This paper investigates the application of a piezoelectric actuator to control deformation of thin arbitrary lay-up composite laminates. A theoretical model based on Rayleigh–Ritz principle is ...developed to predict laminate cured shape and the effect of piezoelectric actuator layer. Several stacking sequences are studied using the model. When applied to pure composite laminates it is observed that cured shape of near-unidirectional laminates is always saddle. When applied to arbitrary lay-up piezo-composite laminates, it is found that the principal direction of the laminates can change with electric field. This is one unique feature of such type of laminates. A new FEA technique is proposed to deal with the multiple solution issue and obtain the stable solution more precisely.
This paper investigates the application of a piezoelectric actuator to control deformation of thin unsymmetric cross-ply composite laminates. A theoretical model based on Rayleigh–Ritz principle is ...developed to predict laminate deformation and the effect of the piezoelectric actuator layer. Several stacking sequences are studied using the model. It is found that two stable shapes still exist for laminates with larger dimensions but the two shapes are not symmetric as in traditional cross-ply laminates. The bifurcation dimension increases when the thickness of piezoelectric layer increases. Laminate curvatures are in a perfectly linear relationship with an electric field applied to the piezoelectric actuator layer. Snap-through from one stable shape to the other can occur by applying an electric field. FEA results match model prediction fairly well. This model can be used as a guide to design piezocomposite laminates.
The erosion of the dimple walls is investigated experimentally and numerically. A mathematical simulation framework was proposed to describe quantitatively the morphological evolution of the dimple ...wall quantitatively. As the wall shape continues to evolve, the wall shear stress, mesh deformation, and erosion rate would decrease and gradually tend to be constant. Two distinct regions have been identified along the dimple’s windward wall surface: the wall’s central area and the lateral area. In the central region, the wall profile flare occurs mainly in the early stage. In the lateral region, profile flare occurs mainly in the later stages of erosion. The microhardness of the wall surface shows a positive correlation with the erosion rate. The liquid–solid two-phase impinges on the wall at a smaller angle, and the wall material removal process is mainly based on the microcutting and slip mechanism. The results provide theoretical implications for the design of dimple-shaped, wide-channel welded plate heat exchangers.
With the continuous improvement of remote sensing satellite technology for Earth observation, satellite video object tracking has become a new research field. Tracking aerial objects in satellite ...video facilitates highly accurate positioning over a wide coverage area which plays a crucial role in remote sensing scenes such as military analysis and disaster prevention. However, for such a data-driven task, most previous satellite video datasets focus on ground object tracking and lack attention to high-speed aerial objects. In this regard, a high-resolution satellite video dataset (AIR-HSAO) for detecting and tracking high-speed aerial objects is built including satellite videos from over 20 regions worldwide, with detailed annotations for approximately 1400 airplane trajectories. Based on the AIR-HSAO, an end-to-end online multiobject tracking method called MGTrack is proposed for high-speed aerial objects. Specifically, the motion prediction (MP) module is proposed to implicitly model object motion and associate objects. Guided by the predicted offsets, the feature warping and fusion (FWF) module aligns and fuses temporal features, fully exploiting the temporal correlations of the video sequence to obtain more accurate feature representations for high-speed objects. Additionally, a trajectory-aware size-enhanced loss is designed to handle the problem of discontinuous trajectories and small-scale objects. Experimental results on AIR-HSAO demonstrate that the proposed MGTrack improves the tracking accuracy by 2.3 MOTA and 1.6 IDF1 compared to the state-of-the-art tracking methods. The code is released at https://github.com/RenLibo-aircas/AIR-HSAT-dataset .
•The one-to-one multi-product straight pipeline scheduling problem is studied.•A MILP model based on the discharging time axis is proposed.•A GRASP-LIKE algorithm with volume optimization operators ...is designed.•A set of instances based on a real case study were generated.•Experimental results demonstrate the effectiveness of the proposed algorithm.
The present work deals with the multi-product straight pipeline scheduling problem. The considered straight pipeline system is used to transport refined petroleum products from a single source (refinery with storage tanks) to a single destination (distribution center). The main objective is to find a sequence of batches which aims to maximize the total volume to be transported via the pipeline, while meeting the daily customer demands over a fixed time horizon. Each batch contains only one product with a volume between its upper and lower bounds. Constraints related to inventory levels, batch settling periods and forbidden sequences between pairs of products must be respected, and pipeline stoppage periods should also be handled. A Mixed Integer Linear Programming (MILP) model and a Greedy Randomized Adaptive Search Procedure (GRASP)-like algorithm are proposed to tackle the problem under study. The MILP model is based on the discharging time axis with continuous representation for both time and volume formulation. The GRASP-like algorithm is composed of a construction method and an improvement procedure. The construction method generates a new sequence of batches in a random way with the use of a repair process to obtain an initial solution that satisfies all demands. Then, the improvement procedure is attempted to increase the fill rate of pipeline using volume optimization operators without change the sequence of products. A set of instances was generated from a real case study in order to validate the proposed approach. The performance of our approach is benchmarked against the MILP model (solved using Gurobi Solver), and the numerical experiments proved that the proposed approach obtains very competitive results both in term of solution quality and CPU time.
Data Warehouse (DW) and OLAP systems are first citizens of Business Intelligence tools. They are widely used in the academic and industrial communities for numerous different fields of application. ...Despite the maturity of DW and OLAP systems, with the advent of Big Data, more and more sources of data are available, and warehousing this data can lead to important quality issues. In this work, we focus on missing numerical and categorical in presence of aggregated facts. Motivated by the lack of a formal approach for the imputation of this kind of data taking into account all type of aggregation functions (distributive, algebraic and holistic), we propose an new methodology based on linear programming. Our methodology allows dealing with the relaxed constraints over classical SQL aggregation functions. The proposed approach is tested on two well-known datasets. Experiments show the effectiveness of the proposed approach.
This paper deals with the capacitated lot-sizing problem with multiple items, setup time and unrelated parallel machines. The aim of the article is to propose an efficient population-based ...metaheuristic to tackle this problem. In the proposed approach, a dynamic constructive heuristic is proposed for generating a set of initial solutions. A path-relinking strategy between solutions in the current population is integrated in the diversification procedure, allowing us to explore the solution space further. The population is then intensified using a local search procedure which uses an operator based on machine capacity relaxation coupled with a repair procedure. The proposed approach is evaluated from the instances introduced in Toledo, F. M. B., and V. A. Armentano (2006."A Lagrangian-Based Heuristic for the Capacitated Lot-Sizing Problem in Parallel Machines." European Journal of Operational Research 175 (2): 1070-1083). The results of the experiment show that the proposed approach yields competitive results in terms of solution quality for most of the instances.
In recent years, transgenic technology has developed rapidly, but the risk of the environmental release of transgenic organisms is still a key issue. Research on the impact on biodiversity is an ...effective way to objectively evaluate the risk. By taking transgenic maize HGK60 with insect-resistant gene Cry1Ah and common maize Zheng 58 as control, a 2-year experiment of arthropod community biodiversity in fields of them were studied using three methods.in 2019 and 2020. The results showed that a total of 124 species and 38537 individuals were observed from the experiment, belonging to 11 orders and 40 families. There was no significant difference in the individual number and species number of herbivorous, predatory and parasitic groups in the two kinds of maize in two years. Only the individual number of HGK60 was significantly higher than that of common maize Zheng 58 at heading stage in 2019. And the percentages of individual number and species number in different groups were basically the same in the two kinds of maize at each stage in two years. Analyses of Richness index, Shannon-Wiener diversity index, Dominance index and Evenness index showed no significant difference between the two kinds of maize in two years. The similarity coefficient of the arthropod community suggested that the arthropod community composition of HGK60 was similar to that of common maize Zheng 58. Furthermore, HGK60 had no significant effect on the relative stability of the arthropod community. These results indicated that despite the presence of a relatively minor difference in arthropod community between the two kinds of maize, the planting of HGK60 had little effect on arthropod community biodiversity. The results provided some data and support for the further studies of environmental risk of transgenic crops.
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