Helicopter Maneuver Trajectory Tracking Control Based on Implicit Model and LADRC

To enhance the stability of helicopter maneuvers during task execution,a composite trajectory tracking controller design based on the implicit model(IM)and linear active disturbance rejection control(LADRC)is proposed.Initially,aerodynamic models of the main and tail rotor are created using the blade element theory and the uniform inflow assumption.Subsequently,a comprehensive flight dynamic model of the helicopter is established through fitting aerodynamic force fitting.Subsequently,for precise helicopter maneuvering,including the spiral,spiral up,and Ranversman maneuver,a regular trim is undertaken,followed by minor perturbation linearization at the trim point.Utilizing the linearized model,controllers are created for the IM attitude inner loop and LADRC position outer loop of the helicopter.Ultimately,a comparison is made between the maneuver trajectory tracking results of the IM‑LADRC and the conventional proportional-integral-derivative(PID)control method is performed.Experimental results demonstrate that utilizing the post-trim minor perturbation linearized model in combination with the IM‑LADRC method can achieve higher precision in tracking results,thus enhancing the accuracy of helicopter maneuver execution.

Light-induced ZnO/Ag/rGO bactericidal photocatalyst with synergistic effect of sustained release of silver ions and enhanced reactive oxygen species

Silver nanoparticles (Ag NPs) can effectively address the issue of antibiotic-resistant bacterial infections to reduce the potential toxicity of Ag NPs. Although challenging, it is, therefore, necessary to achieve the sustainable release of Ag+ ions from a finite amount of Ag NPs. This study aims at designing an efficient and benign antimicrobial silver-based ternary composite composed of photocatalysis zinc oxide (ZnO) and reduced graphene oxide (rGO) as a carrier, in which the reactive oxygen species (ROS) excited from ZnO and Ag+ ions released from the Ag NPs cooperate to realize an effective antibacterial activity against E. coli and S. aureus. The constant effective bacterial performance of the ternary photocatalyst with minimum Ag content can be attributed to the increase in the available quantity of ROS, which results from the enhanced separation efficiency of the photogenerated carriers. The proposed system notably realized the long-term sustainable release of Ag+ ions with low concentration for 30 days when compared with an equivalent amount of silver nitrate. Moreover, the use of the composite prevents biotoxicity and silver wastage, and imparts enhanced stability to the long-lasting antibacterial efficacy.

Preparation and corrosion resistance of superhydrophobic coatings on AZ31 magnesium alloy

In order to improve the corrosion resistance of the Mg alloys, the superhydrophobic coatings on AZ31 Mg alloy wereprepared by a two-step process of micro-arc oxidation treatment and superhydrophobic treatment in stearic acid ethanol solution. Theeffects of voltages, frequencies and treatment time on the contact angle of the superhydrophobic treated sample were investigated.The results showed that with increasing the voltage, frequency and treatment time, all of the contact angles of the superhydrophobictreated sample increased first, and then decreased, reaching the maximum values at 350 V, 1000 Hz and 5 min, respectively. Theoptimal superhydrophobic coating was mainly composed of MgO and Mg2SiO4 phases, with the pore diameter of ～900 nm, thethickness of ～6.86 μm and the contact angle of 156.96°. The corrosion current density of the superhydrophobic AZ31 sampledecreased by three orders of magnitude, and the amount of hydrogen evolution decreased by 94.77% compared with that of the AZ31substrate sample.

Modeling of deformation energy at elevated temperatures and its application in Mg-Li-Al-Y alloy

To control the superplastic flow and fracture and examine the variation in deformation energy,the stress and grain size of Mg-7.28Li-2.19Al-0.091Y alloy were obtained using tensile testing and microstructure quantification,and new high temperature deformation energy models were established.Results show that the grain interior deformation energy increases with increasing the strain rate and decreases with increasing the temperature.The variation in the grain boundary deformation energy is opposite to that in the grain interior deformation energy.At a given temperature,critical cavity nucleation energy decreases with increasing strain rate and cavity nucleation becomes easy,whereas at a given strain rate,critical cavity nucleation energy increases with increasing temperature and cavity nucleation becomes difficult.The newly established models of the critical cavity nucleation radius and energy provide a way for predicting the initiation of microcrack and improving the service life of the forming parts.

Precursor-modified strategy to synthesize thin porous amino-rich graphitic carbon nitride with enhanced photocatalytic degradation of RhB and hydrogen evolution performances

The photocatalytic activity of carbon nitride(CN)materials is mainly limited to small specific surface areas,limited solar absorption,and low separation and mobility of photoinduced carriers.In this study,we developed a precursor-modified strategy for the synthesis of graphitic CN with highly efficient photocatalytic performance.The precursor dicyandiamide reformed by different acids undergoes a basic structural change and transforms into diverse new precursors.The thin porous amino-rich HNO_(3)-CN(5H-CN)was calcined by dicyandiamidine nitrate,formed by concentrated nitric acid modified dicyandiamide,and presented the best photocatalytic degradation rate of Rh B,more than 34 times that of bulk graphitic CN.Moreover,the photocatalytic hydrogen evolution rate of 5H-CN significantly improved.The TG-DSC-FTIR analyses indicated that the distinguishing thermal polymerization process of 5H-CN led to its thin porous amino-rich structure,and the theoretical calculations revealed that the negative conduction band potential of 5H-CN was attributed to its amino-rich structure.It is anticipated that the thin porous structure and the negative conduction band position of 5H-CN play important roles in the improvement of the photocatalytic performance.This study demonstrates that precursor modification is a promising project to induce a new thermal polycondensation process for the synthesis of CN with enhanced photocatalytic performance.

Research on replacement depth of black cotton soil based on cracking behavior of embankment

In order to analyze the influence of replacement depth of black cotton soil(BCS)foundation on the initial cracking depth of a highway embankment,the laboratory tests were performed to construct the constitutive relationship between state variables and stress variables of BCS,and the coupled consolidation theory for unsaturated soils was employed to simulate the change in the major principal stress of the subgrade soils caused by water loss shrinkage of BCS with the help of Abaqus 6.11 codes.The simulation results indicate that the water losing shrinkage of BCS causes tensile stress within the subgrade,which leads to embankment cracking.The crack depth decreases with the increase in the BCS replacement depth and the embankment height,and increases with the increase in the burial depth of BCS.In the distribution area of deep BCS,the key values of foundation replacement depth for controlling the crack depth of the embankment with the height of 1 to 4 m are 1.2 and 1.5 m.In the low filling section,when the buried depth of BCS is 2,3 and 4 m,the key values of the foundation replacement depth to control the crack depth of the embankment are 0.8 and 1.2 m.In order to control the embankment cracking induced by the water losing shrinkage of BCS,a reasonable replacement depth of the foundation should be selected while slope protection is carried out well.

Metal organic framework‐ionic liquid hybrid catalysts for the selective electrochemical reduction of CO_(2) to CH4

The electrochemical reduction of CO_(2) towards hydrocarbons is a promising technology that can utilize CO_(2) and prevent its atmospheric accumulation while simultaneously storing renewable en‐ergy.However,current CO_(2) electrolyzers remain impractical on a large scale due to the low current densities and faradaic efficiencies(FE)on various electrocatalysts.In this study,hybrid HKUST‐1 metal‐organic framework‒fluorinated imidazolium‐based room temperature ionic liquid(RTIL)electrocatalysts are designed to selectively reduce CO_(2) to CH_(4).An impressive FE of 65.5%towards CH_(4) at-1.13 V is achieved for the HKUST‐1/[BMIM][PF_(6)]hybrid,with a stable FE greater than 50%maintained for at least 9 h in an H‐cell.The observed improvements are attributed to the increased local CO_(2) concentration and the improved CO_(2)‐to‐CH_(4) thermodynamics in the presence of the RTIL molecules adsorbed on the HKUST‐1‐derived Cu clusters.These findings offer a novel approach of immobilizing RTIL co‐catalysts within porous frameworks for CO_(2) electroreduction applications.

Advancements in biocatalysis:From computational to metabolic engineering

Through several waves of technological research and un‐matched innovation strategies,bio‐catalysis has been widely used at the industrial level.Because of the value of enzymes,methods for producing value‐added compounds and industrially‐relevant fine chemicals through biological methods have been developed.A broad spectrum of numerous biochemical pathways is catalyzed by enzymes,including enzymes that have not been identified.However,low catalytic efficacy,low stability,inhibition by non‐cognate substrates,and intolerance to the harsh reaction conditions required for some chemical processes are considered as major limitations in applied bio‐catalysis.Thus,the development of green catalysts with multi‐catalytic features along with higher efficacy and induced stability are important for bio‐catalysis.Implementation of computational science with metabolic engineering,synthetic biology,and machine learning routes offers novel alternatives for engineering novel catalysts.Here,we describe the role of synthetic biology and metabolic engineering in catalysis.Machine learning algorithms for catalysis and the choice of an algorithm for predicting protein‐ligand interactions are discussed.The importance of molecular docking in predicting binding and catalytic functions is reviewed.Finally,we describe future challenges and perspectives.

Clay mineral expansion of black cotton soil based on interlayer cation hydration

To analyze the water swelling characteristics of black cotton soil(BCS),X-ray fluorescence and X-ray diffraction characterizations were performed to investigate the chemical compositions and types of clay minerals in BCS.A montmorillonite crystal lattice was established to simulate the hydration of interlayer cations by applying the SPC/E potential energy model,universal force field,algorithm of charge balance,and periodic boundary.Results indicated that the main clay mineral found in the BCS was montmorillonite(32.6%)with small amounts of interstratified illite-montmorillonite(10.9%),illite(2.3%),and kaolinite(1.5%).The high expansive potential of BCS comes from the strong adsorption property of montmorillonite with a high content of magnesium and sodium ions to water molecules.The exchangeable cations of Na^(+)in BCS were only 3.73%,but they enhanced the adsorption capacity of clay to water molecules and accelerated the hydration of Mg^(2+)(47.1%)and Ca^(2+)(4.78%).The free swell index can be used as a classification index of the swelling potential of BCS.

Efficient Construction of Quinoxaline Derivatives by Cesium Hydroxide-Catalyzed Mild Aerobic Annulation Reaction

Simple inorganic base cesium hydroxide is found to be the best catalyst for aerobic annulation reaction of o-phenylenediamine andα-hydroxy-2-phenylacetophenone in constructing the quinoxaline skeleton,i.e.,catalytic amount of cesium hydroxide can catalyze the reaction efficiently under mild conditions of room temperature in air atmosphere.This method is extendable to a series of vicinal diamines andα-hydroxyl ketones,thus having a relatively broad substrate scope.As no transition metal catalyst is required and cesium hydroxide highly water-soluble,cesiume can be effectively removed by washing with water,the prodcuts can be obtained without cesium and transition metal residue contamination.This reaction requires no other stoichiometric oxidants but the readily available and convenient air as the oxidant,and the only byproduct is water,hence a transition metal-free,mild and efficient,green and practical approach for efficient construction of the quinoxaline derivatives is provided.

The Spatio-temporal Evolution of Ecological Risk and Its Drivers in the Weihe River Basin Landscape from 1990 to 2020

The Weihe River Basin has a significant number of tributaries and a delicate ecological environment.Understanding the spatial and temporal evolution and determinants of landscape ecological risk in the Weihe River Basin(WRB)can improve the scientific protection and development of its watershed ecosystems.This study is based on land use statistics from the WRB for a 30-year period represented by 1990,2000,2010,and 2020.An initial model for the assessment of landscaping ecological hazards was created using the software that was also used to generate the landscape ecological risk index,such as ArcGIS 10.4 and Fragstats 4.2-64.Next,the spatial and temporal evolution of landscape ecological risk in the vicinity of the study area was characterized by the trajectory of the center of gravity migration and the spatial autocorrelation of GeoDa.Finally,Geodetector was used to analyze ecological risk drivers in the landscapes.According to the findings,the high-risk and relatively high-risk regions are steadily expanding,while the low-risk and relatively low-risk areas dominate the ecological risk landscape in the WRB.Within the Weihe River Basin,Xianyang and Xi'an are the areas to which the high-risk centers of gravity are migrating.Positive spatial correlations were found between the landscape ecological hazards in the study area,most prominently in the form of high-high and low-low aggregations.The primary drivers are the interplay between the GDP component,temperature,and elevation as a single factor.

Bird Species Diversity and Spatio-temporal Variation in the Sihong Hongze Lake Wetland National Nature Reserve in Eastern China

As an important hub on the East Asian-Australian Flyway(EAAF),Hongze Lake is an important migratory stopover and wintering site for hundreds of thousands of birds.However,research on bird community diversity in this area is still lacking.We conducted a bird survey from July 2020 to June 2021 using the line transect method on the terrestrial habitat,as well as the fixed-point method in the lake wetland at the Sihong Hongze Lake Wetland National Nature Reserve located in northwestern Hongze Lake,and analyzed the temporal-spatial variation in the bird community.The results showed that a total of 170432 detections of 215 bird species belonging to 18 orders and 55 families were recorded.In terms of species composition,the proportion of terrestrial birds was relatively high,followed by waterfowl richness,with high numbers of Anatidae species and shorebirds.For bird species abundance,waterfowl had the highest abundance of common coot(Fulica atra),belonging to the Rallidae family,followed by Anatidae and Ardeidae species.The abundance of shorebirds was extremely low,and that of non-waterfowl was also low.In terms of temporal patterns,the number of bird species and richness index were higher in spring and autumn but lower in winter and summer.The bird abundance was the highest in winter,and the remaining three seasons were similar in terms of bird abundance.The diversity index and evenness index were higher in spring,summer and autumn,and lowest in winter.For the spatial pattern,the open water in the western part of the reserve included the most densely distributed areas for birds,and the number of bird species and their abundance were both the highest in that part.There were significant differences in the bird community structures among the four habitats.The species number and richness index of birds in the reed habitat were the highest,and the bird abundance was also high,but the diversity index and evenness index were low.Although the bird abundance in the lake habitat was much higher than in the other habitats,the diversity index,evenness index and richness index were the lowest.The numbers of bird species and individuals in tourist attraction land and farmland were low,but the diversity index,evenness index and richness index were high.Our results reveal the spatial and temporal patterns of bird species diversity and abundance in Sihong Hongze Lake Wetland National Nature Reserve,and reflect the effects of different habitat types on bird diversity.

The Conceptual Model and Its Empirical Studies of Sustainable Carrying Capacity of Water Resources: A Case Study of China Mainland

Based on the interactive development of new industrialization, rapid urbanization and agricultural modernization(IUAM), and from the viewpoint of interactive responses and supply-demand relationships between regional water resources carrying capacity and economic-social development, this paper puts forward the concepts and characterization methods of water resources relative intensity(WRI), water resources carrying rate(WCR) and sustainable index of water resources system(WSI). Considering the catastrophic trait of water resources carrying capacity and its contradictory relationship with WRI, a modified Catastrophe Model, which combines Catastrophe Theory and Fuzzy Mathematic Theory, was introduced to perform a multi-objective and multi-criterion comprehensive assessment of the sustainability of water resources carrying capacity(WSCC) based on benchmarking. According to these concepts and models, land WSCC for the China mainland was set as an example for empirical analysis. The results showed that at the scale of first-grade water regions, Liaohe River, Yangtze River and Pearl River regions had high WRI of domestic water, while Northwestern Rivers, Southeastern Rivers regions and Yangtze River region in some years had high WRI of eco-environment water. However, they were all in a downtrend, while the other four northern regions had low WRI in an uptrend. The agricultural WRI in Songhua River, Yellow River and Northwestern Rivers regions were relatively high and industrial WRI in Songhua River, Yangtze River and Pearl River regions were also relatively high. At the provincial scale, WSCC of urban domestic water was relatively stable, WSCC of eco-environment was obviously fluctuating, and WSCC of agriculture and industry were constantly rising. Overall, WRI in the China mainland generally decreased. The convergence of provinces with high consumption intensity of water resources and spatial spillover of WUE in high WCR provinces promotes water resources development and utilization, progressing toward doubly sustainable development. In the future, China should try to find new ideas and methods of dynamic management of regional water resources and unified management of basin water resources, building on the foundation of traditional water resources planning. Meanwhile, water resources should be considered in regional PRED(population, resources, ecology and development) systems for integrated dispatching and optimizing configuration so that the improvements of WSCC and harmonious development of water resources and regional populations, eco-environment, economy and society can be achieved.