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Maximizing the network lifetime and data collection are two major functions in WSN. For this aim, mobility is proposed as a solution to improve the data collection process and promote energy efficiency. In this paper, we focus on Sink mobility which has the role of data collection. The problem is how to find an optimal data collection trajectory for the Mobile Sink using approximate optimization techniques. To address this challenge, we propose an optimization model for the Mobile Sink to improve the data collection process and thus to extend the network lifetime of WSN. Our proposition is based on a multiobjective function using a Weighted Sum Method (WSM) by adapting two metaheuristics methods, Tabu Search (TS) and Simulated Annealing (SA), to this problem. To test our proposal by experiment, we designed and developed an Integrated Environment of Optimization and Simulation based on metaheuristics tool (IEOSM). The environment IEOSM helps us to determine the best optimization method in terms of optimal trajectory, execution time, and quality of data collection. The IEOSM also integrates a powerful simulation tool to evaluate the methods in terms of energy consumption, data collection, and latency.

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Wireless sensor networks with mobile collectors or sinks face some challenges regarding the data collection process and the continuous connectivity and delivering of data while the mobile sink is moving throughout the network. These challenges increase as the network grows. For this aim, we propose in this paper a cross-layer routing protocol which supports mobility for large-scale wireless sensor networks, which we name CLR-MSPH. We adapt CLR-MSPH for the hierarchical architecture of the network, and it performs on cluster-based wireless sensor networks where the network is organized in clusters. Our proposed protocol deals with the problem of handover data after the mobile sink leaves the radio range of cluster head without sending all data stored in the cluster head’s buffer. We also introduce a mobility model for the mobile sink for a better data collection process. CLR-MSPH is considered as an extending implementation of BMAC protocol with handover mechanism (BMAC-H). In order to prove the efficiency of the proposed protocol, we compare CLR-MSPH to BMAC-H, where we adapted BMAC-H to perform in cluster-based wireless sensor networks. The simulation results show that CLR-MSPH performs better than BMAC-H in terms of packets reception rate, energy, and latency.

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Face recognition has widespread applications in monitoring system, public security and home entertainment etc.. However, in practical application, there are many problems needed to be solved in face recognition technology. This paper presents a method to detect and locate accurately facial feature points based on local gradient operator. With Adaboost algorithm, we first detect roughly the mouth area in the face image, and then extract contours of mouth using local gradient operator. Finally, we use Ostu threshold to extract the binary contour around mouth corners according to the precise location of chain code tracing. Experimental results show that local gradient operator can detect and locate rapidly and accurately human mouth, and it is relatively robust against change of facial expressions as well as noise, which helps to improve face recognition rate.

This study explored the international research collaboration led by China’s world-class universities and its impact during the first construction cycle of the “Double First-Class” initiative (2016–2020). We collected international collaborative publications based on the Scopus database and examined the performance of international research collaboration in terms of quantity, impact, collaborative networks, and subject areas using scientometric indicators and social network analysis. We found that international collaboration accounts for only a quarter of the total output but is far above the overall level of scientific papers in terms of quality and impact. The United States, the United Kingdom, Australia, and Hong Kong remain China’s closest partners. Meanwhile, ties with Belt and Road partner countries have become stronger with the introduction of foreign policy. China’s medicine and multidisciplinary research have gained prominence in the context of the global health crisis. Thus, international research collaboration effectively improves research performance, deepens academic networks, and disseminates local issues and solutions to the world, thereby enabling China’s world-class universities to reconcile global engagement with Chinese characteristics.

In previous data hiding techniques, binary rules are usually used to guide the fine-tuning of the values of basic objects in the host media to hide bit 0 and bit 1. In this paper, we propose a new data hiding technique for gray images based on querying a 256x256 information table. The information table is constructed by cloning a 3x3 basic block, which we call seed block. Eight unsigned integer values between 0 and 7, i.e., 3 bit binary data, are assigned to different elements of the seed block. Each time, a pair of pixels are chosen from a host image, and their pixel values are used as row and column numbers to look up the information table. If element value obtained by looking up the table is equal to the 3 bit binary data to be hidden, the values of the pixel pair will remain unchanged. Otherwise, take this element as the central point, we call it the focus element, to enclose a 3x3 window in the information table. Then in the window, find the element which is equal to the data to be hidden. Finally, update the pixel values of the pair with the row and column numbers of the found element in the window. Since the row and column numbers are in the range of 0-255, the updated pixel values will not overflow. In the proposed algorithm, a pair of pixels can hide 3 bits of information, so the embedding capacity is very high. Since the adjustment of pixel values is constrained in a 3x3 window, the modification amount of pixel values is small. The proposed technique belongs to fragile digital watermarking, so it can be used for image authentication and tamper localization. By the evaluation of data hiding capacity, security, imperceptibility, computational cost and extensibility, this algorithm is superior to existing information hiding techniques. The proposed technique can also be used in color image and audio data hiding.