10240007)
文摘Manganese was extracted from leaching low-grade manganese ore in sulfuric acid medium. The effects of granule diameter, leaching time, liquid/solid ratio (V/W) and the concentration of sulfuric acid were investigated through orthogonal and single factor experiments. The experimental results showed that the optimal leaching conditions are, size of 0.054mm, 120 minutes of reaction time, 3(V/W) of liquid/solid ratio and 30% of the concentration of sulfuric acid (g/g). Under those conditions, the leaching efficiency is 96.73%. The kinetics of the leaching process is in accordance with the characteristics of fractal reaction.
文摘The sodium silicate, ferric chloride, ferrous sulfate, sodium chlorate and other common inorganic materials were used to synthesize two new poly silicate iron coagulants： Polysilicate Ferric Chloride （PFSiC） and Polymeric Ferric Silicate Sulfate （PFSiS）. Their coagulation effect on micro-polluted water was compared with the poly ferric choride （PFC） saled in the market. The results showed that turbidity, organic matter, total phosphorus, total nitrogen removal rate ofPFSiC, PFSiS coagulant were better than PFC on micro-polluted water treatment at the same dosage. The coagulation effect of PFSiC was the best. The surface morphology of three coagulants was observed by scanning electron microscopy （SEM）, and the coagulation mechanism was discussed preliminarily.
基金Supported by the State Science Foundation of China (No. 20737001)
文摘Structural and thermodynamic parameters of 56 oxygen-containing and 56 sulfur- containing organic compounds were computed at the B3LPY/6-311G＊＊ level using density functional theory （DFT） method. Furthermore,the dependent equations between the experimental data of boiling points （Tb） and theoretical parameters were proposed with SPSS12.0 for windows software,whose correlation coefficients R2 are 0.933 and 0.945. These dependent equations were validated by cross-validation method （q2 are 0.923 and 0.929,respectively）. VIF （variance inflation factors） and t-value methods were also used to verify the significance and self-correlationship of each variable. Results indicate that our dependent equation exhibits good prediction ability,and molecular polarizability （α） is the main factor affecting the Tb of oxygen- and sulfur-containing organic compounds. To our interest,obvious dependence could also be found among the oxygen- and sulfur-containing organic compounds＇ experimental data of boiling points （Tb） with R^2 of 0.857.
基金Supported by the National Natural Science Foundation of China （20977046, 20737001）.
文摘The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It is found that the chlorine substitution pattern strongly influences the thermodynamic properties of the compounds.The thermodynamic properties of congeners with the same number of chlorines also depend on the chlorine substitution pattern,especially for ortho-substituted congeners.PCXT congeners with one phenyl ring fully chlorinated are found to be the least stable among the analogues.The effect of the chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution(NPCS).The results show that the NPCS model may be used to predict the thermodynamic properties for all 135 PCXT congeners. In addition,the values of molar heat capacities at constant pressure(cp,m)from 200 to 1000 K for PCXT congeners are calculated,and the temperature dependence relation of this parameter is obtained using the least-squares method.
基金Supported by National Science and Technology Major Project of China(2017ZX07202004)~~
文摘Organophosphorus flame retardants(OPFRs) are gradually replacing brominated flame retardants(BFRs), which are widely used in the world. The increasing output of OPFRs and the increasing detection of OPFRs in environmental media have attracted wide attention of scholars at home and abroad. OPFRs are generally semi-volatile, easy to enter the environment and accumulate in organisms,causing potential hazards to the environment and human health. In this paper, the pollution status and toxic effects of OPFRs in aquatic environment were introduced,and the research progress of human health risk caused by them was summarized.The existing problems were pointed out, and the future research was prospected. In the future, the analytical methods of various environmental and biological media should be improved, and comprehensive and in-depth environmental investigation and ecological and health risk assessment should be carried out. Attention should be paid to the effects of combined pollution on organisms and the study of biological acceptability.
文摘Waste pyrolysis technology as a new method of waste treatment induces more and more attention. Waste pyrolysis technology is not on- ly good for garbage reduction, but also can restrain the generation of dioxin, reaching the target for harmless decrement. We introduced technique process, development situations at home and abroad, existing problems and improvement measures of waste pyrolytic technology.
基金supported by the National Natural Science Foundation of China(No.22005275)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP,No.2019L0584)the Advantage Disciplines Climbing Plan of Shanxi Province.
文摘Polymer bonded explosives(PBXs)have high energy density,excellent mechanical properties and better thermal stability.In this study,droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres.The effects of different binder types and binder concentrations on the morphology of the microspheres were studied,and results proved that NC/GAP(1:4)provides particles a regular spherical morphology and good dispersion.Subsequently,the influence of the concentration of the dispersed phase and the flow rate of the continuous phase on the particle size distribution of the microspheres was fully studied.The microspheres had narrow particle size distribution and high spherical shape.Under optimized process conditions,HMX/TATB microspheres were prepared and compared with the physical mixtures.The X-ray diffraction,differential scanning calorimetry,flow properties,bulk density,and mechanical sensitivity of the samples were also studied.Results showed that the crystal form of the microspheres remains unchanged,and the binder maintains good compatibility with explosives.In addition,the fluidity,bulk density,real density and safety performance of the microspheres are remarkably better than the physical mixture.This study provides a new method for preparing PBX with narrow particle size distribution,high spherical shape,excellent dispersion and high bulk density.
基金supported by Fundamental Research Program of Shanxi Province(20210302123055)and(201801D221035).
文摘In order to theoretically study the growth morphology of dihydroxylammonium 5,5’-bistetrazole-1,1’-dio late(TKX-50)crystal in different solvent systems,crystal–solvent models were established,and then molecular dynamics(MD)methods were adopted as a means to simulate particle motion.Modified attachment energy(MAE)model was employed to calculate the growth morphology of TKX-50.The simulation results demonstrate that COMPASS force field and RESP charge are suitable for molecular dynamics simulation of TKX-50.The morphologically dominant growth surfaces of TKX-50 in vacuum are(020),(011),(11–1),(100)and(120),respectively.In water(H_(2)O)and N,N-dimethylformamide(DMF)solvents,the(11–1)face is the largest in the habit face,the growth rate of(020)face becomes faster.With the increase of temperature,the aspect ratios of TKX-50 crystal in DMF solvent increase,and the areas of the(120)faces decrease.In ethylene glycol/H_(2)O mixed solvent system with volume ratio of 1/1,aspect ratio of TKX-50 is relatively small.In formic acid/H_(2)O mixed solvents with different volume ratios(1/4,1/3,1/2,1/1 and 2/1),aspect ratio of TKX-50 is relatively small when volume ratio is 1/2.
基金supported by the National Natural Science Foundation,China(41907047)the National Key Research and Development Program of China(2016YFE0202900)the Natural Science Foundation of Tianjin,China(18JCZDJC39600).
文摘Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies.In this study,an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different confluence flows on the erosion process of ephemeral gullies.Results showed that when the confluence flow was larger,the effect of geocell was more evident,and the protection against ephemeral gully erosion was stronger.When the confluence flow rates were 0.6,1.8,2.4,and 3.0 m^(3)/h,ephemeral gully erosion decreased by 37.84%,26.09%,21.40%,and 35.45%.When the confluence flow rates were 2.4 and 3.0 m^(3)/h,the average sediment yield rate of the ephemeral gully was close to 2.14 kg/(m^(2)•min),and the protective effect of ephemeral gully erosion was enhanced.When the flow rate was higher,the surface fracture of the ephemeral gully was more serious.With an increase in confluence flow rate,the ratio of erosion to deposition increased gradually,the erosion area of ephemeral gullies was expanded,and erosion depth changed minimally.In conclusion,geocell measures changed erosion patterns by altering the rill erosion/deposition ratio,converting erosion from rill erosion to sheet erosion.
基金Supported by the Provincial Governmental Foundation for Forestry of Anhui Province in 2013(2136203)
文摘The impact of 500 kV transmission lines of Anqing power plant across the lake wetland reserve along the Yangtze River on the safety of the ecosystem was taken as the researched object.The power frequency electric field intensity(PFEFI),power frequency magnetic field intensity(PFMFI),radio interference,construction noise,vegetation destruction and the influence on water quality were investigated and monitored,and the influences of PFEFI,PFMFI,radio interference and construction noise on wild animals,especially the habitats and migration of birds were mainly researched.The direct and indirect influences on the surrounding environment as well as plants and animals in sensitive areas were analyzed and predicted.The results firstly showed there existed a 182 400m^3 stereo-space(PFEFI>4kV/m)which made flying birds unsafe under the lowest height 11 mof the lines,which fills the gap in the research of this field.Finally,some operational protection countermeasures were put forward at the current technical level to achieve the win-win goal of economic development and natural protection.
基金National Natural Science Foundations of China(Nos.51308079,51408073,51678080,51678081)
文摘Silica( SiO_2) based aerogel/xerogel materials have been received ever-growing attentions for versatile applications. However,the widespread applications are narrowed by the inert properties,fragile and brittle natureof silica materials and cumbersome preparation processes. In this paper,titania( TiO_2) was introduced into SiO_2 matrix to form photocatalytic hybrid gels. The TiO_2/SiO_2 composites were then reinforced by the impregnation of various fibrillary reinforcements,such as glass,mullite mineral and ceramic fibers. The properties of the composites were studied systematically in terms of fiberstability,microstructure,chemical interaction and thermal conductivity. The final xerogel composites displayed improved monolithic geometry,satisfied thermal conductivity(0. 09-0. 25 W·m^(-1)·K^(-1)) and optimized photocatalytic performance(85% removal of model pollutant of methyl orange( Mo)),which could be expected to be a feasible route to multi-functional building facades in the future.
文摘The capacity factors （k＇） of fourteen types ofhalogenated thiophenols in different phases of methanol-water eluent were determined by reversed phased high-performance liquid chromatography （RP-HPLC） and the relationships between the logarithm of capacity factor lgK＇ and methanol ratio ψ were analyzed. A fair linear relationship is found between lgK＇ and ψ, and the correlation coefficients R2 of the constructed linear equations are all greater than 0.990. Relationship between the chromatographic data lgKw＇ when extrapolated to pure water and n-octanol/water partition coefficient lgKow obtained by the group contribution method has shown a good linear correlation with R2= 0.956. The structure parameters of fourteen halogenated thiophenols were calculated by using DFT, and the correlation equation of lgKw＇ and structure parameters was obtained by using SPSS, lgKw＇ = -0.409 ＋ 0.039a and R2 = 0.981, meaning that lgKw＇ is mainly determined by the polarizability α.
基金Supported by the National Natural Science Foundation of China(5120806841101233)
文摘We analyzed the compositions and basic properties of agricultural and forest biomass carbon,and used the pot method to study the influence of such element on the remediation of contaminated soils and growth of crops.Results show that agricultural and forest biomass carbon contains various nutrients that are necessary for crop growth,high specific surface area,and pore structure development.Cotton stalk charcoal can reduce bioavailability of Cadmium(Cd) in soil.Under mild Cd pollution,soil treated with cotton stalk charcoal adsorbs Cd at a rapid rate.With increasing extent of Cd pollution,Cd adsorption rate gradually slows down and Cd adsorption amount gradually increases.In soil treated with cotton stalk charcoal,the amount of Cd accumulated in the edible portions and roots of Brassica chinensis significantly decrease.The Cd mass fraction of the edible portions and roots are reduced by 49.43%- 68.29%,64.14%- 77.66% respectively.Appropriately adding carbon cotton stalks increases crop biomass.At a certain range,increasing cotton stalk charcoal also promotes the absorption of major nutrients in Brassica chinensis.
文摘The effluent quality from a secondary clarifier in an activated sludge process depends on the performance in the secondary clarifier at great extent. Several models have been developed based on the Kynch solid flux theory to improve the clarifier performance at last decades. This paper proposed a model which is established according to the basis sedimentation process of the secondary clarifier and Kynch flux theory for a clarifier with feedwell in upper of tank and the diffusion effective are combined into the model, which benefts the further improvement of the model and makes the solutions fit to the measurement data in secondary clarifier,
