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The attitude tracking control problem of an overdriven quadrotor aircraft experimental platform is studied. The platform has unknown input disturbances and angular velocity cannot be measured, and the motor also has dead zone and saturation nonlinear characteristics. First, a linear perturbed double-integral model of the platform is established. Afterwards, an attitude-tracking robust controller including a proportional-integral-derivative nominal controller and an adaptive extended state observer (AESO) is designed. Among them, the nominal controller is used to ensure the asymptotic stability of the nominal closed-loop system, and AESO is used to estimate the angular velocity and disturbance information of the experimental platform to solve the problem of no velocity measurement and disturbance suppression. Moreover, the overdrive control allocation problem is solved by using the pseudo-inverse matrix method. In addition, an auxiliary system is constructed to weaken the influence of the motor’s dead zone and saturated nonlinear characteristics. Finally, the simulation and experiments verify that the proposed control strategy can effectively solve the problems caused by the dead zone and saturation characteristics of the motor, and can simultaneously take into account the transient overshoot and steady-state error performance of the closed-loop system.

Astronomy is considered by many to be a gateway science owing to its ability to inspire curiosity in everyone irrespective of age, culture, or general inclination towards science. Currently, where there is a global push to get more students engaged in Science, Technology, Engineering, and Mathematics, astronomy provides an invaluable conduit to achieve this shift. This paper highlights the results of a study which has reviewed the presence and extent to which astronomy has been incorporated into the school curriculum of the Organisation for Economic and Cooperative Development (OECD) member countries. In addition, two others strong in astronomy research, China and South Africa, are included together with the International Baccalaureate Diploma science curriculum. A total of 52 curricula from 37 countries were reviewed. The results reveal that astronomy and its related topics are prevalent in at least one grade in all curricula. Of the 52 curricula, 44 of them had astronomy-related topics in grade 6, 40 introduced astronomy-related topics in grade 1, whilst 14 had astronomy-related topics explicitly mentioned in all grades. At all year levels, celestial motion is the dominant content area; however, topics such as stars, physics, cosmology, and planetary science become much more frequent as a proportion towards the higher year levels. The most common keywords employed in the curricula related to basic astronomy concepts were the Earth, Sun, Moon, and stars, all with a high frequency of use. There is hardly any focus on Indigenous Astronomy or the role of prominent women astronomers. Relational textual analysis using Leximancer revealed that all the major concepts could be encompassed within two broad themes: Earth and Physics. Astronomy and Physics are often seen as different domains, with astronomy content being more facts based, than based on concepts.

Ambient sunlight‐driven photothermal green syngas production via reverse water‐gas shift (RWGS) reaction is important for carbon neutrality, which lacks efficient and inexpensive catalysts at low temperatures. This studydemonstrates that the scalable Fe3O4 supported with K atoms modified Ag nanoparticles (AgK/Fe3O4) exhibits a RWGS CO production rate of 1089 mmol g−1 h−1 at 300 °C and 100% CO selectivity through dynamic structural reconstruction, surpassing all reported platinum‐based catalysts. In situ characterization and theoretical simulation indicate that the AgK nanoparticles activate H2 to reduce Fe3O4 as metallic Fe. Subsequently, the metallic Fe spontaneously reacts with CO2 to form CO and Fe3O4, thereby facilitating low‐temperature RWGS. Owing to its superior low‐temperature performance, AgK/Fe3O4 equipped with a homemade photothermal device achieves one sun‐driven photothermal RWGS with a CO production rate of 1925 mmol g−1 h−1 and a 38.7% solar to enthalpy energy conversion efficiency. Furthermore, the enlarged outdoor demonstration yields 100.6 m3day−1 of green syngas with an H2/CO ratio of 3. This work paves the way for designing efficient platinum‐free CO2 hydrogenation catalysts and introduces a new approach for sunlight‐driven scalable green syngas production. [ABSTRACT FROM AUTHOR]

Gas disaster in goaf (by goaf, we mean the area behind the working face after coal mining) of coal mine has always been the key research object of mine safety. A large amount of gas will flood into the goaf during coal mining work, and accurate identification of its gas source is of great significance for clarifying the focus of gas prevention and optimizing mine gas control. In this paper, the 28 118 working face of the Tunlan coal mine is taken as the research object, and the distribution characteristics of carbon and hydrogen isotopes in desorption gas of each coal seam are revealed by field sampling and experimental determination. The results show that the main contribution form of gas source is the coal seam and the lower adjacent layer. The COMSOL numerical simulation software was used to study the distribution law of gas concentration in goaf under different extraction parameters of large-diameter boreholes. The optimal borehole spacing of large-diameter borehole technology was determined to be 20 m, the extraction negative pressure was 10 kPa, and the borehole diameter was 550 mm. On this basis, the comprehensive prevention and control technology of gas in goaf with large-diameter borehole and directional long borehole is proposed. Compared with buried pipe extraction, the proportion of gas concentration in goaf and lower adjacent layer is reduced by 41.5% and 40.2%, respectively, and the gas concentration in upper corner is reduced by 46.77%. The comprehensive prevention and control technology inhibits the emission of main gas sources in goaf and effectively reduces the gas concentration in upper corner, which fundamentally prevents the gas accumulation and overrun in working face. [ABSTRACT FROM AUTHOR]

In order to avert the drawback of traditional information flow integrity analysis on ignoring the specific system architecture and associated attack events, an integrity threat tree to quantify the integrity of the system information flow, and the conditional trigger gate to model the associated attack events were proposed. The attack cost was used to quantify the degree of difficulty on attacking each channel. According to the architecture-related integrity threat tree, the minimum attack cost and corresponding target channel set required to achieve the attack target were solved by using the satisfiability modulo theories. The practicality of our approach was demonstrated by the modeling and analysis of the actual flight control system models, and the influence of the conditional trigger gate parameters on the system integrity was discussed.

The scalable artificial photosynthesis composed of photovoltaic electrolysis and photothermal catalysis is limited by inefficient photothermal CO 2 hydrogenation under weak sunlight irradiation. Herein, NiO nanosheets supported with Ag single atoms [two-dimensional (2D) Ni 1 Ag 0.02 O 1 ] are synthesized for photothermal CO 2 hydrogenation to achieve 1065 mmol g -1 hour -1 of CO production rate under 1-sun irradiation. This performance is attributed to the coupling effect of Ag-O-Ni sites to enhance the hydrogenation of CO 2 and weaken the CO adsorption, resulting in 1434 mmol g -1 hour -1 of CO yield at 300°C. Furthermore, we integrate the 2D Ni 1 Ag 0.02 O 1 -supported photothermal reverse water-gas shift reaction with commercial photovoltaic electrolytic water splitting to construct a 103-m 2 scale artificial photosynthesis system (CO 2 + H 2 O → CO + H 2 + O 2 ), which achieves more than 22 m 3 /day of green syngas with an adjustable H 2 /CO ratio (0.4-3) and a photochemical energy conversion efficiency of >17%. This research charts a promising course for designing practical, natural sunlight-driven artificial photosynthesis systems.

Magnetic resonance imaging (MRI) is extensively used in clinical and basic biomedical research. However, MRI detection of pH changes still poses a technical challenge. Chemical exchange saturation transfer (CEST) imaging is a possible solution to this problem. Using saturation transfer, alterations in the exchange rates between the solute and water protons because of small pH changes can be detected with greater sensitivity. In this study, we examined a fatigued skeletal muscle model in electrically stimulated mice. The measured CEST signal ratio was between 1.96 ppm and 2.6 ppm in the z-spectrum, and this was associated with pH values based on the ratio between the creatine (Cr) and the phosphocreatine (PCr). The CEST results demonstrated a significant contrast change at the electrical stimulation site. Moreover, the pH value was observed to decrease from 7.23 to 7.15 within 20 h after electrical stimulation. This pH decrease was verified by 31 P magnetic resonance spectroscopy and behavioral tests, which showed a consistent variation over time.