The Torque Transmission Capabilities of the Adhesively-Bonded Tubular Single Lap Joint and the Double Lap Joint

With the wide application of fiber-reinforced composite materials in aircraft, space structures and robot arms, the design and manufacture of composite joints have become a very important research area because they are often the weakest areas in composite structures.

In this paper, the stress and torque transmission capabilities of the adhesively-bonded tubular single lap joint and the double lap joint were experimentally tested. In order to compare the experimental results with the calculated results, the stress and torque transmission capabilities were analyzed by the 3-dimensional finite element method taking into consideration the nonlinear properties of the adhesive.

From the experiments it was found that the torque transmission capabilities of the adhesively-bonded double lap joint was 2.7 times as large as that of the single lap joint. Also, it was found that the fatigue limit of the double lap joint was 16 times as large as that of the single lap joint.     

基于动态优先级策略的多AGV无冲突路径规划

自动导引运输车(AGV)路径规划影响柔性制造车间的高效、平稳生产.分析了多AGV在车间执行运输任务时常见的冲突类型,提出了一种基于动态优先级策略的多AGV无冲突路径规划方法.该方法通过时间窗检测冲突类型,并将等待时间、行驶距离、任务紧急程度作为量化动态优先级的考虑因素,进而利用动态优先级作为等待、二次路径规划两种冲突消减方法的选择依据.案例研究表明,在已知各AGV可行路径时,运用所提方法不仅能够实现多AGV的无冲突路径规划,而且能够提升多AGV完成运输任务的整体效率.     

基于动态优先级策略的多AGV无冲突路径规划

自动导引运输车(AGV)路径规划影响柔性制造车间的高效、平稳生产.分析了多AGV在车间执行运输任务时常见的冲突类型,提出了一种基于动态优先级策略的多AGV无冲突路径规划方法.该方法通过时间窗检测冲突类型,并将等待时间、行驶距离、任务紧急程度作为量化动态优先级的考虑因素,进而利用动态优先级作为等待、二次路径规划两种冲突消减方法的选择依据.案例研究表明,在已知各AGV可行路径时,运用所提方法不仅能够实现多AGV的无冲突路径规划,而且能够提升多AGV完成运输任务的整体效率.     

Generic Adaptive Sliding Mode Control for a Quadrotor UAV System Subject to Severe Parametric Uncertainties and Fully Unknown External Disturbance

International Journal of Control, Automation and Systems - This paper aims to provide a generic robust controller that is able to manipulate all kinds of quadrotor unmanned aerial vehicle (UAV)...     

A novel ADRC‑based design for a kind of fexible aerocraft

The paper presents a novel control design, which is based on the idea of active disturbance rejection control (ADRC), for a kind of fexible aerocraft whose controlled variable cannot be measured directly. Since the original frame of ADRC cannot be directly applied, the paper puts forward a new extended state observer (ESO) and the corresponding ADRC law. In order to assign the poles of the closed-loop system to ideal positions such that the vibration can be quickly suppressed, an elastic damping term is added into feedback law. The advantages of the new ESO for efectively estimating both the rigid mode and elastic mode from the measurements are discussed. Moreover, the analysis on the stability, the relative stability and the steady state of the closed-loop system is given. Finally, the efectiveness and robustness of the proposed ADRC are verifed by simulations.     

Noncovalent Functionalized Graphene-Filled Polyimides with Improved Thermal,Mechanical, and Wear Resistance Properties

A facile method is proposed to prepare poly-o-phenylenediamine (PoPD) noncovalent functionalized graphene (G)-reinforced polyimide (PI) nanocomposites. PoPD-G exhibited excellent dispersibility in various organic solvents. The structures of PoPD-G were characterized by Raman and UV spectrum, which verified the π–π interactions between PoPD and G. The effective exfoliation of graphene nanosheets was investigated by observation of the morphology of PoPD-G with SEM, SPM, and TEM. Compared to PI/G composites, the interfacial adhesion between graphene nanosheets and PI matrices promoted efficient stress transfer from PI chains to PoPD-G nanofillers. Polyimide nanocomposites with different incorporations of PoPD-G exhibited outstanding thermal properties. It is interesting to note that only 0.5 wt% PoPD-G-reinforced PI composites increased by 20.8% in hardness, enhanced by 84.0% in storage modulus, and reduced by 72.8% in wear rate compared with neat PI. The eminent enhancement was attributed to the facile dispersion of graphene nanosheets and strong interface adhesion between PI and PoPD-G.     

Kinetic theory for aquatic animal distribution simulation

Identifying the underlying mechanisms that influence the spatial patterns in populations improves the forecasts of the alternative management strategies on the spatial dynamics of the populations, which are critical for assessing and managing the fisheries and improving the water resource management. This paper described a new approach of the numerical model for the prediction of the aquatic animal distribution in the flows. The model was developed based on the kinetic theory of gases, the mechanism of the aquatic animal movement and the flow hydrodynamic patterns. The model was validated using the available experimental data and an acceptable agreement was obtained. A comprehensive parameter study was then conducted to help understand the impact and the sensitivity of each parameter to the aquatic animal distribution. The promising results of the model reveal the prospect of applying this model to the reliable prediction of the aquatic animal distribution within a relatively large water area.     

基于地貌与运动学特征的古滑坡群成因分析

针对四川省雷波县马湖古滑坡群规模的新发现,对其地貌与运动学特征进行详细分析,以期研究该滑坡群的成因.依据钻孔及超声波所测量的马湖湖底地形确定古璜琅河河床特征、古滑坡群平面范围和深度;在古滑坡外形、结构及地质环境现场调查的基础上,重点进行地貌分析、古滑坡群分期和确定各期运动轨迹;运用能量守恒方程计算滑坡速度,辅助确定古滑坡群的形成机制.结果表明:滑坡群规模巨大,面积达18.2 km2(包括湖底部分),体积约20×108 m3;滑坡群按照岩性和结构可以分为3区,形成过程分为4期;古滑坡群为多期地震诱发的顺高陡地层界面的高大、高速、远程滑坡;地貌和运动学分析可作为确定古滑坡成因的一种方法.     

低速翼型绕流的多模态耦合与流动稳定性研究

采用非线性动力学理论对翼型绕流的多模态耦合机制进行研究,并阐释模态耦合作用与流动稳定性的关系。通过特征线有限元方法对翼型绕流问题进行数值计算,建立非定常流场数据库。为了分析流动稳定性和流动特征,利用本征正交分解提取流场中的特征模态,从而分析翼型绕流非定常流场的特征模态之间的相互作用关系,并给出了非线性流体动力系统中的不同模态作用与流动稳定性的关系。     

Electromagnetic wave absorbing properties of Cr2AlB2 powders and the effect of high-temperature oxidation

The electromagnetic (EM) wave absorbing properties of Cr₂AlB₂ powders and those after high-temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr₂AlB₂ with good absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth (E_AB) is 4.4 GHz (13.0-17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding E_AB values, respectively, are 3.8 GHz (13.6-17.4 GHz, 1.7 mm), 4.1 GHz (13.5-17.6 GHz, 1.6 mm), and 4.4 GHz (13.0-17.4 GHz, 1.7 mm). With an absorber thickness of 1.5-4.0 mm, the E_AB with a RL value of less than −10 dB can be tuned in a broad-frequency range 5.0-18.0 GHz, which basically covers C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) bands. These results demonstrate that Cr₂AlB₂, as a high-efficient and oxidation-resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high-temperature oxidation.