In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution ...In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution is examined from multiple theoretical perspectives to explore the impact of these modifications on the BH's geometric,thermodynamic and dynamical properties.We begin by studying the geometrical optics of the spacetime,focusing on the motion of null geodesics.Key features,such as the effective potential,photon sphere,the force acting on photons and the stability of circular photon orbits,are analyzed in detail.Our results show that the presence of GM and CS significantly affects the spacetime geometry and photon dynamics.In addition,the thermodynamic behavior of the modified BH is also investigated.We derive essential quantities such as the Hawking temperature and entropy,demonstrating how the inclusion of GM and CS leads to deviations from the standard thermodynamic relations observed in classical BH solutions.These deviations may offer valuable insights into quantum gravity and the role of topological defects in BH physics.Furthermore,we examine the BH shadow as an observational signature of the underlying geometry.Our analysis shows that the Frolov parameter tends to reduce the apparent size of the shadow,while the presence of topological defects,particularly GM and CS,enlarges it.In addition,we investigate the perturbative dynamics of the BH by studying both scalar(spin-0),fermionic(spin-1/2)and electromagnetic(spin-1)fields through the massless Klein-Gordon and Maxwell equations,respectively.Using the Wentzel-Kramers-Brillouin approximation,we compute the quasinormal modes(QNMs)for scalar and electromagnetic field perturbations.The results confirm the stability of the BH under small perturbations and show that the QNM frequencies and damping rates are strongly influenced by the Frolov parameter,electric charge,GM and CS.展开更多
In this study,we explore a spherically symmetric charged black hole(BH)with a negative cosmological constant under the influence of a Kalb-Ramond field background.We compute the photon sphere and shadow radii,validati...In this study,we explore a spherically symmetric charged black hole(BH)with a negative cosmological constant under the influence of a Kalb-Ramond field background.We compute the photon sphere and shadow radii,validating our findings using observational data from the Event Horizon Telescope,with a particular emphasis on the shadow images of Sagittarius A^(*).Furthermore,we investigate the greybody factors,emission rate,and partial absorption cross section.It is shown that the Lorentz-violating parameter l has an important effect on the absorption cross section.Our analysis also includes an examination of the topological charge,temperature-dependent topology,and generalized free energy.In particular,we regard the AdS charged BH with an antisymmetric tensor background as a topological defect in the thermodynamic space,then the system has the same topological classification to the charged Reissner-Nordström-AdS BH.展开更多
In this study,a Gaussian Process Regression(GPR)surrogate model coupled with a Bayesian optimization algorithm was employed for the single-objective design optimization of fan-shaped film cooling holes on a concave wa...In this study,a Gaussian Process Regression(GPR)surrogate model coupled with a Bayesian optimization algorithm was employed for the single-objective design optimization of fan-shaped film cooling holes on a concave wall.Fan-shaped holes,commonly used in gas turbines and aerospace applications,flare toward the exit to form a protective cooling film over hot surfaces,enhancing thermal protection compared to cylindrical holes.An initial hole configuration was used to improve adiabatic cooling efficiency.Design variables included the hole injection angle,forward expansion angle,lateral expansion angle,and aperture ratio,while the objective function was the average adiabatic cooling efficiency of the concave wall surface.Optimization was performed at two representative blowing ratios,M=1.0 and M=1.5,using the GPR-based surrogate model to accelerate exploration,with the Bayesian algorithm identifying optimal configurations.Results indicate that the optimized fan-shaped holes increased cooling efficiency by 15.2%and 12.3%at low and high blowing ratios,respectively.Analysis of flow and thermal fields further revealed how the optimized geometry influenced coolant distribution and heat transfer,providing insight into the mechanisms driving the improved cooling performance.展开更多
This paper investigates the mechanical behavior of two-dimensional(2D)piezoelectric quasicrystals(PQCs)containing polygonal holes under external forces.Based on the linear elastic theory of quasicrystals(QCs),the anal...This paper investigates the mechanical behavior of two-dimensional(2D)piezoelectric quasicrystals(PQCs)containing polygonal holes under external forces.Based on the linear elastic theory of quasicrystals(QCs),the analytical solutions for the stress and displacement fields are derived with the Stroh formalism,Green's function method,and polygonal mapping functions.Numerical simulations are performed to study the effects of hole geometry and corner sharpness on the stress distribution.The results show that the polygonal hole shapes significantly influence the generalized hoop stress,with sharper corners leading to stronger stress concentration and enhanced piezoelectric coupling effects.The stress concentrations at hole corners reach their maximum values at specific sharpness parameters,depending on the polygon type.The results contribute to a deeper understanding of the defect-induced mechanical behavior in 2D PQCs,and provide theoretical guidance for their structural design and optimization.展开更多
Molecular tailoring of self-assembled hole-transporting monolayers(SAMs)has been proven as an efficient approach for improving the device performance of inverted perovskite solar cells.Herein,a novel SAM with extended...Molecular tailoring of self-assembled hole-transporting monolayers(SAMs)has been proven as an efficient approach for improving the device performance of inverted perovskite solar cells.Herein,a novel SAM with extended conjugation is designed and synthesized,named NaPh-4PACz.Compared to Ph-4PACz,NaPh-4PACz exhibits a larger adsorption energy with the ITO substrate,enabling the formation of a more uniform and dense film,thereby preventing direct contact between the perovskite and ITO.Additionally,NaPh-4PACz also has a stronger interaction with the perovskite,which can reduce buried interface defects and suppress non-radiative recombination.Consequently,NaPh-4PACz-based devices achieved a power conversion efficiency of 25.48%due to their interfacial“adhesive”ability.Importantly,the stability of the NaPh-4PACz-based devices was significantly improved.展开更多
Based on the idea of treating the anti de Sitter(AdS)radius as a fixed parameter,we study the thermodynamics and topology of d-dimensional charged AdS black holes in the restricted phase space utilizing Visser's h...Based on the idea of treating the anti de Sitter(AdS)radius as a fixed parameter,we study the thermodynamics and topology of d-dimensional charged AdS black holes in the restricted phase space utilizing Visser's holographic approach.For the charged black hole with a cloud of strings and quintessence in the higher-dimensional spacetimes with d=(4,5,6),we demonstrate that the topological number remains invariant within the same canonical ensemble;however,a distinct topological number emerges in the grand canonical ensemble for the same black hole system.Notably,these results are independent of the dimension d and other related parameters.The formalism known as restricted phase space thermodynamics is checked in detail and some interesting thermodynamic behavior is revealed in the example case of d-dimensional charged AdS black holes with a cloud of strings and quintessence.This research lays the foundation for establishing a universal framework of restricted phase space thermodynamics and investigating its fundamental thermodynamic properties.展开更多
Large-diameter drilling method is a prevalent method for preventing and controlling rock burst,and the spacing between the large-diameter drilling hole and anchoring hole is a critical factor influencing the roadway s...Large-diameter drilling method is a prevalent method for preventing and controlling rock burst,and the spacing between the large-diameter drilling hole and anchoring hole is a critical factor influencing the roadway stability and relief effectiveness.In this study,a mechanical model for optimal matching between the large-diameter drilling hole and anchoring hole was established following the principle of synergistic control.The influence of large-diameter drilling hole diameter on the optimal spacing under the synergistic relief effect was investigated by integrating theoretical analysis,numerical simulation,and field practice.The results suggest that the hole spacing achieved a synergistic effect in a certain range when the optimal hole spacing increased linearly with the hole diameter.For instance,when the anchoring hole diameter was 20 mm,an increase in the aperture ratio from 5 to 10 brought about an increase in the optimal spacing from 0.25 m to 0.45 m.Additionally,the vertical stress between the large-diameter drilling hole and anchor hole increased nonlinearly under the condition of constant pore ratio but varying hole spacing.Both excessively small and excessively large hole spacings were detrimental to the pressure relief effect.In the engineering practice,optimizing the hole spacing from 0.55 m to 0.45 m in the 1208 working face contributed to reducing coal body drilling cuttings and the roadway moving quantity by 33%and 19.2%,respectively.This demonstrates that the pressure relief-support reinforcement synergistic effect should be fully considered in optimization design.展开更多
Elemental doping of BiVO_(4) crystal lattices effectively enhances carrier separation,thereby facilitating efficient photoelectrochemical water splitting.However,the positive effect of elementally induced lattice dist...Elemental doping of BiVO_(4) crystal lattices effectively enhances carrier separation,thereby facilitating efficient photoelectrochemical water splitting.However,the positive effect of elementally induced lattice distortions on hole extraction has been neglected.Herein,the crystal lattice of BiVO_(4) is distorted by doping with an inexpensive Cs metal;then,CoFe_(2)O_(4) is used as an efficient hole-extraction layer to further modify the surface of the doped photoanode.Benefiting from the above design,the newly prepared CoFe_(2)O_(4)-Cs-BiVO_(4) photoanode achieved a photocurrent density of 5.66 mA cm^(–2) at 1.23 V vs.a reversible hydrogen electrode,indicating a 3.9-fold improvement in photocurrent density.Detailed physicochemical characterization and density functional theory calculations showed that the lattice distortion induced by Cs doping promoted the directional migration of BiVO_(4) bulk-phase holes to the CoFe_(2)O_(4) layer.Additionally,the coupled CoFe_(2)O_(4) can be used as a hole extraction layer to further enhance the interfacial migration of carriers.The synergistic effect of the two effectively promotes the directional migration of photogenerated carriers from the BiVO_(4) bulk phase to the active sites of the oxygen evolution reaction,thereby effectively inhibiting carrier recombination.This study revealed the positive effect of the dual-hole extraction strategy on solar energy conversion,thereby opening new avenues for the rational design of photoanodes.展开更多
Primordial black holes(PBHs) offer a compelling candidate for dark matter. The production of PBHs through well-tested and accepted physical processes is highly worthy of investigation. This work highlights the role of...Primordial black holes(PBHs) offer a compelling candidate for dark matter. The production of PBHs through well-tested and accepted physical processes is highly worthy of investigation. This work highlights the role of turbulences in the very early universe in sustaining intense and persistent fluctuations in energy or mass density,which could provide a natural mechanism for PBH formation in the primordial universe. We analyze the mass range and abundance of PBHs produced in the magnetohydrodynamic turbulence induced by the electroweak phase transition. Remarkably, we find that the mass range of the produced PBHs falls within the most viable“asteroid mass” window from the present-day observations, and within natural parameter regions their abundance can be sufficiently large. These findings suggest that PBHs produced during magnetohydrodynamic turbulence in the very early universe may comprise a dominant part of dark matter.展开更多
We assume exponential corrections to the entropy of 5D charged Ad S black hole solutions,which are derived within the framework of Einstein-Gauss-Bonnet gravity and nonlinear electrodynamics.Additionally,we consider t...We assume exponential corrections to the entropy of 5D charged Ad S black hole solutions,which are derived within the framework of Einstein-Gauss-Bonnet gravity and nonlinear electrodynamics.Additionally,we consider two distinct versions of 5D charged Ad S black holes by setting the parameters q→0 and k→0(where q represents the charge,and k is the non-linear parameter).We investigate these black holes in the extended phase space,where the cosmological constant is interpreted as pressure,demonstrating the first law of black hole thermodynamics.The focus extends to understanding the thermal stability or instability,as well as identifying first and second-order phase transitions.This exploration is carried out through the analysis of various thermodynamic quantities,including heat capacity at constant pressure,Gibbs free energy(GFE),Helmholtz free energy(HFE),and the trace of the Hessian matrix.In order to visualize phase transitions,identify critical points,analyze stability and provide comprehensive analysis,we have made the contour plot of the mentioned thermodynamic quantities and observed that our results are very consistent.These investigations are conducted within the context of exponentially corrected entropies,providing valuable insights into the intricate thermodynamic behavior of these 5D charged Ad S black holes under different parameter limits.展开更多
The comprehension of universal thermodynamic behaviors in the supercritical region is crucial for examining the characteristics of black hole systems under high temperature and pressure.This study is devoted to the an...The comprehension of universal thermodynamic behaviors in the supercritical region is crucial for examining the characteristics of black hole systems under high temperature and pressure.This study is devoted to the analysis of characteristic lines and crossover behaviors within the supercritical region.By making use of the free energy,we introduce three key thermodynamic quantities:scaled variance,skewness,and kurtosis.Our results demonstrate that the Widom line,associated with the maximal scaled variance,can effectively differentiate between small and large black hole-like subphases,each displaying distinct thermodynamic behaviors within the supercritical region.Furthermore,by utilizing quasinormal modes,we identify the Frenkel line,offering a dynamic perspective to distinguish between small and large black hole-like subphases.These contribute to a deeper comprehension of black hole subphases in the supercritical region,thus illuminating new facets of black hole thermodynamics.展开更多
The gravitational memory effect manifests gravitational nonlinearity,degenerate vacua,and asymptotic symmetries;its detection is considered challenging.We propose using a space-borne interferometer to detect memory si...The gravitational memory effect manifests gravitational nonlinearity,degenerate vacua,and asymptotic symmetries;its detection is considered challenging.We propose using a space-borne interferometer to detect memory signals from stellar-mass binary black holes(BBHs),typically targeted by ground-based detectors.We use DECIGO detector as an example.Over 5 years,DECIGO is estimated to detect approximately 2,036 memory signals(SNRs>3)from stellar-mass BBHs.Simulations used frequency-domain memory waveforms for direct SNR estimation.Predictions utilized a GWTC-3 constrained BBH population model(Power law+Peak mass,DEFAULT spin,Madau-Dickinson merger rate).The analysis used conservative lower merger rate limits and considered orbital eccentricity.The high detection rate stems from strong memory signals within DECIGO’s bandwidth and the abundance of stellar-mass BBHs.This substantial and conservative detection count enables statistical use of the memory effect for fundamental physics and astrophysics.DECIGO exemplifies that space interferometers may better detect memory signals from smaller mass binaries than their typical targets.Detectors in lower frequency bands are expected to find strong memory signals from∼10^(4)M⊙binaries.展开更多
The shape of underground chambers in deep mining varies due to their geological environment and intended use,which results in different failure modes under the influence of mining activities.However,the effect of cham...The shape of underground chambers in deep mining varies due to their geological environment and intended use,which results in different failure modes under the influence of mining activities.However,the effect of chamber shape on the mechanism of structural integrity under dynamic load is still unclear.In this paper,granite samples with circular(C),rectangular(R),long ellipse(EL),and short ellipse(ES)holes were prepared.The dynamic mechanical response and cracking mechanism of granite were systematically analyzed using the split Hopkinson pressure bar(SHPB)test system and the hybrid finite and discrete element method(HFDEM).The results indicate that the dynamic strengths of granite with EL and ES represent the maximum and minimum values within the range of close strain rates,respectively.When EL granite is subjected to dynamic load,the axial stress concentration(in the load direction)is weak,and the transverse stress shows relative dispersion,which is the primary reason for its highest dynamic strength.The failure of granite with various holes primarily involves a tensile-shear mixed fracture,with relatively few pure typeⅡcracks.The chamber’s transverse span is the primary factor influencing the distribution range of the fracture area.展开更多
The photon region surrounding a black hole is crucial for distant observers to receive the emitted spectrum from its vicinity.This paper investigates the optical features of a regular spinning antide Sitter(AdS)black ...The photon region surrounding a black hole is crucial for distant observers to receive the emitted spectrum from its vicinity.This paper investigates the optical features of a regular spinning antide Sitter(AdS)black hole.These kinds of black holes hold deviation parameter k,and the cosmological constant A including their mass M and spin a.The cosmological parameter depends on the curvature radius by A=-3/l~2.We investigate the structure of geodesics for unstable circular orbits of photons as observed by an observer at specific Boyer-Lindquist coordinates(r_(O),v_(O))in the region between the outer and cosmological horizon,so-called the domain of outer communication.Our investigations include the analysis of three observables from its shadow plot:the black hole shadow radius(R_(s)),the distortion of the black hole(δ_(s)),and shadow area A.With the help of these observables,we calculate the angular diameter of the apparent size of the shadow.The shadows cast by spinning regular spacetimes are smaller compared to those produced by rotating black holes in both general relativity and regular spacetimes.We also calculate the rate at which energy is emitted from the black hole.展开更多
Increasing the hole expansion ratio is significant for developing high formability parts.Hole expansion tests were carried out on low carbon hot-rolled steel containing 0.11%Ti,0.072%Ti–0.03%Nb and 0.097%Ti–0.059%Nb...Increasing the hole expansion ratio is significant for developing high formability parts.Hole expansion tests were carried out on low carbon hot-rolled steel containing 0.11%Ti,0.072%Ti–0.03%Nb and 0.097%Ti–0.059%Nb,respectively.The effects of microstructure,texture,crack propagation behavior and second phase precipitation behavior on hole expansion ratio were investigated.The precipitation behavior of TiC and(Ti,Nb)C in austenite and ferrite in three groups of steel samples was calculated theoretically.The results showed that the hole expansion ratios of 0.11Ti,0.072Ti–0.03Nb and 0.097Ti–0.059Nb test steels were 51.73%,51.17%and 66.24%following simulated coiling at 600℃,respectively.The microstructure was mainly polygonal ferrite with a small amount of pearlite.The grain refinement of 0.097Ti–0.059Nb test steel and the low texture ratio of{110}//ND improved the hole expansion ratio.The low overall hole expansion ratio was due to the microstructure inhomogeneity.The microstructure uniformity was improved by the quenching and tempering treatment,and the hole expansion ratio of the three test steels was greatly increased.The fastest precipitation temperatures in the austenitic region of 0.11Ti,0.072Ti–0.03Nb and 0.097Ti–0.059Nb test steels were 880,860 and 830℃,while those in the ferrite region were 680,675 and 675℃,respectively.The addition of Nb element increased the volume free energy,so that the critical core size of the nucleation on the dislocation line increased,resulting in the decrease in the fastest precipitation temperature.展开更多
In this work,the influences of surface layer slurry at different temperatures(10℃,14℃,18℃,22℃)on wax patterns deformation,shrinkage,slurry coating characteristics,and the surface quality of the casting were invest...In this work,the influences of surface layer slurry at different temperatures(10℃,14℃,18℃,22℃)on wax patterns deformation,shrinkage,slurry coating characteristics,and the surface quality of the casting were investigated by using a single factor variable method.The surface morphologies of the shell molds produced by different temperatures of the surface(first)layer slurries were observed via electron microscopy.Furthermore,the microscopic composition of these shell molds was obtained by EDS,and the osmotic effect of the slurry on the wax patterns at different temperatures was also assessed by the PZ-200 Contact Angle detector.The forming reasons for the surface cracks and holes of thick and large ZTC4 titanium alloy by investment casting were analyzed.The experimental results show that the surface of the shell molds prepared by the surface layer slurry with a low temperature exhibits noticeable damage,which is mainly due to the poor coating performance and the serious expansion and contraction of wax pattern at low temperatures.The second layer shell material(SiO_(2),Al_(2)O_(3))immerses into the crack area of the surface layer,contacts and reacts with the molten titanium to form surface cracks and holes in the castings.With the increase of the temperature of surface layer slurry,the damage to the shell surface tends to weaken,and the composition of the shell molds'surface becomes more uniform with less impurities.The results show that the surface layer slurry at 22℃is evenly coated on the surface of the wax patterns with appropriate thickness,and there is no surface shell mold rupture caused by sliding slurry after sand leaching.The surface layer slurry temperature is consistent with the wax pattern temperature and the workshop temperature,so there is no damage of the surface layer shell caused by expansion and contraction.Therefore,the shell mold prepared by the surface layer slurry at this temperature has good integrity,isolating the contact between the low inert shell material and the titanium liquid effectively,and the ZTC4 titanium alloy cylinder casting prepared by this shell mold is smooth,without cracks and holes.展开更多
The hole transport layer(HTL)-free carbon-based perovskite solar cells(C-PSCs)are promising for commercialization owing to their excellent operational stability and simple fabrication process.However,the power convers...The hole transport layer(HTL)-free carbon-based perovskite solar cells(C-PSCs)are promising for commercialization owing to their excellent operational stability and simple fabrication process.However,the power conversion efficiencies(PCE)of C-PSCs are inferior to the metal electrode-based devices due to their open-circuit voltage(V_(oc))loss.Herein,time-resolved confocal photoluminescence microscopy reveals that grain boundary defects at the perovskite/carbon interface are very likely to function as nonradiative recombination centers in HTL-free C-PSCs.A versatile additive Li_(2)CO_(3)is used to modify the conformal tin oxide electron transport layer for HTL-free C-PSCs.Li_(2)CO_(3)modification can result in enhanced charge extraction and optimized energy alignment at electron transport layer/perovskite interface,as well as suppressed defects at perovskite top surface due to Li_(2)CO_(3)-induced formation of PbI_(2)crystallites.Such dual interfacial passivation ultimately leads to significantly improved Voc up to 1.142 V,which is comparable to the metal electrode-based devices with HTL.Moreover,a record-high PCE of 33.2%is achieved for Li_(2)CO_(3)-modified C-PSCs under weak light illumination conditions,demonstrating excellent indoor photovoltaic performance.This work provides a practical approach to fabricate low-cost,highly efficient carbon-based perovskite solar cells.展开更多
The surface transfer doping model has been extensively adopted as a mechanism to account for the generation of hole accumulation layers below hydrogen-terminated diamond(H-diamond)surfaces.To achieve effective surface...The surface transfer doping model has been extensively adopted as a mechanism to account for the generation of hole accumulation layers below hydrogen-terminated diamond(H-diamond)surfaces.To achieve effective surface transfer doping,surface electron acceptor materials with high electron affinity(EA)are required to produce a high density of two-dimensional hole gas(2DHG)on the H-diamond subsurface.We have established ingenious theoretical models to demonstrate that even if these solid materials do not have a high EA value,they remain capable of absorbing electrons from the H-diamond surface by forming a negatively charged interface to act as a surface electron acceptor in the surface transfer doping model.Our calculations,particularly for the local density of states,provide compelling evidence that the effect of an interface with negative charges induces an upward band bending on the H-diamond side.Furthermore,the valence band maximum of the diamond atoms at the interface crosses the Fermi level,giving rise to strong surface transfer p-type doping.These results give a strong theoretical interpretation of the origin of 2DHG on H-diamond surfaces.The proposed guidelines contribute to further improvements in the performance of 2DHG H-diamond field effect transistors.展开更多
基金financial support from EMU, TÜBİTAK, ANKOS and SCOAP3
文摘In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution is examined from multiple theoretical perspectives to explore the impact of these modifications on the BH's geometric,thermodynamic and dynamical properties.We begin by studying the geometrical optics of the spacetime,focusing on the motion of null geodesics.Key features,such as the effective potential,photon sphere,the force acting on photons and the stability of circular photon orbits,are analyzed in detail.Our results show that the presence of GM and CS significantly affects the spacetime geometry and photon dynamics.In addition,the thermodynamic behavior of the modified BH is also investigated.We derive essential quantities such as the Hawking temperature and entropy,demonstrating how the inclusion of GM and CS leads to deviations from the standard thermodynamic relations observed in classical BH solutions.These deviations may offer valuable insights into quantum gravity and the role of topological defects in BH physics.Furthermore,we examine the BH shadow as an observational signature of the underlying geometry.Our analysis shows that the Frolov parameter tends to reduce the apparent size of the shadow,while the presence of topological defects,particularly GM and CS,enlarges it.In addition,we investigate the perturbative dynamics of the BH by studying both scalar(spin-0),fermionic(spin-1/2)and electromagnetic(spin-1)fields through the massless Klein-Gordon and Maxwell equations,respectively.Using the Wentzel-Kramers-Brillouin approximation,we compute the quasinormal modes(QNMs)for scalar and electromagnetic field perturbations.The results confirm the stability of the BH under small perturbations and show that the QNM frequencies and damping rates are strongly influenced by the Frolov parameter,electric charge,GM and CS.
基金supported by the Doctoral Foundation of Zunyi Normal University of China (BS [2022] 07)Fundação de Apoio à Pesquisa do Estado da Paraíba (FAPESQ)+5 种基金Conselho Nacional de Desenvolvimento Cientíıfico e Tecnológico (CNPq)-[150891/2023-7] for the financial supportsupported by the Q-CAYLE project, funded by the European Union-Next Generation UE/MICIU/Plan de Recuperacion, Transformacion y Resiliencia/Junta de Castilla y Leon (PRTRC17.11)by project PID2023-148409NB-I00, funded by MICIU/AEI/10.13039/501100011033Financial support of the Department of Education of the Junta de Castilla y LeonFEDER FundsExcellence project Fo S UHK 2203/2025-2026 for the financial support
文摘In this study,we explore a spherically symmetric charged black hole(BH)with a negative cosmological constant under the influence of a Kalb-Ramond field background.We compute the photon sphere and shadow radii,validating our findings using observational data from the Event Horizon Telescope,with a particular emphasis on the shadow images of Sagittarius A^(*).Furthermore,we investigate the greybody factors,emission rate,and partial absorption cross section.It is shown that the Lorentz-violating parameter l has an important effect on the absorption cross section.Our analysis also includes an examination of the topological charge,temperature-dependent topology,and generalized free energy.In particular,we regard the AdS charged BH with an antisymmetric tensor background as a topological defect in the thermodynamic space,then the system has the same topological classification to the charged Reissner-Nordström-AdS BH.
基金supported by the Jiangsu Association for Science and Technology,grant number SKX 0225089the National Natural Science Foundation of China,grant number 52476027.
文摘In this study,a Gaussian Process Regression(GPR)surrogate model coupled with a Bayesian optimization algorithm was employed for the single-objective design optimization of fan-shaped film cooling holes on a concave wall.Fan-shaped holes,commonly used in gas turbines and aerospace applications,flare toward the exit to form a protective cooling film over hot surfaces,enhancing thermal protection compared to cylindrical holes.An initial hole configuration was used to improve adiabatic cooling efficiency.Design variables included the hole injection angle,forward expansion angle,lateral expansion angle,and aperture ratio,while the objective function was the average adiabatic cooling efficiency of the concave wall surface.Optimization was performed at two representative blowing ratios,M=1.0 and M=1.5,using the GPR-based surrogate model to accelerate exploration,with the Bayesian algorithm identifying optimal configurations.Results indicate that the optimized fan-shaped holes increased cooling efficiency by 15.2%and 12.3%at low and high blowing ratios,respectively.Analysis of flow and thermal fields further revealed how the optimized geometry influenced coolant distribution and heat transfer,providing insight into the mechanisms driving the improved cooling performance.
基金Project supported by the National Natural Science Foundation of China(Nos.12272402 and12102458)the Chinese Universities Scientific Fund(No.2025TC014)the China Agricultural University Education Foundation(No.1101-240001)。
文摘This paper investigates the mechanical behavior of two-dimensional(2D)piezoelectric quasicrystals(PQCs)containing polygonal holes under external forces.Based on the linear elastic theory of quasicrystals(QCs),the analytical solutions for the stress and displacement fields are derived with the Stroh formalism,Green's function method,and polygonal mapping functions.Numerical simulations are performed to study the effects of hole geometry and corner sharpness on the stress distribution.The results show that the polygonal hole shapes significantly influence the generalized hoop stress,with sharper corners leading to stronger stress concentration and enhanced piezoelectric coupling effects.The stress concentrations at hole corners reach their maximum values at specific sharpness parameters,depending on the polygon type.The results contribute to a deeper understanding of the defect-induced mechanical behavior in 2D PQCs,and provide theoretical guidance for their structural design and optimization.
基金supported by the National Natural Science Foundation of China(61904053,22279033)the National Key Research and Development Program of China(2023YFB4204502)+2 种基金the 111 Project(B16016)the Fundamental Research Funds for the Central Universities(2025MS043)the Special Foundation for Carbon Peak Carbon Neutralization Technology Innovation Program of Jiangsu Province(BE2022026).
文摘Molecular tailoring of self-assembled hole-transporting monolayers(SAMs)has been proven as an efficient approach for improving the device performance of inverted perovskite solar cells.Herein,a novel SAM with extended conjugation is designed and synthesized,named NaPh-4PACz.Compared to Ph-4PACz,NaPh-4PACz exhibits a larger adsorption energy with the ITO substrate,enabling the formation of a more uniform and dense film,thereby preventing direct contact between the perovskite and ITO.Additionally,NaPh-4PACz also has a stronger interaction with the perovskite,which can reduce buried interface defects and suppress non-radiative recombination.Consequently,NaPh-4PACz-based devices achieved a power conversion efficiency of 25.48%due to their interfacial“adhesive”ability.Importantly,the stability of the NaPh-4PACz-based devices was significantly improved.
基金supported by the Natural Science Foundation of Shanxi Province(202303021211180)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(KF202403)。
文摘Based on the idea of treating the anti de Sitter(AdS)radius as a fixed parameter,we study the thermodynamics and topology of d-dimensional charged AdS black holes in the restricted phase space utilizing Visser's holographic approach.For the charged black hole with a cloud of strings and quintessence in the higher-dimensional spacetimes with d=(4,5,6),we demonstrate that the topological number remains invariant within the same canonical ensemble;however,a distinct topological number emerges in the grand canonical ensemble for the same black hole system.Notably,these results are independent of the dimension d and other related parameters.The formalism known as restricted phase space thermodynamics is checked in detail and some interesting thermodynamic behavior is revealed in the example case of d-dimensional charged AdS black holes with a cloud of strings and quintessence.This research lays the foundation for establishing a universal framework of restricted phase space thermodynamics and investigating its fundamental thermodynamic properties.
基金Project(52274086)supported by the National Natural Science Foundation of ChinaProject(2024KJH069)supported by the Shandong Provincial Youth Innovation and Technology Support Program,ChinaProject(tstp20221126)supported by the Project of Taishan Scholar in Shandong Province,China。
文摘Large-diameter drilling method is a prevalent method for preventing and controlling rock burst,and the spacing between the large-diameter drilling hole and anchoring hole is a critical factor influencing the roadway stability and relief effectiveness.In this study,a mechanical model for optimal matching between the large-diameter drilling hole and anchoring hole was established following the principle of synergistic control.The influence of large-diameter drilling hole diameter on the optimal spacing under the synergistic relief effect was investigated by integrating theoretical analysis,numerical simulation,and field practice.The results suggest that the hole spacing achieved a synergistic effect in a certain range when the optimal hole spacing increased linearly with the hole diameter.For instance,when the anchoring hole diameter was 20 mm,an increase in the aperture ratio from 5 to 10 brought about an increase in the optimal spacing from 0.25 m to 0.45 m.Additionally,the vertical stress between the large-diameter drilling hole and anchor hole increased nonlinearly under the condition of constant pore ratio but varying hole spacing.Both excessively small and excessively large hole spacings were detrimental to the pressure relief effect.In the engineering practice,optimizing the hole spacing from 0.55 m to 0.45 m in the 1208 working face contributed to reducing coal body drilling cuttings and the roadway moving quantity by 33%and 19.2%,respectively.This demonstrates that the pressure relief-support reinforcement synergistic effect should be fully considered in optimization design.
文摘Elemental doping of BiVO_(4) crystal lattices effectively enhances carrier separation,thereby facilitating efficient photoelectrochemical water splitting.However,the positive effect of elementally induced lattice distortions on hole extraction has been neglected.Herein,the crystal lattice of BiVO_(4) is distorted by doping with an inexpensive Cs metal;then,CoFe_(2)O_(4) is used as an efficient hole-extraction layer to further modify the surface of the doped photoanode.Benefiting from the above design,the newly prepared CoFe_(2)O_(4)-Cs-BiVO_(4) photoanode achieved a photocurrent density of 5.66 mA cm^(–2) at 1.23 V vs.a reversible hydrogen electrode,indicating a 3.9-fold improvement in photocurrent density.Detailed physicochemical characterization and density functional theory calculations showed that the lattice distortion induced by Cs doping promoted the directional migration of BiVO_(4) bulk-phase holes to the CoFe_(2)O_(4) layer.Additionally,the coupled CoFe_(2)O_(4) can be used as a hole extraction layer to further enhance the interfacial migration of carriers.The synergistic effect of the two effectively promotes the directional migration of photogenerated carriers from the BiVO_(4) bulk phase to the active sites of the oxygen evolution reaction,thereby effectively inhibiting carrier recombination.This study revealed the positive effect of the dual-hole extraction strategy on solar energy conversion,thereby opening new avenues for the rational design of photoanodes.
基金supported by the International Partnership Program of the Chinese Academy of Sciences (Grant No.025GJHZ2023106GC)。
文摘Primordial black holes(PBHs) offer a compelling candidate for dark matter. The production of PBHs through well-tested and accepted physical processes is highly worthy of investigation. This work highlights the role of turbulences in the very early universe in sustaining intense and persistent fluctuations in energy or mass density,which could provide a natural mechanism for PBH formation in the primordial universe. We analyze the mass range and abundance of PBHs produced in the magnetohydrodynamic turbulence induced by the electroweak phase transition. Remarkably, we find that the mass range of the produced PBHs falls within the most viable“asteroid mass” window from the present-day observations, and within natural parameter regions their abundance can be sufficiently large. These findings suggest that PBHs produced during magnetohydrodynamic turbulence in the very early universe may comprise a dominant part of dark matter.
基金the Deanship of Research and Graduate Studies at King Khalid University for funding this work through Large Research Project under Grant No.RGP2/539/45。
文摘We assume exponential corrections to the entropy of 5D charged Ad S black hole solutions,which are derived within the framework of Einstein-Gauss-Bonnet gravity and nonlinear electrodynamics.Additionally,we consider two distinct versions of 5D charged Ad S black holes by setting the parameters q→0 and k→0(where q represents the charge,and k is the non-linear parameter).We investigate these black holes in the extended phase space,where the cosmological constant is interpreted as pressure,demonstrating the first law of black hole thermodynamics.The focus extends to understanding the thermal stability or instability,as well as identifying first and second-order phase transitions.This exploration is carried out through the analysis of various thermodynamic quantities,including heat capacity at constant pressure,Gibbs free energy(GFE),Helmholtz free energy(HFE),and the trace of the Hessian matrix.In order to visualize phase transitions,identify critical points,analyze stability and provide comprehensive analysis,we have made the contour plot of the mentioned thermodynamic quantities and observed that our results are very consistent.These investigations are conducted within the context of exponentially corrected entropies,providing valuable insights into the intricate thermodynamic behavior of these 5D charged Ad S black holes under different parameter limits.
基金supported by the National Natural Science Foundation of China(Grant Nos.12473001,11975072,11875102,11835009,and 11965013)the National SKA Program of China(Grant Nos.2022SKA0110200 and 2022SKA0110203)+1 种基金the National 111 Project(Grant No.B16009)supported by Yunnan High-level Talent Training Support Plan Young&Elite Talents Project(Grant No.YNWR-QNBJ-2018-181).
文摘The comprehension of universal thermodynamic behaviors in the supercritical region is crucial for examining the characteristics of black hole systems under high temperature and pressure.This study is devoted to the analysis of characteristic lines and crossover behaviors within the supercritical region.By making use of the free energy,we introduce three key thermodynamic quantities:scaled variance,skewness,and kurtosis.Our results demonstrate that the Widom line,associated with the maximal scaled variance,can effectively differentiate between small and large black hole-like subphases,each displaying distinct thermodynamic behaviors within the supercritical region.Furthermore,by utilizing quasinormal modes,we identify the Frenkel line,offering a dynamic perspective to distinguish between small and large black hole-like subphases.These contribute to a deeper comprehension of black hole subphases in the supercritical region,thus illuminating new facets of black hole thermodynamics.
基金supported by the National Natural Science Foundation of China(Grant Nos.11633001,11920101003,and 12205222 for S.H.)the Key Program of the National Natural Science Foundation of China(Grant No.12433001)+1 种基金the Strate-gic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000)the National Key Research and Development Program of China(Grant No.2021YFC2203001 for Z.C.Z.).
文摘The gravitational memory effect manifests gravitational nonlinearity,degenerate vacua,and asymptotic symmetries;its detection is considered challenging.We propose using a space-borne interferometer to detect memory signals from stellar-mass binary black holes(BBHs),typically targeted by ground-based detectors.We use DECIGO detector as an example.Over 5 years,DECIGO is estimated to detect approximately 2,036 memory signals(SNRs>3)from stellar-mass BBHs.Simulations used frequency-domain memory waveforms for direct SNR estimation.Predictions utilized a GWTC-3 constrained BBH population model(Power law+Peak mass,DEFAULT spin,Madau-Dickinson merger rate).The analysis used conservative lower merger rate limits and considered orbital eccentricity.The high detection rate stems from strong memory signals within DECIGO’s bandwidth and the abundance of stellar-mass BBHs.This substantial and conservative detection count enables statistical use of the memory effect for fundamental physics and astrophysics.DECIGO exemplifies that space interferometers may better detect memory signals from smaller mass binaries than their typical targets.Detectors in lower frequency bands are expected to find strong memory signals from∼10^(4)M⊙binaries.
基金Project(52409128)supported by the National Natural Science Foundation of ChinaProject(SDGZK2425)supported by the Opening Fund of State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering,China。
文摘The shape of underground chambers in deep mining varies due to their geological environment and intended use,which results in different failure modes under the influence of mining activities.However,the effect of chamber shape on the mechanism of structural integrity under dynamic load is still unclear.In this paper,granite samples with circular(C),rectangular(R),long ellipse(EL),and short ellipse(ES)holes were prepared.The dynamic mechanical response and cracking mechanism of granite were systematically analyzed using the split Hopkinson pressure bar(SHPB)test system and the hybrid finite and discrete element method(HFDEM).The results indicate that the dynamic strengths of granite with EL and ES represent the maximum and minimum values within the range of close strain rates,respectively.When EL granite is subjected to dynamic load,the axial stress concentration(in the load direction)is weak,and the transverse stress shows relative dispersion,which is the primary reason for its highest dynamic strength.The failure of granite with various holes primarily involves a tensile-shear mixed fracture,with relatively few pure typeⅡcracks.The chamber’s transverse span is the primary factor influencing the distribution range of the fracture area.
基金supported by the National Postdoctoral Fellowship of the Science and Engineering Research Board(SERB),Department of Science and Technology(DST),Government of India,File No.PDF/2021/003491。
文摘The photon region surrounding a black hole is crucial for distant observers to receive the emitted spectrum from its vicinity.This paper investigates the optical features of a regular spinning antide Sitter(AdS)black hole.These kinds of black holes hold deviation parameter k,and the cosmological constant A including their mass M and spin a.The cosmological parameter depends on the curvature radius by A=-3/l~2.We investigate the structure of geodesics for unstable circular orbits of photons as observed by an observer at specific Boyer-Lindquist coordinates(r_(O),v_(O))in the region between the outer and cosmological horizon,so-called the domain of outer communication.Our investigations include the analysis of three observables from its shadow plot:the black hole shadow radius(R_(s)),the distortion of the black hole(δ_(s)),and shadow area A.With the help of these observables,we calculate the angular diameter of the apparent size of the shadow.The shadows cast by spinning regular spacetimes are smaller compared to those produced by rotating black holes in both general relativity and regular spacetimes.We also calculate the rate at which energy is emitted from the black hole.
基金financially supported by the CITIC niobium steel development award Fund(M1656-2021)Central Iron and Steel Research Institute for its independent research and development fund(No.21G62460ZD).
文摘Increasing the hole expansion ratio is significant for developing high formability parts.Hole expansion tests were carried out on low carbon hot-rolled steel containing 0.11%Ti,0.072%Ti–0.03%Nb and 0.097%Ti–0.059%Nb,respectively.The effects of microstructure,texture,crack propagation behavior and second phase precipitation behavior on hole expansion ratio were investigated.The precipitation behavior of TiC and(Ti,Nb)C in austenite and ferrite in three groups of steel samples was calculated theoretically.The results showed that the hole expansion ratios of 0.11Ti,0.072Ti–0.03Nb and 0.097Ti–0.059Nb test steels were 51.73%,51.17%and 66.24%following simulated coiling at 600℃,respectively.The microstructure was mainly polygonal ferrite with a small amount of pearlite.The grain refinement of 0.097Ti–0.059Nb test steel and the low texture ratio of{110}//ND improved the hole expansion ratio.The low overall hole expansion ratio was due to the microstructure inhomogeneity.The microstructure uniformity was improved by the quenching and tempering treatment,and the hole expansion ratio of the three test steels was greatly increased.The fastest precipitation temperatures in the austenitic region of 0.11Ti,0.072Ti–0.03Nb and 0.097Ti–0.059Nb test steels were 880,860 and 830℃,while those in the ferrite region were 680,675 and 675℃,respectively.The addition of Nb element increased the volume free energy,so that the critical core size of the nucleation on the dislocation line increased,resulting in the decrease in the fastest precipitation temperature.
文摘In this work,the influences of surface layer slurry at different temperatures(10℃,14℃,18℃,22℃)on wax patterns deformation,shrinkage,slurry coating characteristics,and the surface quality of the casting were investigated by using a single factor variable method.The surface morphologies of the shell molds produced by different temperatures of the surface(first)layer slurries were observed via electron microscopy.Furthermore,the microscopic composition of these shell molds was obtained by EDS,and the osmotic effect of the slurry on the wax patterns at different temperatures was also assessed by the PZ-200 Contact Angle detector.The forming reasons for the surface cracks and holes of thick and large ZTC4 titanium alloy by investment casting were analyzed.The experimental results show that the surface of the shell molds prepared by the surface layer slurry with a low temperature exhibits noticeable damage,which is mainly due to the poor coating performance and the serious expansion and contraction of wax pattern at low temperatures.The second layer shell material(SiO_(2),Al_(2)O_(3))immerses into the crack area of the surface layer,contacts and reacts with the molten titanium to form surface cracks and holes in the castings.With the increase of the temperature of surface layer slurry,the damage to the shell surface tends to weaken,and the composition of the shell molds'surface becomes more uniform with less impurities.The results show that the surface layer slurry at 22℃is evenly coated on the surface of the wax patterns with appropriate thickness,and there is no surface shell mold rupture caused by sliding slurry after sand leaching.The surface layer slurry temperature is consistent with the wax pattern temperature and the workshop temperature,so there is no damage of the surface layer shell caused by expansion and contraction.Therefore,the shell mold prepared by the surface layer slurry at this temperature has good integrity,isolating the contact between the low inert shell material and the titanium liquid effectively,and the ZTC4 titanium alloy cylinder casting prepared by this shell mold is smooth,without cracks and holes.
基金supported by the National Natural Science Foundation of China(62104059,12104126,61935016,52173153)Nature Science Foundation of Hebei Province(F2021202044)the Science Research Project of Hebei Education Department(ZD2021031)。
文摘The hole transport layer(HTL)-free carbon-based perovskite solar cells(C-PSCs)are promising for commercialization owing to their excellent operational stability and simple fabrication process.However,the power conversion efficiencies(PCE)of C-PSCs are inferior to the metal electrode-based devices due to their open-circuit voltage(V_(oc))loss.Herein,time-resolved confocal photoluminescence microscopy reveals that grain boundary defects at the perovskite/carbon interface are very likely to function as nonradiative recombination centers in HTL-free C-PSCs.A versatile additive Li_(2)CO_(3)is used to modify the conformal tin oxide electron transport layer for HTL-free C-PSCs.Li_(2)CO_(3)modification can result in enhanced charge extraction and optimized energy alignment at electron transport layer/perovskite interface,as well as suppressed defects at perovskite top surface due to Li_(2)CO_(3)-induced formation of PbI_(2)crystallites.Such dual interfacial passivation ultimately leads to significantly improved Voc up to 1.142 V,which is comparable to the metal electrode-based devices with HTL.Moreover,a record-high PCE of 33.2%is achieved for Li_(2)CO_(3)-modified C-PSCs under weak light illumination conditions,demonstrating excellent indoor photovoltaic performance.This work provides a practical approach to fabricate low-cost,highly efficient carbon-based perovskite solar cells.
基金supported by the National Nat-ural Science Foundation of China(Nos.62174122,U2241244,and 52302046)Major Program(JD)of Hubei Province(No.2023BAA008)+2 种基金the Fundamental Research Funds for the Central Universities(Nos.2042023kf0116 and 2042023kf1041)the Guangdong Basic and Applied Basic Research Foundation(Nos.2024A1515011764 and 2024A1515010383)the Open Fund of Hubei Key Laboratory of Electronic Manufacturing and Packaging Integration(Wuhan University)(No.EMPI2023016).
文摘The surface transfer doping model has been extensively adopted as a mechanism to account for the generation of hole accumulation layers below hydrogen-terminated diamond(H-diamond)surfaces.To achieve effective surface transfer doping,surface electron acceptor materials with high electron affinity(EA)are required to produce a high density of two-dimensional hole gas(2DHG)on the H-diamond subsurface.We have established ingenious theoretical models to demonstrate that even if these solid materials do not have a high EA value,they remain capable of absorbing electrons from the H-diamond surface by forming a negatively charged interface to act as a surface electron acceptor in the surface transfer doping model.Our calculations,particularly for the local density of states,provide compelling evidence that the effect of an interface with negative charges induces an upward band bending on the H-diamond side.Furthermore,the valence band maximum of the diamond atoms at the interface crosses the Fermi level,giving rise to strong surface transfer p-type doping.These results give a strong theoretical interpretation of the origin of 2DHG on H-diamond surfaces.The proposed guidelines contribute to further improvements in the performance of 2DHG H-diamond field effect transistors.
