Biochar have received multidisciplinary attention because of their extraordinary physicochemical properties.In this review,the application of biochar and biochar-based materials for the efficient elimination of organi...Biochar have received multidisciplinary attention because of their extraordinary physicochemical properties.In this review,the application of biochar and biochar-based materials for the efficient elimination of organic and inorganic pollutants are summarized.The sorption of organic chemicals and heavy metal ions/radionuclides,degradation/transformation of organic pollutants,and sorption-reduction-solidification of high-valent metal ions are described in detail.The interaction mechanism at molecular level from advanced spectroscopic techniques and theoretical calculations is discussed.Finally,the challenges in the application of biochar and biochar-supported materials in the immobilization of heavy metal ions and photocatalytic degradation of persistent organic pollutants in soils or wastewater are pointed out.This review is helpful for the graduate stu-dents to understand the recent works about biochar and biochar-supported materials in environmental pollutants management.展开更多
The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were wi...The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physicalknowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite,the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance.Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells（PeSCs） and the efficient 2D perovskite lightemitting diodes（PeLEDs）, are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed.展开更多
With the fast development of nanoscience and nanotechnology,the nanomaterials have attracted multidisciplinary interests.The high specific surface area and large numbers of oxygen-containing functional groups of graph...With the fast development of nanoscience and nanotechnology,the nanomaterials have attracted multidisciplinary interests.The high specific surface area and large numbers of oxygen-containing functional groups of graphene oxides(GOs) make them suitable in the preconcentration and solidification of radionuclides from wastewater.In this paper,mainly based on the recent work carried out in our laboratory,the efficient elimination of radionuclides using GOs and GO-based nanomaterials as adsorbents are summarized and the interaction mechanisms are discussed from the results of batch techniques,surface complexation modeling,spectroscopic analysis and theoretical calculations.This review is helpful for the understanding of the interactions of radionuclides with GOs and GO-based nanomaterials,which is also crucial for the application of GOs and GO-based nanomaterials in environmental radionuclide pollution management and also helpful in nuclear waste management.展开更多
With the rapid development of industrial,large amounts of different inorganic and organic pollutants are released into the natural environments.The efficient elimination of environmental pollutants,i.e.,photocatalytic...With the rapid development of industrial,large amounts of different inorganic and organic pollutants are released into the natural environments.The efficient elimination of environmental pollutants,i.e.,photocatalytic degradation of persistent organic pollutants into nontoxic organic/inorganic chemicals,in-situ solidification or sorption-reduction of heavy metal ions,is crucial to protect the environment.Nanomaterials with large surface area,active sites and abundant functional groups could form strong surface complexes with different kinds of pollutants and thereby could efficiently eliminate the pollutants from the aqueous solutions.In this review,wemainly focused on the recent works about the synthesis of nanomaterials and their applications in the efficient elimination of different organic and inorganic pollutants from wastewater and discussed the interaction mechanism from batch experimental results,the advanced spectroscopy techniques and theoretical calculations.The adsorption and the photocatalytic reduction of organic pollutants and the sorption/reduction of heavy metal ions are generally considered as the mainmethods to decrease the concentration of pollutants in the natural environment.This review highlights anew way for the real applications of novel nanomaterials in environmental pollution management,especially for the undergraduate students to understand the recent works in the elimination of different kinds of inorganic and organic chemicals in the natural environmental pollution management.展开更多
An extremely effortless method was applied for successful synthesis of mesoporous carbonaceous materials(MCMs) using well-ordered mesoporous silica as template. Various characterizations(scanning electron microscopy(S...An extremely effortless method was applied for successful synthesis of mesoporous carbonaceous materials(MCMs) using well-ordered mesoporous silica as template. Various characterizations(scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), Raman, X-ray photoelectron spectroscopy(XPS), Brunner-Emmet-Teller(BET) and Zeta potential) confirmed that MCMs had large surface area, uniform pore size distribution, and abundant oxygen-containing functional groups. The batch techniques were employed to study U(VI) adsorption on MCMs under a wide range of experiment conditions. The adsorption kinetics of U(VI) onto MCMs were well-fitted by pseudo-second-order kinetic model, indicating a chemisorption process. The excellent adsorption capacity of MCMs calculated from the Langmuir model was 293.95 mg g^(-1) at pH 4.0. The FT-IR and XPS analyses further evidenced that the binding of U(VI) onto MCMs was ascribed to the plentiful adsorption sites(–OH and –COOH groups) in the internal mesoporous structure, which could efficiently trap guest U(VI) ions. The results presented herein revealed that MCMs were ideal adsorbents in the efficient elimination of uranium or other lanthanides/actinides from aqueous solutions, which would play an important role in environmental pollution management application.展开更多
In this paper, we introduce and study the notion of HB-closed sets in L-topological space. Then, HB-convergence theory for L-molecular nets and L-ideals is established in terms of HB-closedness. Finally, we give a new...In this paper, we introduce and study the notion of HB-closed sets in L-topological space. Then, HB-convergence theory for L-molecular nets and L-ideals is established in terms of HB-closedness. Finally, we give a new definition of fuzzy H-continuous [1] which is called HB-continuity on the basis of the notion of H-bounded L-subsets in L-topological space. Then we give characterizations and properties by making use of HB-converges theory of L-molecular nets and L-ideals.展开更多
Two-dimensional boundary layer flow of an incompressible third grade nanofluid over a stretching surface is investigated.Influence of thermophoresis and Brownian motion is considered in the presence of Newtonian heati...Two-dimensional boundary layer flow of an incompressible third grade nanofluid over a stretching surface is investigated.Influence of thermophoresis and Brownian motion is considered in the presence of Newtonian heating and viscous dissipation.Governing nonlinear problems of velocity, temperature and nanoparticle concentration are solved via homotopic procedure.Convergence is examined graphically and numerically. Results of temperature and nanoparticle concentration are plotted and discussed for various values of material parameters, Prandtl number, Lewis number, Newtonian heating parameter, Eckert number and thermophoresis and Brownian motion parameters. Numerical computations are performed. The results show that the change in temperature and nanoparticle concentration distribution functions is similar when we use higher values of material parameters β1 andβ2. It is seen that the temperature and thermal boundary layer thickness are increasing functions of Newtonian heating parameter γ.An increase in thermophoresis and Brownian motion parameters tends to an enhancement in the temperature.展开更多
Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing t...Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into(FAPbI3)0.85(MAPbBr3)0.15(FA/MA) to form a novel 2D-3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)2.4(FA)n-1PbnI3n+1.4]0.85(MAPbBr3)0.15(n=3, 5, 7, 9 and 11)(A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts;A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency(PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.展开更多
This paper is concerned with a stochastic HBV infection model with logistic growth. First, by constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of ergodic statio...This paper is concerned with a stochastic HBV infection model with logistic growth. First, by constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of ergodic stationary distribution of the solution to the HBV infection model. Then we obtain sufficient conditions for extinction of the disease. The stationary distribution shows that the disease can become persistent in vivo.展开更多
Nanoscale zerovalent iron/magnetic carbon(NZVI/MC) composites were successfully synthesized by simply calcining yellow pine and iron precursors. NZVI/MC pyrolyzed at 800°C(NZVI/MC800) had a higher percentage of N...Nanoscale zerovalent iron/magnetic carbon(NZVI/MC) composites were successfully synthesized by simply calcining yellow pine and iron precursors. NZVI/MC pyrolyzed at 800°C(NZVI/MC800) had a higher percentage of NZVI and displayed better resistance to aggregation and oxidation of NZVI than samples prepared at other temperatures. The NZVI/MC800 material was applied for the elimination of U(Ⅵ) from aqueous solutions. The results suggested that the NZVI/MC800 displayed excellent adsorption capacity(203.94 mg/g)toward U(Ⅵ). The significant adsorption capacity and fast adsorption kinetics were attributed to the presence of well-dispersed NZVI, which could quickly reduce U(Ⅵ) into U(Ⅳ), trapping the guest U(Ⅳ) in the porous biocarbon matrix. The removal of U(Ⅵ) on the NZVI/MC samples was strongly affected by solution pH. The NZVI/MC samples also displayed outstanding reusability for U(Ⅵ) removal after multiple cycles. These findings indicate that NZVI/MC has great potential for remediation of wastewater containing U(Ⅵ).展开更多
Mixed convection flow of magnetohydrodynamic(MHD) Jeffrey nanofluid over a radially stretching surface with radiative surface is studied. Radial sheet is considered to be convectively heated. Convective boundary condi...Mixed convection flow of magnetohydrodynamic(MHD) Jeffrey nanofluid over a radially stretching surface with radiative surface is studied. Radial sheet is considered to be convectively heated. Convective boundary conditions through heat and mass are employed. The governing boundary layer equations are transformed into ordinary differential equations. Convergent series solutions of the resulting problems are derived. Emphasis has been focused on studying the effects of mixed convection, thermal radiation, magnetic field and nanoparticles on the velocity, temperature and concentration fields. Numerical values of the physical parameters involved in the problem are computed for the local Nusselt and Sherwood numbers are computed.展开更多
The graphene oxides （GOs） have attracted multidisciplinary study because of their special physicochemical properties. The high surface area and large amounts of oxygen-containing functional groups make GOs suitable ...The graphene oxides （GOs） have attracted multidisciplinary study because of their special physicochemical properties. The high surface area and large amounts of oxygen-containing functional groups make GOs suitable materials for the efficient elimination of heavy metal ions from aqueous solutions. Herein the sorption of Ni（Ⅱ） on GOs was studied using batch experi- ments, and the results showed that the sorption of Ni（Ⅱ） is strongly dependent on pH and ionic strength at pH〈8, and inde- pendent of ionic strength at pH〉8. The sorption of Ni（Ⅱ） is mainly dominated by outer-sphere surface complexation and ion exchange at low pH, and by inner-sphere surface complexation at high pH. The interaction of Ni（Ⅱ） with GOs was also inves- tigated by theoretical density functional theory （DFT） calculations, and the results show that the sorption of Ni（Ⅱ） on GOs is mainly attributed to the -COH and -COC groups and the DFT calculations show that Ni（Ⅱ） forms stable GO_Ni_triplet struc- ture with the binding energy of -39.44 kcal/mol, which is in good agreement with the batch sorption experimental results. The results are important for the application of GOs as adsorbents in the efficient removal of Ni（Ⅱ） from wastewater in environ- mental pollution cleanup.展开更多
In this paper, we study a boundary value problem of nonlinear fractional dif- ferential equations of order q （1 〈 q 〈 2） with non-separated integral boundary conditions. Some new existence and uniqueness results a...In this paper, we study a boundary value problem of nonlinear fractional dif- ferential equations of order q （1 〈 q 〈 2） with non-separated integral boundary conditions. Some new existence and uniqueness results are obtained by using some standard fixed point theorems and Leray-Schauder degree theory. Some illustrative examples are also presented. We extend previous results even in the integer case q = 2.展开更多
In this work, a facile method was adopted to synthesize molybdenum disulfide/reduced graphene oxide （MoS2/rGO） composites through an c-cysteine-assisted hydrothermal technique, The as-prepared MoS2/ rGO composites w...In this work, a facile method was adopted to synthesize molybdenum disulfide/reduced graphene oxide （MoS2/rGO） composites through an c-cysteine-assisted hydrothermal technique, The as-prepared MoS2/ rGO composites were firstly applied as adsorbents for efficient elimination of Pb（Ⅱ） ions. Batch adsorption experiments showed that the adsorption of Pb（Ⅱ） on MoS2/rGO followed pseudo-second-order kinetic model well. The adsorption of Pb（Ⅱ） was intensely pH-dependent, ionic strength-dependent at pH 〈 9.0 and ionic strength-independent at pH 〉 9,0, The presence of humic acid （HA） enhanced Pb（Ⅱ） adsorption obviously. The MoS2/rGO composites exhibited excellent adsorption capacity of 384.16 mg g 1 at pH 5.0 and T = 298.15 K, which was superior to MOS2 （279.93 mg g 1） and many other adsorbents. The thermodynamic parameters suggested that the adsorption process of Pb（Ⅱ） on MoS2/rGO composites was spontaneous （zSG＂ 〈 O） and endothermic （△H 〉 0）. The interaction of Pb（Ⅱ） and MoS2] rGO was mainly dominated by electrostatic attraction and surface comple^ation between Pb（Ⅱ） and oxygen-containing functional groups of MoS2]rGO. This work highlighted the application of MoS21rGO as novel and promising materials in the efficient elimination of Pb（Ⅱ） from contaminated water and industrial effluents in environmental pollution management.展开更多
To date, extensive research has been carried out,with considerable success, on the development of highperformance perovskite solar cells(PSCs). Owing to its wide absorption range and remarkable thermal stability, the ...To date, extensive research has been carried out,with considerable success, on the development of highperformance perovskite solar cells(PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixedcation perovskite FAxMA1-xPbI3(formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FAxMA1-xPbI3 films contain a high percentage of MA+and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-Pb I2-DMSO(DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08 PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ~30% for 80 days in standard atmospheric conditions.展开更多
The mixed convection stagnation-point flow of an incompressible non-Newtonian fluid over a stretching sheet under convective boundary conditions is investigated.Mathematical formulation is presented for a Casson fluid...The mixed convection stagnation-point flow of an incompressible non-Newtonian fluid over a stretching sheet under convective boundary conditions is investigated.Mathematical formulation is presented for a Casson fluid.The resulting partial differential equations are converted into the ordinary differential equations by the suitable transformations.The velocity and temperature profiles are computed by employing the homotopy analysis method.The plotted graphs illustrate the flow and heat transfer characteristics and their dependence upon the embedded parameters.Numerical values of skin-friction coefficient and Nusselt number are given and examined.Comparison of the present results with the existing solution is also given.展开更多
The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective bound...The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.展开更多
基金Financial supports from National Key Research and Development Program of China(2018YFC1900105)National Natural Science Foundation of China(21836001)Beijing Outstanding Young Scientist Program are acknowledged.
文摘Biochar have received multidisciplinary attention because of their extraordinary physicochemical properties.In this review,the application of biochar and biochar-based materials for the efficient elimination of organic and inorganic pollutants are summarized.The sorption of organic chemicals and heavy metal ions/radionuclides,degradation/transformation of organic pollutants,and sorption-reduction-solidification of high-valent metal ions are described in detail.The interaction mechanism at molecular level from advanced spectroscopic techniques and theoretical calculations is discussed.Finally,the challenges in the application of biochar and biochar-supported materials in the immobilization of heavy metal ions and photocatalytic degradation of persistent organic pollutants in soils or wastewater are pointed out.This review is helpful for the graduate stu-dents to understand the recent works about biochar and biochar-supported materials in environmental pollutants management.
基金supported by the National Key Research and Development Program of China (2016YFA0202401)the 111 Project (B16016)+1 种基金the National Natural Science Foundation of China (51572080, 51702096 and U1705256)the Fundamental Research Funds for the Central Universities (2017XS080)
文摘The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physicalknowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite,the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance.Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells（PeSCs） and the efficient 2D perovskite lightemitting diodes（PeLEDs）, are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed.
基金supported by the National Natural Science Foundation of China (21225730,91326202,and 21577032)the Fundamental Research Funds for the Central Universities (JB2015001)Furong Scholarship of Hunan Province
文摘With the fast development of nanoscience and nanotechnology,the nanomaterials have attracted multidisciplinary interests.The high specific surface area and large numbers of oxygen-containing functional groups of graphene oxides(GOs) make them suitable in the preconcentration and solidification of radionuclides from wastewater.In this paper,mainly based on the recent work carried out in our laboratory,the efficient elimination of radionuclides using GOs and GO-based nanomaterials as adsorbents are summarized and the interaction mechanisms are discussed from the results of batch techniques,surface complexation modeling,spectroscopic analysis and theoretical calculations.This review is helpful for the understanding of the interactions of radionuclides with GOs and GO-based nanomaterials,which is also crucial for the application of GOs and GO-based nanomaterials in environmental radionuclide pollution management and also helpful in nuclear waste management.
基金the Deanship of Scientific Research(DSR)at King Abdulaziz University,Jeddah,under Grant No.KEP-19-130-40The National Key Research and Development Program of China(Grant No.2018YFC1900105)was acknowledged.
文摘With the rapid development of industrial,large amounts of different inorganic and organic pollutants are released into the natural environments.The efficient elimination of environmental pollutants,i.e.,photocatalytic degradation of persistent organic pollutants into nontoxic organic/inorganic chemicals,in-situ solidification or sorption-reduction of heavy metal ions,is crucial to protect the environment.Nanomaterials with large surface area,active sites and abundant functional groups could form strong surface complexes with different kinds of pollutants and thereby could efficiently eliminate the pollutants from the aqueous solutions.In this review,wemainly focused on the recent works about the synthesis of nanomaterials and their applications in the efficient elimination of different organic and inorganic pollutants from wastewater and discussed the interaction mechanism from batch experimental results,the advanced spectroscopy techniques and theoretical calculations.The adsorption and the photocatalytic reduction of organic pollutants and the sorption/reduction of heavy metal ions are generally considered as the mainmethods to decrease the concentration of pollutants in the natural environment.This review highlights anew way for the real applications of novel nanomaterials in environmental pollution management,especially for the undergraduate students to understand the recent works in the elimination of different kinds of inorganic and organic chemicals in the natural environmental pollution management.
基金supported by the National Natural Science Foundation of China(91326202,21577032)the Fundamental Research Funds for the Central Universities(JB2015001,JB2017057)the Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection and the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘An extremely effortless method was applied for successful synthesis of mesoporous carbonaceous materials(MCMs) using well-ordered mesoporous silica as template. Various characterizations(scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), Raman, X-ray photoelectron spectroscopy(XPS), Brunner-Emmet-Teller(BET) and Zeta potential) confirmed that MCMs had large surface area, uniform pore size distribution, and abundant oxygen-containing functional groups. The batch techniques were employed to study U(VI) adsorption on MCMs under a wide range of experiment conditions. The adsorption kinetics of U(VI) onto MCMs were well-fitted by pseudo-second-order kinetic model, indicating a chemisorption process. The excellent adsorption capacity of MCMs calculated from the Langmuir model was 293.95 mg g^(-1) at pH 4.0. The FT-IR and XPS analyses further evidenced that the binding of U(VI) onto MCMs was ascribed to the plentiful adsorption sites(–OH and –COOH groups) in the internal mesoporous structure, which could efficiently trap guest U(VI) ions. The results presented herein revealed that MCMs were ideal adsorbents in the efficient elimination of uranium or other lanthanides/actinides from aqueous solutions, which would play an important role in environmental pollution management application.
文摘In this paper, we introduce and study the notion of HB-closed sets in L-topological space. Then, HB-convergence theory for L-molecular nets and L-ideals is established in terms of HB-closedness. Finally, we give a new definition of fuzzy H-continuous [1] which is called HB-continuity on the basis of the notion of H-bounded L-subsets in L-topological space. Then we give characterizations and properties by making use of HB-converges theory of L-molecular nets and L-ideals.
基金funded by the Deanship of Scientific Research (DSR), King Abdulaziz University (KAU), under Grant No. 37-130-35-HiCi
文摘Two-dimensional boundary layer flow of an incompressible third grade nanofluid over a stretching surface is investigated.Influence of thermophoresis and Brownian motion is considered in the presence of Newtonian heating and viscous dissipation.Governing nonlinear problems of velocity, temperature and nanoparticle concentration are solved via homotopic procedure.Convergence is examined graphically and numerically. Results of temperature and nanoparticle concentration are plotted and discussed for various values of material parameters, Prandtl number, Lewis number, Newtonian heating parameter, Eckert number and thermophoresis and Brownian motion parameters. Numerical computations are performed. The results show that the change in temperature and nanoparticle concentration distribution functions is similar when we use higher values of material parameters β1 andβ2. It is seen that the temperature and thermal boundary layer thickness are increasing functions of Newtonian heating parameter γ.An increase in thermophoresis and Brownian motion parameters tends to an enhancement in the temperature.
基金financially supported by the National Key Research and Development Program of China (2016YFA0202401)the National Natural Science Foundation of China (51572080)
文摘Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into(FAPbI3)0.85(MAPbBr3)0.15(FA/MA) to form a novel 2D-3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)2.4(FA)n-1PbnI3n+1.4]0.85(MAPbBr3)0.15(n=3, 5, 7, 9 and 11)(A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts;A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency(PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.
基金supported by NSFC of China(11371085)the Fundamental Research Funds for the Central Universities(15CX08011A),2016GXNSFBA380006 and KY2016YB370
文摘This paper is concerned with a stochastic HBV infection model with logistic growth. First, by constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of ergodic stationary distribution of the solution to the HBV infection model. Then we obtain sufficient conditions for extinction of the disease. The stationary distribution shows that the disease can become persistent in vivo.
基金supported by the National Natural Science Foundation of China (No.21477133)the Key Lab of Photovoltaic and Energy Conservation Materials,Chinese Academy of Sciences is acknowledged
文摘Nanoscale zerovalent iron/magnetic carbon(NZVI/MC) composites were successfully synthesized by simply calcining yellow pine and iron precursors. NZVI/MC pyrolyzed at 800°C(NZVI/MC800) had a higher percentage of NZVI and displayed better resistance to aggregation and oxidation of NZVI than samples prepared at other temperatures. The NZVI/MC800 material was applied for the elimination of U(Ⅵ) from aqueous solutions. The results suggested that the NZVI/MC800 displayed excellent adsorption capacity(203.94 mg/g)toward U(Ⅵ). The significant adsorption capacity and fast adsorption kinetics were attributed to the presence of well-dispersed NZVI, which could quickly reduce U(Ⅵ) into U(Ⅳ), trapping the guest U(Ⅳ) in the porous biocarbon matrix. The removal of U(Ⅵ) on the NZVI/MC samples was strongly affected by solution pH. The NZVI/MC samples also displayed outstanding reusability for U(Ⅵ) removal after multiple cycles. These findings indicate that NZVI/MC has great potential for remediation of wastewater containing U(Ⅵ).
文摘Mixed convection flow of magnetohydrodynamic(MHD) Jeffrey nanofluid over a radially stretching surface with radiative surface is studied. Radial sheet is considered to be convectively heated. Convective boundary conditions through heat and mass are employed. The governing boundary layer equations are transformed into ordinary differential equations. Convergent series solutions of the resulting problems are derived. Emphasis has been focused on studying the effects of mixed convection, thermal radiation, magnetic field and nanoparticles on the velocity, temperature and concentration fields. Numerical values of the physical parameters involved in the problem are computed for the local Nusselt and Sherwood numbers are computed.
基金supported by the Deanship of Scientific Research,King Abdulaziz University(41-130-36-Hi Ci)
文摘The graphene oxides （GOs） have attracted multidisciplinary study because of their special physicochemical properties. The high surface area and large amounts of oxygen-containing functional groups make GOs suitable materials for the efficient elimination of heavy metal ions from aqueous solutions. Herein the sorption of Ni（Ⅱ） on GOs was studied using batch experi- ments, and the results showed that the sorption of Ni（Ⅱ） is strongly dependent on pH and ionic strength at pH〈8, and inde- pendent of ionic strength at pH〉8. The sorption of Ni（Ⅱ） is mainly dominated by outer-sphere surface complexation and ion exchange at low pH, and by inner-sphere surface complexation at high pH. The interaction of Ni（Ⅱ） with GOs was also inves- tigated by theoretical density functional theory （DFT） calculations, and the results show that the sorption of Ni（Ⅱ） on GOs is mainly attributed to the -COH and -COC groups and the DFT calculations show that Ni（Ⅱ） forms stable GO_Ni_triplet struc- ture with the binding energy of -39.44 kcal/mol, which is in good agreement with the batch sorption experimental results. The results are important for the application of GOs as adsorbents in the efficient removal of Ni（Ⅱ） from wastewater in environ- mental pollution cleanup.
文摘In this paper, we study a boundary value problem of nonlinear fractional dif- ferential equations of order q （1 〈 q 〈 2） with non-separated integral boundary conditions. Some new existence and uniqueness results are obtained by using some standard fixed point theorems and Leray-Schauder degree theory. Some illustrative examples are also presented. We extend previous results even in the integer case q = 2.
基金supported by Science Challenge Project (JCKY2016212A04)the National Natural Science Fondation of China(91326202,21577032,and 21403064)+1 种基金the Fundamental Research Funds for the Central Universities(JB2015001)the National Special Water Programs(2015ZX07203-011,2015ZX07204-007)
文摘In this work, a facile method was adopted to synthesize molybdenum disulfide/reduced graphene oxide （MoS2/rGO） composites through an c-cysteine-assisted hydrothermal technique, The as-prepared MoS2/ rGO composites were firstly applied as adsorbents for efficient elimination of Pb（Ⅱ） ions. Batch adsorption experiments showed that the adsorption of Pb（Ⅱ） on MoS2/rGO followed pseudo-second-order kinetic model well. The adsorption of Pb（Ⅱ） was intensely pH-dependent, ionic strength-dependent at pH 〈 9.0 and ionic strength-independent at pH 〉 9,0, The presence of humic acid （HA） enhanced Pb（Ⅱ） adsorption obviously. The MoS2/rGO composites exhibited excellent adsorption capacity of 384.16 mg g 1 at pH 5.0 and T = 298.15 K, which was superior to MOS2 （279.93 mg g 1） and many other adsorbents. The thermodynamic parameters suggested that the adsorption process of Pb（Ⅱ） on MoS2/rGO composites was spontaneous （zSG＂ 〈 O） and endothermic （△H 〉 0）. The interaction of Pb（Ⅱ） and MoS2] rGO was mainly dominated by electrostatic attraction and surface comple^ation between Pb（Ⅱ） and oxygen-containing functional groups of MoS2]rGO. This work highlighted the application of MoS21rGO as novel and promising materials in the efficient elimination of Pb（Ⅱ） from contaminated water and industrial effluents in environmental pollution management.
基金support from the National Key Research and Development Program of China (2016YFA0202401)the 111 Project (B16016)+2 种基金the National Natural Science Foundation of China (51702096 and U1705256)the Fundamental Research Funds for the Central Universities (2018ZD07)Metatest Scan Pro Laser Scanning System
文摘To date, extensive research has been carried out,with considerable success, on the development of highperformance perovskite solar cells(PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixedcation perovskite FAxMA1-xPbI3(formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FAxMA1-xPbI3 films contain a high percentage of MA+and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-Pb I2-DMSO(DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08 PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ~30% for 80 days in standard atmospheric conditions.
基金Supported by the Deanship of Scientific Research(DSR),King Abdulaziz University,Jeddah,under Grant No HiCi/40-3/1432H.
文摘The mixed convection stagnation-point flow of an incompressible non-Newtonian fluid over a stretching sheet under convective boundary conditions is investigated.Mathematical formulation is presented for a Casson fluid.The resulting partial differential equations are converted into the ordinary differential equations by the suitable transformations.The velocity and temperature profiles are computed by employing the homotopy analysis method.The plotted graphs illustrate the flow and heat transfer characteristics and their dependence upon the embedded parameters.Numerical values of skin-friction coefficient and Nusselt number are given and examined.Comparison of the present results with the existing solution is also given.
基金the Higher Education Commission of Pakistan (HEC) for the financial support through Indigenous program
文摘The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.
