Hard disk drives(HDDs)serve as the primary storage devices in modern data centers.Once a failure occurs,it often leads to severe data loss,significantly degrading the reliability of storage systems.Numerous studies ha...Hard disk drives(HDDs)serve as the primary storage devices in modern data centers.Once a failure occurs,it often leads to severe data loss,significantly degrading the reliability of storage systems.Numerous studies have proposed machine learning-based HDD failure prediction models.However,the Self-Monitoring,Analysis,and Reporting Technology(SMART)attributes differ across HDD manufacturers.We define hard drives of the same brand and model as homogeneous HDD groups,and those from different brands or models as heterogeneous HDD groups.In practical engineering scenarios,a data center is often composed of a heterogeneous population of HDDs,spanning multiple vendors and models.Existing research predominantly focuses on homogeneous datasets,ignoring the model’s generalization capability across heterogeneous HDDs.As a result,HDD models with limited samples often suffer from poor training effectiveness and prediction performance.To address this issue,we investigate generalizable SMART predictors across heterogeneous HDD groups.By extracting time-series features within a fixed sliding time window,we propose a Heterogeneous Disk Failure Prediction Method based on Time Series Features(HDFPM)framework.This method is adaptable to HDD models with limited sample sizes,thereby enhancing its applicability and robustness across diverse drive populations.Experimental results show that the proposed model achieves an F1-score of 0.9518 when applied to two different Seagate HDD models,while maintaining the False Positive Rate(FPR)below 1%.After incorporating the Complexity-Ratio Dynamic Time Warping(CDTW)based feature enhancement method,the best prediction model achieves a True Positive Rate(TPR)of up to 0.93 between the two models.For next-day failure prediction across various Seagate models,the model achieves an F1-score of up to 0.8792.Moreover,the experimental results also show that within the same brand,the higher the proportion of shared SMART attributes across different models,the better the prediction performance.In addition,HDFPMdemonstrates the best stability andmost significant performance in heterogeneous environments.展开更多
This paper considers the initial boundary value problems with three types of the boundary conditions for nonlinear pseudo-hyperbolic equations of generalized nerve conduction type, using foe eigenfunction method, ...This paper considers the initial boundary value problems with three types of the boundary conditions for nonlinear pseudo-hyperbolic equations of generalized nerve conduction type, using foe eigenfunction method, the conditions for which the solutions blow-up and die-out in the finile time are got.展开更多
Based on H1-Galerkin mixed finite element method with nonconforming quasi-Wilson element, a numerical approximate scheme is established for pseudo-hyperbolic equations under arbitrary quadrilateral meshes. The corresp...Based on H1-Galerkin mixed finite element method with nonconforming quasi-Wilson element, a numerical approximate scheme is established for pseudo-hyperbolic equations under arbitrary quadrilateral meshes. The corresponding optimal order error estimate is derived by the interpolation technique instead of the generalized elliptic projection which is necessary for classical error estimates of finite element analysis.展开更多
The big-tapered profiled ring disk is a key component of engines for rockets and missiles.A new forming technology,as called spinning-rolling process,has been proposed previously for the high performance,high efficien...The big-tapered profiled ring disk is a key component of engines for rockets and missiles.A new forming technology,as called spinning-rolling process,has been proposed previously for the high performance,high efficiency and low-cost manufacturing of the component.Blank design is the key part of plastic forming process design.For spinning-rolling process,the shape and size of the blank play a crucial role in process stability,deformation behavior and dimensional accuracy.So this work proposes a blank design method to determine the geometry structure and sizes of the blank.The mathematical model for calculating the blank size has been deduced based on volume conservation and neutral layer length invariance principle.The FE simulation and corresponding trial production of an actual big-tapered profiled ring disk show that the proposed blank design method is applicative.In order to obtain a preferred blank,the influence rules of blank size determined by different deformation degrees(rolling ratio k)on the spinning-rolling process are revealed by comprehensive FE simulations.Overall considering the process stability,circularity of the deformed ring disk and forming forces,a reasonable range of deformation degree(rolling ratio k)is recommended for the blank design of the new spinning-rolling process.展开更多
To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military ...To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.展开更多
Luminosity outbursts of FU Ori-type objects(FUors)allow us to observe in the gas the molecules that are typically present in the ice in protoplanetary disks.In particular,the fraction of deuterated water,which is usua...Luminosity outbursts of FU Ori-type objects(FUors)allow us to observe in the gas the molecules that are typically present in the ice in protoplanetary disks.In particular,the fraction of deuterated water,which is usually mostly frozen in the midplane of a protoplanetary disk,has been measured for the first time in the gas of the disk around FUor V883 Ori.We test the hypothesis that the observed high HDO/H_(2)O ratio in the V883 Ori protoplanetary disk can be explained by luminosity outbursts of different amplitude,including a series of two consecutive outbursts.Using the ANDES astrochemical code,we modeled the distributions of water and deuterated water abundances under the action of luminosity outbursts of different amplitudes(from 400 to10,000 L_(⊙))and at different stellar luminosities at the pre-outburst stage.We show that the best agreement with the observed HDO/H_(2)O profile is obtained for outburst amplitudes of 2000 and 10,000 L_(⊙),while the observed bolometric luminosity of V883 Ori does not exceed 400 L_(⊙).We discuss possible reasons for this discrepancy,including the presence of past luminosity outbursts,the age of the star,and the influence of additional heating mechanisms in the midplane of the protoplanetary disk.We also consider how the high observed HDO/H_(2)O ratio may be related to the evolution of the chemical composition of the ice in the protoplanetary disk and the chemical processes activated under outburst conditions.展开更多
This study explores the dynamics of charged Hayward black holes,focusing on the effects of electric charge and the length factor on accretion disk characteristics.Our results show that increasing both parameters reduc...This study explores the dynamics of charged Hayward black holes,focusing on the effects of electric charge and the length factor on accretion disk characteristics.Our results show that increasing both parameters reduces the size of the event horizon and innermost stable circular orbits(ISCO)radius,with the electric charge exerting a more pronounced influence.Additionally,the length factor and electric charge can effectively replicate the spin of a Kerr black hole.Both parameters also affect the electromagnetic radiation emitted from the accretion disk,increasing the flux,temperature,and radiative efficiency.The peak radiation occurs in the soft x-ray band,with higher values of electric charge and length factor enhancing disk luminosity and shifting the peak to higher frequencies.These findings can offer valuable insights into the accretion processes around black holes and their observable signatures,particularly in x-ray astronomy.展开更多
We consider the recently developed black hole in massive Einstein-dilaton gravity including the coupling of the dilaton scalar field to massive graviton terms.This model has different horizon structures such as event ...We consider the recently developed black hole in massive Einstein-dilaton gravity including the coupling of the dilaton scalar field to massive graviton terms.This model has different horizon structures such as event horizons and inner horizons depending on the values of certain parameters.These variations influence how the black hole interacts with its surroundings.We utilize the well-known Novikov-Thorne model to investigate the thin accretion disks into this interesting model.Our research shows a crucial correlation between the dynamics of the accretion disk and the parameters of dilatonic black holes in dilaton-massive gravity.We observe that dilaton-massive gravity leads to significant contraction and outward expansion.We offer a detailed analysis of accretion by examining both direct and secondary images at various radial distances and observation angles.展开更多
This study investigates the heat transfer and flow dynamics of a ternary hybrid nanofluid comprising alumina,copper,and silica/titania nanoparticles dispersed in water.The analysis considers the effects of suction,mag...This study investigates the heat transfer and flow dynamics of a ternary hybrid nanofluid comprising alumina,copper,and silica/titania nanoparticles dispersed in water.The analysis considers the effects of suction,magnetic field,and Joule heating over a permeable shrinking disk.Amathematicalmodel is developed and converted to a systemof differential equations using similarity transformation which then,solved numerically using the bvp4c solver in Matlab software.The study introduces a novel comparative analysis of alumina-copper-silica and alumina-coppertitania nanofluids,revealing distinct thermal conductivity behaviors and identifying critical suction values necessary for flow stabilization.Dual solutions are found within a specific range of parameters such that the minimum required suction values for flow stability,with S_(c)=1.2457 for alumina-copper-silica/water and S_(c)=1.2351 for alumina-coppertitania/water.The results indicate that increasing suction by 1%enhances the skin friction coefficient by up to 4.17%and improves heat transfer efficiency by approximately 1%,highlighting its crucial role in stabilizing the opposing flow induced by the shrinking disk.Additionally,the inclusion of 1%silica nanoparticles reduces both skin friction and heat transfer rate by approximately 0.28%and 0.85%,respectively,while 1%titania concentration increases skin friction by 3.02%but results in a slight heat transfer loss of up to 0.61%.These findings confirm the superior thermal performance of alumina-copper-titania/water,making it a promising candidate for enhanced cooling systems,energy-efficient heat exchangers,and industrial thermal management applications.展开更多
This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity a...This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity and thermal slip boundary conditions are also examined.The considered hybrid nano-fluid contains silver(Ag)and iron oxide(Fe_(3)O_(4))nanoparticles dispersed in the water to prepare the Ag-Fe_(3)O_(4)/water-based hybrid nanofluid.The requisite posited partial differential equations model is converted to ordinary differential equations using similarity transformations.For a numerical solution,the shooting method in Maple is employed.Moreover,the duality in solutions is achieved for both cases of the disk(stretching(λ>0)and shrinking(λ<0)).At the same time,a unique solution is observed for λ=0.No solution is found for them at λ<λ_(c),whereas the solutions are split at the λ=λ_(c).Besides,the value of the λ_(c) is dependent on the φ_(hnf).Meanwhile,the values of f″(0)and -θ′(0)intensified with increasing φ_(hnf).Stability analysis has been applied using bvp4c in MATLAB software due to a dual solution.Furthermore,analysis shows that the first solution is stable and feasible physically.For the slip parameters,an increase in the velocity slip parameter increases the velocity and shear stress profiles while increasing the temperature profile in the first solutions.While the rise in thermal slip parameter reduces the temperature profile nanoparticle volume fractions increase it.展开更多
Stars can form and evolve within gaseous disks around active galactic nuclei(AGNs).In the sub-parsec region of disks around~10~8M_(☉)black holes,stars accrete rapidly,reaching■200 M_(☉)and settling into a quasi-ste...Stars can form and evolve within gaseous disks around active galactic nuclei(AGNs).In the sub-parsec region of disks around~10~8M_(☉)black holes,stars accrete rapidly,reaching■200 M_(☉)and settling into a quasi-steady state in which accretion balances wind-driven mass loss.Within this environment,their ultimate fate depends critically on the radiative-zone diffusion coefficient(Dmix),which encapsulates various mixing processes and governs chemical transport between surface and core.Using the MESA stellar evolution code,we simulate AGN stars across a range of mixing efficiencies.We find a critical threshold floor value D_(mix,min)≈1010 cm~2 s^(-1)that separates two distinct fates:1."Immortal stars"—when mixing is over-efficient(D_(mix,min)■10^(10)cm~2 s^(-1)),rapid hydrogen replenishment sustains core hydrogen burning,maintains main-sequence equilibrium,rendering the star effectively“immortal.”2."Metamorphic stars"—when mixing is merely efficient(D_(mix,min)<1010 cm~2 s^(-1)),stars exhaust core hydrogen,evolve off-main-sequence,shed mass to≈15 M_(☉),and produce super-solar a-abundances consistent with AGN observations.We conclude that maintaining a mixing floor below this threshold is sufficient to avoid immortality,as flux-induced extra mixing can be effectively modeled via constant floor values.Our estimates provide a foundation for future work on disk enrichment and stellar evolution.展开更多
基金supported by the Tianjin Manufacturing High Quality Development Special Foundation(No.20232185)the Roycom Foundation(No.70306901).
文摘Hard disk drives(HDDs)serve as the primary storage devices in modern data centers.Once a failure occurs,it often leads to severe data loss,significantly degrading the reliability of storage systems.Numerous studies have proposed machine learning-based HDD failure prediction models.However,the Self-Monitoring,Analysis,and Reporting Technology(SMART)attributes differ across HDD manufacturers.We define hard drives of the same brand and model as homogeneous HDD groups,and those from different brands or models as heterogeneous HDD groups.In practical engineering scenarios,a data center is often composed of a heterogeneous population of HDDs,spanning multiple vendors and models.Existing research predominantly focuses on homogeneous datasets,ignoring the model’s generalization capability across heterogeneous HDDs.As a result,HDD models with limited samples often suffer from poor training effectiveness and prediction performance.To address this issue,we investigate generalizable SMART predictors across heterogeneous HDD groups.By extracting time-series features within a fixed sliding time window,we propose a Heterogeneous Disk Failure Prediction Method based on Time Series Features(HDFPM)framework.This method is adaptable to HDD models with limited sample sizes,thereby enhancing its applicability and robustness across diverse drive populations.Experimental results show that the proposed model achieves an F1-score of 0.9518 when applied to two different Seagate HDD models,while maintaining the False Positive Rate(FPR)below 1%.After incorporating the Complexity-Ratio Dynamic Time Warping(CDTW)based feature enhancement method,the best prediction model achieves a True Positive Rate(TPR)of up to 0.93 between the two models.For next-day failure prediction across various Seagate models,the model achieves an F1-score of up to 0.8792.Moreover,the experimental results also show that within the same brand,the higher the proportion of shared SMART attributes across different models,the better the prediction performance.In addition,HDFPMdemonstrates the best stability andmost significant performance in heterogeneous environments.
文摘This paper considers the initial boundary value problems with three types of the boundary conditions for nonlinear pseudo-hyperbolic equations of generalized nerve conduction type, using foe eigenfunction method, the conditions for which the solutions blow-up and die-out in the finile time are got.
文摘Based on H1-Galerkin mixed finite element method with nonconforming quasi-Wilson element, a numerical approximate scheme is established for pseudo-hyperbolic equations under arbitrary quadrilateral meshes. The corresponding optimal order error estimate is derived by the interpolation technique instead of the generalized elliptic projection which is necessary for classical error estimates of finite element analysis.
基金the National Natural Science Foundation of China(No.52275378)the National Key Laboratory for Precision Hot Processing of Metals(6142909200208)。
文摘The big-tapered profiled ring disk is a key component of engines for rockets and missiles.A new forming technology,as called spinning-rolling process,has been proposed previously for the high performance,high efficiency and low-cost manufacturing of the component.Blank design is the key part of plastic forming process design.For spinning-rolling process,the shape and size of the blank play a crucial role in process stability,deformation behavior and dimensional accuracy.So this work proposes a blank design method to determine the geometry structure and sizes of the blank.The mathematical model for calculating the blank size has been deduced based on volume conservation and neutral layer length invariance principle.The FE simulation and corresponding trial production of an actual big-tapered profiled ring disk show that the proposed blank design method is applicative.In order to obtain a preferred blank,the influence rules of blank size determined by different deformation degrees(rolling ratio k)on the spinning-rolling process are revealed by comprehensive FE simulations.Overall considering the process stability,circularity of the deformed ring disk and forming forces,a reasonable range of deformation degree(rolling ratio k)is recommended for the blank design of the new spinning-rolling process.
基金supported by the National Major Science and Technology Project,China(No.J2019-Ⅳ-0007-0075)the Fundamental Research Funds for the Central Universities,China(No.JKF-20240036)。
文摘To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.
基金supported by the Ministry of Science and Higher Education of the Russian Federation,State Assignment No.GZ0110/23-10-IF。
文摘Luminosity outbursts of FU Ori-type objects(FUors)allow us to observe in the gas the molecules that are typically present in the ice in protoplanetary disks.In particular,the fraction of deuterated water,which is usually mostly frozen in the midplane of a protoplanetary disk,has been measured for the first time in the gas of the disk around FUor V883 Ori.We test the hypothesis that the observed high HDO/H_(2)O ratio in the V883 Ori protoplanetary disk can be explained by luminosity outbursts of different amplitude,including a series of two consecutive outbursts.Using the ANDES astrochemical code,we modeled the distributions of water and deuterated water abundances under the action of luminosity outbursts of different amplitudes(from 400 to10,000 L_(⊙))and at different stellar luminosities at the pre-outburst stage.We show that the best agreement with the observed HDO/H_(2)O profile is obtained for outburst amplitudes of 2000 and 10,000 L_(⊙),while the observed bolometric luminosity of V883 Ori does not exceed 400 L_(⊙).We discuss possible reasons for this discrepancy,including the presence of past luminosity outbursts,the age of the star,and the influence of additional heating mechanisms in the midplane of the protoplanetary disk.We also consider how the high observed HDO/H_(2)O ratio may be related to the evolution of the chemical composition of the ice in the protoplanetary disk and the chemical processes activated under outburst conditions.
文摘This study explores the dynamics of charged Hayward black holes,focusing on the effects of electric charge and the length factor on accretion disk characteristics.Our results show that increasing both parameters reduces the size of the event horizon and innermost stable circular orbits(ISCO)radius,with the electric charge exerting a more pronounced influence.Additionally,the length factor and electric charge can effectively replicate the spin of a Kerr black hole.Both parameters also affect the electromagnetic radiation emitted from the accretion disk,increasing the flux,temperature,and radiative efficiency.The peak radiation occurs in the soft x-ray band,with higher values of electric charge and length factor enhancing disk luminosity and shifting the peak to higher frequencies.These findings can offer valuable insights into the accretion processes around black holes and their observable signatures,particularly in x-ray astronomy.
基金The authors extend their appreciation to the Deanship of Scientific Research at Northern Border University,Arar,KSA for funding this research work through the project number NBU-FFR-2025-1102-06.
文摘We consider the recently developed black hole in massive Einstein-dilaton gravity including the coupling of the dilaton scalar field to massive graviton terms.This model has different horizon structures such as event horizons and inner horizons depending on the values of certain parameters.These variations influence how the black hole interacts with its surroundings.We utilize the well-known Novikov-Thorne model to investigate the thin accretion disks into this interesting model.Our research shows a crucial correlation between the dynamics of the accretion disk and the parameters of dilatonic black holes in dilaton-massive gravity.We observe that dilaton-massive gravity leads to significant contraction and outward expansion.We offer a detailed analysis of accretion by examining both direct and secondary images at various radial distances and observation angles.
基金funded by Universiti Teknikal Malaysia Melaka,through Fakulti Teknologi dan Kejuruteraan Mekanikal(FTKM)’s publication fund-K23003.
文摘This study investigates the heat transfer and flow dynamics of a ternary hybrid nanofluid comprising alumina,copper,and silica/titania nanoparticles dispersed in water.The analysis considers the effects of suction,magnetic field,and Joule heating over a permeable shrinking disk.Amathematicalmodel is developed and converted to a systemof differential equations using similarity transformation which then,solved numerically using the bvp4c solver in Matlab software.The study introduces a novel comparative analysis of alumina-copper-silica and alumina-coppertitania nanofluids,revealing distinct thermal conductivity behaviors and identifying critical suction values necessary for flow stabilization.Dual solutions are found within a specific range of parameters such that the minimum required suction values for flow stability,with S_(c)=1.2457 for alumina-copper-silica/water and S_(c)=1.2351 for alumina-coppertitania/water.The results indicate that increasing suction by 1%enhances the skin friction coefficient by up to 4.17%and improves heat transfer efficiency by approximately 1%,highlighting its crucial role in stabilizing the opposing flow induced by the shrinking disk.Additionally,the inclusion of 1%silica nanoparticles reduces both skin friction and heat transfer rate by approximately 0.28%and 0.85%,respectively,while 1%titania concentration increases skin friction by 3.02%but results in a slight heat transfer loss of up to 0.61%.These findings confirm the superior thermal performance of alumina-copper-titania/water,making it a promising candidate for enhanced cooling systems,energy-efficient heat exchangers,and industrial thermal management applications.
基金the Researchers Supporting Project number(RSPD2025R997),King Saud University,Riyadh,Saudi Arabia.
文摘This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity and thermal slip boundary conditions are also examined.The considered hybrid nano-fluid contains silver(Ag)and iron oxide(Fe_(3)O_(4))nanoparticles dispersed in the water to prepare the Ag-Fe_(3)O_(4)/water-based hybrid nanofluid.The requisite posited partial differential equations model is converted to ordinary differential equations using similarity transformations.For a numerical solution,the shooting method in Maple is employed.Moreover,the duality in solutions is achieved for both cases of the disk(stretching(λ>0)and shrinking(λ<0)).At the same time,a unique solution is observed for λ=0.No solution is found for them at λ<λ_(c),whereas the solutions are split at the λ=λ_(c).Besides,the value of the λ_(c) is dependent on the φ_(hnf).Meanwhile,the values of f″(0)and -θ′(0)intensified with increasing φ_(hnf).Stability analysis has been applied using bvp4c in MATLAB software due to a dual solution.Furthermore,analysis shows that the first solution is stable and feasible physically.For the slip parameters,an increase in the velocity slip parameter increases the velocity and shear stress profiles while increasing the temperature profile in the first solutions.While the rise in thermal slip parameter reduces the temperature profile nanoparticle volume fractions increase it.
文摘Stars can form and evolve within gaseous disks around active galactic nuclei(AGNs).In the sub-parsec region of disks around~10~8M_(☉)black holes,stars accrete rapidly,reaching■200 M_(☉)and settling into a quasi-steady state in which accretion balances wind-driven mass loss.Within this environment,their ultimate fate depends critically on the radiative-zone diffusion coefficient(Dmix),which encapsulates various mixing processes and governs chemical transport between surface and core.Using the MESA stellar evolution code,we simulate AGN stars across a range of mixing efficiencies.We find a critical threshold floor value D_(mix,min)≈1010 cm~2 s^(-1)that separates two distinct fates:1."Immortal stars"—when mixing is over-efficient(D_(mix,min)■10^(10)cm~2 s^(-1)),rapid hydrogen replenishment sustains core hydrogen burning,maintains main-sequence equilibrium,rendering the star effectively“immortal.”2."Metamorphic stars"—when mixing is merely efficient(D_(mix,min)<1010 cm~2 s^(-1)),stars exhaust core hydrogen,evolve off-main-sequence,shed mass to≈15 M_(☉),and produce super-solar a-abundances consistent with AGN observations.We conclude that maintaining a mixing floor below this threshold is sufficient to avoid immortality,as flux-induced extra mixing can be effectively modeled via constant floor values.Our estimates provide a foundation for future work on disk enrichment and stellar evolution.
