On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorab...On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.展开更多
In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Levy process. We shall prove that under some appropriate conditions, the exponential stability...In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Levy process. We shall prove that under some appropriate conditions, the exponential stability of the solutions holds. Finally, we give two examples to illustrate our results.展开更多
Using the approach of D. Landriault et al. and B. Li and X. Zhou, for a one-dimensional time-homogeneous diffusion process X and constants c 〈 a 〈 b 〈 d, we find expressions of double Laplace transforms of the form...Using the approach of D. Landriault et al. and B. Li and X. Zhou, for a one-dimensional time-homogeneous diffusion process X and constants c 〈 a 〈 b 〈 d, we find expressions of double Laplace transforms of the form Ex[e--θTd--λ∫o Td1a 〈Xs〈b ds; Td 〈 Tc], where Tx denotes the first passage time of level x. As applications, we find explicit Laplace transforms of the corresponding occupation time and occupation density for the Brownian motion with two-valued drift and that of occupation time for the skew Ornstein- Uhlenbeck process, respectively. Some known results are also recovered.展开更多
We study a strongly elliptic partial differential operator with time- varying coefficient in a parabolic diagonalizable stochastic equation driven by fractional noises. Based on the existence and uniqueness of the sol...We study a strongly elliptic partial differential operator with time- varying coefficient in a parabolic diagonalizable stochastic equation driven by fractional noises. Based on the existence and uniqueness of the solution, we then obtain a kernel estimator of time-varying coefficient and the convergence rates. An example is given to illustrate the theorem.展开更多
A guaranteed cost sliding mode control(SMC)algorithm is investigated to further improve the control accuracy of looper-tension systems in hot strip finishing mills.First,a global sliding mode surface function is desig...A guaranteed cost sliding mode control(SMC)algorithm is investigated to further improve the control accuracy of looper-tension systems in hot strip finishing mills.First,a global sliding mode surface function is designed by linear matrix inequalities and guaranteed cost technique,which can force the system states into switching region initially,and can guarantee the system robustness with a good performance during the whole control process.Then,a novel reaching law is designed,which can satisfy the sliding mode reaching conditions.Simulation results demonstrate that the proposed control scheme has good stability and robustness comparing with traditional SMC.The designed controller can regulate the strip tension and looper angle to ensure better performance,which is very suitable for complex looper systems.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12104127 and 22131006)the Doctoral Starting Up Foundation of Hebei Normal University for Nationalities(Grant No.DR2020001)+1 种基金the Clean Energy(Carbon Peaking and Carbon Neutrality)Industry Research Institute of Chengde(Grant No.202205B090)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QA060)。
文摘On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.
基金supported by National Natural Science Foundation of China(11571190)the Fundamental Research Funds for the Central Universities+3 种基金supported by the China Scholarship Council(201807315008)National Natural Science Foundation of China(11501565)the Youth Project of Humanities and Social Sciences of Ministry of Education(19YJCZH251)supported by National Natural Science Foundation of China(11701084 and 11671084)
文摘In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Levy process. We shall prove that under some appropriate conditions, the exponential stability of the solutions holds. Finally, we give two examples to illustrate our results.
基金Acknowledgements The authors thank the anonymous referees for helpful comments. Yingqiu Li's work was supported by the National Natural Science Foundation of China (Grant No. 11171044) und the Natural Science Foundation of Hunan Province (Grant No. llJ32001) Suxin Wang's work was supported by the Natural Sciences and Engineering Research Council of Canada.
文摘Using the approach of D. Landriault et al. and B. Li and X. Zhou, for a one-dimensional time-homogeneous diffusion process X and constants c 〈 a 〈 b 〈 d, we find expressions of double Laplace transforms of the form Ex[e--θTd--λ∫o Td1a 〈Xs〈b ds; Td 〈 Tc], where Tx denotes the first passage time of level x. As applications, we find explicit Laplace transforms of the corresponding occupation time and occupation density for the Brownian motion with two-valued drift and that of occupation time for the skew Ornstein- Uhlenbeck process, respectively. Some known results are also recovered.
文摘We study a strongly elliptic partial differential operator with time- varying coefficient in a parabolic diagonalizable stochastic equation driven by fractional noises. Based on the existence and uniqueness of the solution, we then obtain a kernel estimator of time-varying coefficient and the convergence rates. An example is given to illustrate the theorem.
基金supported by the Science and Technology Project of Hebei Province[grant number 15211028]the Technology Support Project of Northeastern University at Qinhuangdao[grant number XNK201604],[grant number XNK201407]+2 种基金the National Natural Science Foundation of China[grant number 61403069]the Natural Science Foundation of Hebei Province[grant number F2014501055]the Program of Science and Technology Research of Hebei University[grant number ZD20132003].
文摘A guaranteed cost sliding mode control(SMC)algorithm is investigated to further improve the control accuracy of looper-tension systems in hot strip finishing mills.First,a global sliding mode surface function is designed by linear matrix inequalities and guaranteed cost technique,which can force the system states into switching region initially,and can guarantee the system robustness with a good performance during the whole control process.Then,a novel reaching law is designed,which can satisfy the sliding mode reaching conditions.Simulation results demonstrate that the proposed control scheme has good stability and robustness comparing with traditional SMC.The designed controller can regulate the strip tension and looper angle to ensure better performance,which is very suitable for complex looper systems.