In the Chinese history, no commodity has had a greater impact upon both China and the world other than tea. In the formation of the unitary multi-ethnic country of China, the brick tea trade ran ...through every stage of the country’s history since the Tang and Song Dynasties as a commercial activity through which the Central Plains dynasties exchanged tea from the Han regions for horses and other commodities from nomads in the northern grasslands and Qinghai-Tibet Plateau. Throughout the trick tea trade that continued for one thousand years, all ethnic groups were involved, consciously or passively, in the production, processing, transport and marketing of the tea, and collaborated in all trading chains and links, thus creating the largest trading activity in the history of China or even the world and exerting a significant influence on the formation of the unitary multi-ethnic country of China as a result.
Geohazard prevention and mitigation are highly complex and remain challenges for researchers and practitioners. Artificial intelligence (AI) has become an effective tool for addressing these ...challenges. Therefore, for decades, an increasing number of researchers have begun to conduct AI research in the field of geohazards leading to rapid growth in the number of related papers. This has made it difficult for researchers and practitioners to grasp information on cutting-edge developments in the field, thus necessitating a comprehensive review and analysis of the current state of development in the field. In this study, a comprehensive scientometric analysis appraising the state-of-the-art research for geohazard was performed based on 9226 scientometric records from the Web of Science core collection database. Multiple types of scientometric techniques, including coauthor analysis, co-citation analysis, and cluster analysis were employed to identify the most productive researchers, institutions, and hot research topics. The results show that research related to the application of AI in the field of geohazards experienced a period of rapid growth after 2000, with major developments in the field occurring in China, the United States, and Italy. The hot research topics in this field are ground motion, deep learning (DL), and landslides. The commonly used AI algorithms include DL, support vector machine (SVM), and decision tree (DT). The obtained visualization on research networks offers valuable insights and an in-depth understanding of the key researchers, institutions, fundamental articles, and salient topics through animated maps. We believe that this scientometric review offers useful reference points for early-stage researchers and provides valuable in-depth information to experienced researchers and practitioners in the field of geohazard research. This scientometric analysis and visualization are promising for reflecting the global picture of AI-based geohazard research comprehensively and possess potential for the visualization of the emerging trends in other research fields.
Despite the common belief that substantial capacity gains can be achieved by using more antennas at the base-station (BS) side in cellular networks, the effect of BS antenna topology on the capacity ...scaling behavior is little understood. In this paper, we present a comparative study on the ergodic capacity of a downlink single-user multiple-input-multiple-output (MIMO) system where BS antennas are either co-located at the center or grouped into uniformly distributed antenna clusters in a circular cell. By assuming that the number of BS antennas and the number of user antennas go to infinity with a fixed ratio L ≫ 1, the asymptotic analysis reveals that the average per-antenna capacities in both cases logarithmically increase with L, but in the orders of log 2 L and α/2 log 2 L, for the co-located and distributed BS antenna layouts, respectively, where α > 2 denotes the path-loss factor. The analysis is further extended to the multiuser case where a 1-tier (7-cell) MIMO cellular network with K ≫1 uniformly distributed users in each cell is considered. By assuming that the number of BS antennas and the number of user antennas go to infinity with a fixed ratio L ≫ K, an asymptotic analysis is presented on the downlink rate performance with block diagonalization (BD) adopted at each BS. It is shown that the average per-antenna rates with the co-located and distributed BS antenna layouts scale in the orders of log 2 L/K and log 2 (L-K+1) α/2 /K, respectively. The rate performance of MIMO K cellular networks with small cells is also discussed, which highlights the importance of employing a large number of distributed BS antennas for the next-generation cellular networks.
Optimal Oxygen Excess Ratio Control for PEM Fuel Cells Chen, Jian; Liu, Zhiyang; Wang, Fan ...
IEEE transactions on control systems technology,
2018-Sept., 2018-9-00, 20180901, Letnik:
26, Številka:
5
Journal Article
Recenzirano
In this paper, a feedback linearization controller is proposed for the van compressor in the air supply system of a proton exchange membrane fuel cell. The control goal is to avoid oxygen starvation ...and reduce power consumption by tracking an optimal reference oxygen excess ratio. Specifically, an improved control-oriented third-order model of the air supply system is proposed with the model identification of the air compressor. The optimal reference oxygen excess ratio is obtained from experiments to maintain a maximum net power. Based on the air supply system model, a nonlinear controller is designed to track the optimal oxygen excess ratio using feedback linearization. Lyapunov-based technique is utilized to analyze the stability of the closed-loop system. Effectiveness of the proposed approach is illustrated by experimental results.
Efficient organic photosensitizers (PSs) have attracted much attention because of their promising applications in photodynamic therapy (PDT). However, guidelines on their molecular design are rarely ...reported. In this work, a series of PSs are designed and synthesized based on a triphenylamine-azafluorenone core. Their structure–property-application relationships are systematically studied. Cationization is an effective strategy to enhance the PDT efficiency of PSs by targeting mitochondria. From the molecularly dispersed state to the aggregate state, the fluorescence and the reactive oxygen species generation efficiency of PSs with aggregation-induced emission (AIE) increase due to the restriction of the intramolecular motions and enhancement of intersystem crossing. Cationized mitochondrion-targeting PSs show higher PDT efficiency than that of nonionized ones targeting lipid droplets. The ability of AIE PSs to kill cancer cells can be further enhanced by combination of PDT with radiotherapy. Such results should trigger research enthusiasm for designing and synthesizing AIE PSs with better PDT efficiency and properties.
This paper studies a real-time control problem for a hybrid power system consisting of a proton exchange membrane fuel cell (FC), a unidirectional boost converter, and a lithium-ion battery. An ...adaptive control strategy is proposed to manage the power sharing in this hybrid power system. System constraints, including the slow dynamics of the FC and the state of charge of the battery, are explicitly considered. The controller achieves tracking a dynamically changing load demand while satisfying the system constraints based on parameter estimations. The main contribution is that, compared with the previous control methods, the proposed control design for hybrid power systems has provable stability and convergence closed-loop properties. Simulation and experimental results are provided to validate the control design.
Dynamic liquid level monitoring and measurement in oil wells is essential in ensuring the safe and efficient operation of oil extraction machinery and formulating rational extraction policies that ...enhance the productivity of oilfields. This paper presents an intelligent infrasound-based measurement method for oil wells’ dynamic liquid levels; it is designed to address the challenges of conventional measurement methods, including high costs, low precision, low robustness and inadequate real-time performance. Firstly, a novel noise reduction algorithm is introduced to effectively mitigate both periodic and stochastic noise, thereby significantly improving the accuracy of dynamic liquid level detection. Additionally, leveraging the PyQT framework, a software platform for real-time dynamic liquid level monitoring is engineered, capable of generating liquid level profiles, computing the sound velocity and liquid depth and visualizing the monitoring data. To bolster the data storage and analytical capabilities, the system incorporates an around-the-clock unattended monitoring approach, utilizing Internet of Things (IoT) technology to facilitate the transmission of the collected dynamic liquid level data and computed results to the oilfield’s central data repository via LoRa and 4G communication modules. Field trials on dynamic liquid level monitoring and measurement in oil wells demonstrate a measurement range of 600 m to 3000 m, with consistent and reliable results, fulfilling the requirements for oil well dynamic liquid level monitoring and measurement. This innovative system offers a new perspective and methodology for the computation and surveillance of dynamic liquid level depths.
The development of solid‐state intelligent materials, in particular those showing photoresponsive luminescence (PRL), is highly desirable for their cutting‐edge applications in sensors, displays, ...data‐storage, and anti‐counterfeiting, but is challenging. Few PRL materials are constructed by tethering the classic photochromic systems with newly‐emerged solid‐state emitters. Selective solid‐state photoreactions are demanded to precisely manipulate the luminescent behavior of these emitters, which require dramatic structural change and enough free space, thus limiting the scope of the PRL family. Here, a new PRL material, TPE‐4N, that features sensitive and reversible fluorescence switching is reported. The interesting on–off luminescent property of TPE‐4N can be facilely tuned through fast phototriggering and thermal annealing. Experimental and theoretical investigations reveal that subtle molecular conformation variation induces the corresponding PRL behavior. The crystalline and amorphous state endows an efficient and weak ISC process, respectively, to turn on and off the emission. The readily fabricated thin‐film of TPE‐4N exhibits non‐destructive PRL behavior with high contrast (>102), good light transmittance (>72.3%), and great durability and reversibility under room light for months. Remarkably, a uniform thin‐film with such fascinating PRL properties allows high‐tech applications in invisible anti‐counterfeiting and dynamic optical data storage with micro‐resolution.
Solid‐state intelligent materials, in particular those showing photoresponsive luminescence (PRL), is desirable for their cutting‐edge applications, but challenging. A PRL material that features sensitive and reversible fluorescence switching through phototriggering and thermal annealing is reported. The behavior is attributed to subtle molecular conformation variations. Excellent quality of thin‐films and high PRL performance allows interesting applications in invisible anti‐counterfeiting and dynamic optical data storage with micro‐resolution.
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