In this research, a new method based on singular spectrum analysis (SSA) and fuzzy entropy is developed for damage detection on thin wall-like structures, and the normalized fuzzy entropy is employed as an indicator to identify the severity of the damage. The Lead Zirconate Titanate (PZT) transducers are used in this research to generate and detect the Lamb waves. During the detection, the collected signals from the PZT sensors are firstly decomposed and reconstructed by SSA to extract the feature of the damage, and then the reconstructed signals with the feature of the damage are processed to obtain the normalized fuzzy entropy. An experimental setup of an aluminium plate with added magnets is fabricated to validate the proposed method. The experimental results show that when magnets are attached on the aluminium plate, the normalized fuzzy entropy is smaller than that when there are no magnets. That is because when magnets are placed on the plate, the movement and some vibration modes of Lamb waves are disturbed by the added magnets and this disturbing effect can be enhanced by increasing the number and locations of the added magnets, and eventually the complexity and nonlinearity of the waves are weakened. The experimental results of a single damage with different number of magnets indicate that the normalized fuzzy entropy decreases linearly as the number of the added magnets increases, which demonstrates that the proposed method can be used to detect the severity of the damage. Moreover, the experimental results of multi-damage on different locations indicate that the normalized fuzzy entropy is relevant with both the total number and locations of the added magnets. The normalized fuzzy entropy decreases linearly as the total number of the magnets increases, and the entropy of a single damage is smaller than that of the multi-damage with the same total number of magnets, which demonstrates that the proposed method also can be used for multi-damage detection on a thin plate. This study provides us a new approach to identifying a single or multiple damages on thin wall-like structures.

In the transport process, continual shock loads are typical stresses for packaged products. The studies of the effects of continual shock loads were performed on test specimens in the laboratory. The findings of these studies were used to deduce the relationship between acceleration amplitude and the number of continual shocks to failure, and a corresponding mathematical model was developed. On the basis of the individual mathematical models for the products tested, two further models were proposed for all products. This makes it possible to arrive at a better assessment of the fragility of different product types when exposed to continual shock loads. These models are capable of producing substantial cost reductions in the design of packages, as they allow the cushioning to be tailored more precisely to the fragility of the products.

This paper presents a new method to describe the selection design of directional control valves in the form of matrix. The directional control valves in hybrid are the basic units to implement the distribution of flow in the hydraulic system. Both the design requirements of the hybrid hydraulic system and the basic units are expressed by the adjacency matrices. Therefore, the selection design of directional control valves is the process to decompose the adjacency matrix of the system into a series of sub-matrices according to the decomposition rules. The defined rules of adjacency matrices are obtained according with the composite physical model of several valves. For obtaining easily the selection design of directional control valves, the library of basic units is established. The style of directional control valves is obtained by matching the sub-matrices with the matrices of basic units. Through configuring the others components, a thorough conceptual design process of the hydraulic system is established. Example is given to illustrate the whole design process in detail.

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