Suchergebnisse

Wireless sensor networks (WSNs) have been widely studied for detection and estimation problems. When a coherent multiple access channel is employed between the sensor nodes and fusion center (FC), each sensor takes a noisy measurement of the signal of interest, amplifies and forwards the measurement to a FC through a wireless fading channel, and the FC makes a decision about the presence of the signal and estimates its parameters based on the coherent sum of the signals from all the sensor nodes. To minimize estimation error or maximize probability of detection, the transmit power at the sensors is optimized under either sum or individual power constraints.Most of the existing works assume that the FC is configured with a single antenna. It is well-known that multiple antennas can effectively increase the throughput of a wireless link, and in this thesis, we investigate how to exploit the benefit of the multiple antennas in WSN, and we study the detection and estimation performance of a coherent amplify-and-forward WSN, in which the sensor node has single antenna and the FC is configured with a massive number of antennas. When the perfect channel state information (CSI) is available at FC, we derive optimal closed-form sensor transmission gains to optimize the performance of Neyman-Pearson (NP) detector and the linear minimum mean-squared error estimator (LMMSE), and if CSI is unknown at FC, we find the optimal sensor transmission gains to maximize the deflection coefficient of the energy detector (ED). Regarding the energy efficiency, our analysis show that the performance of NP detector and LMMSE estimator remain asymptotically constant if the sensor transmit power decreases proportionally with the increase in the number of antennas, and for the ED which does not require CSI, we show that a constant deflection can be asymptotically achieved if the sensor transmit power scales as the inverse square root of the number of FC antennas.Additionally, we consider the problem of optimize the sensor phase to minimize the estimation error at FC, when the FC has a limited number of antennas. Two phase optimization algorithms are proposed and the sensor selection problem is formulated and solved. In addition to the case with multi-antenna FC, we also investigate the optimal power allocation for the WSN with single-antenna FC, when the FC use sensor measurements as input for a Kalman filter to track a dynamic parameter of interest. When a fixed network infrastructure is not available (e.g. in military or disaster response scenarios), we investigate how to use the multi-antenna unmanned aerial vehicles (UAVs) as a relay to improve the connectivity between the mobile sensor nodes and the FC, which may be separated by a distances greater than their communication range. Several algorithms are proposed to optimize the trajectory of UAV.

Abstract
This article provides an overview of frontier issues of policing in China by examining the roles of police during the pandemic. It starts with a short introduction to the challenges and overall performance of China in keeping social order in the context of coronavirus disease (COVID-19). Then, it outlines four major missions the Chinese police have pursued, each with a sketch of what has been done and how law enforcement officials have managed to achieve their goals. It follows with a further insight into their strategies in social control in connection with the latest reforms on policing. Finally, it concludes briefly with features of Chinese policing.

Escalating geopolitical factors are closely related to climate warming, but researchers have not fully considered this. Therefore, the purpose of this study is to explore the interaction between geopolitical risk (GPR) and carbon dioxide (CO2) in China. This paper uses the recently developed GPR index and a bootstrap Granger rolling-window estimation. Empirical results spanning different subsamples reveal a two-way causal relationship between GPR and CO2. GPR transforms energy consumption and economic activities through trade disputes, military deployments and energy issues, which have a complex impact on CO2 emissions. Oppositely, CO2 emissions affect GPR through changes in international cooperation and shaping of geopolitical systems. In view of these empirical results, we put forward several policy recommendations. The Chinese government can effectively consider GPR to control CO2 emissions by increasing green investment and signing environmental contracts. Enterprises must focus on research and development (R&D) and investment in new energy innovations. In addition, international organizations can be a useful tool for monitoring decarbonization policies and resolving conflicts between countries.

AbstractThis study delves into the perspectives of Chinese police academy undergraduate students concerning their education and career paths within police academies. Employing a qualitative research design, in-depth interviews were conducted with undergraduate students from a leading police academy in China. The focus of the interviews centered on unraveling the cognitive transitions experienced by undergraduate students during their academy tenure, encompassing their perceptions of the police community and adherence to rigorous police discipline. The analysis revealed a profound transformation in undergraduate students, evolving from high-school graduates into aspiring law enforcement officers, manifesting in both behavioral and psychological dimensions. Undergraduate students developed a strong sense of identity with the police community and embraced the principles of police discipline, aligning themselves closely with these foundational concepts. Notably, robust collectivism was observed among undergraduate students. While showcasing a high level of enthusiasm for academic pursuits, concerns regarding potential challenges in their future policing roles were also articulated. This exploration establishes connections with the Social Cognitive Career Theory, shedding light on the dynamic cognitive processes and identity development experienced by police academy undergraduate students as they navigate their educational and career trajectories.