摘要：The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.

摘要：In order to study the engineering behaviors of reinforced gabion retaining wall,laboratory model test was carried *** load and unload of five levels(0-50,0-100,0-50,0-200 and 0-250 kPa) were *** earth pressure,lateral earth pressure,deformation behaviors of reinforcements,potential failure surface and deformation behaviors of wall face were *** show that vertical earth pressure is less than theoretical value,the ratio of vertical earth pressure to theoretical value increases nearly linearly with increasing load,and the correlation coefficient of regression equation is 0.92 for the second layer and 0.79 for the fifth *** distribution of lateral earth pressure along the wall back is nonlinear and it is less than theoretical value especially when the load imposed at the top of retaining wall is ***,reinforced gabion retaining wall will be in great safety when current method is *** deformation behaviors of reinforcements both in the third layer and the fifth layer are single-peak distributions,and the position of the maximum strain is behind that determined by 0.3H(Here H refers to the height of retaining wall) method or Rankine *** deformation of wall face increases with increasing load,and the largest lateral deformation occurs in the fourth layer,which lead to a bulging in the middle of wall face.

摘要：To strengthen Specific Energy-Absorption(SEA)behavior of Sandwich Composite Structure(SCS),a kind of light-weight vertical stiffener is proposed for the corrugated *** vertical stiffener,embedded in the corrugated core,can not only absorb part of energy but also simultaneously enhance Energy-Absorption(EA)of other *** Hashin damage model considering the shear stress and ductile damage model is adopted to predict the failure of carbon fiber face-sheets and aluminum-core,*** perfect bonding is modeled for interfaces between the face-sheet and core due to little realistic *** finite element model is verified by available data of conventional *** obtain more design ideas,several stiffeners with different thicknesses,numbers,and positions are *** the predicted results,both the flexural load and deformation of SCS correlate well with experimental *** is highlighted that the SCSs with different vertical stiffeners exhibit 9.74%-58.48%higher SEA than the SCS without *** complex reinforcement mechanisms are extensively revealed by underlying coupling EA and deformation *** parameter analysis shows that the thickness and number have significant effects on the flexural behavior and SEA of reinforced SCS.

摘要：A novel layout has been proposed to reduce the single event upset(SEU) vulnerability of SRAM *** 3-D technology computer-aided design(TCAD) simulation analyses show that the proposed layout can recover the upset-state much easier than conventional layout for larger space of PMOS *** the angle incidence,the proposed layout is immune from ion hit in two plans,and is more robust against SEU in other two plans than the conventional *** ability of anti-SEU is enhanced by at least 33% while the area cost reduced by 47%.Consequently,the layout strategy proposed can gain both reliability and area cost benefit simultaneously.

摘要：The new AUV driven by multi-vectored thrusters not only has unique kinematic characteristics during the actual cruise but also exists uncertain factors such as hydrodynamic coefficients perturbation and unknown interference of tail fluid, which bring difficult to the stability of the AUV＇s control system. In order to solve the nonlinear term and unmodeled dynamics existing in the new AUV＇s attitude control and the disturbances caused by the external marine environment, a second-order sliding mode controller with double-loop structure that considering the dynamic characteristics of the rudder actuators is designed, which improves the robustness of the system and avoids the control failure caused by the problem that the design theory of the sliding mode controller does not match with the actual application conditions. In order to avoid the loss of the sliding mode caused by the amplitude and rate constraints of the rudder actuator in the new AUV＇s attitude control, the dynamic boundary layer method is used to adjust the sliding boundary layer thickness so as to obtain the best anti-chattering effects. Then the impacts of system parameters, rudder actuator＇s constraints and boundary layer on the sliding mode controller are computed and analyzed to verify the effectiveness and robustness of the sliding mode controller based on dynamic boundary layer. The computational results show that the original divergent second-order sliding mode controller can still effectively implement the AUV＇s attitude control through dynamically adjusting the sliding boundary layer thickness. The dynamic boundary layer method ensures the stability of the system and does not exceed the amplitude constraint of the rudder actuator, which provides a theoretical guidance and technical support for the control system design of the new AUV in real complex sea conditions.

摘要：Transverse pressure gradient(TPG)is one of the key factors influencing the boundary layer airflow diversion in a bump *** paper proposes a novel TPG-based hypersonic bump inlet design *** method consists of two ***,a parametric optimization approach is employed to design a series of 2D inlets with various compression ***,according to the prescribed TPG,the optimized inlets are placed in different osculating planes to generate a 3D bump *** method provides a means to directly control the aerodynamic parameters of the bump rather than the geometric *** performing this method to a hypersonic chin inlet,a long and wide bump surface is formed in the compression wall,which leads to good integration of the bump/*** show that a part of the near-wall boundary layer flow is diverted by the bump,resulting in a slight decrease in the mass flow but a significant improvement in the total pressure *** addition,the starting ability is significantly improved by adding the bump *** reveals that the bump has a 3D rebuilding effect on the large-scale separation bubble of the unstarted ***,a mass flow correction is performed on the designed bump inlet to increase the mass flow to full airflow *** results show that the mass flow rate of the corrected bump inlet reaches up to 0.9993,demonstrating that the correction method is effective.

摘要：Oscillation of fluid flow may cause the dynamic instability of nanotubes,which should be valued in the design of hanoelectromechanical *** dynamic instability of the fluid-conveying nanotube transporting the pulsating harmonic flow is *** nanotube is composed of two surface layers made of functionally graded materials and a viscoelastic *** nonlocal strain gradient model coupled with surface effect is established based on Gurtin-Murdoch's surface elasticity theory and nonlocal strain gradient ***,the size-dependence of the nanofluid is *** the slip flow *** stability boundary is obtained by the two-step perturbation-Galerkin truncation-Incremental harmonic balance(IHB)method·and compared with the linear solutions by using Bolotin's ***,the Runge-Kutta method is utilized to plot the amplitudefrequency bifurcation curves inside/outside the *** reveal the influence of nonlocal stress,strain gradient,surface elasticity and slip flow on the *** also suggest that the stability boundary obtained by the IHB method represents two bifurcation points when sweeping from high frequency to low ***,when sweeping to ***,there exists a hysteresis boundary where amplitude jump will occur.

摘要：流体输送纳米管在纳米机电系统中起着关键作用.本文研究了输送高速纳米流体石墨烯增强复合材料(GRC)纳米管在横向低速冲击下的接触动态响应和应力场,建立了考虑滑移流、非局部应力和应变梯度效应的尺寸相关模型.基于精细梁理论,推导了流致后屈曲和接触振动的控制方程,其中后屈曲平衡路径为冲击振动分析提供了初始构型.采用两步摄动-高阶Galerkin截断-Runge-Kutta(R-K)方法的计算模式研究接触动力响应.通过收敛性分析,得到了保证精度所需的截断项.获得了接触力曲线、跨中位移时程曲线和应力场,以指导强度设计.此外,还揭示了流致后屈曲纳米管在冲击作用下的动态跳跃失稳行为.结果揭示了非局部应力和应变梯度对接触动态响应和应力场的双重影响,并提供了对尺寸效应敏感的流速范围.

摘要：A rigorous back analysis of shear strength parameters of landslide slip was presented. Kinematical element method was adopted to determine factor of safety and critical failure surface, which overcomes the disadvantage of limit equilibrium method. The theoretical relationship between the combination of shear strength parameters and stability state was studied. The results show that the location of critical slip surface, F/tan f and F/c depend only on the value of c/tan f. The failure surface moves towards the inside of slope as c/tan f increases. According to the information involving factor of safety and critical failure surface in a specific cross-section, strength parameters can be back calculated based on the above findings. Three examples were given for demonstrating the validity of the present method. The shear strength parameters obtained by back analysis are almost consistent with their correct solutions or test results.

摘要：Landfill leaks pose a serious threat to environmental health,risking the contamination of both groundwater and soil *** investigation of these sites is essential for implementing effective prevention and control *** self-potential(SP)stands out for its sensitivity to contamination plumes,offering a solution for monitoring and detecting the movement and seepage of subsurface ***,traditional SP inversion techniques heavily rely on precise subsurface resistivity *** this study,we propose the Attention U-Net deep learning network for rapid SP *** incorporating an attention mechanism,this algorithm effectively learns the relationship between array-style SP data and the location and extent of subsurface contaminated *** designed a synthetic landfill model with a heterogeneous resistivity structure to assess the performance of Attention U-Net deep learning ***,we conducted further validation using a laboratory model to assess its practical *** results demonstrate that the algorithm is not solely dependent on resistivity information,enabling effective locating of the source distribution,even in models with intricate subsurface *** work provides a promising tool for SP data processing,enhancing the applicability of this method in the field of near-subsurface environmental monitoring.