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An iterative evaluation method for testability of avionics electronic system in field is proposed to improve the accuracy of testability evaluation and solve the problems of few testability evaluation samples and low evaluation accuracy of avionics electronic system after aircraft service. Firstly, the idea of field testability evaluation based on Bayesian framework is expounded. Secondly, according to the prior information, the maximum entropy method, combined with PSO algorithm, is used to find hyper-parameters in the prior distribution of fault detection rate, and hyper-parameters consistency check is carried out. Then, the posterior distribution is obtained by Bayes formula, and the iterative estimation results of fault detection rate are obtained. Combined with the example, the comparison and analyses between this method and existing method further proved the correctness and advantages of the proposed method.

AbstractFlexible rolling (FR) is a novel process for manufacturing doubly curved shallow shells with various shapes based on a pair of small-diameter bendable rolls. In this paper, the fundamental reason for bi-directional bending of the sheet metal in FR is explained. For the purpose of predicting the forming radii in the transverse and longitudinal directions more effectively, the exit velocity is divided into linear velocity and interference velocity, with the latter so small as to be considered to cause only elastic deformation of the sheet. The theoretical calculation model of the pre-curvature radius resulted from linear velocity is established. Using the mechanical theory of the doubly curved shallow shell, the transverse and longitudinal curvature changes caused by the interference velocity are derived and solved by the analytical approach, which are added to the transverse and longitudinal pre-curvatures respectively so that the actual curvature radii are obtained. In order to verify the reliability of the proposed shape prediction method of FR, numerical simulations and forming experiments for convex and saddle-shaped parts are carried out. Through measurement and comparison, it is found that the simulated and experimental results are extremely consistent with the theoretical data. Besides, the effect of important parameters on elastic deformation is investigated by means of the deduced formulas. [ABSTRACT FROM AUTHOR]

Disentangled ultrahigh molecular weight polyethylene (dis‐UHMWPE) has excellent processability but can be achieved under extreme conditions. Herein, we report ethylene polymerization with the binuclear half‐sandwich scandium complexes C1‐Sc2 and C2‐Sc2 to afford UHMWPE. C1‐Sc2 bearing a short linker shows higher activity and gives higher molecular weight PEs than C2‐Sc2 containing a flexible spacer and the mononuclear Sc1. Strikingly, all UHMWPEs isolated from C1‐Sc2 under broad temperature range (25–120 °C) and wide ethylene pressures (2–13 bar) feature very low degree of entanglement as proved by rheological test, DSC annealing study and SEM. These dis‐UHMWPEs are facilely mediated solid‐state‐process at 130 °C and their tensile strength and modulus reach up to 149.2 MPa and 1.5 GPa, respectively. DFT simulations reveal that the formation of dis‐UHMWPE is attributed to the binuclear synergic effect and the agostic interaction between the active center and the growing chain. [ABSTRACT FROM AUTHOR]

The surface quality of an aluminum foam sandwich panel (AFSP) is very important for its appearance and application. This paper mainly studies the surface quality of AFSP after plastic forming. Combined with three-dimensional (3D) scanning technology, the normal deviation between the experimental AFSP and the target surface was obtained, and the surface quality parameters S q , S z and d max were calculated to evaluate surface quality. The AFSP models with cubic-spherical (CS) and tetrakaidecahedral (TKD) as foam structures were established respectively. A series of numerical simulations of multi-point forming (MPF) were then carried out. Equivalent strain and deformation characteristics of spherical and saddle-shaped AFSP were discussed. The main surface defects produced by AFSP in plastic forming, such as surface wrinkle, the local straight face effect and surface dimpling were analyzed. Finally, MPF experiments were carried out, and it was found that the numerical simulation results were significantly corresponded to the experimental AFSP in terms of the degree and distribution of normal deviation and surface quality evaluation parameters. The TKD model was more consistent with the experimental results than the CS model. Moreover, the results show that the surface quality can be improved by thicker face sheets and smaller core cell sizes. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the traditional similarity-based remaining useful lifetime (RUL) prediction method does not consider the difference of operating conditions, which affects the accuracy of prediction and the scientific of components reserve strategy, an improved similarity-based RUL prediction and economic reserve strategy of equipment components is proposed. Based on the proposed improved similarity method, distinguishing the operating condition categories of equipment components, the RUL of the service components is predicted by the performance state similarity between the service components and the reference components in each category. Based on RUL prediction results, the economic reserve strategy decision model is established by taking the lowest total cost of equipment components maintenance and reserve as the objective and the resource utilization as the constraint. The differential evolution algorithm is used to optimize the model to obtain the optimal equipment components reserve strategy. The results of numerical example analysis show that the proposed method can effectively improve the accuracy of the RUL prediction and the scientific of components reserve strategy, which has engineering application value. [ABSTRACT FROM AUTHOR]