This paper investigates the physical properties and predicted radii of compact stars generated by the Tolman-IV complexity-free model within the background of modified gravity theory,particularly the f(R,T)-gravity th...This paper investigates the physical properties and predicted radii of compact stars generated by the Tolman-IV complexity-free model within the background of modified gravity theory,particularly the f(R,T)-gravity theory,under complexity formalism for a spherically symmetric spacetime proposed by L.Herrera[Phys Rev D 97:044010,2018].By solving the resulting set of differential equations,we obtain the explicit forms of the energy-momentum(EM)tensor components,including the density,radial pressure,and tangential pressure.The influence of the parameterχon various physical properties of the star is thoroughly investigated.The model undergoes a series of rigorous tests to determine its physical relevance.The findings indicate that the model exhibits regularity,stability,and a surface with vanishing pressure.The boundary of this surface is determined by carefully selecting the parameter space.The complexity method employed in f(R,T)gravity offers an interesting approach for developing astrophysical models that are consistent with observable events as demonstrated by recent experiments.In this regard,we use observational data from the GW190814 event,detected by the LIGO and Virgo observatories,to investigate the validity of the Tolman-IV model in f(R,T)gravity.The analysis includes comparing the model's predictions with the observed characteristics of the compact object involved in the merger.In addition,data from two-millisecond pulsars,PSR J1614-2230 and PSR J0952-0607,are incorporated to further constrain the theoretical theories.However,we present a diagram depicting the relationship between the total mass and radius of the compact object candidates for different values ofχ.展开更多
A new medium-temperature (200-400 °C) adsorbent material for oxygen removal and air separation, YBaCo4O7+δ, was prepared by the solid-state reaction method. This new adsorbent could adsorb a large quantity of ox...A new medium-temperature (200-400 °C) adsorbent material for oxygen removal and air separation, YBaCo4O7+δ, was prepared by the solid-state reaction method. This new adsorbent could adsorb a large quantity of oxygen in the temperature range of 200-370 °C. Adsorbed oxygen could be released by raising temperature over 400 °C or by switching the atmosphere from oxygen to nitrogen. This oxygen adsorption and desorption process had good reproducibility. Taking advantage of this unique oxygen intake/release behavior, a nitrogen purification process was investigated. The results showed that YBaCo4O7+δ material was a promising candidate for the oxygen sorption process and could be used to produce high-purity nitrogen or to remove trace oxygen from other gases.展开更多
A new europium(Ⅲ)complex containing(4-Methyl-2-oxo-2 H-chromen-7-yloxy)-acetic acid moiety(CMMC)was synthesized,characterized,and confirmed as antitumor agent and fluorescent probe.The spectroscopic measurements of ...A new europium(Ⅲ)complex containing(4-Methyl-2-oxo-2 H-chromen-7-yloxy)-acetic acid moiety(CMMC)was synthesized,characterized,and confirmed as antitumor agent and fluorescent probe.The spectroscopic measurements of Eu(Ⅲ)in the presence of CMMC were obtained in different solvents.The results show that the strongest Eu(Ⅲ)emission bands were monitored in iso-propyl alcohol while the weakest Eu(Ⅲ)emission band was observed in acetonitrile.The interaction of Eu(Ⅲ)-(CMMC)2 complex with DNA was monitored using absorption and emission techniques.From fluorescence titration measurements,the binding constants of DNA with Eu(Ⅲ)-(CMMC)_2 complex were found to be 1.04×10~5 L·mol^(-1) in Tris-HCl and 1.17×10~7 L·mol^(-1) in DMSO-Tris-HCl buffer(9∶1 V/V).Hypochromism was observed from the absorption titration experiment which indicates the intercalation of Eu(Ⅲ)-complex between the base pair of DNA.This result further confirmed by fluorescent Ethidium bromide displacement assay.The fluorescence calibration curve was used for the determination of DNA with LOD of 1.2 ng in DMSO-Tris-HCl buffer(9∶1 V/V)and 5 ng in Tris-HCl buffer.The preliminary antitumor investigation shows promising cytotoxicity against MDA-MB-231,MCF-7(mammary cancer),and PC-3(prostate carcinoma)cell lines with IC50 values of 40.63,25.42 and 30.25μmol·L^(-1),respectively.展开更多
Bi- and Cu-substituted Ca3Co4O9 samples were prepared by conventional solid-state reaction method and the effect of element substitution on the microstructures and thermoelectric properties was investigated. Partial s...Bi- and Cu-substituted Ca3Co4O9 samples were prepared by conventional solid-state reaction method and the effect of element substitution on the microstructures and thermoelectric properties was investigated. Partial substitution of Cu for Co leads to an increase in electrical conductivity and a decrease in Seebeck coefficient due to the rise of hole concentration. The microstructure of Cu-substituted sample is almost unchanged compared with undoped Ca3Co4O9. On the other hand, partial substitution of Bi for Ca gives rise to a significant increase in the grain size, and c-axis-oriented structure can be formed in Ca2.7Bi0.3Co4O9, resulting in an obvious increase in electrical conductivity. Cu and Bi co-substitution further increases the grain growth and the electrical conductivity of Ca2.7Bi0.3Co3.7Cu0.3O9. Thus, Cu and Bi co-substitution samples possess the optimal thermoelectric performance at high temperature and the highest value of power factor can reach 3.1×10^-4 Wm^-1.K^-2 at 1000 K.展开更多
We consider a SIR epidemic model with saturated incidence rate and treatment. We show that if the basic reproduction number, R0 is less than unity and the disease free equilibrium is locally asymptotically stable. Mor...We consider a SIR epidemic model with saturated incidence rate and treatment. We show that if the basic reproduction number, R0 is less than unity and the disease free equilibrium is locally asymptotically stable. Moreover, we show that if R0 > 1, the endemic equilibrium is locally asymptotically stable. In the end, we give some numerical results to compare our model with existing model and to show the effect of the treatment term on the model.展开更多
In this paper,the author introduces new Triebel-Lizorkin spaces and Besov spaces associated with different homogeneities and proves that the composition of two Calderón-Zygmund singular integral operators with di...In this paper,the author introduces new Triebel-Lizorkin spaces and Besov spaces associated with different homogeneities and proves that the composition of two Calderón-Zygmund singular integral operators with different homogeneities is bounded on these new Triebel-Lizorkin spaces and Besov spaces.展开更多
In this work,we have explored wormhole(WH)solutions in F(R,L_(m))gravity by assuming the Morris-Thorne WH metric and F(R,Lm)=R/2+(1+γR)L_(m),whereγis the free model parameter.We determined the WH solutions by utiliz...In this work,we have explored wormhole(WH)solutions in F(R,L_(m))gravity by assuming the Morris-Thorne WH metric and F(R,Lm)=R/2+(1+γR)L_(m),whereγis the free model parameter.We determined the WH solutions by utilizing two newly developed shape functions(SF)that satisfy all basic conditions for a WH’s physical validity.We also observe that the null energy condition(NEC)behaves negatively.Finally,for both models,we use the volume integral quantifier(VIQ)and Tolman-Oppenheimer-Volkoff(TOV)equation to determine how much exotic matter is needed near the WH throat and the stability of the WH.The extensive detailed discussions of the matter components have been done via graphical analysis.The obtained WH geometries meet the physically acceptable conditions for a stable wormhole.展开更多
The oxygen adsorption/desorption properties of YBaCo4O7 at high temperature were investigated by thermogravimetry(TG) method,in which two types of oxygen adsorption were combined.The first type adsorbed oxygen at abou...The oxygen adsorption/desorption properties of YBaCo4O7 at high temperature were investigated by thermogravimetry(TG) method,in which two types of oxygen adsorption were combined.The first type adsorbed oxygen at about 700 °C and released the adsorbed oxygen at 880 °C.After the first type oxygen desorption,even the temperature and oxygen flow were kept the same,a second type oxygen adsorption at about 880 °C occurred and the adsorbed oxygen were released at above 980 °C.The combination of these two types of...展开更多
For waves in inhomogeneous media,variable-coefficient evolution equations can arise.It is known that the Manakov model can derive two models for propagation in uniform optical fibers.If the fiber is nonuniform,one wou...For waves in inhomogeneous media,variable-coefficient evolution equations can arise.It is known that the Manakov model can derive two models for propagation in uniform optical fibers.If the fiber is nonuniform,one would expect that the coefficients in the model are not constants.We present a variable-coefficient Manakov model and derive its Lax pair using the generalized dressing method.As an application of the generalized dressing method,soliton solutions of the variable-coefficient Manakov model are obtained.展开更多
The interaction of arbitrarily distributed penny-shaped cracks in three-dimensional solids is analyzed in this paper. Using oblate spheroidal coordinates and displacement functions, an analytic method is devel- oped i...The interaction of arbitrarily distributed penny-shaped cracks in three-dimensional solids is analyzed in this paper. Using oblate spheroidal coordinates and displacement functions, an analytic method is devel- oped in which the opening and the sliding displacements on each crack surface are taken as the basic unknown functions. The basic unknown functions can be expanded in series of Legendre polynomials with unknown coefficients. Based on superposition technique, a set of governing equations for the unknown coefficients are formulated from the traction free conditions on each crack surface. The boundary collocation procedure and the average method for crack-surface tractions are used for solving the governing equations. The solution can be obtained for quite closely located cracks. Numerical examples are given for several crack problems. By comparing the present results with other existing results, one can conclude that the present method provides a direct and efficient approach to deal with three-dimensional solids containing multiple cracks.展开更多
Polycrystalline samples of Bi 1.5 Pb 0.5 Sr 2-x La x Co 2 O y （x = 0.1, 0.2, 0.3） with a layered structure were prepared by solid-state reaction method. All samples are p-type semiconductors. The thermoelectric prop...Polycrystalline samples of Bi 1.5 Pb 0.5 Sr 2-x La x Co 2 O y （x = 0.1, 0.2, 0.3） with a layered structure were prepared by solid-state reaction method. All samples are p-type semiconductors. The thermoelectric properties, namely, the electric resistivity （ρ）, Seebeck coefficient （S）, and power factor （S 2 /ρ） of the samples are dependent on chemical composition. The values of ρ, S, and S 2 /ρ increase with an increase in temperature for all samples. The substitution of Pb 2＋ for Bi 3＋ and La 3＋ for Sr 2＋ improves the thermoelectric properties of the Bi 2 Sr 2 Co 2 O y system owing to the simultaneous decrease of electric resistivity and increase of Seebeck coefficient. As a result, the optimal thermoelectric property has been obtained in Bi 1.5 Pb 0.5 Sr 1.7 La 0.3 Co 2 O y and the power factor can reach 2.1 × 10-4 W·m-1 K-2 at 998 K.展开更多
Based on the LaSalle invariance principle, we propose a simple adaptive-feedback for controlling the unified chaotic system. We show explicitly with numerical proofs that our method can easily achieve the control of c...Based on the LaSalle invariance principle, we propose a simple adaptive-feedback for controlling the unified chaotic system. We show explicitly with numerical proofs that our method can easily achieve the control of chaos in the unified chaotic system using only a single variable feedback. The present controller, to our knowledge, is the simplest control scheme for controlling a unified chaotic system.展开更多
A SIQS epidemic model with saturated incidence rate is studied. Two equilibrium points exist for the system, disease-free and endemic equilibrium. The stability of the disease-free equilibrium and endemic equilibrium ...A SIQS epidemic model with saturated incidence rate is studied. Two equilibrium points exist for the system, disease-free and endemic equilibrium. The stability of the disease-free equilibrium and endemic equilibrium exists when the basic reproduction number R0, is less or greater than unity respectively. The global stability of the disease-free and endemic equilibrium is proved using Lyapunov functions and Poincare-Bendixson theorem plus Dulac’s criterion respectively.展开更多
In this paper, an investigation of unsteady free convective magneto-hydro dynamic (MHD) flow of salty water in the presence of a transverse magnetic field has been carried out. An electrically conducting and incompres...In this paper, an investigation of unsteady free convective magneto-hydro dynamic (MHD) flow of salty water in the presence of a transverse magnetic field has been carried out. An electrically conducting and incompressible fluid is assumed to flow past a semi-infinite vertical porous plate. A constant magnetic field is applied normally to the vertical plate. The Prandtl numbers for salt water are taken to be 1 at 20<span style="white-space:nowrap;">˚</span>C. The governing equations of the problem contain non-linear partial differential equations that are transformed into ordinary differential equations. An explicit finite difference scheme has been used to solve the transformed ordinary equations generated from this flow problem. The velocity profiles and temperature distribution of the flow field have been discussed and presented graphically.展开更多
The laminar analytic solutions of velocities and pressure in the central zone of the inlet region of pipe flow are given under the condition of uniform inflow, based on the Navier-Stokes equations of incompressible vi...The laminar analytic solutions of velocities and pressure in the central zone of the inlet region of pipe flow are given under the condition of uniform inflow, based on the Navier-Stokes equations of incompressible viscous flow.展开更多
A direct numerical simulation is performed on 256~3 grids for decaying isotropic tur- bulence.The total kinematic energy,Taylor micro-scale,Taylor micro-scale Reynolds number and the velocity derivative skewness are c...A direct numerical simulation is performed on 256~3 grids for decaying isotropic tur- bulence.The total kinematic energy,Taylor micro-scale,Taylor micro-scale Reynolds number and the velocity derivative skewness are calculated.The snapshots of energy spectra and energy transfer spectra are plotted.These measurements verify the DIA predictions:decaying isotropic turbulence has the energy propagation and occupies the final decay periods.The skewness remains to some level with small variation even in the final decay period.展开更多
In this paper, an improved algorithm for the solution of Generalized Burger-Fisher’s Equation is presented. A Maple code is generated for the algorithm and simulated. It was observed that the algorithm gives the solu...In this paper, an improved algorithm for the solution of Generalized Burger-Fisher’s Equation is presented. A Maple code is generated for the algorithm and simulated. It was observed that the algorithm gives the solution with less computation. The solution gives a better result when compared with the numerical solutions in the existing literature.展开更多
We study the coupled mKdV equation by the dressing method via local Riemann-Hilbert problem. With the help of the Lax pairs, we obtain the matrix Riemann-Hilbert problem with zeros. The explicit solutions for the coup...We study the coupled mKdV equation by the dressing method via local Riemann-Hilbert problem. With the help of the Lax pairs, we obtain the matrix Riemann-Hilbert problem with zeros. The explicit solutions for the coupled mKdV equation are derived with the aid of the regularization of the Riemann-Hilbert problem.展开更多
By using the generalized version of the dressing method, we consider a Dirac system. The types of nonlinear evolution equations discussed involve the integrable variable-coefficient Dirac equation and the defocusing n...By using the generalized version of the dressing method, we consider a Dirac system. The types of nonlinear evolution equations discussed involve the integrable variable-coefficient Dirac equation and the defocusing nonlinear Schrodinger equation. As an application, their explicit solutions and Lax pairs are given.展开更多
The current research focuses the light on the characterization of buoyancy-driven non-linear mixed convection and non-linear radiation in a Newtonian flow over a nonlinearly stretching vertical sheet,and this type of ...The current research focuses the light on the characterization of buoyancy-driven non-linear mixed convection and non-linear radiation in a Newtonian flow over a nonlinearly stretching vertical sheet,and this type of flow has useful applications in many industrial processes,such as the paper and pulp industry,polymer industry,electronic device cooling,solar collectors,gas turbine plants,and nuclear power.Using appropriate transformations,governing PDEs for non-linear mixed convection are reduced to higher-order non-linear ODEs and those are numerically solved.Along with tabular presentations of computed results,the graphical representations are generated to elucidate the effects of involved parameters on convection transport properties and their inter-relations.It demonstrates that flow velocity increases near the surface and decreases away from the surface as the non-linear convection parameter increases.Furthermore,increments in the thermal buoyancy,temperature ratio and non-linear radiation parameters result in the boost of velocity.The temperature decreases as linear and non-linear buoyancy-related parameters(non-linear convection and thermal buoyancy parameters)are of higher levels.In contrast,the temperature rises with two non-linear thermal radiation-related parameters(thermal ratio and non-linear radiation parameters).For greater values of the non-linear stretching related parameter,a lower velocity and a higher temperature are witnessed.The non-linear convection,thermal buoyancy,thermal ratio and non-linear radiation parameters contribute toward the reduction of the magnitude of surface-drag force and growth of the surface cooling rate.But,with the non-linearity in surface stretching there are significant percentage hikes of surface-drag force magnitude and surface cooling rate.展开更多
基金supported via funding from Prince Sattam bin Abdulaziz University project number(PSAU/2024/R/1445).
文摘This paper investigates the physical properties and predicted radii of compact stars generated by the Tolman-IV complexity-free model within the background of modified gravity theory,particularly the f(R,T)-gravity theory,under complexity formalism for a spherically symmetric spacetime proposed by L.Herrera[Phys Rev D 97:044010,2018].By solving the resulting set of differential equations,we obtain the explicit forms of the energy-momentum(EM)tensor components,including the density,radial pressure,and tangential pressure.The influence of the parameterχon various physical properties of the star is thoroughly investigated.The model undergoes a series of rigorous tests to determine its physical relevance.The findings indicate that the model exhibits regularity,stability,and a surface with vanishing pressure.The boundary of this surface is determined by carefully selecting the parameter space.The complexity method employed in f(R,T)gravity offers an interesting approach for developing astrophysical models that are consistent with observable events as demonstrated by recent experiments.In this regard,we use observational data from the GW190814 event,detected by the LIGO and Virgo observatories,to investigate the validity of the Tolman-IV model in f(R,T)gravity.The analysis includes comparing the model's predictions with the observed characteristics of the compact object involved in the merger.In addition,data from two-millisecond pulsars,PSR J1614-2230 and PSR J0952-0607,are incorporated to further constrain the theoretical theories.However,we present a diagram depicting the relationship between the total mass and radius of the compact object candidates for different values ofχ.
基金Project supported by the Science and Technology Foundation of Henan Province (082300440140, 092102210263) and the Natural Science Foundation of Department of Education, lien,an Province (2009B430003)
文摘A new medium-temperature (200-400 °C) adsorbent material for oxygen removal and air separation, YBaCo4O7+δ, was prepared by the solid-state reaction method. This new adsorbent could adsorb a large quantity of oxygen in the temperature range of 200-370 °C. Adsorbed oxygen could be released by raising temperature over 400 °C or by switching the atmosphere from oxygen to nitrogen. This oxygen adsorption and desorption process had good reproducibility. Taking advantage of this unique oxygen intake/release behavior, a nitrogen purification process was investigated. The results showed that YBaCo4O7+δ material was a promising candidate for the oxygen sorption process and could be used to produce high-purity nitrogen or to remove trace oxygen from other gases.
基金supported by grants 4590/1434 by Deanship of Scientific Resea rch at Taibah University in Saudi Arabia for financial assistance
文摘A new europium(Ⅲ)complex containing(4-Methyl-2-oxo-2 H-chromen-7-yloxy)-acetic acid moiety(CMMC)was synthesized,characterized,and confirmed as antitumor agent and fluorescent probe.The spectroscopic measurements of Eu(Ⅲ)in the presence of CMMC were obtained in different solvents.The results show that the strongest Eu(Ⅲ)emission bands were monitored in iso-propyl alcohol while the weakest Eu(Ⅲ)emission band was observed in acetonitrile.The interaction of Eu(Ⅲ)-(CMMC)2 complex with DNA was monitored using absorption and emission techniques.From fluorescence titration measurements,the binding constants of DNA with Eu(Ⅲ)-(CMMC)_2 complex were found to be 1.04×10~5 L·mol^(-1) in Tris-HCl and 1.17×10~7 L·mol^(-1) in DMSO-Tris-HCl buffer(9∶1 V/V).Hypochromism was observed from the absorption titration experiment which indicates the intercalation of Eu(Ⅲ)-complex between the base pair of DNA.This result further confirmed by fluorescent Ethidium bromide displacement assay.The fluorescence calibration curve was used for the determination of DNA with LOD of 1.2 ng in DMSO-Tris-HCl buffer(9∶1 V/V)and 5 ng in Tris-HCl buffer.The preliminary antitumor investigation shows promising cytotoxicity against MDA-MB-231,MCF-7(mammary cancer),and PC-3(prostate carcinoma)cell lines with IC50 values of 40.63,25.42 and 30.25μmol·L^(-1),respectively.
基金supported by the Foundation for University Key Teacher of Henan Province, China (2008136)Doctoral Fund of Henan Institute of Engineering(D2007011), China
文摘Bi- and Cu-substituted Ca3Co4O9 samples were prepared by conventional solid-state reaction method and the effect of element substitution on the microstructures and thermoelectric properties was investigated. Partial substitution of Cu for Co leads to an increase in electrical conductivity and a decrease in Seebeck coefficient due to the rise of hole concentration. The microstructure of Cu-substituted sample is almost unchanged compared with undoped Ca3Co4O9. On the other hand, partial substitution of Bi for Ca gives rise to a significant increase in the grain size, and c-axis-oriented structure can be formed in Ca2.7Bi0.3Co4O9, resulting in an obvious increase in electrical conductivity. Cu and Bi co-substitution further increases the grain growth and the electrical conductivity of Ca2.7Bi0.3Co3.7Cu0.3O9. Thus, Cu and Bi co-substitution samples possess the optimal thermoelectric performance at high temperature and the highest value of power factor can reach 3.1×10^-4 Wm^-1.K^-2 at 1000 K.
文摘We consider a SIR epidemic model with saturated incidence rate and treatment. We show that if the basic reproduction number, R0 is less than unity and the disease free equilibrium is locally asymptotically stable. Moreover, we show that if R0 > 1, the endemic equilibrium is locally asymptotically stable. In the end, we give some numerical results to compare our model with existing model and to show the effect of the treatment term on the model.
文摘In this paper,the author introduces new Triebel-Lizorkin spaces and Besov spaces associated with different homogeneities and proves that the composition of two Calderón-Zygmund singular integral operators with different homogeneities is bounded on these new Triebel-Lizorkin spaces and Besov spaces.
基金S Chaudhary expresses his gratitude to the Central University of Haryana for providing a University Research Fellowship (URF) under the Reg. No. 222019the Department of Mathematics, Central University of Haryanathe University Grant Commission (UGC), New Delhi, India under the NTA Ref. No. 211610000030 for providing financial support
文摘In this work,we have explored wormhole(WH)solutions in F(R,L_(m))gravity by assuming the Morris-Thorne WH metric and F(R,Lm)=R/2+(1+γR)L_(m),whereγis the free model parameter.We determined the WH solutions by utilizing two newly developed shape functions(SF)that satisfy all basic conditions for a WH’s physical validity.We also observe that the null energy condition(NEC)behaves negatively.Finally,for both models,we use the volume integral quantifier(VIQ)and Tolman-Oppenheimer-Volkoff(TOV)equation to determine how much exotic matter is needed near the WH throat and the stability of the WH.The extensive detailed discussions of the matter components have been done via graphical analysis.The obtained WH geometries meet the physically acceptable conditions for a stable wormhole.
基金supported by Science and Technology Foundation of Henan Province,China (092102210263)Natural Science Foundation of Department of Education of Henan Province,China (2009B430003)
文摘The oxygen adsorption/desorption properties of YBaCo4O7 at high temperature were investigated by thermogravimetry(TG) method,in which two types of oxygen adsorption were combined.The first type adsorbed oxygen at about 700 °C and released the adsorbed oxygen at 880 °C.After the first type oxygen desorption,even the temperature and oxygen flow were kept the same,a second type oxygen adsorption at about 880 °C occurred and the adsorbed oxygen were released at above 980 °C.The combination of these two types of...
基金Supported by City University of Hong Kong under Grant No 7002366the National Natural Science Foundation of China under Grant No 10871182.
文摘For waves in inhomogeneous media,variable-coefficient evolution equations can arise.It is known that the Manakov model can derive two models for propagation in uniform optical fibers.If the fiber is nonuniform,one would expect that the coefficients in the model are not constants.We present a variable-coefficient Manakov model and derive its Lax pair using the generalized dressing method.As an application of the generalized dressing method,soliton solutions of the variable-coefficient Manakov model are obtained.
文摘The interaction of arbitrarily distributed penny-shaped cracks in three-dimensional solids is analyzed in this paper. Using oblate spheroidal coordinates and displacement functions, an analytic method is devel- oped in which the opening and the sliding displacements on each crack surface are taken as the basic unknown functions. The basic unknown functions can be expanded in series of Legendre polynomials with unknown coefficients. Based on superposition technique, a set of governing equations for the unknown coefficients are formulated from the traction free conditions on each crack surface. The boundary collocation procedure and the average method for crack-surface tractions are used for solving the governing equations. The solution can be obtained for quite closely located cracks. Numerical examples are given for several crack problems. By comparing the present results with other existing results, one can conclude that the present method provides a direct and efficient approach to deal with three-dimensional solids containing multiple cracks.
基金supported by the Program for Innovative Research Team (in Science and Technology) (No. 2009IRTHNIE05) in Henan Institute of Engineeringthe Foundation for University Key Teachers of Henan Province (No. 2008136)+1 种基金the Natural Science Fund of Henan Education Department, China (No. 2010C140001)the Youth Fund of Henan Institute of Engineering (No. Y10021)
文摘Polycrystalline samples of Bi 1.5 Pb 0.5 Sr 2-x La x Co 2 O y （x = 0.1, 0.2, 0.3） with a layered structure were prepared by solid-state reaction method. All samples are p-type semiconductors. The thermoelectric properties, namely, the electric resistivity （ρ）, Seebeck coefficient （S）, and power factor （S 2 /ρ） of the samples are dependent on chemical composition. The values of ρ, S, and S 2 /ρ increase with an increase in temperature for all samples. The substitution of Pb 2＋ for Bi 3＋ and La 3＋ for Sr 2＋ improves the thermoelectric properties of the Bi 2 Sr 2 Co 2 O y system owing to the simultaneous decrease of electric resistivity and increase of Seebeck coefficient. As a result, the optimal thermoelectric property has been obtained in Bi 1.5 Pb 0.5 Sr 1.7 La 0.3 Co 2 O y and the power factor can reach 2.1 × 10-4 W·m-1 K-2 at 998 K.
文摘Based on the LaSalle invariance principle, we propose a simple adaptive-feedback for controlling the unified chaotic system. We show explicitly with numerical proofs that our method can easily achieve the control of chaos in the unified chaotic system using only a single variable feedback. The present controller, to our knowledge, is the simplest control scheme for controlling a unified chaotic system.
文摘A SIQS epidemic model with saturated incidence rate is studied. Two equilibrium points exist for the system, disease-free and endemic equilibrium. The stability of the disease-free equilibrium and endemic equilibrium exists when the basic reproduction number R0, is less or greater than unity respectively. The global stability of the disease-free and endemic equilibrium is proved using Lyapunov functions and Poincare-Bendixson theorem plus Dulac’s criterion respectively.
文摘In this paper, an investigation of unsteady free convective magneto-hydro dynamic (MHD) flow of salty water in the presence of a transverse magnetic field has been carried out. An electrically conducting and incompressible fluid is assumed to flow past a semi-infinite vertical porous plate. A constant magnetic field is applied normally to the vertical plate. The Prandtl numbers for salt water are taken to be 1 at 20<span style="white-space:nowrap;">˚</span>C. The governing equations of the problem contain non-linear partial differential equations that are transformed into ordinary differential equations. An explicit finite difference scheme has been used to solve the transformed ordinary equations generated from this flow problem. The velocity profiles and temperature distribution of the flow field have been discussed and presented graphically.
文摘The laminar analytic solutions of velocities and pressure in the central zone of the inlet region of pipe flow are given under the condition of uniform inflow, based on the Navier-Stokes equations of incompressible viscous flow.
文摘A direct numerical simulation is performed on 256~3 grids for decaying isotropic tur- bulence.The total kinematic energy,Taylor micro-scale,Taylor micro-scale Reynolds number and the velocity derivative skewness are calculated.The snapshots of energy spectra and energy transfer spectra are plotted.These measurements verify the DIA predictions:decaying isotropic turbulence has the energy propagation and occupies the final decay periods.The skewness remains to some level with small variation even in the final decay period.
文摘In this paper, an improved algorithm for the solution of Generalized Burger-Fisher’s Equation is presented. A Maple code is generated for the algorithm and simulated. It was observed that the algorithm gives the solution with less computation. The solution gives a better result when compared with the numerical solutions in the existing literature.
文摘We study the coupled mKdV equation by the dressing method via local Riemann-Hilbert problem. With the help of the Lax pairs, we obtain the matrix Riemann-Hilbert problem with zeros. The explicit solutions for the coupled mKdV equation are derived with the aid of the regularization of the Riemann-Hilbert problem.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10471132 and 10871182, and the Henan Natural Science Foundation for Basic Research under Grant Nos 082300410430 and 092300410202.
文摘By using the generalized version of the dressing method, we consider a Dirac system. The types of nonlinear evolution equations discussed involve the integrable variable-coefficient Dirac equation and the defocusing nonlinear Schrodinger equation. As an application, their explicit solutions and Lax pairs are given.
基金funded by CSIR[09/013(0742)/2018-EMR-I]the research of A.K.Gautam is supported by UGC[1220/(CSIR-UGC NET DEC.2016)].
文摘The current research focuses the light on the characterization of buoyancy-driven non-linear mixed convection and non-linear radiation in a Newtonian flow over a nonlinearly stretching vertical sheet,and this type of flow has useful applications in many industrial processes,such as the paper and pulp industry,polymer industry,electronic device cooling,solar collectors,gas turbine plants,and nuclear power.Using appropriate transformations,governing PDEs for non-linear mixed convection are reduced to higher-order non-linear ODEs and those are numerically solved.Along with tabular presentations of computed results,the graphical representations are generated to elucidate the effects of involved parameters on convection transport properties and their inter-relations.It demonstrates that flow velocity increases near the surface and decreases away from the surface as the non-linear convection parameter increases.Furthermore,increments in the thermal buoyancy,temperature ratio and non-linear radiation parameters result in the boost of velocity.The temperature decreases as linear and non-linear buoyancy-related parameters(non-linear convection and thermal buoyancy parameters)are of higher levels.In contrast,the temperature rises with two non-linear thermal radiation-related parameters(thermal ratio and non-linear radiation parameters).For greater values of the non-linear stretching related parameter,a lower velocity and a higher temperature are witnessed.The non-linear convection,thermal buoyancy,thermal ratio and non-linear radiation parameters contribute toward the reduction of the magnitude of surface-drag force and growth of the surface cooling rate.But,with the non-linearity in surface stretching there are significant percentage hikes of surface-drag force magnitude and surface cooling rate.
