This paper presents a risk-informed data-driven safe control design approach for a class of stochastic uncertain nonlinear discrete-time systems.The nonlinear system is modeled using linear parameter-varying(LPV)syste...This paper presents a risk-informed data-driven safe control design approach for a class of stochastic uncertain nonlinear discrete-time systems.The nonlinear system is modeled using linear parameter-varying(LPV)systems.A model-based probabilistic safe controller is first designed to guarantee probabilisticλ-contractivity(i.e.,stability and invariance)of the LPV system with respect to a given polyhedral safe set.To obviate the requirement of knowing the LPV system model and to bypass identifying its open-loop model,its closed-loop data-based representation is provided in terms of state and scheduling data as well as a decision variable.It is shown that the variance of the closedloop system,as well as the probability of safety satisfaction,depends on the decision variable and the noise covariance.A minimum-variance direct data-driven gain-scheduling safe control design approach is presented next by designing the decision variable such that all possible closed-loop system realizations satisfy safety with the highest confidence level.This minimum-variance approach is a control-oriented learning method since it minimizes the variance of the state of the closed-loop system with respect to the safe set,and thus minimizes the risk of safety violation.Unlike the certainty-equivalent approach that results in a risk-neutral control design,the minimum-variance method leads to a risk-averse control design.It is shown that the presented direct risk-averse learning approach requires weaker data richness conditions than existing indirect learning methods based on system identification and can lead to a lower risk of safety violation.Two simulation examples along with an experimental validation on an autonomous vehicle are provided to show the effectiveness of the presented approach.展开更多
现有电力负荷预测方法面临诸多挑战,尤其是在考虑气象因素对负荷波动的影响时,传统方法往往忽视气象特征与负荷之间复杂的非线性关系,导致预测精度不足。对此文中提出一种基于气象相似日修正(meteorological similar day correction,MS...现有电力负荷预测方法面临诸多挑战,尤其是在考虑气象因素对负荷波动的影响时,传统方法往往忽视气象特征与负荷之间复杂的非线性关系,导致预测精度不足。对此文中提出一种基于气象相似日修正(meteorological similar day correction,MSDC)和改进鹦鹉优化(improved parrot optimizer,IPO)线性分解(decomposition-based linear,DLinear)的日前电力负荷预测模型。首先运用Logistic映射、自适应变异策略、螺旋波动搜索IPO对DLinear超参数进行优化,然后由DLinear提取数据的周期性和趋势性特征,最后通过比对气象特征欧氏距离修正负荷预测值,形成基于IPO-DLinear-MSDC的日前电力负荷预测模型。采用2024年6月至10月湖南株洲地区总电力负荷数据集进行仿真分析,IPO-DLinear-MSDC模型的输出平均绝对百分比误差(mean absolute percentage error,MAPE)、决定系数R2分别为4.67%、0.833,相较于IPO-DLinear与PO-DLinear模型,MAPE分别下降了0.83个百分点、1.43个百分点,R2分别提升了0.074、0.125。展开更多
The growing prevalence of exercise-induced tibial stress fractures demands wearable sensors capable of monitoring dynamic musculoskeletal loads with medical-grade precision.While flexible pressure-sensing insoles show...The growing prevalence of exercise-induced tibial stress fractures demands wearable sensors capable of monitoring dynamic musculoskeletal loads with medical-grade precision.While flexible pressure-sensing insoles show clinical potential,their development has been hindered by the intrinsic trade-off between high sensitivity and full-range linearity(R^(2)>0.99 up to 1 MPa)in conventional designs.Inspired by the tactile sensing mechanism of human skin,where dermal stratification enables wide-range pressure adaptation and ion-channelregulated signaling maintains linear electrical responses,we developed a dual-mechanism flexible iontronic pressure sensor(FIPS).This innovative design synergistically combines two bioinspired components:interdigitated fabric microstructures enabling pressure-proportional contact area expansion(αP1/3)and iontronic film facilitating self-adaptive ion concentration modulation(αP^(2/3)),which together generate a linear capacitance-pressure response(CαP).The FIPS achieves breakthrough performance:242 kPa^(-1)sensitivity with 0.997linearity across 0-1 MPa,yielding a record linear sensing factor(LSF=242,000).The design is validated across various substrates and ionic materials,demonstrating its versatility.Finally,the FIPS-driven design enables a smart insole demonstrating 1.8%error in tibial load assessment during gait analysis,outperforming nonlinear counterparts(6.5%error)in early fracture-risk prediction.The biomimetic design framework establishes a universal approach for developing high-performance linear sensors,establishing generalized principles for medical-grade wearable devices.展开更多
Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects...Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects as nextgeneration microwave receivers.Linear gain and linear dynamic range(LDR)are critical metrics for assessing receiver sensitivity and demodulation fidelity,respectively.We numerically solve the four-level master equation and then employ particle swarm optimization(PSO)algorithm to co-optimize linear gain and LDR in atomic superheterodyne receivers based on balanced homodyne detection.Further,we systematically account for dominant dephasing mechanisms in the simulation,encompassing spontaneous decay,transit dephasing,collision dephasing,laser linewidth dephasing,and Doppler averaging.Homodyne readout utilizes both the real and imaginary parts of polarizability for sensing.In the case of the photon shot noise limit,its signal-to-noise ratio(SNR)expression resembles that of direct optical-intensity readout.However,the inherent coherent subtraction operation in homodyne detection significantly suppresses common-mode noise,while appropriately increasing the reference beam power enhances the gain in practical experiments.Indeed,this co-optimization problem,characterized by a high-dimensional variable space,two objectives,and non-convexity,is well-suited for solution by PSO.In addition,probe and coupling detuning contribute equivalently to polarizability and compensate for each other owing to Doppler averaging,thereby reducing the optimization variable space by one.By adopting a product form of linear gain and LDR as the fitness function,the PSO achieves rapid convergence.Here,the effectiveness of the PSO results is verified via the total harmonic distortion(THD).The relative error-based LDR calculation method we proposed efficiently measures receiver response linearity with consuming fewer computational resources.This research is expected to offer valuable insights into enhancing the performance of Rydberg-atom-based superheterodyne receivers.展开更多
In this paper,we study a class of Linear Fractional Programming on a nonempty bounded set,called the Problem(LFP),and design a branch and bound algorithm to find the global optimal solution of the problem(LFP).First,w...In this paper,we study a class of Linear Fractional Programming on a nonempty bounded set,called the Problem(LFP),and design a branch and bound algorithm to find the global optimal solution of the problem(LFP).First,we convert the problem(LFP)to the equivalent problem(EP2).Secondly,by applying the linear relaxation technique to the problem(EP2),the linear relaxation programming problem(LRP2Y)was obtained.Then,the overall framework of the algorithm is given,and the convergence and complexity of the algorithm are analyzed.Finally,experimental results are listed to illustrate the effectiveness of the algorithm.展开更多
Knowing the precise relationship between fuel loading and reactivity is essential for guiding reactor criticality extrapolation and online refueling in molten salt reactors(MSRs).This study aims to explore and explain...Knowing the precise relationship between fuel loading and reactivity is essential for guiding reactor criticality extrapolation and online refueling in molten salt reactors(MSRs).This study aims to explore and explain the linear relationship between reactivity and the reciprocal of uranium concentration in thermal-spectrum MSRs.By applying neutron balance theory,we analyzed the neutron absorption cross sections of various nuclides in single-lattice models with varying fuel concentrations.Our findings reveal a simple linear correlation between reactivity and the reciprocal of uranium concentration,which can be explained from the perspective of nuclear reaction cross sections that adhere to the 1/v law in the thermal neutron spectrum.Furthermore,we identified that the neutron absorption single-group cross sections of structural materials and carrier salts exhibit an approximately linear relationship with the fission single-group cross section of ^(235) U;similarly,the reciprocal of ^(235)U’s fission cross section exhibits an approximately linear relationship with uranium concentration.This linear relationship deviates as the volume fraction of molten salt increases,due to a greater proportion of neutrons being captured in the resonance energy spectrum.However,it remains valid for molten salt volume fractions up to 25%and demonstrates broad applicability in the physical design and operation of thermal molten salt reactors.展开更多
The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programmi...The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programming(LGP)has been developed for a full-scale annular ramjet combustor.The LGP is used to generate control laws that include multi-frequency forcing.These laws are then transformed into square waves to actuate the solenoid valve,which modulates the kerosene supply for open-loop control.The results show that the duty cycle has little effect on instability amplitude,whereas an increase in frequency leads to a remarked reduction in combustion amplitude.After five generations evolvements,the pressure amplitude is reduced by 40.6% under the optimal control law generated by LGP.Furthermore,the machine learning process is depicted using a proximity map of control law similarity,with the search pathway visualized by the steepest descent.All individuals go forward to the upper left corner of the map with the evolution process,terminating at the optimal individual of the fifth generation.展开更多
NaNbO_(3)-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors.However,their development is hindered by low recoverable energy storage density(W_(rec))and...NaNbO_(3)-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors.However,their development is hindered by low recoverable energy storage density(W_(rec))and energy storage efficiency(η).Herein,novel NaNbO_(3)-based ceramics,(1-x)[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–xCaTiO_(3),were created by adding CaTiO_(3) linear dielectric,aiming to improve their energy storage performance(ESP).The phase structure,microstructure,dielectric properties,energy storage and charge–discharge performances of the ceramics were methodically analyzed.All components of the ceramics exhibit a perovskite structure consisting of two phases:antiferroelectric P-phase(AFE P)and antiferroelectric R-phase(AFE R),with the AFE R phase increasing as x rises.All ceramic surfaces exhibit clear grain morphology.The resultant ceramics have an appropriate dielectric constant and a small dielectric loss,which are beneficial for improving breakdown field strength(E_(b)).Finally,at an E_(b) of 470 kV/cm,0.85[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–0.15CaTiO_(3) ceramic achieves optimal ESP:W_(rec)=3.9 J/cm^(3),η=72.49%.In addition,it has remarkable stability with temperature and frequency in energy storage and displays ultrafast speed in the charge–discharge process(t_(0.9)=27 ns).展开更多
During the use of robotics in applications such as antiterrorism or combat,a motion-constrained pursuer vehicle,such as a Dubins unmanned surface vehicle(USV),must get close enough(within a prescribed zero or positive...During the use of robotics in applications such as antiterrorism or combat,a motion-constrained pursuer vehicle,such as a Dubins unmanned surface vehicle(USV),must get close enough(within a prescribed zero or positive distance)to a moving target as quickly as possible,resulting in the extended minimum-time intercept problem(EMTIP).Existing research has primarily focused on the zero-distance intercept problem,MTIP,establishing the necessary or sufficient conditions for MTIP optimality,and utilizing analytic algorithms,such as root-finding algorithms,to calculate the optimal solutions.However,these approaches depend heavily on the properties of the analytic algorithm,making them inapplicable when problem settings change,such as in the case of a positive effective range or complicated target motions outside uniform rectilinear motion.In this study,an approach employing a high-accuracy and quality-guaranteed mixed-integer piecewise-linear program(QG-PWL)is proposed for the EMTIP.This program can accommodate different effective interception ranges and complicated target motions(variable velocity or complicated trajectories).The high accuracy and quality guarantees of QG-PWL originate from elegant strategies such as piecewise linearization and other developed operation strategies.The approximate error in the intercept path length is proved to be bounded to h^(2)/(4√2),where h is the piecewise length.展开更多
In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-f...In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-field air-burst experiments are conducted.The damage modes and characteristics of the target plates are compared and analyzed.Each flat plate section is completely punctured,resulting in a penetration hole.The damage modes induced by the three charge types on the stiffened plate structure are consistent,characterized by shear failure in the central region of the flat plate due to penetration by the penetrator,localized plastic deformation of the flat plate,and local penetration failure resulting from partial perforation of the central stiffener.The penetration lengths caused by ELSC and ELEFP are 45.1%and 46.1% larger than that of LSC,while the half-width of the penetration hole generated by ELEFP is 54.2% and 24.7% smaller than that of ELSC and LSC,respectively.The penetration height caused by ELEFP are 17.5%and 62.1% larger than that of ELSC and LSC,respectively.The stiffener effectively segments the damage area,enhancing the local structural strength and limiting the extent of plastic deformation in the flat plate section.The comparative results show that the ELSC proves to be more effective for efficient large-scale damage,and ELEFP is more suitable for achieving efficient localized damage.展开更多
Dear Editor,Linear and whorled nevoid hypermelanosis(LWNH)is a rare,sporadic pigmentary disorder characterized by hyperpigmented macules arranged in linear streaks and whorls along Blaschko's lines,typically appea...Dear Editor,Linear and whorled nevoid hypermelanosis(LWNH)is a rare,sporadic pigmentary disorder characterized by hyperpigmented macules arranged in linear streaks and whorls along Blaschko's lines,typically appearing within the first few weeks of life[1],and remains a challenge to treat.Here,we report a case of LWNH and review the relevant literature to help clinicians better understand this disease.展开更多
A high-speed train travelling from the open air into a narrow tunnel will cause the“sonic boom”at tunnel exit.When the maglev train’s speed reaches 600 km/h,the train-tunnel aerodynamic effect is intensified,so a n...A high-speed train travelling from the open air into a narrow tunnel will cause the“sonic boom”at tunnel exit.When the maglev train’s speed reaches 600 km/h,the train-tunnel aerodynamic effect is intensified,so a new mitigation method is urgently expected to be explored.This study proposed a novel asymptotic linear method(ALM)for micro pressure wave(MPW)mitigation to achieve a constant gradient of initial c ompression waves(ICWs),via a study with various open ratios on hoods.The properties of ICWs and MPWs under various open ratios of hoods were analyzed.The results show that as the open ratio increases,the MPW amplitude at the tunnel exit initially decreases before rising.At the open ratio of 2.28%,the slope of the ICW curve is linearly coincident with a supposed straight line in the ALM,which further reduces the MPW amplitude by 26.9%at 20 m and 20.0%at 50 m from the exit,as compared to the unvented hood.Therefore,the proposed method effectively mitigates MPW and quickly determines the upper limit of alleviation for the MPW amplitude at a fixed train-tunnel operation condition.All achievements provide a ne w potential measure for the adaptive design of tunnel hoods.展开更多
The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the micr...The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the microstructure evolution and mechanical properties of the joint was analyzed,and the joint electrochemical corrosion behavior as well as the hot corrosion behavior was studied.The results show that the joint hardness of Base Metal(BM)increases after pre-weld heat treatment,and the strengthening phasesγ′andγ″further precipitate.However,the precipitation phases dissolve significantly in the Weld Zone(WZ)due to the thermal process of LFW.The corrosion resistance in BM is reduced after the pre-weld heat treatment,while it is similar in WZ with a slight decrease.The surface morphology of the BM and WZ can be generally divided into a loose and porous matrix and a scattered oxide particle layer after hot corrosion.The joint cross section exhibits a Cr-depleted zone with the diffusion of Cr to form an oxide film.The corrosion product mainly consists of Fe_(2)O_(3)/Fe_(3)O_(4) as the outer layer and Cr_(2)O_(3) as the inner layer.展开更多
GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 58...GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 582 MPa and 820 MPa,respectively.The HCF strength of joint reaches 400 MPa,which is slightly lower than that of Base Metal(BM),indicating reliable quality of this type of joint.The microstructure observation results show that all cracks initiate at the inside of specimens and transfer into deeper region with decrease of external stress,and the crack initiation site is related with microhardness of matrix.The Electron Backscattered Diffraction(EBSD)results of the observed regions with different distances to fracture show that plastic deformation plays a key role in HCF,and the Schmid factor of most grains near fracture exceeds 0.4.In addition,the generation of twins plays a vital role in strain concentration release and coordinating plastic deformation among grains.展开更多
This paper is concerned with event-triggered control of discrete-time systems with or without input saturation.First,an accumulative-error-based event-triggered scheme is devised for control updates.When the accumulat...This paper is concerned with event-triggered control of discrete-time systems with or without input saturation.First,an accumulative-error-based event-triggered scheme is devised for control updates.When the accumulated error between the current state and the latest control update exceeds a certain threshold,an event is triggered.Such a scheme can ensure the event-generator works at a relatively low rate rather than falls into hibernation especially after the system steps into its steady state.Second,the looped functional method for continuous-time systems is extended to discrete-time systems.By introducing an innovative looped functional that links the event-triggered scheme,some sufficient conditions for the co-design of control gain and event-triggered parameters are obtained in terms of linear matrix inequalities with a couple of tuning parameters.Then,the proposed method is applied to discrete-time systems with input saturation.As a result,both suitable control gains and event-triggered parameters are also co-designed to ensure the system trajectories converge to the region of attraction.Finally,an unstable reactor system and an inverted pendulum system are given to show the effectiveness of the proposed method.展开更多
The hyperloop idea,which is one of the most ecofriendly,low-carbon emissions,and fossil fuel-efficient modes of transportation,has recently become quite popular.In this study,a double-sided linear induction motor(LIM)...The hyperloop idea,which is one of the most ecofriendly,low-carbon emissions,and fossil fuel-efficient modes of transportation,has recently become quite popular.In this study,a double-sided linear induction motor(LIM)with 500 W of output power,60 N of thrust force and 200 V/38.58 Hz of supply voltage was designed to be used in hyperloop development competition hosted by the scientific and technological research council of turkey(TüB?TAK)rail transportation technologies institute(RUTE).In contrast to the studies in the literature,concentrated winding is preferred instead of distributed winding due to mechanical constraints.The electromagnetic design of LIM,whose mechanical and electrical requirements were determined considering the hyperloop development competition,was carried out by following certain steps.Then,the designed model was simulated and analyzed by finite element method(FEM),and the necessary optimizations have been performed to improve the motor characteristics.By examining the final model,the applicability of the concentrated winding type LIM for hyperloop technology has been investigated.Besides,the effects of primary material,railway material,and mechanical air-gap length on LIM performance were also investigated.In the practical phase of the study,the designed LIM has been prototyped and tested.The validation of the experimental results was achieved through good agreement with the finite element analysis results.展开更多
Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this cha...Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.展开更多
Let a_(1),a_(2),a_(3)be nonzero integers with gcd(a_(1),a_(2),a_(3))=1,and let k be any positive integer,K=max[3,|a_(1)|,|a_(2)|,|a_(3)|,k].Suppose that l_(1),l_(2),l_(3)are integers each coprime to k.Suppose further ...Let a_(1),a_(2),a_(3)be nonzero integers with gcd(a_(1),a_(2),a_(3))=1,and let k be any positive integer,K=max[3,|a_(1)|,|a_(2)|,|a_(3)|,k].Suppose that l_(1),l_(2),l_(3)are integers each coprime to k.Suppose further that b is any integer satisfying some necessary congruent conditions.The solvability of linear equation a_(1)p_(1)+a_(2)p_(2)+a_(3)p_(3)=b(p_(j)=l_(j)(mod k),1≤j≤3)with prime variables pi,p_(2),ps is investigated.It is proved that if ai,a_(2),a_(3)are all positive,then the above equation is solvable whenever b≥K^(25);if a,a_(2),a_(3)are not all of the same sign,then the above equation has a solution p_(1),p_(2),p_(3)satisfying max(p_(1),p_(2),p_(3))≤3|b|+K^(25).展开更多
Incremental Nonlinear Dynamic Inversion(INDI)is a control approach that has gained popularity in flight control over the past decade.Besides the INDI law,several common additional components complement an INDI-based c...Incremental Nonlinear Dynamic Inversion(INDI)is a control approach that has gained popularity in flight control over the past decade.Besides the INDI law,several common additional components complement an INDI-based controller.This paper,the second part of a two-part series of surveys on INDI,aims to summarize the modern trends in INDI and its related components.Besides a comprehensive components specification,it addresses their most common challenges,compares different variants,and discusses proposed advances.Further important aspects of INDI are gain design,stability,and robustness.This paper also provides an overview of research conducted concerning these aspects.This paper is written in a tutorial style to familiarize researchers with the essential specifics and pitfalls of INDI and its components.At the same time,it can also serve as a reference for readers already familiar with INDI.展开更多
基金supported in part by the Department of Navy award (N00014-22-1-2159)the National Science Foundation under award (ECCS-2227311)。
文摘This paper presents a risk-informed data-driven safe control design approach for a class of stochastic uncertain nonlinear discrete-time systems.The nonlinear system is modeled using linear parameter-varying(LPV)systems.A model-based probabilistic safe controller is first designed to guarantee probabilisticλ-contractivity(i.e.,stability and invariance)of the LPV system with respect to a given polyhedral safe set.To obviate the requirement of knowing the LPV system model and to bypass identifying its open-loop model,its closed-loop data-based representation is provided in terms of state and scheduling data as well as a decision variable.It is shown that the variance of the closedloop system,as well as the probability of safety satisfaction,depends on the decision variable and the noise covariance.A minimum-variance direct data-driven gain-scheduling safe control design approach is presented next by designing the decision variable such that all possible closed-loop system realizations satisfy safety with the highest confidence level.This minimum-variance approach is a control-oriented learning method since it minimizes the variance of the state of the closed-loop system with respect to the safe set,and thus minimizes the risk of safety violation.Unlike the certainty-equivalent approach that results in a risk-neutral control design,the minimum-variance method leads to a risk-averse control design.It is shown that the presented direct risk-averse learning approach requires weaker data richness conditions than existing indirect learning methods based on system identification and can lead to a lower risk of safety violation.Two simulation examples along with an experimental validation on an autonomous vehicle are provided to show the effectiveness of the presented approach.
文摘现有电力负荷预测方法面临诸多挑战,尤其是在考虑气象因素对负荷波动的影响时,传统方法往往忽视气象特征与负荷之间复杂的非线性关系,导致预测精度不足。对此文中提出一种基于气象相似日修正(meteorological similar day correction,MSDC)和改进鹦鹉优化(improved parrot optimizer,IPO)线性分解(decomposition-based linear,DLinear)的日前电力负荷预测模型。首先运用Logistic映射、自适应变异策略、螺旋波动搜索IPO对DLinear超参数进行优化,然后由DLinear提取数据的周期性和趋势性特征,最后通过比对气象特征欧氏距离修正负荷预测值,形成基于IPO-DLinear-MSDC的日前电力负荷预测模型。采用2024年6月至10月湖南株洲地区总电力负荷数据集进行仿真分析,IPO-DLinear-MSDC模型的输出平均绝对百分比误差(mean absolute percentage error,MAPE)、决定系数R2分别为4.67%、0.833,相较于IPO-DLinear与PO-DLinear模型,MAPE分别下降了0.83个百分点、1.43个百分点,R2分别提升了0.074、0.125。
基金supported by the National Natural Science Foundation of China(NSFC 52175281,52475315)Youth Innovation Promotion Association of CAS(2021382)。
文摘The growing prevalence of exercise-induced tibial stress fractures demands wearable sensors capable of monitoring dynamic musculoskeletal loads with medical-grade precision.While flexible pressure-sensing insoles show clinical potential,their development has been hindered by the intrinsic trade-off between high sensitivity and full-range linearity(R^(2)>0.99 up to 1 MPa)in conventional designs.Inspired by the tactile sensing mechanism of human skin,where dermal stratification enables wide-range pressure adaptation and ion-channelregulated signaling maintains linear electrical responses,we developed a dual-mechanism flexible iontronic pressure sensor(FIPS).This innovative design synergistically combines two bioinspired components:interdigitated fabric microstructures enabling pressure-proportional contact area expansion(αP1/3)and iontronic film facilitating self-adaptive ion concentration modulation(αP^(2/3)),which together generate a linear capacitance-pressure response(CαP).The FIPS achieves breakthrough performance:242 kPa^(-1)sensitivity with 0.997linearity across 0-1 MPa,yielding a record linear sensing factor(LSF=242,000).The design is validated across various substrates and ionic materials,demonstrating its versatility.Finally,the FIPS-driven design enables a smart insole demonstrating 1.8%error in tibial load assessment during gait analysis,outperforming nonlinear counterparts(6.5%error)in early fracture-risk prediction.The biomimetic design framework establishes a universal approach for developing high-performance linear sensors,establishing generalized principles for medical-grade wearable devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62331024 and 62571549)the National Key Research and Development Program of China(Grant No.2022YFB2802804)。
文摘Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects as nextgeneration microwave receivers.Linear gain and linear dynamic range(LDR)are critical metrics for assessing receiver sensitivity and demodulation fidelity,respectively.We numerically solve the four-level master equation and then employ particle swarm optimization(PSO)algorithm to co-optimize linear gain and LDR in atomic superheterodyne receivers based on balanced homodyne detection.Further,we systematically account for dominant dephasing mechanisms in the simulation,encompassing spontaneous decay,transit dephasing,collision dephasing,laser linewidth dephasing,and Doppler averaging.Homodyne readout utilizes both the real and imaginary parts of polarizability for sensing.In the case of the photon shot noise limit,its signal-to-noise ratio(SNR)expression resembles that of direct optical-intensity readout.However,the inherent coherent subtraction operation in homodyne detection significantly suppresses common-mode noise,while appropriately increasing the reference beam power enhances the gain in practical experiments.Indeed,this co-optimization problem,characterized by a high-dimensional variable space,two objectives,and non-convexity,is well-suited for solution by PSO.In addition,probe and coupling detuning contribute equivalently to polarizability and compensate for each other owing to Doppler averaging,thereby reducing the optimization variable space by one.By adopting a product form of linear gain and LDR as the fitness function,the PSO achieves rapid convergence.Here,the effectiveness of the PSO results is verified via the total harmonic distortion(THD).The relative error-based LDR calculation method we proposed efficiently measures receiver response linearity with consuming fewer computational resources.This research is expected to offer valuable insights into enhancing the performance of Rydberg-atom-based superheterodyne receivers.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12571317 and 12071133).
文摘In this paper,we study a class of Linear Fractional Programming on a nonempty bounded set,called the Problem(LFP),and design a branch and bound algorithm to find the global optimal solution of the problem(LFP).First,we convert the problem(LFP)to the equivalent problem(EP2).Secondly,by applying the linear relaxation technique to the problem(EP2),the linear relaxation programming problem(LRP2Y)was obtained.Then,the overall framework of the algorithm is given,and the convergence and complexity of the algorithm are analyzed.Finally,experimental results are listed to illustrate the effectiveness of the algorithm.
基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2020261)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA02010000)the Young Potential Program of the Shanghai Institute of Applied Physics,Chinese Academy of Sciences(No.SINAP-YXJH-202412)。
文摘Knowing the precise relationship between fuel loading and reactivity is essential for guiding reactor criticality extrapolation and online refueling in molten salt reactors(MSRs).This study aims to explore and explain the linear relationship between reactivity and the reciprocal of uranium concentration in thermal-spectrum MSRs.By applying neutron balance theory,we analyzed the neutron absorption cross sections of various nuclides in single-lattice models with varying fuel concentrations.Our findings reveal a simple linear correlation between reactivity and the reciprocal of uranium concentration,which can be explained from the perspective of nuclear reaction cross sections that adhere to the 1/v law in the thermal neutron spectrum.Furthermore,we identified that the neutron absorption single-group cross sections of structural materials and carrier salts exhibit an approximately linear relationship with the fission single-group cross section of ^(235) U;similarly,the reciprocal of ^(235)U’s fission cross section exhibits an approximately linear relationship with uranium concentration.This linear relationship deviates as the volume fraction of molten salt increases,due to a greater proportion of neutrons being captured in the resonance energy spectrum.However,it remains valid for molten salt volume fractions up to 25%and demonstrates broad applicability in the physical design and operation of thermal molten salt reactors.
基金support from the National Natural Science Foundation of China(No.12002372)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2022QNRC001)the Natural Science Foundation of Hunan Province,China(No.2021JJ40674)。
文摘The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programming(LGP)has been developed for a full-scale annular ramjet combustor.The LGP is used to generate control laws that include multi-frequency forcing.These laws are then transformed into square waves to actuate the solenoid valve,which modulates the kerosene supply for open-loop control.The results show that the duty cycle has little effect on instability amplitude,whereas an increase in frequency leads to a remarked reduction in combustion amplitude.After five generations evolvements,the pressure amplitude is reduced by 40.6% under the optimal control law generated by LGP.Furthermore,the machine learning process is depicted using a proximity map of control law similarity,with the search pathway visualized by the steepest descent.All individuals go forward to the upper left corner of the map with the evolution process,terminating at the optimal individual of the fifth generation.
基金Project supported by the Natural Science Foundation of Anhui Provincial Education Department(Grant No.KJ2019A0054)。
文摘NaNbO_(3)-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors.However,their development is hindered by low recoverable energy storage density(W_(rec))and energy storage efficiency(η).Herein,novel NaNbO_(3)-based ceramics,(1-x)[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–xCaTiO_(3),were created by adding CaTiO_(3) linear dielectric,aiming to improve their energy storage performance(ESP).The phase structure,microstructure,dielectric properties,energy storage and charge–discharge performances of the ceramics were methodically analyzed.All components of the ceramics exhibit a perovskite structure consisting of two phases:antiferroelectric P-phase(AFE P)and antiferroelectric R-phase(AFE R),with the AFE R phase increasing as x rises.All ceramic surfaces exhibit clear grain morphology.The resultant ceramics have an appropriate dielectric constant and a small dielectric loss,which are beneficial for improving breakdown field strength(E_(b)).Finally,at an E_(b) of 470 kV/cm,0.85[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–0.15CaTiO_(3) ceramic achieves optimal ESP:W_(rec)=3.9 J/cm^(3),η=72.49%.In addition,it has remarkable stability with temperature and frequency in energy storage and displays ultrafast speed in the charge–discharge process(t_(0.9)=27 ns).
基金supported by the National Natural Sci‐ence Foundation of China(Grant No.62306325)。
文摘During the use of robotics in applications such as antiterrorism or combat,a motion-constrained pursuer vehicle,such as a Dubins unmanned surface vehicle(USV),must get close enough(within a prescribed zero or positive distance)to a moving target as quickly as possible,resulting in the extended minimum-time intercept problem(EMTIP).Existing research has primarily focused on the zero-distance intercept problem,MTIP,establishing the necessary or sufficient conditions for MTIP optimality,and utilizing analytic algorithms,such as root-finding algorithms,to calculate the optimal solutions.However,these approaches depend heavily on the properties of the analytic algorithm,making them inapplicable when problem settings change,such as in the case of a positive effective range or complicated target motions outside uniform rectilinear motion.In this study,an approach employing a high-accuracy and quality-guaranteed mixed-integer piecewise-linear program(QG-PWL)is proposed for the EMTIP.This program can accommodate different effective interception ranges and complicated target motions(variable velocity or complicated trajectories).The high accuracy and quality guarantees of QG-PWL originate from elegant strategies such as piecewise linearization and other developed operation strategies.The approximate error in the intercept path length is proved to be bounded to h^(2)/(4√2),where h is the piecewise length.
基金supported by the National Natural Science Foundation of China(Grant Nos.52271307,52061135107,52192692,11802025)the Liao Ning Excellent Youth Fund Program(Grant No.2023JH3/10200012)+1 种基金the Liao Ning Revitalization Tal-ents Program(Grant No.XLYC1908027)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT20RC(3)025,DUT20TD108,DUT20LAB308)。
文摘In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-field air-burst experiments are conducted.The damage modes and characteristics of the target plates are compared and analyzed.Each flat plate section is completely punctured,resulting in a penetration hole.The damage modes induced by the three charge types on the stiffened plate structure are consistent,characterized by shear failure in the central region of the flat plate due to penetration by the penetrator,localized plastic deformation of the flat plate,and local penetration failure resulting from partial perforation of the central stiffener.The penetration lengths caused by ELSC and ELEFP are 45.1%and 46.1% larger than that of LSC,while the half-width of the penetration hole generated by ELEFP is 54.2% and 24.7% smaller than that of ELSC and LSC,respectively.The penetration height caused by ELEFP are 17.5%and 62.1% larger than that of ELSC and LSC,respectively.The stiffener effectively segments the damage area,enhancing the local structural strength and limiting the extent of plastic deformation in the flat plate section.The comparative results show that the ELSC proves to be more effective for efficient large-scale damage,and ELEFP is more suitable for achieving efficient localized damage.
文摘Dear Editor,Linear and whorled nevoid hypermelanosis(LWNH)is a rare,sporadic pigmentary disorder characterized by hyperpigmented macules arranged in linear streaks and whorls along Blaschko's lines,typically appearing within the first few weeks of life[1],and remains a challenge to treat.Here,we report a case of LWNH and review the relevant literature to help clinicians better understand this disease.
基金Project(24A0006)supported by the Key Project of Scientific Research Fund of Hunan Provincial Department of Education,ChinaProject(2024JJ5430)supported by the Natural Science Foundation of Hunan Province,ChinaProjects(2024JK2045,2023RC3061)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘A high-speed train travelling from the open air into a narrow tunnel will cause the“sonic boom”at tunnel exit.When the maglev train’s speed reaches 600 km/h,the train-tunnel aerodynamic effect is intensified,so a new mitigation method is urgently expected to be explored.This study proposed a novel asymptotic linear method(ALM)for micro pressure wave(MPW)mitigation to achieve a constant gradient of initial c ompression waves(ICWs),via a study with various open ratios on hoods.The properties of ICWs and MPWs under various open ratios of hoods were analyzed.The results show that as the open ratio increases,the MPW amplitude at the tunnel exit initially decreases before rising.At the open ratio of 2.28%,the slope of the ICW curve is linearly coincident with a supposed straight line in the ALM,which further reduces the MPW amplitude by 26.9%at 20 m and 20.0%at 50 m from the exit,as compared to the unvented hood.Therefore,the proposed method effectively mitigates MPW and quickly determines the upper limit of alleviation for the MPW amplitude at a fixed train-tunnel operation condition.All achievements provide a ne w potential measure for the adaptive design of tunnel hoods.
基金supported by the National Natural Science Foundation of China(Nos.52074228,52305420 and 51875470)the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University,China(No.PF2024053)the Xi’an Beilin District Science and Technology Planning Project,China(No.GX2349).
文摘The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the microstructure evolution and mechanical properties of the joint was analyzed,and the joint electrochemical corrosion behavior as well as the hot corrosion behavior was studied.The results show that the joint hardness of Base Metal(BM)increases after pre-weld heat treatment,and the strengthening phasesγ′andγ″further precipitate.However,the precipitation phases dissolve significantly in the Weld Zone(WZ)due to the thermal process of LFW.The corrosion resistance in BM is reduced after the pre-weld heat treatment,while it is similar in WZ with a slight decrease.The surface morphology of the BM and WZ can be generally divided into a loose and porous matrix and a scattered oxide particle layer after hot corrosion.The joint cross section exhibits a Cr-depleted zone with the diffusion of Cr to form an oxide film.The corrosion product mainly consists of Fe_(2)O_(3)/Fe_(3)O_(4) as the outer layer and Cr_(2)O_(3) as the inner layer.
基金supported by the National Natural Science Foundation of China(Nos.52074228,52305420,and 51875470)the China Postdoctoral Science Foundation(No.2023M742830)。
文摘GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 582 MPa and 820 MPa,respectively.The HCF strength of joint reaches 400 MPa,which is slightly lower than that of Base Metal(BM),indicating reliable quality of this type of joint.The microstructure observation results show that all cracks initiate at the inside of specimens and transfer into deeper region with decrease of external stress,and the crack initiation site is related with microhardness of matrix.The Electron Backscattered Diffraction(EBSD)results of the observed regions with different distances to fracture show that plastic deformation plays a key role in HCF,and the Schmid factor of most grains near fracture exceeds 0.4.In addition,the generation of twins plays a vital role in strain concentration release and coordinating plastic deformation among grains.
基金supported in part by the National Natural Science Foundation of China(62473221)the Natural Science Foundation of Shandong Province,China(ZR2024MF006)Qingdao Natural Science Foundation(24-4-4-zrjj-165-jch)。
文摘This paper is concerned with event-triggered control of discrete-time systems with or without input saturation.First,an accumulative-error-based event-triggered scheme is devised for control updates.When the accumulated error between the current state and the latest control update exceeds a certain threshold,an event is triggered.Such a scheme can ensure the event-generator works at a relatively low rate rather than falls into hibernation especially after the system steps into its steady state.Second,the looped functional method for continuous-time systems is extended to discrete-time systems.By introducing an innovative looped functional that links the event-triggered scheme,some sufficient conditions for the co-design of control gain and event-triggered parameters are obtained in terms of linear matrix inequalities with a couple of tuning parameters.Then,the proposed method is applied to discrete-time systems with input saturation.As a result,both suitable control gains and event-triggered parameters are also co-designed to ensure the system trajectories converge to the region of attraction.Finally,an unstable reactor system and an inverted pendulum system are given to show the effectiveness of the proposed method.
基金the Istanbul Technical University Scientific Research Projects Unit with grant number MGA-2022-43948。
文摘The hyperloop idea,which is one of the most ecofriendly,low-carbon emissions,and fossil fuel-efficient modes of transportation,has recently become quite popular.In this study,a double-sided linear induction motor(LIM)with 500 W of output power,60 N of thrust force and 200 V/38.58 Hz of supply voltage was designed to be used in hyperloop development competition hosted by the scientific and technological research council of turkey(TüB?TAK)rail transportation technologies institute(RUTE).In contrast to the studies in the literature,concentrated winding is preferred instead of distributed winding due to mechanical constraints.The electromagnetic design of LIM,whose mechanical and electrical requirements were determined considering the hyperloop development competition,was carried out by following certain steps.Then,the designed model was simulated and analyzed by finite element method(FEM),and the necessary optimizations have been performed to improve the motor characteristics.By examining the final model,the applicability of the concentrated winding type LIM for hyperloop technology has been investigated.Besides,the effects of primary material,railway material,and mechanical air-gap length on LIM performance were also investigated.In the practical phase of the study,the designed LIM has been prototyped and tested.The validation of the experimental results was achieved through good agreement with the finite element analysis results.
基金funded by the National Key R&D Program of China(Grant No.2022YFC2903904)the National Natural Science Foundation of China(Grant Nos.51904057 and U1906208).
文摘Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.
文摘Let a_(1),a_(2),a_(3)be nonzero integers with gcd(a_(1),a_(2),a_(3))=1,and let k be any positive integer,K=max[3,|a_(1)|,|a_(2)|,|a_(3)|,k].Suppose that l_(1),l_(2),l_(3)are integers each coprime to k.Suppose further that b is any integer satisfying some necessary congruent conditions.The solvability of linear equation a_(1)p_(1)+a_(2)p_(2)+a_(3)p_(3)=b(p_(j)=l_(j)(mod k),1≤j≤3)with prime variables pi,p_(2),ps is investigated.It is proved that if ai,a_(2),a_(3)are all positive,then the above equation is solvable whenever b≥K^(25);if a,a_(2),a_(3)are not all of the same sign,then the above equation has a solution p_(1),p_(2),p_(3)satisfying max(p_(1),p_(2),p_(3))≤3|b|+K^(25).
文摘Incremental Nonlinear Dynamic Inversion(INDI)is a control approach that has gained popularity in flight control over the past decade.Besides the INDI law,several common additional components complement an INDI-based controller.This paper,the second part of a two-part series of surveys on INDI,aims to summarize the modern trends in INDI and its related components.Besides a comprehensive components specification,it addresses their most common challenges,compares different variants,and discusses proposed advances.Further important aspects of INDI are gain design,stability,and robustness.This paper also provides an overview of research conducted concerning these aspects.This paper is written in a tutorial style to familiarize researchers with the essential specifics and pitfalls of INDI and its components.At the same time,it can also serve as a reference for readers already familiar with INDI.
