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Take-off and landing performance, which is supposed to satisfy high standard and always plays an important role during the whole lifespan of an aircraft, is necessary to be fully considered and systematically evaluated during the ...
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Take-off and landing performance, which is supposed to satisfy high standard and always plays an important role during the whole lifespan of an aircraft, is necessary to be fully considered and systematically evaluated during the designing process. In this paper, aiming at determining the take-off and landing demands for low-cost UAVs, aero-dynamic analysis and mechanical modeling are launched to calculate the key parameters of related take-off and landing performance. According to different conditions of application, two theoretical models for take-off as well as two for landing process are established in detail, and an original method for correcting aerodynamic drag and fric-tion is proposed. The calculating methods for the time and distance during take-off and landing period are provided while simulation based on MATLAB is carried out to visually present the results. Based on the output of calculation and numerical analysis, the effectiveness and feasibility of the models are verified. The results indicate that the models proposed in this paper are efficient to estimate the take-off and landing performance of low-cost UAVs and also provide rapid and convenient support to carry out demands analysis and the design of low-cost UAVs especially in the preliminary phase.
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Glass is valuable evidence of cultural exchanges between my country and the West through the Silk Road, and ancient glass is extremely susceptible to weathering due to the impact of the burial environment. During the weathering pr...
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Glass is valuable evidence of cultural exchanges between my country and the West through the Silk Road, and ancient glass is extremely susceptible to weathering due to the impact of the burial environment. During the weathering process, internal elements undergo a substantial exchange with environmental elements, resulting in changes in their compositional proportions that affect the correct judgment of their category. In order to improve the accuracy of glass classification, this paper conducts statistical analysis based on the given glass data to summarize the statistical laws of chemical composition and weathering, and establishes a machine learning model to analyze and identify glass cultural relics. First, the chi-square test was used to confirm the correlation between whether the glass was weathered and various factors, and a descriptive statistical analysis was performed on the change law of the chemical composition before and after weathering. Then, according to the weathering situation, the glass cultural relics were divided into high-potassium or lead-barium categories, and the system clustering model and random forest model were respectively established to obtain the classification results; in this case, the cluster analysis is carried out, and the significant difference value of the clustering results is used as the basis for the selection of the appropriate chemical composition, and the subcategories are divided by comparing the Euclidean distance between the samples; finally, the correlation analysis is carried out on the classified glass cultural relics, and the correlation Coefficient heatmaps show chemical composition correlations and differences for different classes of glasses. The validity of the proposed method is verified on a batch of detection data of ancient glass products in my country, and the perturbation experiments with different intervals are set for each chemical composition, which proves that the model has good robustness.
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Aiming at the problem that the large flutter of mobile platform makes the camera screen blur, a compound image stabilization system was designed which includes mechanical and electronic image stabilization. In this system, the mec...
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Aiming at the problem that the large flutter of mobile platform makes the camera screen blur, a compound image stabilization system was designed which includes mechanical and electronic image stabilization. In this system, the mechanical part is used to compensate the deflection, which can maintain the elementary stability of the camera. At the same time, the electronic part based on sub-block gray projection algorithm can maintain the stability of video images and effectively restrain the interference of local moving objects such as vehicles in the pictures. The experimental results show that the average PSNR of video images is raised 16dB after stabilization and the system can meet the real-time requirement.
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Aiming at the ghost problem in Vibe algorithm, a fast optimization method based on gray histogram and Minkowski distance was proposed. Firstly, the pixels identified as foreground were labeled and the foreground blocks were connec...
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Aiming at the ghost problem in Vibe algorithm, a fast optimization method based on gray histogram and Minkowski distance was proposed. Firstly, the pixels identified as foreground were labeled and the foreground blocks were connected by morphological processing. Then, the histogram of the current foreground block and the corresponding region of the specified frame were counted respectively. Finally, the similarity between the two gray-scale distributions was measured by Minkowski distance, and compared with the dynamic threshold to determine ghost area. In the target detection experiment, the algorithm could remove the ghosts in the Vibe, restrain the jitter disturbances in the background and reduce the false detection rate of the algorithm while preserving the fastness and real-time performance of the traditional Vibe algorithm, and the algorithm processing speed was between the original Vibe algorithm and mixed Gaussian method, the running time of each frame was 20ms. The experimental results show that this method is feasible for hardware system with real-time requirement.
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摘要 :
Aiming at the ghost problem in Vibe algorithm, a fast optimization method based on gray histogram and Minkowski distance was proposed. Firstly, the pixels identified as foreground were labeled and the foreground blocks were connec...
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Aiming at the ghost problem in Vibe algorithm, a fast optimization method based on gray histogram and Minkowski distance was proposed. Firstly, the pixels identified as foreground were labeled and the foreground blocks were connected by morphological processing. Then, the histogram of the current foreground block and the corresponding region of the specified frame were counted respectively. Finally, the similarity between the two gray-scale distributions was measured by Minkowski distance, and compared with the dynamic threshold to determine ghost area. In the target detection experiment, the algorithm could remove the ghosts in the Vibe, restrain the jitter disturbances in the background and reduce the false detection rate of the algorithm while preserving the fastness and real-time performance of the traditional Vibe algorithm, and the algorithm processing speed was between the original Vibe algorithm and mixed Gaussian method, the running time of each frame was 20ms. The experimental results show that this method is feasible for hardware system with real-time requirement.
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摘要 :
Aiming at the ghost problem in Vibe algorithm, a fast optimization method based on gray histogram and Minkowski distance was proposed. Firstly, the pixels identified as foreground were labeled and the foreground blocks were connec...
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Aiming at the ghost problem in Vibe algorithm, a fast optimization method based on gray histogram and Minkowski distance was proposed. Firstly, the pixels identified as foreground were labeled and the foreground blocks were connected by morphological processing. Then, the histogram of the current foreground block and the corresponding region of the specified frame were counted respectively. Finally, the similarity between the two gray-scale distributions was measured by Minkowski distance, and compared with the dynamic threshold to determine ghost area. In the target detection experiment, the algorithm could remove the ghosts in the Vibe, restrain the jitter disturbances in the background and reduce the false detection rate of the algorithm while preserving the fastness and real-time performance of the traditional Vibe algorithm, and the algorithm processing speed was between the original Vibe algorithm and mixed Gaussian method, the running time of each frame was 20ms. The experimental results show that this method is feasible for hardware system with real-time requirement.
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The hydraulic characteristics of submerged jump in the stilling basin with a horizontal bottom in the downstream of a camel-back-type sluice weir has been researched based on experimental model. It can be considered that when the ...
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The hydraulic characteristics of submerged jump in the stilling basin with a horizontal bottom in the downstream of a camel-back-type sluice weir has been researched based on experimental model. It can be considered that when the Froude number F_r1 before submerged jump is from 3.4 to 7.3 and the submergence coefficient is less than 0.7, the flow condition in stilling basin and its downstream area will not worsen even the free jump becomes submerged. The energy dissipation effect of the submerged hydraulic jump is better than that of the free hydraulic jump.
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摘要 :
Moving objects may cause local motion interference and have negative effects for the performance of digital image stabilization. The paper presents a novel method based on corner detection and feature block matching with Hausdorff...
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Moving objects may cause local motion interference and have negative effects for the performance of digital image stabilization. The paper presents a novel method based on corner detection and feature block matching with Hausdorff distance. SUSAN operator is used for corner extraction in large scale feature blocks of uniform distribution. The similarity of the two corner sets of feature blocks between two frames is calculated by introducing weighted corner response function into partial mean Hausdorff distance, and the local motion vectors can be obtained. The final effective motion vectors are determined by checking consistency. The experimental results show that the proposed algorithm can stabilize image sequences with heavy local motion interference, and the average PSNR increases 21.03 dB after stabilization.
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摘要 :
Moving objects may cause local motion interference and have negative effects for the performance of digital image stabilization. The paper presents a novel method based on corner detection and feature block matching with Hausdorff...
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Moving objects may cause local motion interference and have negative effects for the performance of digital image stabilization. The paper presents a novel method based on corner detection and feature block matching with Hausdorff distance. SUSAN operator is used for corner extraction in large scale feature blocks of uniform distribution. The similarity of the two corner sets of feature blocks between two frames is calculated by introducing weighted corner response function into partial mean Hausdorff distance, and the local motion vectors can be obtained. The final effective motion vectors are determined by checking consistency. The experimental results show that the proposed algorithm can stabilize image sequences with heavy local motion interference, and the average PSNR increases 21.03 dB after stabilization.
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Financial institutions' shareholding provides financial support for enterprises, which not only meets the financing needs of enterprises, but also has some impact on enterprise innovation. The State Taxation Administration of Chin...
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Financial institutions' shareholding provides financial support for enterprises, which not only meets the financing needs of enterprises, but also has some impact on enterprise innovation. The State Taxation Administration of China has also issued a set of preferential tax policies to support enterprise innovation. The existing literature finds that financial institutions' shareholding can promote corporate innovation, but there is a gap in the moderation effect of tax preferences on the relationship between financial institutions' shareholding and corporate innovation. Based on moderating effect regression model, using a sample of listed firms in China's manufacturing industry during the period of 2007-2018, this paper investigates how tax preferences influence the relationship between financial institutions' shareholding and enterprise innovation. This paper finds that tax preferences exert a strengthening effect on the promotion of financial institutions' shareholding on enterprise innovation.
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