In this paper,we explicitly establish Poincaréinequality for 1≤p<∞ over simple geometric domains,such as segment,rectangle,triangle or tetrahedron.We obtain sharper bounds of the constant in Poincaré in...In this paper,we explicitly establish Poincaréinequality for 1≤p<∞ over simple geometric domains,such as segment,rectangle,triangle or tetrahedron.We obtain sharper bounds of the constant in Poincaré inequality and,in particular,the explicit relation between the constant and the geometric characters of the domain.展开更多
A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that th...A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that the loading parameters(initial normal stress,normal stiffness,and shear velocity)determine propagation paths of the wing and secondary cracks in rock bridges during the initial shear cycle,creating different morphologies of macroscopic step-path rupture surfaces and asperities on them.The differences in stress state and rupture surface induce different cyclic shear responses.It shows that high initial normal stress accelerates asperity degradation,raises shear resistance,and promotes compression of intermittent joints.In addition,high normal stiffness provides higher normal stress and shear resistance during the initial cycles and inhibits the dilation and compression of intermittent joints.High shear velocity results in a higher shear resistance,greater dilation,and greater compression.Finally,shear strength is most sensitive to initial normal stress,followed by shear velocity and normal stiffness.Moreover,average dilation angle is most sensitive to initial normal stress,followed by normal stiffness and shear velocity.During the shear cycles,frictional coefficient is affected by asperity degradation,backfilling of rock debris,and frictional area,exhibiting a non-monotonic behavior.展开更多
The Newtonian gravitational constant G is one of the most important fundamental constants of nature, but still remains resistant to the standard model of physics and disconnected from quantum theory. During the past &...The Newtonian gravitational constant G is one of the most important fundamental constants of nature, but still remains resistant to the standard model of physics and disconnected from quantum theory. During the past >100 years, hundreds of G values have been measured to be ranging around 6.66 to 6.7559 × 10−11 m3·kg−1·s−2 using macroscopic masses. More recently, however, a G value ((6.04 ± 0.06) × 10−11 m3·kg−1·s−2) measured using millimetre-sized masses shows significant deviation (by ~9%) from the reference G value, which the authors explained is resulted from “the known systematic uncertainties”. However, based on the observation of historical G values and the protocol of the millimetre-sized masses based experiment, here we proposed a theory that this deviation is not from “systematic uncertainties” but actually G will rapidly decrease when masses sphere diameter is less than 0.02 metres. Moreover, this theory predicted the G value will be 5.96 × 10−11 m3·kg−1·s−2 between masses whose diameter are 2 millimetres (0.002 metres), which matches the measured G value very well.展开更多
This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain...This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.展开更多
In this paper,we introduce a new geometric constant R_(X)(κ)based on isosceles orthogonality.First,we explore some basic properties of this new constant and then provide several examples to estimate its exact values ...In this paper,we introduce a new geometric constant R_(X)(κ)based on isosceles orthogonality.First,we explore some basic properties of this new constant and then provide several examples to estimate its exact values in certain specific Banach spaces.Next,we investigate the relationships between this new constant and other classical constants.Specifically,we establish an inequality relationship between it and the J(X)constant,as well as an identity relationship between it and theρX(t)constant.Furthermore,we characterize some geometric properties of Banach spaces by means of this new constant.Finally,by restricting the above-mentioned constant to the unit sphere,we introduce another new constant,calculate its upper and lower bounds,and present a relevant example.展开更多
Efficient battery charging requires a power conversion system capable of providing precise voltage regulation tailored to the battery’s needs.This study develops a buck converter with a 36 V input for charging a 14 V...Efficient battery charging requires a power conversion system capable of providing precise voltage regulation tailored to the battery’s needs.This study develops a buck converter with a 36 V input for charging a 14 V battery using the Constant Voltage(CV)method.The system is designed to ensure safe and efficient charging while protecting the battery from overcharging and extending its lifespan.In the proposed design,the converter maintains a constant output voltage while the charging current decreases as the battery approaches full capacity.Pulse Width Modulation(PWM)is used as a control strategy to modify the duty cycle of the converter.This keeps the voltage output stable whenever the load changes.The design process involves simulation and experimental validation to evaluate the system’s performance and efficiency.The test results show the significant impact of Proportional-Integral-Derivative(PID)control on the stability of the output voltage to meet the requirements for 14 V battery charging and the efficiency of the battery charging process.The output voltage becomes more stable,with reduced oscillation and minimal steadystate error.The State of Charge(SOC)increases more stably,controllably,and efficiently thanks to the PID controller’s ability to adjust the duty cycle in real time based on system feedback.This dynamic adjustment ensures that the output current and voltage remain within the optimal range,which directly improves the battery charging process.In addition,PID control significantly improves the dynamic response of the system,reducing overshoot and settling time while maintaining precise voltage regulation.This speeds up the battery charging process and contributes to better energy efficiency,reduced power loss,and extended battery life.This research provides a reliable and cost-effective solution for applications in electric vehicles,renewable energy systems,and other battery-powered devices.展开更多
Charge-neutral method(CNM)is extensively used in investigating the performance of catalysts and the mechanism of N_(2)electrochemical reduction(NRR).However,disparities remain between the predicted potentials required...Charge-neutral method(CNM)is extensively used in investigating the performance of catalysts and the mechanism of N_(2)electrochemical reduction(NRR).However,disparities remain between the predicted potentials required for NRR by the CNM methods and those observed experimentally,as the CNM method neglects the charge effect from the electrode potential.To address this issue,we employed the constant electrode potential(CEP)method to screen atomic transition metal-N-graphene(M_(1)/N-graphene)as NRR electrocatalysts and systematically investigated the underlying catalytic mechanism.Among eight types of M_(1)/N-graphene(M_(1)=Mo,W,Fe,Re,Ni,Co,V,Cr),W_(1)/N-graphene emerges as the most promising NRR electrocatalyst with a limiting potential as low as−0.13 V.Additionally,the W_(1)/N-graphene system consistently maintains a positive charge during the reaction due to its Fermi level being higher than that of the electrode.These results better match with the actual circumstances compared to those calculated by conventional CNM method.Thus,our work not only develops a promising electrocatalyst for NRR but also deepens the understanding of the intrinsic electrocatalytic mechanism.展开更多
The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of thre...The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.展开更多
Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient ...Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient penetration depth,caused by excessive jet distances,presents challenges during the perforation process.To overcome this,an optimization design of the nozzle structure is required to enhance the perforation efficiency.In this paper,a computational fluid-dynamic model for conical-cylindrical nozzles has been elaborated.To further improve the rock-breaking efficiency of the jet nozzle,a fillet design is introduced at the nozzle inlet section.The SST k-ωmodel is employed to account for turbulent flow effects in submerged conditions.The results indicate that the nozzle’s geometric parameters greatly influence the flow characteristics.The orthogonal experimental method is employed to optimize the flow channel structure of the nozzle,taking the length of constant velocity core as the evaluation index.The following optimized geometric parameters for the conical-cylindrical nozzle have been determined accordingly:a cylindrical segment diameter of 3.2 mm,a contraction angle of 12°,a contraction segment length of 8 mm,a cylindrical segment length of 6.4 mm,and a fillet radius of 2 mm.展开更多
With resource exploitation and engineering construction gradually going deeper,the surrounding rock dynamic disaster becomes frequent and violent.The anchorage support is a common control method of surrounding rock in...With resource exploitation and engineering construction gradually going deeper,the surrounding rock dynamic disaster becomes frequent and violent.The anchorage support is a common control method of surrounding rock in underground engineering.To study the dynamic damage characteristics of anchored rock and the energy absorption control mechanism of dynamic disasters,a new type of constant resistance and energy absorption(CREA)material with high strength,high elongation and high energy absorption characteristics is developed.A contrast test of rockbursts in anchored rock with different support materials is conducted.The test results show that the surface damage rates and energy release degree of anchored rock with common bolt(CB)and CREA are lower than those of unanchored rock,respectively.The total energy,average energy and maximum energy released by CREA anchored rock are 30.9%,94.3%and 84.4%lower than those of CB anchored rock.Compared with unanchored rock,the rockburst peak stress in the CREA anchored rock is increased by 39.9%,and the rockburst time is delayed by 53.2%.Based on the rockburst energy calculation model,the evolution law of rockburst peak stress and energy release is investigated.The control mechanism of CREA support units on rock dynamic failure is clarified.展开更多
Traceability is the fundamental premise of all metrological activities. The establishment of a traceability chain characterized by a shortened structure, while simultaneously enabling on-site traceability, represents ...Traceability is the fundamental premise of all metrological activities. The establishment of a traceability chain characterized by a shortened structure, while simultaneously enabling on-site traceability, represents a key trend in the advancement of metrology. This study explores the periodic accuracy and overall uniformity of self-traceable gratings, employing multilayer film gratings with a nominal period of 25.00 nm as the medium. We present a comparative analysis of measurement capabilities in a self-traceable grating calibration system characterized by a ‘top-down’ calibration approach and a Si lattice constant calibration system characterized by a ‘bottom-up’ calibration approach. The results indicate that the values obtained for the multilayer film grating periods, calibrated using the self-traceable grating system, are 24.40 nm with a standard deviation of 0.11 nm. By comparing with the values derived from the Si lattice constant, which yield 24.34 nm with a standard deviation of 0.14 nm, the validity and feasibility of the self-traceable calibration system are confirmed. This system extends and complements existing metrological frameworks, offering a precise pathway for traceability in precision engineering and nanotechnology research.展开更多
In this paper,we first generalize the constant dimension and orbit codes over finite fields to the constant rank and orbit codes over finite chain rings.Then we provide a relationship between constant rank codes over ...In this paper,we first generalize the constant dimension and orbit codes over finite fields to the constant rank and orbit codes over finite chain rings.Then we provide a relationship between constant rank codes over finite chain rings and constant dimension codes over the residue fields.In particular,we prove that an orbit submodule code over a finite chain ring is a constant rank code.Finally,for special finite chain ring F_(q)+γF_(q),we define a Gray mapφfrom(F_(q)+γF_(q))^(n)to F^(2n)_(q),and by using cyclic codes over F_(q)+γF_(q),we obtain a method of constructing an optimum distance constant dimension code over F_(q).展开更多
This paper aims to enhance the array Beamforming(BF) robustness by tackling issues related to BF weight state estimation encountered in Constant Modulus Blind Beamforming(CMBB). To achieve this, we introduce a novel a...This paper aims to enhance the array Beamforming(BF) robustness by tackling issues related to BF weight state estimation encountered in Constant Modulus Blind Beamforming(CMBB). To achieve this, we introduce a novel approach that incorporates an L1-regularizer term in BF weight state estimation. We start by explaining the CMBB formation mechanism under conditions where there is a mismatch in the far-field signal model. Subsequently, we reformulate the BF weight state estimation challenge using a method known as variable-splitting, turning it into a noise minimization problem. This problem combines both linear and nonlinear quadratic terms with an L1-regularizer that promotes the sparsity. The optimization strategy is based on a variable-splitting method, implemented using the Alternating Direction Method of Multipliers(ADMM). Furthermore, a variable-splitting framework is developed to enhance BF weight state estimation, employing a Kalman Smoother(KS) optimization algorithm. The approach integrates the Rauch-TungStriebel smoother to perform posterior-smoothing state estimation by leveraging prior data. We provide proof of convergence for both linear and nonlinear CMBB state estimation technology using the variable-splitting KS and the iterated extended Kalman smoother. Simulations corroborate our theoretical analysis, showing that the proposed method achieves robust stability and effective convergence, even when faced with signal model mismatches.展开更多
Poly(m-phenylene isophthalamide)(PMIA),a key aromatic polyamide,is widely used for its outstanding mechanical strength,high thermal stability,and excellent insulation properties.However,different applications demand v...Poly(m-phenylene isophthalamide)(PMIA),a key aromatic polyamide,is widely used for its outstanding mechanical strength,high thermal stability,and excellent insulation properties.However,different applications demand varying dielectric properties,so tailoring its dielectric per-formance is essential.PMIA was first synthesized in this study,followed by introducing pores and developing porous PMIA films and PMIA-based composites with reduced dielectric constants.Porous PMIA films were fabricated using the wet phase inversion process with N,N-dimethylac-etamide(DMAC)solvent and water as the non-solvent.The impact of casting solution composi-tion and coagulation bath temperature on pore structures was analyzed.A film produced with 18%PMIA and 5%LiCl in a 35℃coagulation bath achieved the lowest dielectric constant of 1.76 at 1 Hz,48%lower than the standard PMIA film,which had a tensile strength of 18.5 MPa and an initial degradation temperature of 320℃.展开更多
The long-term stability of rocks is crucial for ensuring safety in deep engineering,where the prolonged influence of shear loading is a key factor in delayed engineering disasters.Despite its significance,research on ...The long-term stability of rocks is crucial for ensuring safety in deep engineering,where the prolonged influence of shear loading is a key factor in delayed engineering disasters.Despite its significance,research on time-dependent shear failures under true triaxial stress to reflect in situ stress conditions remains limited.This study presents laboratory shear creep measurements on intact sandstone samples under constant normal load(CNL)and constant normal stiffness(CNS)conditions,which are typical of shallow and deep engineering cases,respectively.Our investigation focuses on the effects of various lateral stresses and boundary conditions on the mechanical behaviors and failure modes of the rock samples.Results indicate that lateral stress significantly reduces shear creep deformation and decreases creep rates.Without lateral stress constraints,the samples are prone to lateral tensile fractures leading to macroscopic spalling,likely due to“shear-induced tensile”stress.This failure behavior is mitigated under lateral stress constraints.Additionally,compared to CNL condition,samples under CNS condition demonstrate enhanced long-term shear resistance,reduced shear creep rates,and rougher shear failure surfaces.These findings suggest the need to improve our understanding of rock mass stability and to develop effective disaster prevention and mitigation strategies in engineering applications.展开更多
The fine-structure constant (α) at low and high energies is herein computed from control numbers in the theory of the golden section (φ). Countless attempts at deriving, or otherwise explaining the origin of αhave ...The fine-structure constant (α) at low and high energies is herein computed from control numbers in the theory of the golden section (φ). Countless attempts at deriving, or otherwise explaining the origin of αhave so far focused and somewhat succeeded on αat low energy. This manuscript, therefore, provides a more complete solution. That αpermeates even the golden section is not only further confirmation of the ubiquity of this constant of physics, but also leads to the inescapable conclusion that it originates in the golden section, a geometrical constant ubiquitous in physical phenomena.展开更多
This study uses the PΔV term in the ideal gas equation PΔV = nRΔT to show how the 1-degree temperature increase that expands the occupied volume of a gas by ΔV against constant pressure P also causes the system to...This study uses the PΔV term in the ideal gas equation PΔV = nRΔT to show how the 1-degree temperature increase that expands the occupied volume of a gas by ΔV against constant pressure P also causes the system to increase its entropy by ΔS. As the volume available to a gas sample increases, the locations for disordered molecular relocation also increase. The causal agent linking a volume increase ΔV and an entropy increase ΔS is absolute temperature T measured in kelvin units. Since a volume increase is empirically observable while an increase in randomized molecular disorder is not, a per-kelvin increase in gas volume provides a method for estimating entropy increase. Both volume and entropy are extensive variables dependent upon the number of molecules in the system. Both are deemed to be at their absolute minima at the absolute zero of temperature. This study provides an insight into how a per-kelvin temperature increase causes both a linear increase in gas volume and a linear increase in gas entropy. When people talk about randomized disorder without specifying absolute temperature and molecule-count for the system, they are discussing a concept other than thermodynamic entropy.展开更多
This paper aims to investigate the role of bi-directional shear in the mechanical behaviour of granular materials and macro-micro relations by conducting experiments and discrete element method(DEM)modelling.The bi-di...This paper aims to investigate the role of bi-directional shear in the mechanical behaviour of granular materials and macro-micro relations by conducting experiments and discrete element method(DEM)modelling.The bi-directional shear consists of a static shear consolidation and subsequent shear under constant vertical stress and constant volume conditions.A side wall node loading method is used to exert bi-directional shear of various angles.The results show that bi-directional shear can significantly influence the mechanical behaviour of granular materials.However,the relationship between bidirectional shear and mechanical responses relies on loading conditions,i.e.constant vertical stress or constant volume conditions.The stress states induced by static shear consolidation are affected by loading angles,which are enlarged by subsequent shear,consistent with the relationship between bidirectional shear and principal stresses.It provides evidence for the dissipation of stresses accompanying static liquefaction of granular materials.The presence of bi-directional principal stress rotation(PSR)is demonstrated,which evidences why the bi-directional shear of loading angles with components in two directions results in faster dissipations of stresses with static liquefaction.Contant volume shearing leads to cross-anisotropic stress and fabric at micro-contacts,but constant vertical stress shearing leads to complete anisotropic stress and fabric at micro-contacts.It explains the differentiating relationship between stress-strain responses and fabric anisotropy under these two conditions.Micromechanical signatures such as the slip state of micro-contacts and coordination number are also examined,providing further insights into understanding granular behaviour under bi-directional shear.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.12001170 and 11601124)Innovative Funds Plan of Henan University of Technology(Grant No.2021ZKCJ11).
文摘In this paper,we explicitly establish Poincaréinequality for 1≤p<∞ over simple geometric domains,such as segment,rectangle,triangle or tetrahedron.We obtain sharper bounds of the constant in Poincaré inequality and,in particular,the explicit relation between the constant and the geometric characters of the domain.
基金financially supported by the National Natural Science Foundation of China(Grant No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group(Grant No.SNKJ 2022A01-R26).
文摘A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that the loading parameters(initial normal stress,normal stiffness,and shear velocity)determine propagation paths of the wing and secondary cracks in rock bridges during the initial shear cycle,creating different morphologies of macroscopic step-path rupture surfaces and asperities on them.The differences in stress state and rupture surface induce different cyclic shear responses.It shows that high initial normal stress accelerates asperity degradation,raises shear resistance,and promotes compression of intermittent joints.In addition,high normal stiffness provides higher normal stress and shear resistance during the initial cycles and inhibits the dilation and compression of intermittent joints.High shear velocity results in a higher shear resistance,greater dilation,and greater compression.Finally,shear strength is most sensitive to initial normal stress,followed by shear velocity and normal stiffness.Moreover,average dilation angle is most sensitive to initial normal stress,followed by normal stiffness and shear velocity.During the shear cycles,frictional coefficient is affected by asperity degradation,backfilling of rock debris,and frictional area,exhibiting a non-monotonic behavior.
文摘The Newtonian gravitational constant G is one of the most important fundamental constants of nature, but still remains resistant to the standard model of physics and disconnected from quantum theory. During the past >100 years, hundreds of G values have been measured to be ranging around 6.66 to 6.7559 × 10−11 m3·kg−1·s−2 using macroscopic masses. More recently, however, a G value ((6.04 ± 0.06) × 10−11 m3·kg−1·s−2) measured using millimetre-sized masses shows significant deviation (by ~9%) from the reference G value, which the authors explained is resulted from “the known systematic uncertainties”. However, based on the observation of historical G values and the protocol of the millimetre-sized masses based experiment, here we proposed a theory that this deviation is not from “systematic uncertainties” but actually G will rapidly decrease when masses sphere diameter is less than 0.02 metres. Moreover, this theory predicted the G value will be 5.96 × 10−11 m3·kg−1·s−2 between masses whose diameter are 2 millimetres (0.002 metres), which matches the measured G value very well.
基金Project(52174069) supported by the National Natural Science Foundation of ChinaProject(8202033) supported by the Beijing Natural Science Foundation,ChinaProject(KCF2203) supported by the Henan Key Laboratory for Green and Efficient Mining&Comprehensive Utilization of Mineral Resources (Henan Polytechnic University),China。
文摘This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.
基金Supported by the Higher Education Science Research Project(Natural Science)of Anhui Province(Grant No.2023AH050487)。
文摘In this paper,we introduce a new geometric constant R_(X)(κ)based on isosceles orthogonality.First,we explore some basic properties of this new constant and then provide several examples to estimate its exact values in certain specific Banach spaces.Next,we investigate the relationships between this new constant and other classical constants.Specifically,we establish an inequality relationship between it and the J(X)constant,as well as an identity relationship between it and theρX(t)constant.Furthermore,we characterize some geometric properties of Banach spaces by means of this new constant.Finally,by restricting the above-mentioned constant to the unit sphere,we introduce another new constant,calculate its upper and lower bounds,and present a relevant example.
文摘Efficient battery charging requires a power conversion system capable of providing precise voltage regulation tailored to the battery’s needs.This study develops a buck converter with a 36 V input for charging a 14 V battery using the Constant Voltage(CV)method.The system is designed to ensure safe and efficient charging while protecting the battery from overcharging and extending its lifespan.In the proposed design,the converter maintains a constant output voltage while the charging current decreases as the battery approaches full capacity.Pulse Width Modulation(PWM)is used as a control strategy to modify the duty cycle of the converter.This keeps the voltage output stable whenever the load changes.The design process involves simulation and experimental validation to evaluate the system’s performance and efficiency.The test results show the significant impact of Proportional-Integral-Derivative(PID)control on the stability of the output voltage to meet the requirements for 14 V battery charging and the efficiency of the battery charging process.The output voltage becomes more stable,with reduced oscillation and minimal steadystate error.The State of Charge(SOC)increases more stably,controllably,and efficiently thanks to the PID controller’s ability to adjust the duty cycle in real time based on system feedback.This dynamic adjustment ensures that the output current and voltage remain within the optimal range,which directly improves the battery charging process.In addition,PID control significantly improves the dynamic response of the system,reducing overshoot and settling time while maintaining precise voltage regulation.This speeds up the battery charging process and contributes to better energy efficiency,reduced power loss,and extended battery life.This research provides a reliable and cost-effective solution for applications in electric vehicles,renewable energy systems,and other battery-powered devices.
基金Natural Science Foundation of Guangdong Province(No.2024A1515011094(C.Q Sun))National Natural Science Foundation of China(Nos.12304243(H.X.Fang),12150100(B.Wang))is gratefully acknowledged。
文摘Charge-neutral method(CNM)is extensively used in investigating the performance of catalysts and the mechanism of N_(2)electrochemical reduction(NRR).However,disparities remain between the predicted potentials required for NRR by the CNM methods and those observed experimentally,as the CNM method neglects the charge effect from the electrode potential.To address this issue,we employed the constant electrode potential(CEP)method to screen atomic transition metal-N-graphene(M_(1)/N-graphene)as NRR electrocatalysts and systematically investigated the underlying catalytic mechanism.Among eight types of M_(1)/N-graphene(M_(1)=Mo,W,Fe,Re,Ni,Co,V,Cr),W_(1)/N-graphene emerges as the most promising NRR electrocatalyst with a limiting potential as low as−0.13 V.Additionally,the W_(1)/N-graphene system consistently maintains a positive charge during the reaction due to its Fermi level being higher than that of the electrode.These results better match with the actual circumstances compared to those calculated by conventional CNM method.Thus,our work not only develops a promising electrocatalyst for NRR but also deepens the understanding of the intrinsic electrocatalytic mechanism.
基金supported by the Natural Science Foundation of Inner Mongolia(No.2020MS01023).
文摘The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.
基金The authors gratefully acknowledge the financial support by the National Natural Science Foundation of China(No.52405272)the CNOOC’s major project during the 14th Five-Year Plan period“Key Technologies and Equipment for Measurement,Recording,and Testing-Development and Engineering of Integrated Perforation Technology Equipment Based on Reservoir Geology”and the National Science Foundation of Jiangsu Province(No.BK20220533).
文摘Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient penetration depth,caused by excessive jet distances,presents challenges during the perforation process.To overcome this,an optimization design of the nozzle structure is required to enhance the perforation efficiency.In this paper,a computational fluid-dynamic model for conical-cylindrical nozzles has been elaborated.To further improve the rock-breaking efficiency of the jet nozzle,a fillet design is introduced at the nozzle inlet section.The SST k-ωmodel is employed to account for turbulent flow effects in submerged conditions.The results indicate that the nozzle’s geometric parameters greatly influence the flow characteristics.The orthogonal experimental method is employed to optimize the flow channel structure of the nozzle,taking the length of constant velocity core as the evaluation index.The following optimized geometric parameters for the conical-cylindrical nozzle have been determined accordingly:a cylindrical segment diameter of 3.2 mm,a contraction angle of 12°,a contraction segment length of 8 mm,a cylindrical segment length of 6.4 mm,and a fillet radius of 2 mm.
基金supported by the National Key Research and Development Program of China(No.2023YFC2907600)the National Natural Science Foundation of China(Nos.42477166 and 42277174)+2 种基金the Fundamental Research Funds for the Central Universities,China(No.2024JCCXSB01)the Opening Project of State Key Laboratory of Explosion Science and Safety Protection,Beijing Institute of Technology(No.KFJJ24-01M)the Open Foundation of Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources(No.HLCX2024-04)。
文摘With resource exploitation and engineering construction gradually going deeper,the surrounding rock dynamic disaster becomes frequent and violent.The anchorage support is a common control method of surrounding rock in underground engineering.To study the dynamic damage characteristics of anchored rock and the energy absorption control mechanism of dynamic disasters,a new type of constant resistance and energy absorption(CREA)material with high strength,high elongation and high energy absorption characteristics is developed.A contrast test of rockbursts in anchored rock with different support materials is conducted.The test results show that the surface damage rates and energy release degree of anchored rock with common bolt(CB)and CREA are lower than those of unanchored rock,respectively.The total energy,average energy and maximum energy released by CREA anchored rock are 30.9%,94.3%and 84.4%lower than those of CB anchored rock.Compared with unanchored rock,the rockburst peak stress in the CREA anchored rock is increased by 39.9%,and the rockburst time is delayed by 53.2%.Based on the rockburst energy calculation model,the evolution law of rockburst peak stress and energy release is investigated.The control mechanism of CREA support units on rock dynamic failure is clarified.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61925504 and 52475563)the National Key Research and Development Program of China (Grant Nos. 2022YFF0607600 and 2022YFF0605502)+1 种基金Key Laboratory of Metrology and Calibration Technology Fund Project (Grant No. JLKG2023001B001)Aeronautical Science Foundation Project (Grant No. 20230056038001)。
文摘Traceability is the fundamental premise of all metrological activities. The establishment of a traceability chain characterized by a shortened structure, while simultaneously enabling on-site traceability, represents a key trend in the advancement of metrology. This study explores the periodic accuracy and overall uniformity of self-traceable gratings, employing multilayer film gratings with a nominal period of 25.00 nm as the medium. We present a comparative analysis of measurement capabilities in a self-traceable grating calibration system characterized by a ‘top-down’ calibration approach and a Si lattice constant calibration system characterized by a ‘bottom-up’ calibration approach. The results indicate that the values obtained for the multilayer film grating periods, calibrated using the self-traceable grating system, are 24.40 nm with a standard deviation of 0.11 nm. By comparing with the values derived from the Si lattice constant, which yield 24.34 nm with a standard deviation of 0.14 nm, the validity and feasibility of the self-traceable calibration system are confirmed. This system extends and complements existing metrological frameworks, offering a precise pathway for traceability in precision engineering and nanotechnology research.
基金Supported by Research Funds of Hubei Province(D20144401,Q20174503)。
文摘In this paper,we first generalize the constant dimension and orbit codes over finite fields to the constant rank and orbit codes over finite chain rings.Then we provide a relationship between constant rank codes over finite chain rings and constant dimension codes over the residue fields.In particular,we prove that an orbit submodule code over a finite chain ring is a constant rank code.Finally,for special finite chain ring F_(q)+γF_(q),we define a Gray mapφfrom(F_(q)+γF_(q))^(n)to F^(2n)_(q),and by using cyclic codes over F_(q)+γF_(q),we obtain a method of constructing an optimum distance constant dimension code over F_(q).
基金supported in Natural Science Foundation of Shandong Province,China(ZR2013FM018)。
文摘This paper aims to enhance the array Beamforming(BF) robustness by tackling issues related to BF weight state estimation encountered in Constant Modulus Blind Beamforming(CMBB). To achieve this, we introduce a novel approach that incorporates an L1-regularizer term in BF weight state estimation. We start by explaining the CMBB formation mechanism under conditions where there is a mismatch in the far-field signal model. Subsequently, we reformulate the BF weight state estimation challenge using a method known as variable-splitting, turning it into a noise minimization problem. This problem combines both linear and nonlinear quadratic terms with an L1-regularizer that promotes the sparsity. The optimization strategy is based on a variable-splitting method, implemented using the Alternating Direction Method of Multipliers(ADMM). Furthermore, a variable-splitting framework is developed to enhance BF weight state estimation, employing a Kalman Smoother(KS) optimization algorithm. The approach integrates the Rauch-TungStriebel smoother to perform posterior-smoothing state estimation by leveraging prior data. We provide proof of convergence for both linear and nonlinear CMBB state estimation technology using the variable-splitting KS and the iterated extended Kalman smoother. Simulations corroborate our theoretical analysis, showing that the proposed method achieves robust stability and effective convergence, even when faced with signal model mismatches.
文摘Poly(m-phenylene isophthalamide)(PMIA),a key aromatic polyamide,is widely used for its outstanding mechanical strength,high thermal stability,and excellent insulation properties.However,different applications demand varying dielectric properties,so tailoring its dielectric per-formance is essential.PMIA was first synthesized in this study,followed by introducing pores and developing porous PMIA films and PMIA-based composites with reduced dielectric constants.Porous PMIA films were fabricated using the wet phase inversion process with N,N-dimethylac-etamide(DMAC)solvent and water as the non-solvent.The impact of casting solution composi-tion and coagulation bath temperature on pore structures was analyzed.A film produced with 18%PMIA and 5%LiCl in a 35℃coagulation bath achieved the lowest dielectric constant of 1.76 at 1 Hz,48%lower than the standard PMIA film,which had a tensile strength of 18.5 MPa and an initial degradation temperature of 320℃.
基金support from the National Natural Science Foundation of China(Grant No.52209125).
文摘The long-term stability of rocks is crucial for ensuring safety in deep engineering,where the prolonged influence of shear loading is a key factor in delayed engineering disasters.Despite its significance,research on time-dependent shear failures under true triaxial stress to reflect in situ stress conditions remains limited.This study presents laboratory shear creep measurements on intact sandstone samples under constant normal load(CNL)and constant normal stiffness(CNS)conditions,which are typical of shallow and deep engineering cases,respectively.Our investigation focuses on the effects of various lateral stresses and boundary conditions on the mechanical behaviors and failure modes of the rock samples.Results indicate that lateral stress significantly reduces shear creep deformation and decreases creep rates.Without lateral stress constraints,the samples are prone to lateral tensile fractures leading to macroscopic spalling,likely due to“shear-induced tensile”stress.This failure behavior is mitigated under lateral stress constraints.Additionally,compared to CNL condition,samples under CNS condition demonstrate enhanced long-term shear resistance,reduced shear creep rates,and rougher shear failure surfaces.These findings suggest the need to improve our understanding of rock mass stability and to develop effective disaster prevention and mitigation strategies in engineering applications.
文摘The fine-structure constant (α) at low and high energies is herein computed from control numbers in the theory of the golden section (φ). Countless attempts at deriving, or otherwise explaining the origin of αhave so far focused and somewhat succeeded on αat low energy. This manuscript, therefore, provides a more complete solution. That αpermeates even the golden section is not only further confirmation of the ubiquity of this constant of physics, but also leads to the inescapable conclusion that it originates in the golden section, a geometrical constant ubiquitous in physical phenomena.
文摘This study uses the PΔV term in the ideal gas equation PΔV = nRΔT to show how the 1-degree temperature increase that expands the occupied volume of a gas by ΔV against constant pressure P also causes the system to increase its entropy by ΔS. As the volume available to a gas sample increases, the locations for disordered molecular relocation also increase. The causal agent linking a volume increase ΔV and an entropy increase ΔS is absolute temperature T measured in kelvin units. Since a volume increase is empirically observable while an increase in randomized molecular disorder is not, a per-kelvin increase in gas volume provides a method for estimating entropy increase. Both volume and entropy are extensive variables dependent upon the number of molecules in the system. Both are deemed to be at their absolute minima at the absolute zero of temperature. This study provides an insight into how a per-kelvin temperature increase causes both a linear increase in gas volume and a linear increase in gas entropy. When people talk about randomized disorder without specifying absolute temperature and molecule-count for the system, they are discussing a concept other than thermodynamic entropy.
基金the funding support from National Natural Science Foundation of China(Grant No.42307243)Henan Province Science and Technology Research Project(Grant No.232102321102)Shanxi Provincial Key Research and Development Project(Grant No.202102090301009).
文摘This paper aims to investigate the role of bi-directional shear in the mechanical behaviour of granular materials and macro-micro relations by conducting experiments and discrete element method(DEM)modelling.The bi-directional shear consists of a static shear consolidation and subsequent shear under constant vertical stress and constant volume conditions.A side wall node loading method is used to exert bi-directional shear of various angles.The results show that bi-directional shear can significantly influence the mechanical behaviour of granular materials.However,the relationship between bidirectional shear and mechanical responses relies on loading conditions,i.e.constant vertical stress or constant volume conditions.The stress states induced by static shear consolidation are affected by loading angles,which are enlarged by subsequent shear,consistent with the relationship between bidirectional shear and principal stresses.It provides evidence for the dissipation of stresses accompanying static liquefaction of granular materials.The presence of bi-directional principal stress rotation(PSR)is demonstrated,which evidences why the bi-directional shear of loading angles with components in two directions results in faster dissipations of stresses with static liquefaction.Contant volume shearing leads to cross-anisotropic stress and fabric at micro-contacts,but constant vertical stress shearing leads to complete anisotropic stress and fabric at micro-contacts.It explains the differentiating relationship between stress-strain responses and fabric anisotropy under these two conditions.Micromechanical signatures such as the slip state of micro-contacts and coordination number are also examined,providing further insights into understanding granular behaviour under bi-directional shear.
