In the Unmanned Aerial Vehicle （UAV）-assisted and Non-Orthogonal Multiple Access （NOMA）-enabled data collection system， the total energy efficiency of all sensors is maximized by jointly optimizing the three-dimensional placement design of the UAVs and the power allocation of sensors under the ground-air probabilistic channel model and the quality-of-service requirements. To solve the original mixed-integer non-convex programming problem， an energy efficiency optimization mechanism was proposed based on convex optimization theory， deep learning theory and Harris Hawk Optimization （HHO） algorithm. Under any given three-dimensional placement of the UAVs， first， the power allocation sub-problem was equivalently transformed into a convex optimization problem. Then， based on the optimal power allocation strategy， the Deep Neural Network （DNN） was applied to construct the mapping from the positions of the sensors to the three-dimensional placement of the UAVs， and the HHO algorithm was further utilized to train the model parameters corresponding to the optimal mapping offline. The trained mechanism only involved several algebraic operations and needed to solve a single convex optimization problem. Simulation experimental results show that compared with the travesal search mechanism based on particle swarm optimization algorithm， the proposed mechanism reduces the average operation time by 5 orders of magnitude while sacrificing only about 4.73% total energy efficiency in the case of 12 sensors.

Ring artifact is one of the most common artifacts in various types of CT （Computed Tomography） images， which is usually caused by the inconsistent response of detector pixels to X-rays. Effective removal of ring artifacts， which is a necessary step in CT image reconstruction， will greatly improve the quality of CT images and enhance the accuracy of later diagnosis and analysis. Therefore， the methods of ring artifact removal （also known as ring artifact correction） were systematically reviewed. Firstly， the performance and causes of ring artifacts were introduced， and commonly used datasets and algorithm libraries were given. Secondly， ring artifact removal methods were divided into three categories to introduce. The first category was based on detector calibration. The second category was based on analytical and iterative solution， including projection data preprocessing， CT image reconstruction and CT image post-processing. The last category was based on deep learning methods such as convolutional neural network and generative adversarial network. The principle， development process， advantages and limitations of each method were analyzed. Finally， the technical bottlenecks of existing ring artifact removal methods in terms of robustness， dataset diversity and model construction were summarized， and the solutions were prospected.

Sparse-view projection can reduce the scan does and scan time of Cone-Beam Computed Tomography （CBCT） effectively but brings a lot of streak artifacts to the reconstructed images. Sinogram inpainting can generate projection data for missing angles and improve the quality of reconstructed images. Based on the above， a Residual Encoder-Decoder Generative Adversarial Network （RED-GAN） was proposed for sinogram inpainting to reconstruct sparse-view CBCT images. In this network， the U-Net generator in Pix2pixGAN （Pix2pix Generative Adversarial Network） was replaced with the Residual Encoder-Decoder （RED） module. In addition， the conditional discriminator based on PatchGAN （Patch Generative Adversarial Network） was used to distinguish between the repaired sinograms from the real sinograms， thereby further improving the network performance. After the network training using real CBCT projection data， the proposed network was tested under 1/2， 1/3 and 1/4 sparse-view sampling conditions， and compared with linear interpolation method， Residual Encoder-Decoder Convolutional Neural Network （RED-CNN） and Pix2pixGAN. Experimental results indicate that the sinogram inpainting results of RED-GAN are better than those of the comparison methods under all the three conditions. Under the 1/4 sparse-view sampling condition， the proposed network has the most obvious advantages. In the sinogram domain， the proposed network has the Root Mean Square Error （RMSE） decreased by 7.2%， Peak Signal-to-Noise Ratio （PSNR） increased by 1.5% and Structural Similarity （SSIM） increased by 1.4%； in the reconstructed image domain， the proposed network has the RMSE decreased by 5.4%， PSNR increased by 1.6% and SSIM increased by 1.0%. It can be seen that RED-GAN is suitable for high-quality CBCT reconstruction and has potential application value in the field of fast low-dose CBCT scanning.

In order to solve the problems of insufficient stability and poor accuracy of label propagation algorithms， a label propagation overlapping community detection algorithm OCKELP （Overlapping Community detection algorithm combining K-shell and label Entropy in Label Propagation） was proposed， which combined K-shell and label entropy. Firstly， the K-shell algorithm was used to reduce the label initialization time， and the update sequence of label entropy was used to improve the stability of the algorithm. Secondly， the comprehensive influence was introduced for label selection， and the community level information and node local information were fused to improve the accuracy of the algorithm. Compared with Community Overlap PRopagation Algorithm （COPRA）， Overlapping community detection in complex networks based on Multi Kernel Label Propagation（OMKLP） and Speaker-listener Label Propagation Algorithm （SLPA）， OCKELP algorithm has the greatest modularity improvement of about 68.64%， 53.99% and 42.29% respectively on the real network datasets. It also has obvious advantages over the other three algorithms in the Normalized Mutual Information （NMI） value of the artificial network datasets， and with the increase of the number of communities to which overlapping nodes belong， the real structures of the communities can also be excavated.

Under the condition of being confronted with highly concurrent requests, the existing Web services would bring about the increase of the response time, even the problem that server goes down. To solve this problem, a kind of distributed self-elasticity architecture for the Web system named ECAP (self-Elasticity Cloud Application Platform) was proposed based on cloud computing. The architecture built on the Infrastructure as a Service (IaaS) platform of OpenStack. It combined Platform as a Service (PaaS) platform of Cloudify to realize the ECAP. In addition, it realized the fuzzy analytic hierarchy scheduling method by building the fuzzy matrix in the scale values of virtual machine resource template. At last, the test applications were uploaded in the cloud platform, and the test analysis was given by using the tool of pressure test. The experimental result shows that ECAP performs better in the average response time and the load performance than that of the common application server.

At present, the safety analysis of SNAKE algorithm is mainly about interpolation attack and impossible differential attack. The paper evaluated the security of SNAKE(2) block cipher against integral attack. Based on the idea of higher-order integral attack, an 8-round distinguisher was designed. Using the distinguisher, integral attacks were made on 9/10 round SNAKE(2) block cipher. The attack results show that the 10-round SNAKE(2) block cipher is not immune to integral attack.