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Design of multi-section luffing apple pruning equipment and cutting test of the key components

International Journal of Agricultural and Biological Engineering 2024年第1期17卷 109-117页

作者： Siyuan Tong Wenbin Li Yaxiong Wang Lei Zhang Feng Kang School of Technology Beijing Forestry UniversityKey Lab of State Forestry and Grassland Administration for Forestry Equipment and AutomationBeijing 100083China

In order to reduce the labor intensity and improve the efficiency of pruning,this study designed a multi-section luffing apple pruning equipment suitable for apple orchards in hilly and mountainous areas of *** the essay,the structure and working principle of the equipment are expounded,the cutter was analyzed,and the parameters were *** the self-made test bench to simulate the field experiment,this study selected the ratio of cutting speed to feeding speed and feeding speed as the influencing factors and took the cut-off rate,cutting efficiency and cutting power as the objectives to carry out single factor experiment and quadratic regression orthogonal *** test results show that the cutting power increases with the increase of ratio of cutting speed to feeding speed,and the cut-off rate and cutting efficiency first increase and then *** the feeding speed increases,the cutting efficiency and power increase,and the cut-off rate *** the cutoff rate was greater than 80%,the optimal combination of operating parameters was the feeding speed of 0.55 m/s and ratio of cutting speed to feeding speed of *** this combination,the cut-off rate was 84.9%,the cutting efficiency was 13.1,and the cutting power was 175.7 *** error between the predicted target value of the model and the average measured target value was less than 7%,so the test results are *** to the obtained optimal operating parameters,the actual cutting experiment of the pruning equipment in the field was carried out,and the cutting rate was 96.3%,which meet the design *** study can also meet the needs of mechanized pruning of fruit trees with different crown shapes,improve the applicability of pruning equipment,and provide support for the development of mechanized pruning equipment in China.

关键词： apple pruning equipment cutting test optimal parameters regression analysis

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Object use in insects

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Insect science 2024年第4期31卷 1001-1014页

作者： Chao Wen Cai Wang Xiaoli Guo Hongyu Li Haijun Xiao Junbao Wen Shikui Dong School of grassland science Beijing Forestry UniversityBeijingChina College of Forestry and Landscape Architecture South China Agricultural UniversityGuangzhouChina beijing key laboratory for Forest Pest Control Beijing Forestry UniversityBeijingChina

Insects are the most diverse group of organisms in the animal kingdom,and some species exhibit complex social *** research on insect object use is still in its early stages,insects have already been shown to display rich object-use *** review focuses on patterns and behavioral flexibility in insect object-use behavior,and the role of cultural evolution in the development of object-use *** use in insects is not widespread but has been documented in a diverse set of *** insects can use objects flexibly and display various object-use *** mammals and birds,insects use objects in diverse activities,including foraging,predator defense,courtship,and ***,pre-existing manipulative behaviors,and anatomical structure affect innovations in object *** addition,learning and imitation are the main mechanisms underlying the spread of object-use behaviors within *** that insects are one of the major animal groups engaging in object use,studies of insect object use could provide general insights into object use in the animal kingdom.

关键词： cognition evolution insects learning object use

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Single-atom alloys prepared by two-step thermal evaporation

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Nano Research 2024年第4期17卷 2808-2813页

作者： Honglin Wang Jing Li Meirong Huang Jizhe Cui Zhiying Cheng Rong Yu Hongwei Zhu State key lab of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China State key lab of Solid Waste Reuse for Building Materials Beijing Building Materials Academy of Science ResearchBeijing 100041China

Single-atom alloys(SAAs)have gained significant attention due to their remarkable atomic utilization efficiency,interactions between single atoms(SAs)and metal supports,and free-atom-like electronic structure of dopant *** this work,we observed the formation of SAs in pre-deposited metal particles by a two-step thermal evaporation technique,thereby establishing the first instance of discovering SAAs by thermal *** discovery of SAAs by thermal evaporation extends the range of SAAs preparation methods to include this traditional synthetic technique,which offers convenience,cost-efficiency,and *** formation mechanism of SAAs prepared using this technique was elucidated by density functional theory *** was demonstrated that thermal evaporation can be utilized to prepare SAAs with multiple SAs,further highlighting its universal applicability.

关键词： single-atom alloys thermal evaporation density functional theory

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Mechanical Behavior of Bamboo,and Its Biomimetic Composites and Structural Members:A Systematic Review

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Journal of Bionic Engineering 2024年第1期21卷 56-73页

作者： Shanyu Han Yuyuan He Hanzhou Ye Xueyong Ren Fuming Chen Kewei Liu Sheldon Q.Shi Ge Wang Institute of Biomaterials for Bamboo and Rattan Resources International Centre for Bamboo and RattanBeijing 100102China key laboratory of National Forestry and grassland Administration/beijing for Bamboo&Rattan science and Technology Beijing 100102China National Forestry and grassland Engineering Technology Center for Wood Resources Recycling College of Materials Science and TechnologyBeijing Forestry UniversityBeijing 100083China International Bamboo and Rattan Organization Beijing 100102China School of Civil Engineering Tsinghua UniversityBeijing 100084China Mechanical Engineering Department University of North TexasDentonTX 762077102USA

Bamboo is a typical biological material widely growing in nature with excellent physical and mechanical *** is lightweight with high strength and *** naturally optimized bamboo structure,which has inspired global material scientists and engineers for decades,is significantly important for the bionic design of novel structural materials with ultra-light,ultra-strong,or ultra-tough and comprehensive *** literature on innovative composite materials and structural members inspired by bamboo are reviewed in this paper,and the research progress and prospects in this field are expounded in three ***,the structural characteristics of the bamboo wall layer along the thickness and height directions are described in terms of chemical composition,gradient structure,pore structure,and hollow structure with variable ***,this paper summarizes the research progress on new composite materials and structural components by applying bamboo’s structural features from the perspective of sustainability,designability,and ***,given the limitations of current research,the biomimetic scientific research on bamboo’s structural characteristics is prospected from the interpretation of bamboo structure,new bamboo-like materials,and structural design optimization perspectives,providing a reference for future research on biomimetic aspects of biomass.

关键词： Bamboo Structural characteristics-Bamboo-like material Physical and mechanical properties

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Remote heteroepitaxy of transition metal dichalcogenides through monolayer hexagonal boron nitride

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Nano Research 2024年第4期17卷 3224-3231页

作者： Jidong Huang Jingren Chen Junhua Meng Siyu Zhang Ji Jiang Jingzhen Li Libin Zeng Zhigang Yin Jinliang Wu Xingwang Zhang key lab of Semiconductor Materials science Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of Materials science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Faculty of science Beijing University of TechnologyBeijing 100124China

As a very promising epitaxy technology,the remote epitaxy has attracted extensive attention in recent years,in which graphene is the most used interlayer *** an isomorphic of graphene,two-dimensional(2D)hexagonal boron nitride(h-BN),is another promising interlayer for the remote ***,there is a current debate on the feasibility of using h-BN as interlayer in the remote ***,we demonstrate that the potential field of sapphire can completely penetrate monolayer h-BN,and hence the remote epitaxy of ZrS_(2) layers can be realized on sapphire substrates through monolayer *** field of sapphire can only partially penetrate the bilayer h-BN and result in the mixing of remote epitaxy and van der Waals(vdWs)*** to the weak interfacial scattering and high crystalline quality of ZrS_(2) epilayer,the ZrS_(2) photodetector with monolayer h-BN shows the best performance,with an on/off ratio of more than 2×10^(5) and a responsivity up to 379 mA·W^(-1).This work provides an efficient approach to prepare single-crystal transition metal dichalcogenides and their heterojunctions with h-BN,which have great potential in developing large-area 2D electronic devices.

关键词： remote epitaxy hexagonal boron nitride transition metal dichalcogenides chemical vapor deposition photodetectors

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Effects of the initiation position on the damage and fracture characteristics of linear-charge blasting in rock

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International Journal of Minerals,Metallurgy and Materials 2024年第3期31卷 443-451页

作者： Chenxi Ding Renshu Yang Xiao Guo Zhe Sui Chenglong Xiao Liyun Yang School of Civil and Resource Engineering University of Science and Technology BeijingBeijing 100083China School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing 100083China School of Mathematics and Physics University of Science and Technology BeijingBeijing 100083China State key lab of Explosion science and Technology Beijing Institute of TechnologyBeijing 100081China

To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections Ⅰ and Ⅱ is less than that of Sections Ⅲ and Ⅳ. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional(3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.

关键词： blasting linear charge initiation position computed tomography three-dimensional reconstruction damage

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Anti-aging performance improvement and enhanced combustion efficiency of boron via the coating of PDA

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Defence Technology（防务技术） 2024年第3期33卷 399-410页

作者： Shuai Ma Qinghai Shu Mengyang Zhang Hongyu Huang Yansong Shi Xijuan Lv Shuai Zhao School of Materials science and Engineering Beijing Institute of TechnologyBeijing100081China key lab of Advanced Optoelectronic Quantum Architecture and Measurement(MOE) Beijing Key Lab of Nanophotonics&Ultrafine Optoelectronic SystemsSchool of PhysicsBeijing Institute of TechnologyBeijing100081China Tangshan Research Institute of beijing Institute of Technology Tangshan063000HebeiChina

Boron is an ambitious fuel in energetic materials since its high heat release values,but its application is prohibited by low combustion efficiency and oxidization during *** polydopamine(PDA)was introduced into boron particles,investigating the impact of PDA content on the energetic behavior of *** results indicated that the PDA coating formed a fishing net structure on the surface of boron *** heat release results showed that the combustion calorific value of B@PDA was higher than that of the raw ***,the actual combustion heat of boron powder in B@10%PDA increased by 38.08%.Meanwhile,the DSC peak temperature decreased by 100.65℃under similar oxidation rate compared to raw ***,the B@PDA@AP and B@AP composites were prepared,and their combustion properties were *** was demonstrated that B@10%PDA@AP exhibited superior performance in terms of peak pressure and burning time,*** peak pressure is 12.43 kPa more than B@AP and burning time is 2.22 times higher than B@***,the coating of PDA effectively inhibits the oxidization of boron during storage and enhances the energetic behavior of boron and corresponding composites.

关键词： Boron particles Polydopamine Anti-aging performance improvement Heat release

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The Combination of Achnatherum inebrians Extracts and Soil Microorganisms Inhibited Seed Germination and Seedling Growth in Elymus nutans

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Phyton-International Journal of Experimental Botany 2024年第3期93卷 567-580页

作者： Rui Zhang Taixiang Chen Zhenjiang Chen Hao Chen Xuekai Wei Malik Kamran Chunjie Li State key laboratory of Herbage Improvement and grassland Agro-Ecosystems Key Laboratory of Animal Husbandry InnovationMinistry of Agriculture and Rural AffairsEngineering Research Center of Grassland AgricultureMinistry of EducationWest Gansu Province Prataculture Technology Innovation CenterCollege of Pastoral Agriculture Science and TechnologyLanzhou UniversityLanzhou730020China Center for grassland Research National Forestry and Grassland AdministrationCaFBeijing100091China

In a greenhouse experiment,the effects of soil microorganisms and extracts of Achnatherum inebrians on the seed germination and seedling growth of Elymus nutans were *** results showed that both the extracts from aboveground and belowground parts of *** signiﬁcantly inhibited the germination rate,germination potential,germination index,vigor index,seedling height,root length,and fresh weight of ***,but increased malondialdehyde content,catalase,peroxidase and superoxide dismutase activity of *** seedlings(p<0.05).The allelopathy of aqueous extracts of the aboveground parts of *** was stronger than that of the *** extracts of the aboveground parts of *** decreased seed germination rate,germination potential,germination index,vigor index,seedling length,root length,and seedling fresh weight by 10.45%-74.63%,24.18%-32.50%,19.03%-73.36%,37.83%-88.41%,21.42%-53.14%,2.65%-40.21%,and 20.45%-61.36%,respectively,and malondialdehyde content,peroxidase,catalase,and superoxide dismutase activity increased by 8.09%-62.24%,27.83%-86.47%,22.90%-93.17%,and 11.15%-75.91%,*** above indexes were higher in live soil than in sterilized *** microorganisms increased the allelopathy of *** seed germination rate,germination potential,germination index,vigor index,seedling length,and seedling fresh weight of *** planted in live soil decreased by 8.22%-48.48%,10.00%-51.85%,8.19%-53.26%,16.43%-60.03%,12.91%-28.81%,and 9.09%-22.86%compared with sterilized soil,*** content,peroxidase,catalase,and superoxide dismutase activity of *** planted in live soil increased by 53.91%-81.06%,15.71%-57.34%,33.33%-86.31%,and 9.78%-52.51%compared with sterilized soil,*** existence of soil microorganisms enhanced the allelopathy of the secondary metabolites of ***.A combination of microorganisms and aqueous extracts from the aboveground parts of *** had the s

关键词： Achnatherum inebrians water immersion liquid aqueous leachate precipitate allelopathy Elymus nutans soil microorganisms

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Grain size refinement of additive manufactured Ce-TZP ceramics by coupled two-step pre-sintering and HIP

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Journal of Advanced Ceramics 2024年第5期13卷 621-629页

作者： Ruoshi Zhao Hongbing Yang Xintong Liu Hezhen Li Chang-An Wang Jing Ma Yanhao Dong State key lab of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Ceria-stabilized tetragonal zirconia polycrystal(Ce-TZP)has exceptional fracture toughness and flaw tolerance due to facile t‒m phase transformation ***,its wider-range applications are limited by its relatively low strength due to its large grain size and low transformation stress,which results in yield-like ***,we combined additive manufacturing(AM),pressureless two-step sintering,and hot isostatic pressing(HIP),and addressed the challenging grain size refinement problem in *** successfully produced dense ultrafine-grained Ce-TZP ceramics with an average grain size below 500 nm,a three-point bending strength above 800 MPa,and a single-edge-notch-beam fracture toughness in the range of 11‒12 MPa·m^(1/2).The critical roles of processing design,mixed Ce valences,and ***-stabilization of tetragonal polymorphs were *** work offers insights and strategies for the future development of stronger and tougher Ce-TZP ceramics that can compete with tetragonal yttria-stabilized zirconia in various applications,including additive manufacturing.

关键词： zirconia additive manufacturing(AM) two-step sintering hot isostatic pressing(HIP) grain size refinement

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Universal dynamic scaling and Contact dynamics in quenched quantum gases

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Frontiers of physics 2024年第2期19卷 213-220页

作者： Jia-Nan Cui Zhengqiang Zhou Mingyuan Sun School of science Beijing University of Posts and TelecommunicationsBeijing 100876China State key lab of Information Photonics and Optical Communications Beijing University of Posts and TelecommunicationsBeijing 100876China

Recently universal dynamic scaling is observed in several systems,which exhibit a spatiotemporal self-similar scaling behavior,analogous to the spatial scaling near phase *** latter one arises from the emergent continuous scaling *** by this,we investigate the possible relation between the scaling dynamics and the continuous scaling symmetry in this *** derive a theorem that the scaling invariance of the quenched Hamiltonian and the initial density matrix can lead to the universal dynamic *** is further demonstrated both in a two-body system analytically and in a many-body system *** the latter one,we calculate the dynamics of quantum gases quenched from the zero interaction to a finite interaction via the non-equilibrium high-temperature virial expansion.A dynamic scaling of the momentum distribution appears in certain momentum-time windows at unitarity as well as in the weak interacting ***,this universal scaling dynamics persists approximately with smaller scaling exponents even if the scaling symmetry is fairly *** findings may offer a new perspective to interpret the related *** also study the Contact dynamics in the BEC−BCS ***,the half-way time displays a maximum near unitarity while some damping oscillations occur on the BEC side due to the dimer state,which can be used to detect possible two-body bound states in experiments.

关键词： dynamic scaling Contact dynamics quantum gases cold atom quench dynamics virial expansion continuous scaling symmetry

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