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The intriguing optical phenomena of photochromism and photoluminescence, when integrated into a solitary material, can offer innovative applications in optical memory devices and multimode anti-counterfeiting. However, the exploration and utilization of such materials with dynamic anti-counterfeiting still presents a substantial challenge. This study puts forth an innovative strategy to attain a convergence between the photochromic absorption peak and the photoluminescent emission peak, fundamental to the creation of high-efficiency dynamic anti-counterfeiting materials. By sintering in a reducing atmosphere, a large number of oxygen vacancies are introduced into Ba3MgSi2O8:Er3+ ceramics, which exhibits a reversible white-pink color change with excellent fatigue resistance upon alternate 330 nm illumination and thermal stimulus. Furthermore, Ba3MgSi2O8:Er3+ ceramics demonstrate a distinct fluorescence emission, transitioning from yellow-green to orange to red under 330 nm continuous irradiation. This fascinating behavior can be attributed to the fluorescence resonance energy transfer process, facilitating efficient energy transfer between the luminescent centers and coloring centers. The exceptional optical properties exhibited by Ba3MgSi2O8:Er3+ ceramics have enabled the successful implementation of dynamic anti-counterfeiting applications in this study. This advancement is anticipated to fuel endeavours towards luminescence modulation instigated by photochromism. [ABSTRACT FROM AUTHOR]

Wearable electrochemical sensors have attracted tremendous attention and have been experiencing rapid growth in recent years. Sweat, one of the most suitable biological fluids for non-invasive monitoring, contains various chemical elements relating abundant information about human health conditions. In this work, a new type of non-invasive and highly stretchable potentiometric sweat sensor was developed based on all-solid-state ion-selective electrode (ISE) coupled with poly(dimethylsiloxane; PDMS) and polyurethane (PU). This highly stretchable composite of PDMS-PU allows the sensor to be robust, with the PDMS providing a flexible backbone and the PU enhancing the adhesion between the electrodes and the substrate. In addition, graphene–carbon nanotube (CNT) network 3D nanomaterials were introduced to modify the ion selective membrane (ISM) in order to increase the charge transfer activity of the ISEs, which also could minimize the formation of water layers on the electrode surface, as such nanomaterials are highly hydrophobic. As a result, the sensor demonstrated a wide detection range of NH4+ from 10−6 M to 10−1 M with high stability and sensitivity—showing a high sensitivity of 59.6 ± 1.5 mV/log [NH4+] and an LOD lower than 10−6 M. Under a strain of 40%, the sensor still showed a sensitivity of 42.7 ± 3.1 mV/log [NH4+]. The proposed highly stretchable and robust electrochemical sweat sensor provides a new choice for wearable-device-based personal daily healthcare management beyond hospital-centric healthcare monitoring. [ABSTRACT FROM AUTHOR]

Wireless Powered Communication (WPC) provides an effective solution to the contradiction between information transmission and energy consumption for Internet of Things (IoT) terminals. In this paper, a clustered-Non-Orthogonal Multiple Access (C-NOMA) based WPC model is proposed. Base Station (BS) transfers Radio Frequency (RF) energy to all terminals in the downlink, while terminals transmit information to BS in the uplink by utilizing the harvested energy. A terminal clustering scheme based on maximizing the sum of channel condition difference between terminals is adopted. Specifically, Orthogonal Frequency Division Multiple Access (OFDMA) is used for inter-cluster terminals, while NOMA is used for intra-cluster terminals. In addition, a time-sharing mechanism is adopted to decode information. The sum rate in the uplink is maximized by jointly optimizing transmit power of BS, uplink and downlink subslot. Simulation results demonstrate that, the proposed C-NOMA based WPC model can not only maximize the sum rate in the uplink, but also enhance the fairness between terminals. [ABSTRACT FROM AUTHOR]

The key technologies for applying fifth generation in high-altitude platform station (HAPS) communication systems have many outstanding advantages, especially large-scale antenna array technology. HAPS communication systems have inherent advantages that can perfectly complement large-scale array antenna technology and solve the problems of many existing ground communication systems. The chances of long-packet data users and short-packet data users being serviced are different due to the differing data length of each user's packet. According to the user's channel environment and data length, the user with the smallest delay is selected for transmission. Dynamic and interdependent characteristics between systems and the evaluation of the efficiency of wireless resources are studied in this article. Game theory is applied to the evaluation of the wireless resource efficiency of the system, and an efficiency evaluation model is constructed. In addition, the efficiency of this preliminary work is verified by simulation. [ABSTRACT FROM AUTHOR]

An information system formed by HAP (High Altitude Platform) will be a new generation-system for the wireless communications and HAPS (HAP Station) communication system combines the advantages of both terrestrial and satellite communication systems and avoids, to different extents, their disadvantages. The scope of this paper is to evaluate the link performance of HAPS CDMA air interface. The simulation approach has, with respect to others methods (e.g. hardware prototypes, analytical evaluations), some advantages like lower costs, accuracy, inherent flexibility, etc. The link performance is the necessary input for system capacity and coverage evaluations which are definitely the most important aspects for a telecommunication operator. [ABSTRACT FROM AUTHOR]

High altitude platform station (HAPS) communication employs multiple high altitude platforms with the same bandwidth in order to serve the same region. This working mode greatly increases user capacity and improves frequency spectrum utilization, thus endowing HAPS communication with its superiority in solving hot spot issues. In this study, a standard for deciding the minimum distance in mobile user access systems was derived. Using this standard, channel allocation approaches based on the prediction of user number change and call volume change were proposed. These proposed approaches could effectively remove the problem of insufficient or wasted channels caused by the lack of proactive cooperation in conventional channel allocation methods. These approaches are validated through simulation, in which the proposed channel allocation approaches demonstrated the reasonable allocation of channels and the avoidance of call blocking while improving the utilization of channels. [ABSTRACT FROM PUBLISHER]