This paper studies the problem of the spectral radius of the uniform hypergraph determined by the signless Laplacian matrix.The upper bound of the spectral radius of a uniform hypergraph is obtained by using Rayleigh ...This paper studies the problem of the spectral radius of the uniform hypergraph determined by the signless Laplacian matrix.The upper bound of the spectral radius of a uniform hypergraph is obtained by using Rayleigh principle and the perturbation of the spectral radius under moving the edge operation,and the extremal hypergraphs are characterized for both supertree and unicyclic hypergraphs.The spectral radius of the graph is generalized.展开更多
At our school,we have to wear uniforms every day.The problem is that all my classmates think the uniforms are ugly.We think young people should look smart,because①we would like to wear our own clothes.Our teachers th...At our school,we have to wear uniforms every day.The problem is that all my classmates think the uniforms are ugly.We think young people should look smart,because①we would like to wear our own clothes.Our teachers think that if we do that,we will concentrate much②on our clothes than our studies.We don't agree.展开更多
The double-sided lapping process is extensively employed in the manufacturing of wafers,optical windows,and seal rings due to its high efficiency and ability to achieve precise flatness.However,limited research has ex...The double-sided lapping process is extensively employed in the manufacturing of wafers,optical windows,and seal rings due to its high efficiency and ability to achieve precise flatness.However,limited research has explored the thickness uniformity among different workpieces after double-sided lapping,and the underlying mechanism remains unclear.To address the demand for higher precision,this paper first analyzed the relative kinematic model between the workpiece and the lapping plate to clarify the causes of thickness variations among workpieces after double-sided lapping.Subsequently,a finite element method(FEM)model was developed to account for the pressure distribution on the workpiece surfaces at the initial stage of the process.The results indicate that the number of workpieces influences the final thickness variation.Then,various sets of thin copper plates with different thicknesses were lapped,and the findings revealed that five copper plates processed simultaneously exhibited more uniform thickness compared to the three plates.The experimental results align well with the theoretical analysis.Ultimately,a thickness variation of less than 6μm was achieved on five copper plates measuringΦ100×2.9 mm.This study presents a comprehensive analysis of the mechanisms influencing thickness uniformity in the double-sided lapping process and provides practical guidelines for optimizing the process to achieve stringent precision standards in industrial applications.展开更多
In this study,we present a unified sparsity-driven framework that significantly enhances motion deblurring performance by integrating two key components:a custom-designed dataset and a low-rank module(LRM).This framew...In this study,we present a unified sparsity-driven framework that significantly enhances motion deblurring performance by integrating two key components:a custom-designed dataset and a low-rank module(LRM).This framework leverages the inherent sparsity of per-pixel blur kernels to bolster both deblurring accuracy and model interpretability.Firstly,we propose an adaptive-basis decomposition-based deblurring(ADD)approach,which constructs a tailored training dataset to enhance the generalization capacity of the deblurring network.The ADD framework adaptively decomposes motion blur into sparse basis elements,effectively addressing the intricacies associated with non-uniform blurs.Secondly,an LRM is proposed to improve the interpretability of deblurring models as a plug-and-play module,primarily designed to identify and harness the intrinsic sparse features in sharp images.A series of ablation studies have been conducted to substantiate the synergistic advantages of combining the proposed ADD with the LRM for overall improvement in deblurring efficacy.Subsequently,we empirically demonstrate through rigorous experimentation that incorporating the LRM into an existing Uformer network leads to substantial enhancement in reconstruction performance.This integration yields a sparsity-guided low-rank network(SGLRN).Operating under the overarching principle of sparsity,SGLRN consistently outperforms state-of-the-art methods across multiple standard deblurring benchmarks.Comprehensive experimental results,assessed through quantitative metrics and qualitative visual evaluations,provide compelling evidence of its effectiveness.The overall deblurring results are available at Google Drive.展开更多
The mineralization process of microbial-induced calcium carbonate precipitation(MICP)is influenced by many factors,and the uniformity of the calcium carbonate precipitation has become the main focus and challenge for ...The mineralization process of microbial-induced calcium carbonate precipitation(MICP)is influenced by many factors,and the uniformity of the calcium carbonate precipitation has become the main focus and challenge for MICP technology.In this study,the uniformity of the saturated calcareous sand treated with MICP was in-vestigated through one-dimensional calcareous sand column tests and model tests.The coefficient of variation was employed in one-dimensional sand column tests to investigate the impact of injection rate,cementation solution concentration,and number of injection cycles on the uniformity of the MICP treatment.Additionally,model tests were conducted to investigate the impact of injection pressure and methods on the treatment range and uniformity under three-dimensional seepage conditions.Test results demonstrate that the reinforcement strength and uniformity are significantly influenced by the injection rate of the cementation solution,with a rate of 3 mL/min,yielding a favorable treatment effect.Excessive concentration of the cementation solution can lead to significant non-uniformity and a reduction in the compressive strength of MICP-treated samples.Conversely,excessively low concentrations may result in decreased bonding efficiency.Among the four considered con-centrations,0.5 mol/L and 1 mol/L exhibit superior reinforcing effects.The morphological development of calcareous sandy foundation reinforcement is associated with the spatial distribution pattern of the bacterial solution,exhibiting a relatively larger reinforcement area in proximity to the lower region of the model and a gradually decreasing range towards the upper part.Under three-dimensional seepage conditions,in addition to the non-uniform radial cementation along the injection pipe,there is also vertical heterogeneity of cementation along the length of the injection pipe due to gravitational effects,resulting in preferential deposition of calcium carbonate at the lower section,The application of injection pressure and a double-pipe circulation injection method can mitigate the accumulation of bacterial solution and cementation solution at the bottom,thereby improving the reinforcement range and uniformity.展开更多
On the morning of May 31st,the parallel forum"Seeking Harmony without Uniformity in Mutual Learning:Diversity of Civilisations from the Sinologists'Perspective"was held in Dunhuang.The forum was hosted b...On the morning of May 31st,the parallel forum"Seeking Harmony without Uniformity in Mutual Learning:Diversity of Civilisations from the Sinologists'Perspective"was held in Dunhuang.The forum was hosted by the Chinese Association for International Understanding and organised by Beijing Language and Culture University.Leading Sinologists and Chinese culture researchers from Europe,Asia and Latin America gathered to discuss the theme of civilisational diversity and explore pathways for coexistence and mutual enrichment.展开更多
Ceramic hollow spheres have great potential for deep-sea applications.However,the irregularity of the conventional molding process,among other reasons,results in low wall thickness uniformity of hollow spheres.To solv...Ceramic hollow spheres have great potential for deep-sea applications.However,the irregularity of the conventional molding process,among other reasons,results in low wall thickness uniformity of hollow spheres.To solve this problem,in this work,we developed a biaxial rotation grouting process for deep-sea ceramic hollow buoyancy spheres,which improves the drawbacks of the traditional rotary grouting method that results in poor wall thickness uniformity of the hollow spheres due to its irregular rotational processing.In this paper,an experimental study was carried out to investigate the effects of different rotational methods,rotational speeds,rotational time,solid phase content,etc.on the wall thickness uniformity of ceramic hollow spheres.The results show that the hollow floating balls prepared by the biaxial rotation method have the lowest wall thickness standard deviation(0.04)when the rotation speed is 60 rpm,the molding time is 8 min,and the solid phase content is 70 wt%.After the hydrostatic pressure test of 120 MPa,the hydrostatic compressive strength of hollow spheres prepared by the biaxial rotation method was increased by 31.67%compared with that of the traditional process.展开更多
Characteristics of heat transfer and flow of Newtonian and non-Newtonian fluids through porous walls and in porous media are studied due to their wide range of applications including geothermal reservoirs,heat exchang...Characteristics of heat transfer and flow of Newtonian and non-Newtonian fluids through porous walls and in porous media are studied due to their wide range of applications including geothermal reservoirs,heat exchangers,marine propulsion,and aerodynamics.The current study investigates the characteristics of heat transport in a reactive third-grade fluid,moving through permeable parallel plates,with uniform suction/injection velocity.The two permeable,parallel plates are maintained at the same,constant temperature.After being transformed into its dimensionless equivalent,governing equations are solved by employing the Least Squares Method(LSM).The LSM results are further validated with numerical solutions for temperature and velocity.The impact of cross-flow Reynolds number,Peclet number,heat generation parameter,non-Newtonian parameter,and Brinkman number on entropy generation,velocity,temperature,and Bejan number are investigated.Theresults indicate that temperature distribution is significantly influenced by the third-grade fluid parameter.The maximum temperature drops from almost 0.12 to 0.10 as the third-grade fluid parameter increases from0.05 to 0.4.When the cross-flow Reynolds number is raised from 0.05 to 3,the maximum temperature drops from 0.12 to around 0.09.Temperature is strongly influenced by the heat generation parameter.A greater understanding of the thermal characteristics necessary for the design of a variety of systems,such as heat exchangers,marine propulsion,aerodynamic systems,etc.,may be gained from the findings of the current study.展开更多
1 Introduction In highway construction,flled embankments are trapezoidal,and the ground is always improved by sand wells or columns.During embankment construction,because the width and height of the embankment are cha...1 Introduction In highway construction,flled embankments are trapezoidal,and the ground is always improved by sand wells or columns.During embankment construction,because the width and height of the embankment are changing,a non-uniform load that varies with time and lateral location is applied to the underlying ground.The consolidation phenomenon under two-dimensional(2D)conditions will keep pace with the construction of the embankment.In addition,because of evaporation and rainfall,the soils are mostly unsaturated.Therefore,it is meaningful to research the consolidation properties of unsaturated ground under non-uniform loading.展开更多
In soil dynamics,cyclic tests on sands have been extensively studied over the past several decades.Among the natural materials most susceptible to strength loss due to earthquakes,sands are commonly tested under varyi...In soil dynamics,cyclic tests on sands have been extensively studied over the past several decades.Among the natural materials most susceptible to strength loss due to earthquakes,sands are commonly tested under varying loading,frequency,and drainage conditions.Traditionally,it has been assumed that pore pressure increases with constant strength loss once the threshold for pore pressure build-up is reached.However,recent studies have revealed that at small strains,the material initially hardens despite the generation of pore pressure.This paper presents the response and degradation of uniformly graded Drava River sand(DrOS018),similar to well-known sands such as Toyoura,Nevada or Ottawa sands,and the initial hardening phenomena that occur around threshold strains.Tests were conducted using a triaxial cyclic device at three relative densities and cell pressures(100 kPa,200 kPa,and 400 kPa)under undrained conditions.Strain-controlled tests were conducted at 0.1 Hz and 0.05 Hz using sinusoidal loading,with samples prepared by under-compaction.After crossing the threshold,the sand initially shows hardening(degradation index greater than 1)with up to a 35%increase in pore pressure,followed by strength degradation at higher strains.This study is critical for seismic design and safety,particularly for fully saturated sands in coastal and high water table areas.The findings enhance our understanding of liquefaction potential and site response,aiding more informed engineering practices by contributing to enhanced knowledge in soil dynamics and improved predictive models.The results support effective mitigation strategies and infrastructure resilience in earthquake-prone regions such as Croatia.展开更多
The spatial pattern of trees is an important feature of forests,and different spatial patterns of trees exhibit different ecological stability.Research has confirmed that natural forests with random patterns have high...The spatial pattern of trees is an important feature of forests,and different spatial patterns of trees exhibit different ecological stability.Research has confirmed that natural forests with random patterns have higher biodiversity and stronger resistance to unstable factors such as pests and diseases.Even if they are disturbed or destroyed by unstable factors such as pests and diseases,they can still recover and rescue themselves;while artificial forests with uniform and clustered patterns have lower biodiversity and are susceptible to unstable factors such as pests and diseases.And once pests and diseases occur,it’s more difficult for them to recover.In order to promote the healthy and stable develop-ment of the forestry industry and protect the diversity of the biological environment,it is necessary to protect the random pattern of natural forests from being destroyed in the process of forest management,while effectively transforming the spatial pattern of artificial forests into a random pattern.Therefore,in order to ensure the convenient and accurate determination of the type of forest spatial pattern,research on methods for determining forest spatial pattern has become particularly important.Based on the theory of uniformity,this study proposes definitions and related theories of included exclusive sphere,included exclusive body,included random pattern,and included uniformity.Under the guidance of the definition of inclusion uniformity and related theories,and by using mathematical method,it is proved that the uniformity of inclusion(CL)is asymptotically subject to the Eq.18,Therefore,the relationship between the included uniformity(CL)and the number of trees in the sample plot was established,and the corresponding relationship formula was obtained,and then the determination of the spatial pattern type of trees was completed by using the corresponding relationship formula.Through rigorous reasoning and case verification,the determination method of forest spatial pattern is effective.展开更多
Uniform linear array(ULA)radars are widely used in the collision-avoidance radar systems of small unmanned aerial vehicles(UAVs).In practice,a ULA's multi-target direction of arrival(DOA)estimation performance suf...Uniform linear array(ULA)radars are widely used in the collision-avoidance radar systems of small unmanned aerial vehicles(UAVs).In practice,a ULA's multi-target direction of arrival(DOA)estimation performance suffers from significant performance degradation owing to the limited number of physical elements.To improve the underdetermined DOA estimation performance of a ULA radar mounted on a small UAV platform,we propose a nonuniform linear motion sampling underdetermined DOA estimation method.Using the motion of the UAV platform,the echo signal is sampled at different positions.Then,according to the concept of difference co-array,a virtual ULA with multiple array elements and a large aperture is synthesized to increase the degrees of freedom(DOFs).Through position analysis of the original and motion arrays,we propose a nonuniform linear motion sampling method based on ULA for determining the optimal DOFs.Under the condition of no increase in the aperture of the physical array,the proposed method obtains a high DOF with fewer sampling runs and greatly improves the underdetermined DOA estimation performance of ULA.The results of numerical simulations conducted herein verify the superior performance of the proposed method.展开更多
During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have ...During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.展开更多
In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiat...In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.展开更多
The frost deterioration and deformation of porous rock are commonly investigated under uniform freeze-thaw(FT)conditions.However,the unidirectional FT condition,which is also prevalent in engineering practice,has rece...The frost deterioration and deformation of porous rock are commonly investigated under uniform freeze-thaw(FT)conditions.However,the unidirectional FT condition,which is also prevalent in engineering practice,has received limited attention.Therefore,a comparative study on frost deformation and microstructure evolution of porous rock under both uniform and unidirectional FT conditions was performed.Firstly,frost deformation experiments of rock were conducted under cyclic uniform and unidirectional FT action,respectively.Results illustrate that frost deformation of saturated rock exhibits isotropic characteristics under uniform FT cycles,while it shows anisotropic characteristics under unidirectional FT condition with both the frost heaving strain and residual strain along FT direction much higher than those perpendicular to FT direction.Moreover,the peak value and residual value of cumulative frost strain vary as logarithmic functions with cycle number under both uniform and unidirectional FT conditions.Subsequently,the microstructure evolution of rock suffered cyclic uniform and unidirectional FT action were measured.Under uniform FT cycles,newly generated pores uniformly distribute in rock and pore structure of rock remains isotropic in micro scale,and thus the frost deformation shows isotropic characteristics in macro scale.Under unidirectional FT cycles,micro-cracks or pore belts generate with their orientation nearly perpendicular to the FT direction,and rock structure gradually becomes anisotropic in micro scale,resulting in the anisotropic characteristics of frost deformation in macro scale.展开更多
Enhancing plasma uniformity can be achieved by modifying coil and chamber structures in radio frequency inductively coupled plasma(ICP)to meet the demand for large-area and uniformly distributed plasma in industrial m...Enhancing plasma uniformity can be achieved by modifying coil and chamber structures in radio frequency inductively coupled plasma(ICP)to meet the demand for large-area and uniformly distributed plasma in industrial manufacturing.This study utilized a two-dimensional self-consistent fluid model to investigate how different coil configurations and chamber aspect ratios affect the radial uniformity of plasma in radio frequency ICP.The findings indicate that optimizing the radial spacing of the coil enhances plasma uniformity but with a reduction in electron density.Furthermore,optimizing the coil within the ICP reactor,using the interior point method in the Interior Point Optimizer significantly enhances plasma uniformity,elevating it from 56%to 96%within the range of the model sizes.Additionally,when the chamber aspect ratio k changes from 2.8 to 4.7,the plasma distribution changes from a center-high to a saddleshaped distribution.Moreover,the plasma uniformity becomes worse.Finally,adjusting process parameters,such as increasing source power and gas pressure,can enhance plasma uniformity.These findings contribute to optimizing the etching process by improving plasma radial uniformity.展开更多
It is well accepted that a lithiophilic interface can effectively regulate Li deposition behaviors,but the influence of the lithiophilic interface is gradually diminished upon continuous Li deposition that completely ...It is well accepted that a lithiophilic interface can effectively regulate Li deposition behaviors,but the influence of the lithiophilic interface is gradually diminished upon continuous Li deposition that completely isolates Li from the lithiophilic metals.Herein,we perform in-depth studies on the creation of dynamic alloy interfaces upon Li deposition,arising from the exceptionally high diffusion coefficient of Hg in the amalgam solid solution.As a comparison,other metals such as Au,Ag,and Zn have typical diffusion coefficients of 10-20 orders of magnitude lower than that of Hg in the similar solid solution phases.This difference induces compact Li deposition pattern with an amalgam substrate even with a high areal capacity of 55 mAh cm^(-2).This finding provides new insight into the rational design of Li anode substrate for the stable cycling of Li metal batteries.展开更多
Two-dimensional(2D)nitrogen-doped graphene(NG)films have attracted considerable attention as promis-ing metal-free electrochemical catalysts for the oxygen reduction reaction(ORR).Thermal evaporation is a versatile th...Two-dimensional(2D)nitrogen-doped graphene(NG)films have attracted considerable attention as promis-ing metal-free electrochemical catalysts for the oxygen reduction reaction(ORR).Thermal evaporation is a versatile thin film deposition technique.However,the conventional thermal evaporation techniques present challenges in producing nitrogen-rich NG thin films because of the difficulties of a controllable manner for doping graphene with N atoms.To address this,we designed a vacuum thermal evaporation system for the large-scale preparation of 2D NG thin films.Using poly(2,5-benzimidazole)(ABPBI)as a nitrogen and carbon precursor,we deposited nitrogen-rich NG thin films with a size of 50×50 mm^(2) and controllable thickness within the range of 0.5–1.5 nm.The 2D NG samples exhibited a uniform thin film structure with moderate defects.The nitrogen-rich ABPBI precursor and defects,as well as the beneficial morphology and structure,endowed the optimal catalyst(2D NG-900)with a comparable ORR activity and superior stability compared with the commercial Pt/C(20 wt%)catalyst.This paper proposes a feasible strategy for fabricating 2D NG films as effective metal-free catalysts for the ORR.展开更多
基金Supported by Natural Science Foundation of HuBei Province(2022CFB299).
文摘This paper studies the problem of the spectral radius of the uniform hypergraph determined by the signless Laplacian matrix.The upper bound of the spectral radius of a uniform hypergraph is obtained by using Rayleigh principle and the perturbation of the spectral radius under moving the edge operation,and the extremal hypergraphs are characterized for both supertree and unicyclic hypergraphs.The spectral radius of the graph is generalized.
文摘At our school,we have to wear uniforms every day.The problem is that all my classmates think the uniforms are ugly.We think young people should look smart,because①we would like to wear our own clothes.Our teachers think that if we do that,we will concentrate much②on our clothes than our studies.We don't agree.
基金Supported by the Liaoning Provincial Natural Science Foundation(Grant No.2023-MSBA-008)Unveiling and Commanding Program of Liaoning Province(Grant No.2022JH1/10800080)the Fundamental Research Funds for the Central Universities(Grant No.DUT24MS008).
文摘The double-sided lapping process is extensively employed in the manufacturing of wafers,optical windows,and seal rings due to its high efficiency and ability to achieve precise flatness.However,limited research has explored the thickness uniformity among different workpieces after double-sided lapping,and the underlying mechanism remains unclear.To address the demand for higher precision,this paper first analyzed the relative kinematic model between the workpiece and the lapping plate to clarify the causes of thickness variations among workpieces after double-sided lapping.Subsequently,a finite element method(FEM)model was developed to account for the pressure distribution on the workpiece surfaces at the initial stage of the process.The results indicate that the number of workpieces influences the final thickness variation.Then,various sets of thin copper plates with different thicknesses were lapped,and the findings revealed that five copper plates processed simultaneously exhibited more uniform thickness compared to the three plates.The experimental results align well with the theoretical analysis.Ultimately,a thickness variation of less than 6μm was achieved on five copper plates measuringΦ100×2.9 mm.This study presents a comprehensive analysis of the mechanisms influencing thickness uniformity in the double-sided lapping process and provides practical guidelines for optimizing the process to achieve stringent precision standards in industrial applications.
基金supported by the National Natural Science Foundation of China(No.62206143)the Key Research and Development and Promotion Special Project in Henan Province(Nos.222102210141 and 232102211015)。
文摘In this study,we present a unified sparsity-driven framework that significantly enhances motion deblurring performance by integrating two key components:a custom-designed dataset and a low-rank module(LRM).This framework leverages the inherent sparsity of per-pixel blur kernels to bolster both deblurring accuracy and model interpretability.Firstly,we propose an adaptive-basis decomposition-based deblurring(ADD)approach,which constructs a tailored training dataset to enhance the generalization capacity of the deblurring network.The ADD framework adaptively decomposes motion blur into sparse basis elements,effectively addressing the intricacies associated with non-uniform blurs.Secondly,an LRM is proposed to improve the interpretability of deblurring models as a plug-and-play module,primarily designed to identify and harness the intrinsic sparse features in sharp images.A series of ablation studies have been conducted to substantiate the synergistic advantages of combining the proposed ADD with the LRM for overall improvement in deblurring efficacy.Subsequently,we empirically demonstrate through rigorous experimentation that incorporating the LRM into an existing Uformer network leads to substantial enhancement in reconstruction performance.This integration yields a sparsity-guided low-rank network(SGLRN).Operating under the overarching principle of sparsity,SGLRN consistently outperforms state-of-the-art methods across multiple standard deblurring benchmarks.Comprehensive experimental results,assessed through quantitative metrics and qualitative visual evaluations,provide compelling evidence of its effectiveness.The overall deblurring results are available at Google Drive.
基金support of Natural Science Foundation of China(Grant No.52108324,No.52008207,and No.52108298)for conducting this study.
文摘The mineralization process of microbial-induced calcium carbonate precipitation(MICP)is influenced by many factors,and the uniformity of the calcium carbonate precipitation has become the main focus and challenge for MICP technology.In this study,the uniformity of the saturated calcareous sand treated with MICP was in-vestigated through one-dimensional calcareous sand column tests and model tests.The coefficient of variation was employed in one-dimensional sand column tests to investigate the impact of injection rate,cementation solution concentration,and number of injection cycles on the uniformity of the MICP treatment.Additionally,model tests were conducted to investigate the impact of injection pressure and methods on the treatment range and uniformity under three-dimensional seepage conditions.Test results demonstrate that the reinforcement strength and uniformity are significantly influenced by the injection rate of the cementation solution,with a rate of 3 mL/min,yielding a favorable treatment effect.Excessive concentration of the cementation solution can lead to significant non-uniformity and a reduction in the compressive strength of MICP-treated samples.Conversely,excessively low concentrations may result in decreased bonding efficiency.Among the four considered con-centrations,0.5 mol/L and 1 mol/L exhibit superior reinforcing effects.The morphological development of calcareous sandy foundation reinforcement is associated with the spatial distribution pattern of the bacterial solution,exhibiting a relatively larger reinforcement area in proximity to the lower region of the model and a gradually decreasing range towards the upper part.Under three-dimensional seepage conditions,in addition to the non-uniform radial cementation along the injection pipe,there is also vertical heterogeneity of cementation along the length of the injection pipe due to gravitational effects,resulting in preferential deposition of calcium carbonate at the lower section,The application of injection pressure and a double-pipe circulation injection method can mitigate the accumulation of bacterial solution and cementation solution at the bottom,thereby improving the reinforcement range and uniformity.
文摘On the morning of May 31st,the parallel forum"Seeking Harmony without Uniformity in Mutual Learning:Diversity of Civilisations from the Sinologists'Perspective"was held in Dunhuang.The forum was hosted by the Chinese Association for International Understanding and organised by Beijing Language and Culture University.Leading Sinologists and Chinese culture researchers from Europe,Asia and Latin America gathered to discuss the theme of civilisational diversity and explore pathways for coexistence and mutual enrichment.
基金Funded by the Key Research and Development Program of Shandong Province(No.2020JMRH0101)。
文摘Ceramic hollow spheres have great potential for deep-sea applications.However,the irregularity of the conventional molding process,among other reasons,results in low wall thickness uniformity of hollow spheres.To solve this problem,in this work,we developed a biaxial rotation grouting process for deep-sea ceramic hollow buoyancy spheres,which improves the drawbacks of the traditional rotary grouting method that results in poor wall thickness uniformity of the hollow spheres due to its irregular rotational processing.In this paper,an experimental study was carried out to investigate the effects of different rotational methods,rotational speeds,rotational time,solid phase content,etc.on the wall thickness uniformity of ceramic hollow spheres.The results show that the hollow floating balls prepared by the biaxial rotation method have the lowest wall thickness standard deviation(0.04)when the rotation speed is 60 rpm,the molding time is 8 min,and the solid phase content is 70 wt%.After the hydrostatic pressure test of 120 MPa,the hydrostatic compressive strength of hollow spheres prepared by the biaxial rotation method was increased by 31.67%compared with that of the traditional process.
文摘Characteristics of heat transfer and flow of Newtonian and non-Newtonian fluids through porous walls and in porous media are studied due to their wide range of applications including geothermal reservoirs,heat exchangers,marine propulsion,and aerodynamics.The current study investigates the characteristics of heat transport in a reactive third-grade fluid,moving through permeable parallel plates,with uniform suction/injection velocity.The two permeable,parallel plates are maintained at the same,constant temperature.After being transformed into its dimensionless equivalent,governing equations are solved by employing the Least Squares Method(LSM).The LSM results are further validated with numerical solutions for temperature and velocity.The impact of cross-flow Reynolds number,Peclet number,heat generation parameter,non-Newtonian parameter,and Brinkman number on entropy generation,velocity,temperature,and Bejan number are investigated.Theresults indicate that temperature distribution is significantly influenced by the third-grade fluid parameter.The maximum temperature drops from almost 0.12 to 0.10 as the third-grade fluid parameter increases from0.05 to 0.4.When the cross-flow Reynolds number is raised from 0.05 to 3,the maximum temperature drops from 0.12 to around 0.09.Temperature is strongly influenced by the heat generation parameter.A greater understanding of the thermal characteristics necessary for the design of a variety of systems,such as heat exchangers,marine propulsion,aerodynamic systems,etc.,may be gained from the findings of the current study.
基金supported by the National Nature Science Foundation of China(No.12172211)the National Key Research and Development Program of China(No.2019YFC1509800)。
文摘1 Introduction In highway construction,flled embankments are trapezoidal,and the ground is always improved by sand wells or columns.During embankment construction,because the width and height of the embankment are changing,a non-uniform load that varies with time and lateral location is applied to the underlying ground.The consolidation phenomenon under two-dimensional(2D)conditions will keep pace with the construction of the embankment.In addition,because of evaporation and rainfall,the soils are mostly unsaturated.Therefore,it is meaningful to research the consolidation properties of unsaturated ground under non-uniform loading.
基金Project Research Infrastructure for Campus-based Laboratories at the University of Rijeka(RC.2.2.06-0001)funded by the Ministry of Science,EducationSports of the Republic of Croatia.This project has been co-funded by the European Fund for Regional Development(ERDF)The support is gratefully acknowledged.This research was partially supported by the project“Laboratory Research of Static and Cyclic Behavior at Landslide Activation”(uniri-tehnic-18-113)funded by the University of Rijeka,Croatia.
文摘In soil dynamics,cyclic tests on sands have been extensively studied over the past several decades.Among the natural materials most susceptible to strength loss due to earthquakes,sands are commonly tested under varying loading,frequency,and drainage conditions.Traditionally,it has been assumed that pore pressure increases with constant strength loss once the threshold for pore pressure build-up is reached.However,recent studies have revealed that at small strains,the material initially hardens despite the generation of pore pressure.This paper presents the response and degradation of uniformly graded Drava River sand(DrOS018),similar to well-known sands such as Toyoura,Nevada or Ottawa sands,and the initial hardening phenomena that occur around threshold strains.Tests were conducted using a triaxial cyclic device at three relative densities and cell pressures(100 kPa,200 kPa,and 400 kPa)under undrained conditions.Strain-controlled tests were conducted at 0.1 Hz and 0.05 Hz using sinusoidal loading,with samples prepared by under-compaction.After crossing the threshold,the sand initially shows hardening(degradation index greater than 1)with up to a 35%increase in pore pressure,followed by strength degradation at higher strains.This study is critical for seismic design and safety,particularly for fully saturated sands in coastal and high water table areas.The findings enhance our understanding of liquefaction potential and site response,aiding more informed engineering practices by contributing to enhanced knowledge in soil dynamics and improved predictive models.The results support effective mitigation strategies and infrastructure resilience in earthquake-prone regions such as Croatia.
基金funded in part by Research on Intelligent Control System of Variable Fertilization of Deep Application Liquid Fertilizer(GXKS2022GKY003)Research on Vehicle Ranging System Based on Object Detection and Monocular Vision(2022KY0854).
文摘The spatial pattern of trees is an important feature of forests,and different spatial patterns of trees exhibit different ecological stability.Research has confirmed that natural forests with random patterns have higher biodiversity and stronger resistance to unstable factors such as pests and diseases.Even if they are disturbed or destroyed by unstable factors such as pests and diseases,they can still recover and rescue themselves;while artificial forests with uniform and clustered patterns have lower biodiversity and are susceptible to unstable factors such as pests and diseases.And once pests and diseases occur,it’s more difficult for them to recover.In order to promote the healthy and stable develop-ment of the forestry industry and protect the diversity of the biological environment,it is necessary to protect the random pattern of natural forests from being destroyed in the process of forest management,while effectively transforming the spatial pattern of artificial forests into a random pattern.Therefore,in order to ensure the convenient and accurate determination of the type of forest spatial pattern,research on methods for determining forest spatial pattern has become particularly important.Based on the theory of uniformity,this study proposes definitions and related theories of included exclusive sphere,included exclusive body,included random pattern,and included uniformity.Under the guidance of the definition of inclusion uniformity and related theories,and by using mathematical method,it is proved that the uniformity of inclusion(CL)is asymptotically subject to the Eq.18,Therefore,the relationship between the included uniformity(CL)and the number of trees in the sample plot was established,and the corresponding relationship formula was obtained,and then the determination of the spatial pattern type of trees was completed by using the corresponding relationship formula.Through rigorous reasoning and case verification,the determination method of forest spatial pattern is effective.
基金National Natural Science Foundation of China(61973037)National 173 Program Project(2019-JCJQ-ZD-324)。
文摘Uniform linear array(ULA)radars are widely used in the collision-avoidance radar systems of small unmanned aerial vehicles(UAVs).In practice,a ULA's multi-target direction of arrival(DOA)estimation performance suffers from significant performance degradation owing to the limited number of physical elements.To improve the underdetermined DOA estimation performance of a ULA radar mounted on a small UAV platform,we propose a nonuniform linear motion sampling underdetermined DOA estimation method.Using the motion of the UAV platform,the echo signal is sampled at different positions.Then,according to the concept of difference co-array,a virtual ULA with multiple array elements and a large aperture is synthesized to increase the degrees of freedom(DOFs).Through position analysis of the original and motion arrays,we propose a nonuniform linear motion sampling method based on ULA for determining the optimal DOFs.Under the condition of no increase in the aperture of the physical array,the proposed method obtains a high DOF with fewer sampling runs and greatly improves the underdetermined DOA estimation performance of ULA.The results of numerical simulations conducted herein verify the superior performance of the proposed method.
基金Beijing Postdoctoral Research Activity Funding Project,Grant/Award Number:2022-ZZ-097Beijing Municipal Natural Science Foundation,Grant/Award Number:8182048。
文摘During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.
基金Supported by National Key R&D Program of China(2019YFA0405400)。
文摘In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.
基金This research was supported by the National Natural Science Foundation of China(52108370)Jiangxi Provincial Natural Science Foundation(No.20212BAB214062,20224BAB204061).
文摘The frost deterioration and deformation of porous rock are commonly investigated under uniform freeze-thaw(FT)conditions.However,the unidirectional FT condition,which is also prevalent in engineering practice,has received limited attention.Therefore,a comparative study on frost deformation and microstructure evolution of porous rock under both uniform and unidirectional FT conditions was performed.Firstly,frost deformation experiments of rock were conducted under cyclic uniform and unidirectional FT action,respectively.Results illustrate that frost deformation of saturated rock exhibits isotropic characteristics under uniform FT cycles,while it shows anisotropic characteristics under unidirectional FT condition with both the frost heaving strain and residual strain along FT direction much higher than those perpendicular to FT direction.Moreover,the peak value and residual value of cumulative frost strain vary as logarithmic functions with cycle number under both uniform and unidirectional FT conditions.Subsequently,the microstructure evolution of rock suffered cyclic uniform and unidirectional FT action were measured.Under uniform FT cycles,newly generated pores uniformly distribute in rock and pore structure of rock remains isotropic in micro scale,and thus the frost deformation shows isotropic characteristics in macro scale.Under unidirectional FT cycles,micro-cracks or pore belts generate with their orientation nearly perpendicular to the FT direction,and rock structure gradually becomes anisotropic in micro scale,resulting in the anisotropic characteristics of frost deformation in macro scale.
基金supported by the Scientific Research Foundation of Xijing University,China(No.XJ19T03)the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory(No.ZHD201701)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2024JC-YBMS-342).
文摘Enhancing plasma uniformity can be achieved by modifying coil and chamber structures in radio frequency inductively coupled plasma(ICP)to meet the demand for large-area and uniformly distributed plasma in industrial manufacturing.This study utilized a two-dimensional self-consistent fluid model to investigate how different coil configurations and chamber aspect ratios affect the radial uniformity of plasma in radio frequency ICP.The findings indicate that optimizing the radial spacing of the coil enhances plasma uniformity but with a reduction in electron density.Furthermore,optimizing the coil within the ICP reactor,using the interior point method in the Interior Point Optimizer significantly enhances plasma uniformity,elevating it from 56%to 96%within the range of the model sizes.Additionally,when the chamber aspect ratio k changes from 2.8 to 4.7,the plasma distribution changes from a center-high to a saddleshaped distribution.Moreover,the plasma uniformity becomes worse.Finally,adjusting process parameters,such as increasing source power and gas pressure,can enhance plasma uniformity.These findings contribute to optimizing the etching process by improving plasma radial uniformity.
基金supported by the National Key Research and Development Program of China(2019YFA0205700)Scientific Research Projects of Colleges and Universities in Hebei Province(JZX2023004)+2 种基金Research Program of Local Science and Technology Development under the Guidance of Central(216Z4402G)support from Ministry of Science and Higher Education of Russian Federation(project FFSG-2022-0001(122111700046-3),"Laboratory of perspective electrode materials for chemical power sources")support from"Yuanguang"Scholar Program of Hebei University of Technology
文摘It is well accepted that a lithiophilic interface can effectively regulate Li deposition behaviors,but the influence of the lithiophilic interface is gradually diminished upon continuous Li deposition that completely isolates Li from the lithiophilic metals.Herein,we perform in-depth studies on the creation of dynamic alloy interfaces upon Li deposition,arising from the exceptionally high diffusion coefficient of Hg in the amalgam solid solution.As a comparison,other metals such as Au,Ag,and Zn have typical diffusion coefficients of 10-20 orders of magnitude lower than that of Hg in the similar solid solution phases.This difference induces compact Li deposition pattern with an amalgam substrate even with a high areal capacity of 55 mAh cm^(-2).This finding provides new insight into the rational design of Li anode substrate for the stable cycling of Li metal batteries.
基金the National Natural Science Foundation of China(Grant No.22105114)the Fundamental Research Funds for the Central Universities(Grant No.2024MS014).
文摘Two-dimensional(2D)nitrogen-doped graphene(NG)films have attracted considerable attention as promis-ing metal-free electrochemical catalysts for the oxygen reduction reaction(ORR).Thermal evaporation is a versatile thin film deposition technique.However,the conventional thermal evaporation techniques present challenges in producing nitrogen-rich NG thin films because of the difficulties of a controllable manner for doping graphene with N atoms.To address this,we designed a vacuum thermal evaporation system for the large-scale preparation of 2D NG thin films.Using poly(2,5-benzimidazole)(ABPBI)as a nitrogen and carbon precursor,we deposited nitrogen-rich NG thin films with a size of 50×50 mm^(2) and controllable thickness within the range of 0.5–1.5 nm.The 2D NG samples exhibited a uniform thin film structure with moderate defects.The nitrogen-rich ABPBI precursor and defects,as well as the beneficial morphology and structure,endowed the optimal catalyst(2D NG-900)with a comparable ORR activity and superior stability compared with the commercial Pt/C(20 wt%)catalyst.This paper proposes a feasible strategy for fabricating 2D NG films as effective metal-free catalysts for the ORR.
