The dynamic characteristics of compacted loess are of great significance to the seismic construction of the Loess Plateau area in Northwest China,where earthquakes frequently occur.To study the change in the dynamic m...The dynamic characteristics of compacted loess are of great significance to the seismic construction of the Loess Plateau area in Northwest China,where earthquakes frequently occur.To study the change in the dynamic modulus of the foundation soil under the combined action of vertical and horizontal earthquakes,a hollow cy-lindrical torsion shear instrument capable of vibrating in four directions was used to perform two-way coupling of compression and torsion of Xi'an compacted loess under different dry density and deviator stress ratios.The results show that increasing the dry density can improve the initial dynamic compression modulus and initial dynamic shear modulus of compacted loess.With an increase in the deviator stress ratio,the initial dynamic compression modulus increases,to a certain extent,but the initial dynamic shear modulus decreases slightly.The dynamic modulus gradually decreases with the development of dynamic strain and tends to be stable,and the dynamic modulus that reaches the same strain increases with an increasing dry density.At the initial stage of dynamic loading,the attenuation of the dynamic shear modulus with the strain development is faster than that of the dynamic compression modulus.Compared with previous research results,it is determined that the dynamic modulus of loess under bidirectional dynamic loading is lower and the attenuation rate is faster than that under single-direction dynamic loading.The deviator stress ratio has a more obvious effect on the dynamic compression modulus.The increase in the deviator stress ratio can increase the dynamic compression modulus,to a certain extent.However,the deviator stress ratio has almost no effect on the dynamic shear modulus,and can therefore be ignored.展开更多
In this paper,two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyze...In this paper,two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyzed when the target and defender using the differential game guidance law based on the linear model.The core ideas underlying the two guidance laws are the attacker evading to a critical safe boundary from the defender,and then maintaining a critical miss distance.The guidance law more appropriate for the attacker to win the game differs according to the initial parameters.Unlike other guidance laws,when using the derived guidance laws there is no need to know the target and the defender’s control efforts.The results of numerical simulations show that the attacker can evade the defender and hit the target successfully by using the proposed derived guidance laws.展开更多
This paper investigates a new approach for a scenario in which an Attacker attempts to intercept a defended aerial Target. The problem is formulated as a game among three players, an Attacker, a Defender, and a Target...This paper investigates a new approach for a scenario in which an Attacker attempts to intercept a defended aerial Target. The problem is formulated as a game among three players, an Attacker, a Defender, and a Target, with bounded controls. In the considered pursuit–evasion problem, the Target uses an optimal evasion strategy and the Defender uses an optimal pursuit strategy.The proposed approach focuses on the miss distance as the outcome of the conflict. The infeasible region for the initial Zero-Effort-Miss（ZEM） distance between the Attacker and the Defender, for a scenario in which the Attacker evades the Defender, is analyzed, assuming that the Attacker uses a control effort chosen from the permitted control region. The sufficient conditions are investigated under which, for ideal players, the Attacker can pursue the Target while evading the Defender launched by the Target. The guidance provided on how the Attacker can accomplish the task is divided into two parts. During the final time between the Attacker and the Defender, the Attacker chooses the control effort that guarantees the miss distance, and then uses the optimal pursuit strategy to accomplish the task. The derived guidance law is verified by nonlinear simulation.展开更多
Fabrication of lateral heterostructures （LHS） is promising for a wide range of next-generation devices and could sufficiently unlock the potential of two-dimensional materials.Herein,we demonstrate the design of lat...Fabrication of lateral heterostructures （LHS） is promising for a wide range of next-generation devices and could sufficiently unlock the potential of two-dimensional materials.Herein,we demonstrate the design of lateral heterostructures based on new building materials,namely 1S-MX2 LHS,using first-principles calculations.1S-MX2 LHS exhibits excellent stability,demonstrating high feasibility in the experiment.The desired bandgap opening can endure application at room temperature and was confirmed in 1S-MX2 LHS with spin-orbit coupling （SOC）.A strain strategy further resulted in efficient bandgap engineering and an intriguing phase transition.We also found that black phosphorus can serve as a competent substrate to support 1S-MX2 LHS with a coveted type-Ⅱ band alignment,allowing versatile functionalized bidirectional heterostructures with built-in device functions.Furthermore,the robust electronic features could be maintained in the 1S-MX2 LHS with larger components.Our findings will not only renew interest in LHS studies by enriching their categories and properties,but also highlight the promise of these lateral heterostructures as appealing materials for future integrated devices.展开更多
This paper investigates a cooperative strategy for protecting an aerial target.The problem is solved as a game among four players（a target,two defenders,and a missile）.In this scenario,the target launches two defend...This paper investigates a cooperative strategy for protecting an aerial target.The problem is solved as a game among four players（a target,two defenders,and a missile）.In this scenario,the target launches two defenders（defender-1 and defender-2）simultaneously,to establish a oneway cooperation system（OCS）against an attacking missile.A new optimal evasion strategy for the target is also derived.During the engagement,the target takes into account the reaction of the attacking missile,and guides defender-1 to the interception point by receiving information from defender-1.Depending on the control effort of the target,defender-2 can choose appropriate launch conditions and use very limited maneuvering capability to intercept the missile.For adversaries with first-order dynamics,simulation results show that the OCS allows two defenders to intercept the missile.During the engagement,even if one defender or communication channel is broken,the OCS still allows an interception to be made,thus increasing the target’s survivability.展开更多
基金the National Natural Science Foundation of China(No.41272320,52108342)the Key Scientific Research Projects of Higher Education Institutions in Henan Province,China(No.21A560009).
文摘The dynamic characteristics of compacted loess are of great significance to the seismic construction of the Loess Plateau area in Northwest China,where earthquakes frequently occur.To study the change in the dynamic modulus of the foundation soil under the combined action of vertical and horizontal earthquakes,a hollow cy-lindrical torsion shear instrument capable of vibrating in four directions was used to perform two-way coupling of compression and torsion of Xi'an compacted loess under different dry density and deviator stress ratios.The results show that increasing the dry density can improve the initial dynamic compression modulus and initial dynamic shear modulus of compacted loess.With an increase in the deviator stress ratio,the initial dynamic compression modulus increases,to a certain extent,but the initial dynamic shear modulus decreases slightly.The dynamic modulus gradually decreases with the development of dynamic strain and tends to be stable,and the dynamic modulus that reaches the same strain increases with an increasing dry density.At the initial stage of dynamic loading,the attenuation of the dynamic shear modulus with the strain development is faster than that of the dynamic compression modulus.Compared with previous research results,it is determined that the dynamic modulus of loess under bidirectional dynamic loading is lower and the attenuation rate is faster than that under single-direction dynamic loading.The deviator stress ratio has a more obvious effect on the dynamic compression modulus.The increase in the deviator stress ratio can increase the dynamic compression modulus,to a certain extent.However,the deviator stress ratio has almost no effect on the dynamic shear modulus,and can therefore be ignored.
基金co-supported by the National Natural Science Foundation of China(No.11672093)the Shanghai Aerospace Science and Technology Innovation Foundation,China(No.SAST2016039)
文摘In this paper,two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyzed when the target and defender using the differential game guidance law based on the linear model.The core ideas underlying the two guidance laws are the attacker evading to a critical safe boundary from the defender,and then maintaining a critical miss distance.The guidance law more appropriate for the attacker to win the game differs according to the initial parameters.Unlike other guidance laws,when using the derived guidance laws there is no need to know the target and the defender’s control efforts.The results of numerical simulations show that the attacker can evade the defender and hit the target successfully by using the proposed derived guidance laws.
基金supported by the National Natural Science Foundation of China (No. 11672093)Shanghai Aerospace Science and Technology Innovation Foundation of China (No. SAST2016039)
文摘This paper investigates a new approach for a scenario in which an Attacker attempts to intercept a defended aerial Target. The problem is formulated as a game among three players, an Attacker, a Defender, and a Target, with bounded controls. In the considered pursuit–evasion problem, the Target uses an optimal evasion strategy and the Defender uses an optimal pursuit strategy.The proposed approach focuses on the miss distance as the outcome of the conflict. The infeasible region for the initial Zero-Effort-Miss（ZEM） distance between the Attacker and the Defender, for a scenario in which the Attacker evades the Defender, is analyzed, assuming that the Attacker uses a control effort chosen from the permitted control region. The sufficient conditions are investigated under which, for ideal players, the Attacker can pursue the Target while evading the Defender launched by the Target. The guidance provided on how the Attacker can accomplish the task is divided into two parts. During the final time between the Attacker and the Defender, the Attacker chooses the control effort that guarantees the miss distance, and then uses the optimal pursuit strategy to accomplish the task. The derived guidance law is verified by nonlinear simulation.
基金This work is supported by the National Basic Research Program of China （973 program, No. 2013CB632401）, the National Natural Science foundation of China （Nos. 11374190 and 21333006）, and the Taishan Scholar Program of Shandong Province, and 111 project B13029. L. Yo thanks the Natural Science Foundation of Shandong Province （No. ZR2013AM021）.
文摘Fabrication of lateral heterostructures （LHS） is promising for a wide range of next-generation devices and could sufficiently unlock the potential of two-dimensional materials.Herein,we demonstrate the design of lateral heterostructures based on new building materials,namely 1S-MX2 LHS,using first-principles calculations.1S-MX2 LHS exhibits excellent stability,demonstrating high feasibility in the experiment.The desired bandgap opening can endure application at room temperature and was confirmed in 1S-MX2 LHS with spin-orbit coupling （SOC）.A strain strategy further resulted in efficient bandgap engineering and an intriguing phase transition.We also found that black phosphorus can serve as a competent substrate to support 1S-MX2 LHS with a coveted type-Ⅱ band alignment,allowing versatile functionalized bidirectional heterostructures with built-in device functions.Furthermore,the robust electronic features could be maintained in the 1S-MX2 LHS with larger components.Our findings will not only renew interest in LHS studies by enriching their categories and properties,but also highlight the promise of these lateral heterostructures as appealing materials for future integrated devices.
基金co-supported by the National Natural Science Foundation of China (No. 11672093)the Shanghai Aerospace Science and Technology Innovation Foundation (No. SAST2016039)
文摘This paper investigates a cooperative strategy for protecting an aerial target.The problem is solved as a game among four players（a target,two defenders,and a missile）.In this scenario,the target launches two defenders（defender-1 and defender-2）simultaneously,to establish a oneway cooperation system（OCS）against an attacking missile.A new optimal evasion strategy for the target is also derived.During the engagement,the target takes into account the reaction of the attacking missile,and guides defender-1 to the interception point by receiving information from defender-1.Depending on the control effort of the target,defender-2 can choose appropriate launch conditions and use very limited maneuvering capability to intercept the missile.For adversaries with first-order dynamics,simulation results show that the OCS allows two defenders to intercept the missile.During the engagement,even if one defender or communication channel is broken,the OCS still allows an interception to be made,thus increasing the target’s survivability.
