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Food security is the foundation of national security, which is related to economic development and social stability. Shanxi Province, as China’s grain production and marketing balance area, has rich agricultural resources and profound farming civilization, its food security situation is not only related to its own economic development, but also has a strategic position that can not be ignored in the national food security system. Based on the concept and goal of the development of food security in Shanxi Province, from the five aspects of quantity security, economic security, policy security, resource sustainability and ecological sustainability, this paper constructs the evaluation index system of food security in Shanxi Province, including the fluctuation rate of grain production and the sown area of grain, and establishes the entropy TOPSIS model to evaluate the development level of food security in Shanxi Province. The results show that the overall level of food security in Shanxi Province from 2001 to 2022 shows a trend of first decline and then rise, and the importance of food economic security, policy security and resource sustainability is increasing year by year. In the process of improving the level of food security development in Shanxi Province, it is also affected by structural imbalance, scientific and technological level, grain storage and transportation. Finally, the paper puts forward some policy suggestions to ensure food security in Shanxi Province.

Going beyond the conventional theory, non-Abelian band topology reveals the global quantum geometry of multiple Bloch bands and unveils a new paradigm for topological physics. However, to date, experimental studies on non-Abelian topological states beyond one dimension are still restricted to systems with time-reversal ( T ) symmetry. Here, exploiting a designer gyromagnetic photonic crystal, we find rich T -broken non-Abelian topological phases and their transitions with an unexpected connection to multigap antichiral edge states. By in-situ tuning the magnetic field in the gyromagnetic photonic crystal, we can create, braid, merge, and split the non-Abelian topological nodes in a unique way. Alongside this process, the multigap antichiral edge states can be tuned versatilely, giving rise to topological edge waveguiding with frequency-dependent directionality. These findings open a new avenue for non-Abelian topological physics and topological photonics. Non-Abelian band topology reveals the global quantum geometry of multiple Bloch bands and unveils a new paradigm for topological physics. Here, authors find rich T-broken non-Abelian topological phases and their transitions with an unexpected connection to multigap antichiral edge states.

Carbon dioxide emission is an important environmental issue, and it has also become an important reference factor for governments to formulate social and economic policies. The objective and accurate prediction of carbon dioxide emissions can provide reference and early warning for the implementation of the government’s environmental strategy. The change of the original data of carbon dioxide emissions is S-type, but not saturated S-type. The grey Verhulst model is mainly used to describe the process with saturation state, which is suitable for modeling S-type data series. However, it is found that there are inherent errors and limitations in this model. In this paper, the grey action of the grey Verhulst model is improved, a new action Verhulst model is obtained, and its properties are studied. Finally, the new model is used to predict the carbon dioxide emissions of China and Russia, and ARIMA model is added for comparison. The results show that compared with the original Verhulst model, the simulation and prediction accuracy of the optimized Verhulst model are improved by more than 10%, and the ARIMA model underestimates the carbon dioxide emissions. From the result analysis, China and Russia need to formulate strong energy conservation and emission reduction policies, vigorously develop clean energy industry, and promote green production and lifestyle.

The study of the adsorption characteristics of coal is of great significance to gas prevention and CO 2 geological storage. To explore the adsorption mechanism of coal, this study focuses on columnar anthracite. Adsorption tests on coal rock under a range of physical field conditions were conducted using the volumetric method. The adsorption characteristics of anthracite for CO 2 , CH 4 , and N 2 gases under different conditions were investigated using Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The results showed that the adsorption capacities of anthracite for these three gases are in the order of CO 2 > CH 4 > N 2 , and that the adsorption capacity increases with increasing gas injection pressure. The CO 2 /CH 4 /N 2 gas molecule adsorption capacity of the anthracite macromolecular structure model decreases with increasing temperature. The increase in temperature has the greatest influence on the CO 2 absorption capacity, followed by the CH 4 and N 2 adsorption capacities. The research offers a theoretical basis for the control of coal mine gas and the geological storage of CO 2 .

Incorporating active materials into metamaterials is expected to yield exciting advancements in the unprecedented versatility of dynamically controlling optical properties, which sheds new light on the future optoelectronics. The exploration of emerging semiconductors into terahertz (THz) meta‐atoms potentially allows achieving ultrafast nanodevices driven by various applications, such as biomedical sensing/imaging, ultrawide‐band communications and security scanners. However, ultrafast optical switching of THz radiation is currently limited to a single level of tuning speed, which is a main hurdle to achieve multifunctionalities. Here, a hybrid metadevice which can realize the pump‐wavelength controlled ultrafast switching response by the functionalization of double photoactive layers is demonstrated experimentally. A whole cycle of electromagnetically induced transparency switching with a half‐recovery state changes from 0.78 ns to 8.8 ps as pump wavelength varies from near infrared to near ultraviolet regions. The observed pump‐color selective switching speed changing from nanosecond scale to picosecond scale is ascribed to the wavelength‐dependent penetration length of Ge and the contrasting defect states between noncrystalline Ge and epitaxial Si layers. It is believed that the schemes regarding pump‐color controllable ultrafast switching behavior introduced here can inspire more innovations across the field of ultrafast photonics and can boost the reconfigurable metamaterial applications. All‐optical terahertz modulators with pump‐color selective ultrafast switching speed are realized by combining double layers of semiconductors with electromagnetically induced transparency meta‐atoms. The transmission/group delay of terahertz wave is modulated at contrasting switching speeds from sub‐nanoseconds to picoseconds when pumped by the near‐infrared and near‐ultraviolet beams. This work opens up new avenues for manipulating the dynamics of ultrafast metaphotonic devices.

The classical population growth models include the Malthus population growth model and the logistic population growth model, each of which has its advantages and disadvantages. To address the disadvantages of the two models, this paper establishes a grey logistic population growth prediction model, based on the modeling mechanism of the grey prediction model and the characteristics of the logistic model, which uses the least-squares method to estimate the maximum population capacity. In accordance with the data characteristics of population growth, the weakening buffer operator is used to establish the weakening buffer operator grey logistic population growth prediction model, which improves its accuracy, thus improving the classic population prediction model. Four actual case datasets are used simultaneously, and the two classical grey prediction models are compared. The results of the six evaluation indicators show that the effects of the new model demonstrate obvious advantages. Finally, the new model is applied to the population forecast of Chongqing, China. The prediction results suggest that the population may reach a peak in 2020 and decline in the future. This finding is consistent with the logistic population growth model.

The ability to actively manipulate free-space optical signals by using tunable metasurfaces is extremely appealing for many device applications. However, integrating photoactive semiconductors into terahertz metamaterials still suffers from a limited functionality. The ultrafast switching in picosecond timescale can only be operated at a single frequency channel. In the hybrid metasurface proposed here, we experimentally demonstrate a dual-optically tunable metaphotonic device for ultrafast terahertz switching at frequency-agile channels. Picosecond ultrafast photoswitching with a 100% modulation depth is realized at a controllable operational frequency of either 0.55 THz or 0.86 THz. The broadband frequency agility and ultrafast amplitude modulation are independently controlled by continuous wave light and femtosecond laser pulse, respectively. The frequency-selective, temporally tunable, and multidimensionally-driven features can empower active metamaterials in advanced multiplexing of information, dual-channel wireless communication, and several other related fields.

Helicity-dependent ultrafast spin current generated by circularly polarized photons in topological materials holds the crux to many technological improvements, such as quantum communications, on-chip communication processing and storage. Here, we present the manipulation of helicity-dependent terahertz emission generated in a nodal line semimetal candidate Mg3Bi2 by using photon polarization states. The terahertz emission is mainly ascribed to the helicity-dependent photocurrent that is originated from circular photogalvanic effects, and the helicity-independent photocurrent that is attributed to linear photogalvanic effect. Our work will inspire more explorations into novel nodal line semimetals and open up new opportunities for developing ultrafast optoelectronics in the topological system.

Topological photonics offers a powerful platform for next-generation nanophotonic chips, capitalizing on their remarkable resilience to disorder and defects. Among the two-dimensional (2D) photonic topological insulators, valley-Hall (VH) and pseudo-spin-Hall (PSH) topological insulators have emerged as the most practical designs, as they do not require breaking time-reversal symmetry. These photonic topological insulators support robust edge states, demonstrating promising potential for a wide range of applications, from on-chip communication to optical computing and sensing. However, the conversion between distinct topological phases (VH and PSH) in terahertz (THz) band has not been achieved. Here we experimentally demonstrate a THz on-chip spin–valley converter through adiabatic evolution in 2D parameter space without closing the bulk bandgap. By leveraging the adiabatic phase transition, we confirm the high-efficiency conversion between two valley states in a valley–spin–valley converter. In addition, we verify the robustness of THz PSH topological energy transport through sharply twisted corners. Our findings not only advance the understanding of topological phases in photonics but also hold promise for the development of innovative photonic devices with enhanced performance and functionality.