Suboptimal Safety-Critical Control for Continuous Systems Using Prediction-Correction Online Optimization

This paper investigates the control barrier function (CBF) based safety-critical control for continuous nonlinear control affine systems using more efficient online algorithms by the time-varying optimization method. The idea of the algorithms is that when quadratic programming (QP) or other convex optimization algorithms needed in the CBF-based method is not computation affordable, the alternative suboptimal feasible solutions can be obtained more economically. By using the barrier-based interior point method, the constrained CBF-QP problems are transformed into unconstrained ones with suboptimal solutions tracked by two continuous descent-based algorithms. Considering the lag effect of tracking and exploiting the system information, the prediction method is added to the algorithms, which achieves exponential convergence to the time-varying suboptimal solutions. The convergence and robustness of the designed methods as well as the safety criteria of the algorithms are studied theoretically. The effectiveness is illustrated by simulations on the anti-swing and obstacle avoidance tasks

Sustainable ultra‐strong thermally conductive wood‐based antibacterial structural materials with anti‐corrosion and ultraviolet shielding

In light of the uprising global development on sustainability, an innovative and environmental friendly wood-based material derived from natural pinewood has been developed as a high-performance alternative to petrochemical-based materials. The wood-based functional material, named as BC-CaCl2, is synthesized through the coordination of carboxyl groups (−COOH) present in pinewood with calcium ions (Ca2+), which facilitates the formation of a high-density cross-linking structure through the combined action of intermolecular hydrogen bonds. The as-prepared BC-CaCl2 exhibits excellent tensile strength (470.5 MPa) and flexural strength (539.5 MPa), establishing a robust structural basis for the materials. Meanwhile, BC-CaCl2 shows good water resistance, thermal conductivity, thermal stability, UV resistance, corrosion resistance, and antibacterial properties. BC-CaCl2 represents a viable alternative to petrochemical-based materials. Its potential application areas include waterproof enclosure structure of buildings, indoor underfloor heating, outdoor UV resistant protective cover, and anti-corrosion materials for installation engineering, and so forth

UV-B Radiation Effects on the Alpine Plant Kobresia humilis in a Qinghai-Tibet Alpine Meadow

Enhanced UV-B radiation resulting from stratospheric ozone depletion has been documented both globally and on the Qinghai-Tibet Plateau in China. The response of Kobresia humilis, an important alpine meadow plant species, to enhanced UV-B radiation was experimentally investigated at the Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′ N, 101°12′–101°23′ E; alt. 3200 m). K. humilis was exposed to UV-B radiation including ambient UV-B and enhanced UV-B (simulating a 14% reduction in the ozone layer) in a randomized design with three replications of each treatment. Enhanced UV-B radiation resulted in a significant increase of both leaf area and fresh weight chlorophyll and carotenoid but had no effect on UV-B absorbing pigments. Similarly, enhanced UV-B radiation did not significantly change the photosynthetic O2 elevation rate while leaf thickness, width, and length significantly increased (p < 0.01). The enhanced UV-B radiation was associated with 2–3 days earlier flowering and a larger number of flowers per spikelet. The enhanced UV-B generally resulted in larger leaves and more flowers but earlier phenology. In summary, these findings suggest that alpine species of K. humilis have adapted to the strong solar UV-B radiation intensity presented on the Qinghai-Tibet Plateau, but the interspecies differences and their influence on trophic level should be more concerning

Preparation and Characterization of Printed LTCC Substrates for Microwave Devices

A novel LTCC substrate manufacturing process based on 3D printing was investigated in this paper. Borosilicate glass-alumina substrates with controlled size and thickness were successfully manufactured using a self-developed dual-nozzle hybrid printing system. The printing parameters were carefully analyzed. The mechanical and dielectric properties of the printed substrate were examined. The results show that the printed substrates obtain smooth surface (Ra=0.92 μm), compact microstructure (relative density 93.7%), proper bending strength (156 mPa), and low dielectric constant and loss (Ɛr=6.2, 1/tan⁡δ=0.0055, at 3 GHz). All of those qualify the printed glass–ceramic substrates to be used as potential LTCC substrates in the microwave applications. The proposed method could simplify the traditional LTCC technology

Testing and selection of ad hoc protocol for proximity vehicle test in open-pit coal mine

The paper pointed out that GPS integrated wireless communication technology is most suitable for application of proximity vehicle detection in open-pit coal mine on the basis of analyzing existing proximity vehicle testing technologies, such as ultrasonic sensing technology, pulse radar and laser detection technology, computer vision technology, RFID and electronic tag technology, GPS technology. It put forward a wireless communication system for proximity vehicle testing with GPS integrating ad hoc in open-pit coal mine: as long as the proximity vehicles are in communication distance range, it can adopt IEEE 802.11 agreement between vehicles, and exchange GPS positioning data by single-hop or multiple-hop method. Taking the system as research object, the real scene of open-pit coal mine was simulated, the received signal strength and the effective communication distance for IEEE 802.11a/b/p were tested and analyzed under the following conditions of line of sight, non line of sight, the receiver at bottom of slope, and receiver at top of slope. The testing results show that protocol packet reception rate of IEEE 802.11b is higher, effective communication distance is farther compared with IEEE 802.11a/p , and is more suitable for proximity vehicle testing in open-pit coal mine

Power Control for Passive QAM Multisensor Backscatter Communication Systems

To achieve good quality of service level such as throughput, power control is of great importance to passive quadrature amplitude modulation (QAM) multisensor backscatter communication systems. First, we established the RF energy harvesting model and gave the energy condition. In order to minimize the interference of subcarriers and increase the spectral efficiency, then, the colocated passive QAM backscatter communication signal model is presented and the nonlinear optimization problems of power control are solved for passive QAM backscatter communication systems. Solutions include maximum and minimum access interval, the maximum and minimum duty cycle, and the minimal RF-harvested energy under the energy condition for node operating. Using the solutions above, the maximum throughput of passive QAM backscatter communication systems is analyzed and numerical calculation is made finally. Numerical calculation shows that the maximal throughput decreases with the consumed power and the number of sensors, and the maximum throughput is decreased quickly with the increase of the number of sensors. Especially, for a given consumed power of sensor, it can be seen that the throughput decreases with the duty cycle and the number of sensors has little effect on the throughput

Data Naming Mechanism of LEO Satellite Mega-Constellations for the Internet of Things

The low earth orbit (LEO) mega constellation for the internet of thing (IoT) has become one of the hot spots for B5G and 6G concerns. Information-centric networking (ICN) provides a new approach to the interconnection of everything in the LEO mega constellation. In ICN, data objects are independent of location, application, storage and transport methods. Therefore, data naming is one of the fundamental issues of ICN, and research on the data naming mechanism of the LEO mega constellation for the IoT is thus the focus of this study. Adopting a fusion of hierarchical, multicomponent, and hash flat as one structure, a data naming mechanism is proposed, which can meet the needs of the IoT multiservice attributes and high-performance transmission. Additionally, prefix tokens are used to describe hierarchical names with various embedded semantic functions to support multisource content retrieval for in-network functions. To verify the performance of the proposed data naming mechanism, an NS-3-based simulation platform for LEO mega constellations for the IoT is designed and developed. The test simulation results show that, compared with the IP address, the ICN-HMcH naming mechanism can increase throughput by as much as 54% and reduce the transmission delay of the LEO mega satellites for the IoT by 53.97%. The proposed data naming mechanism can provide high quality of service (QoS) transmission performance for the LEO mega constellation for IoT and performs better than IP-based transmission

Structural characteristics of microbial exopolysaccharides in association with their biological activities: a review

Abstract Many microbial exopolysaccharides (EPS) have been reported in the last decade, and their fermentation processes, functional properties and applications, structural characterization, and biological activities have been extensively studied. Despite the great diversity of biological activities already described for EPS, only a few have been exploited industrially. The main reason for this is that the structure–activity relationship of EPS has not been clearly defined. In this review, we collected EPS-related publications from two databases, the Web of Science and China National Knowledge Infrastructure, and reviewed the correlation between the structural characteristics of EPS and observed biological activity, as reported in studies over the last decade. This review focused on the antioxidant, antitumor, immunomodulatory, hypoglycemic, antibacterial, and gut microbial-modulating activities of EPS. This review aimed to lay a foundation for researching the structure–activity relationship of EPS and provide a theoretical basis for important scientific studies and applications of EPS. Graphical Abstrac

Transmit Power Allocation with Connectivity Probability for Multi-QoS in Cluster Flight Spacecraft Network

In this paper, we investigate the transmit power allocation problem to minimize the average packet error rate at the access point in the cluster flight spacecraft network, which adopts the CSMA/CA channel access mechanism. First, the node mobility, nodal distance distribution, and probabilistic adjacency matrix were formulated for cluster flight spacecraft network based on twin-satellite mode. Then, the optimization-theoretic model described the optimized transmit power allocation strategy and its implementation algorithm was proposed. And the problem of minimizing the packet error rate of the cluster flight spacecraft network system can be converted into maximizing the expectation of the binary probabilistic adjacency matrix, i.e., maximizing the sum of the nondiagonal elements in the probabilistic adjacency matrix. Due to discreteness of nodal distance distribution, Monte Carlo method was applied to solve the transmit power allocation problem. Yet importantly, the influence of node transmit power on the QoS performance of cluster flight spacecraft network was simulated and analyzed under the assumption of finite overall network transmit power and low traffic load. Finally, the results show that the pocket error rate increases with the provided traffic load, but the pocket error rate hardly changes with the same traffic load in different sequential time slots of any orbital hyperperiod or in the same time slot of different orbital hyperperiods, and by maximizing the sum of the nondiagonal elements in the probabilistic adjacency matrix, the pocket error rate minimum is achieved for a given total network transmit power at any time slot for cluster flight spacecraft network