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THE SUPERCLOSENESS OF THE FINITE ELEMENT METHOD FOR A SINGULARLY PERTURBED CONVECTION-DIFFUSION PROBLEM ON A BAKHVALOV-TYPE MESH IN 2D

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Acta Mathematica Scientia 2024年第4期44卷 1572-1593页

作者： Chunxiao zhang Jin zhang School of Mathematics and Statistics Shandong Normal UniversityJinan 250014China

For singularly perturbed convection-diffusion problems,supercloseness analysis of the finite element method is still open on Bakhvalov-type meshes,especially in the case of *** difficulties arise from the width of the mesh in the layer adjacent to the transition point,resulting in a suboptimal estimate for *** analysis techniques cannot handle these difficulties *** fill this gap,here a novel interpolation is designed delicately for the smooth part of the solution,bringing about the optimal supercloseness result of almost order 2 under an energy norm for the finite element *** theoretical result is uniform in the singular perturbation parameterεand is supported by the numerical experiments.

关键词： singularly perturbed convection-diffusion finite element method supercloseness Bakhvalov-type mesh

Distributed velocity-free formation tracking control for clustered UAVs under virtual leader-follower framework

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Science China(Technological Sciences) 2024年第5期67卷 1538-1552页

作者： zhang ZhaoYu DUAN HaiBin School of Automation Science and Electrical Engineering Beihang UniversityBeijing100083China

The collective formation control problem of a cluster of rotorcraft unmanned aerial vehicles(UAVs)is investigated in this *** consensus tracking towards formation centroid with following UAVs forming a predefined configuration around the leader is considered as the *** prior studies,the information of the central reference trajectory,which is deemed as a virtual leader in the leader-follower topology,is not directly accessible for partial nodes through the communication ***,a novel distributed formation tracking control scheme is ***,a decentralized saturation observer is employed to estimate the reference acceleration signal of the virtual *** the absence of linear velocity measurement,two sliding manifolds are proposed by introducing the relative discrepancy terms of position and *** a smooth saturation operator in the form of a sigmoid function is applied to generate the command force ***,under the dilemma of constrained capabilities of the airborne sensors equipped on the rotorcrafts,the angular velocity is difficult to *** cascaded auxiliary attitude error systems are established on each rotorcraft system to synthesize the rotating torque with no need to require the angular velocity *** to the strong coupling and nonlinearity of the rotorcraft UAV system,the command angular velocity and the derivatives of command input are hard to *** a continuous nonlinear differentiator is proposed to work with the difficulties in deriving the explicit expression of system ***,a detailed stability analysis is conducted progressively on the angular control loop,reference trajectory observer loop,and the position control loop.A simulation scheme for a cluster of four rotorcraft UAVs tracking sinusoidal trajectory are presented and the formation control results are proven advantageous in comparison with the control protocol in previous literature.

关键词： distributed formation control unmanned rotorcraft clusters velocity-free tracking nonlinear differentiator

Translucent ceramic enabling next-generation lasing-driven near-infrared light source

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Science China Materials 2024年第4期67卷 1359-1360页

作者： Hongjie zhang Engineering Research Center of Advanced Rare Earth Materials(Ministry of Education) Department of ChemistryTsinghua UniversityBeijing 100084China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry(CIAC)Chinese Academy of Sciences(CAS)Changchun 130022China

Broadband near-infrared(NIR) light sources demonstrate great potential in quantitative food analysis, material identification,invasive brain imaging diagnosis, and real-time health monitoring fields, etc. [1–3]. Compared with competing technologies based on quantum dots and organic crystals, NIR-emitting phosphor converted light-emitting diodes(pc-LEDs) favor high spectral modulation and physicochemical stability [4].

关键词： light ceramic lasing

Complex adaptive system theory,agent-based modeling,and simulation in dominant technology formation

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Journal of Systems Engineering and Electronics 2024年第1期35卷 130-153页

作者： zhang Ruihan SUN Bing Glorious Sun School of Business and Management Donghua UniversityShanghai 200051China School of Economics and Management Harbin Engineering UniversityHarbin 150001China

Dominant technology formation is the key for the hightech industry to“cross the chasm”and gain an established foothold in the market(and hence disrupt the regime).Therefore,a stimulus-response model is proposed to investigate the dominant technology by exploring its formation process and ***,based on complex adaptive system theory and the basic stimulus-response model,we use a combination of agent-based modeling and system dynamics modeling to capture the interactions between dominant technology and the socio-technical *** results indicate the following:(i)The dynamic interaction is“stimulus-reaction-selection”,which promotes the dominant technology’s formation.(ii)The dominant technology’s formation can be described as a dynamic process in which the adaptation intensity of technology standards increases continuously until it becomes the leading technology under the dual action of internal and external mechanisms.(iii)The dominant technology’s formation in the high-tech industry is influenced by learning ability,the number of adopting users and ***,a“critical scale”of learning ability exists to promote the formation of leading technology:a large number of adopting users can promote the dominant technology’s formation by influencing the adaptive response of technology standards to the socio-technical landscape and the choice of technology standards by the socio-technical *** is a minimum threshold and a maximum threshold for the role of adaptability in the dominant technology’s formation.(iv)The socio-technical landscape can promote the leading technology’s shaping in the high-tech industry,and different elements have different *** study promotes research on the formation mechanism of dominant technology in the high-tech industry,presents new perspectives and methods for researchers,and provides essential enlightenment for managers to formulate technology strategies.

关键词： complex adaptive system theory agent-based modeling and simulation dominant technology socio-technical landscape adaptation-choice

Seasonal thermal energy storage using natural structures:GIS-based potential assessment for northern China

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Building Simulation 2024年第4期17卷 561-574页

作者： Yichi zhang Jianjun Xia Midea HVAC Heating&Ventilation Equipment Co. LtdFoshan528311China Building Energy Research Center Tsinghua UniversityBeijing100084China

Seasonal thermal energy storage(STES)allows storing heat for long-term and thus promotes the shifting of waste heat resources from summer to winter to decarbonize the district heating(DH)*** being a promising solution for sustainable energy system,large-scale STES for urban regions is lacking due to the relatively high initial investment and extensive land *** close the gap,this study assesses the potentials of using two naturally available structures for STES,namely valley and ground pit *** on geographical information system(GIS)methods,the available locations are searched from digital elevation model and selected considering several criteria from land uses and construction *** costs of dams to impound the reservoir and the yielded storage capacities are then quantified to guide the choice of suitable *** assessment is conducted for the northern China where DH systems and significant seasonal differences of energy demand *** total,2,273 valley sites and 75 ground pit sites are finally identified with the energy storage capacity of 15.2 billion GJ,which is much larger than the existing DH demand in northern *** results also prove that 682 valley sites can be achieved with a dam cost lower than 20 CNY/m^(3).By conducting sensitivity analysis on the design dam wall height and elevations,the choices of available natural structures are expanded but practical issues about water pressures and constructions are also ***,the identified sites are geographically mapped with nearest urban regions to reveal their roles in the DH *** general,560 urban regions are found with potential STES units and most of them have STES storage capacities larger than their own DH *** novel planning methodology of this study and publicly available datasets create possibilities for the implementations of large-scale STES in urban DH systems.

关键词： seasonal thermal energy storage geographical information system district heating water reservoir

Geometric Error Identification of Gantry-Type CNC Machine Tool Based on Multi-Station Synchronization Laser Tracers

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Chinese Journal of Mechanical Engineering 2024年第2期37卷 150-162页

作者： Jun Zha Huijie zhang School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China Xi’an Jiaotong University Suzhou Academy Suzhou 215123China

Laser tracers are a three-dimensional coordinate measurement system that are widely used in industrial *** propose a geometric error identification method based on multi-station synchronization laser tracers to enable the rapid and high-precision measurement of geometric errors for gantry-type computer numerical control(CNC)machine *** method also improves on the existing measurement efficiency issues in the single-base station measurement method and multi-base station time-sharing measurement *** consider a three-axis gantry-type CNC machine tool,and the geometric error mathematical model is derived and established based on the combination of screw theory and a topological analysis of the machine kinematic *** four-station laser tracers position and measurement points are realized based on the multi-point positioning principle.A self-calibration algorithm is proposed for the coordinate calibration process of a laser tracer using the Levenberg-Marquardt nonlinear least squares method,and the geometric error is solved using Taylor’s first-order linearization *** experimental results show that the geometric error calculated based on this modeling method is comparable to the results from the Etalon laser *** a volume of 800 mm×1000 mm×350 mm,the maximum differences of the linear,angular,and spatial position errors were 2.0μm,2.7μrad,and 12.0μm,respectively,which verifies the accuracy of the proposed *** research proposes a modeling method for the precise measurement of errors in machine tools,and the applied nature of this study also makes it relevant both to researchers and those in the industrial sector.

关键词： Multi-point positioning Multi-station synchronization CNC machine tool Geometric error Error separation

Preface:Special issue on soil ecology and sustainability for celebrating the 70th anniversary of ISSCAS

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Pedosphere 2024年第1期34卷 1-2页

作者： Fusuo zhang China Agricultural University Beijing 100193China

The Institute of Soil Science, Chinese Academy of Sciences (ISSAS) was founded in 1953. The institute aims to solve the problems of agricultural development, ecological conservation, and environmental protection and to promote the development of soil ***’s arable land is facing dual pressure of construction occupation and ecological degradation. This is because the rapid urbanization and industrialization continue to occupy high-quality arable land and the quality of complementary arable land is relatively low (Cumming et al., 2014;Wang S T et al., 2021). To ensure national food security, agricultural product quality, and agricultural ecology security,it is particularly important to ensure soil health to maintain sustainable agricultural production.

关键词： soil occupation maintain

Insights into the mechanism of multiple Cu-doped Co Fe_(2)O_(4)nanocatalyst activated peroxymonosulfate for efficient degradation of Rhodamine B

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Journal of Environmental Sciences 2024年第3期137卷 382-394页

作者： Yuanmin Mo Xiaoping zhang School of Environment&Energy South China University of TechnologyGuangzhou Higher Education Mega CentreGuangzhou 510006China The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters of Ministry of Education Guangzhou 510006China Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling Guangzhou 510006China Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal Guangzhou 510006China

The multiple metal catalyst as a promising nanomaterial has shown excellent activity in the peroxymonosulfate(PMS)activation for pollutant ***,the role of special sites and in-depth understanding of the PMS activation mechanism are not fully *** this study,a Cu-doped CoFe_(2)O_(4)nanocatalyst(0.5CCF)was synthesized by a sol-gel and calcination method,and used for PMS activation to remove Rhodamine B(RhB).The results showed that the Cu doping obviously enhanced the catalytic performance of CoFe_(2)O_(4),with 99.70%of RhB removed by 0.5CCF while 74.91%in the CoFe_(2)O_(4)within 15 *** on the X-ray photoelectron spectroscopy and electrochemical analysis,this could be ascribed to the more low valence of Co and Fe species generated on the 0.5CCF and faster electron transfers occurred in the 0.5CCF due to the Cu *** addition,Cu doping could provide more reaction sites for the 0.5CCF to activate PMS for RhB *** metal species and the surface hydroxyl were the reaction sites of PMS activation,and the surface hydroxyl played an important role in surface-bound reactive species *** the PMS activation,the Cu not only activated PMS to produce reactive oxygen species(ROS),but also regenerated Co^(2+)and Fe^(2+)to accelerate the PMS *** non-radical of ^(1)O_(2)was the main ROS with a 99.35%of contribution rate,and the SO_(5)^(·–)self-reaction was its major *** study provides a new insight to enhance the PMS activation performance of multiple metal catalysts by Cu doping in wastewater treatment.

关键词： Cu-doped CoFe_(2)O_(4)nanocatalyst PMS activation Mechanism Rhodamine B removal

Dynamic recrystallization mechanism, texture evolution development and mechanical characteristics of a Mg–8.7Gd–4.18Y–0.42Zr magnesium alloy by ECAP

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Progress in Natural Science:Materials International 2024年第2期34卷 376-388页

作者： Ling zhang Yinglong Li School of Materials Science and Engineering Northeastern University School of Mechanical and Engineering Ningxia Institute of Science and Technology

Equal channel angle pressing is recognized for its ability to refine alloy grains and alter grain orientation, thereby achieve better mechanical performance of the magnesium alloy. This study investigates the microstructures,dynamic recrystallization mechanism, texture development, and mechanical performance of GW94K(Mg–8.7Gd–4.18Y–0.42Zr wt. %) Mg alloy following ECAP-4 passes at 400°C and 3 mm/min. Results show that when high-temperature deformation is undertaken, twin formation is suppressed while dislocation slip is facilitated, increasing dislocation density during deformation. Following ECAP deformation, the sample displayed higher fracture elongation, TYS, and UTS than the as-solutioned GW94K alloy. In particular, the GW94K alloy performed well mechanically after ECAP-4 passes, with an ultimate TYS of 231 MPa, an UTS of 290 MPa, and an elongation of 14.8 %. DDRX and shear bands induce CDRX, both of which are important in plastic deformation. as well as in modifying microstructure and grain orientation during ECAP deformation.

关键词： Dynamic recrystallization mechanism Equal channel angular pressing Magnesium alloy Mechanical performance Mg-Gd-Y-Zr alloy Texture development