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Development of multi-functional anchorage support dynamic-static coupling performance test system and its application

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International Journal of Mining Science and Technology 2024年第3期34卷 339-349页

作者： Qi Wang Shuo Xu Bei Jiang Chong zhang Zhe Sun Jingxuan Liu Cailin jiao State Key Laboratory for Tunnel Engineering China University of Mining&Technology-BeijingBeijing 100083China Research Center of Geotechnical and Structural Engineering Shandong UniversityJinan 250061China

In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high *** is essential to study the support components performance under dynamic-static coupling *** on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so *** bolt and cable mechanical tests are conducted by MAC system under different prestress *** results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly *** the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress *** the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress *** MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.

关键词： Anchorage support system Development of test system Dynamic-static coupling test Combined stress

Flow field, sedimentation, and erosion characteristics around folded linear HDPE sheet sand fence: Numerical simulation study

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Journal of Mountain Science 2024年第1期21卷 113-130页

作者： zhang Kai zhang Hailong tian Jianjin QU Jianjun zhang Xingxin WANG Zhenghui XIAO jianhua College of Civil Engineering Lanzhou Jiaotong UniversityLanzhou 730000China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China College of Civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Wind and sand hazards are serious in the Milan Gobi area of the Xinjiang section of the Korla Railway. In order to ensure the safe operation of railroads, there is a need for wind and sand protection in heavily sandy areas. The wind and sand flow in the region is notably bi-directional. To shield railroads from sand, a unique sand fence made of folded linear high-density polyethylene(HDPE) is used, aligning with the principle that the dominant wind direction is perpendicular to the fence. This study employed field observations and numerical simulations to investigate the effectiveness of these HDPE sand fences in altering flow field distribution and offering protection. It also explored how these fences affect the deposition and erosion of sand particles. Findings revealed a significant reduction in wind speed near the fence corner;the minimum horizontal wind speed on the leeward side of the first sand fence(LSF) decreased dramatically from 3 m/s to 0.64 m/s. The vortex area on the LSF markedly impacted horizontal wind speeds. Within the LSF, sand deposition was a primary occurrence. As wind speeds increased, the deposition zone shrank, whereas the positive erosion zone expanded. Close to the folded corners of the HDPE sand fence, there was a notable shift from the positive erosion zone to a deposition zone. Field tests and numerical simulations confirmed the high windproof efficiency(WE) and sand resistance efficiency(SE) in the HDPE sand fence. Folded linear HDPE sheet sand fence can effectively slow down the incoming flow and reduce the sand content, thus achieving good wind and sand protection. This study provides essential theoretical guidance for the design and improvement of wind and sand protection systems in railroad engineering.

关键词： Folded linear HDPE sheet sand fence Numerical simulation Flow field characteristics Protection benefits

Ru-doped functional porous materials for electrocatalytic water splitting

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Nano Research 2024年第3期17卷 982-1002页

作者： Chongao tian Rui Liu Yu zhang Wenxiu Yang Bo Wang Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials Advanced Technology Research Institute(Jinan)Advanced Research Institute of Multidisciplinary ScienceSchool of Chemistry and Chemical EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Library Beijing Institute of TechnologyBeijing 100081China

Electrolytic water splitting(EWS)is an attractive and promising technique for the production of hydrogen ***,the sluggish kinetic rate of hydrogen/oxygen evolution reactions leads to a high overpotential and low energy *** to date,Pt/Ir-based nanocatalysts have become the state-of-the-art EWS catalysts,but disadvantages such as high cost and low earth abundance greatly limit their applications in EWS *** an attractive candidate for the Pt/Ir catalysts,series of Ru-based nanomaterials have aroused much attention for their low price,Pt-like hydrogen bond strength,and high EWS *** particular,Ru-doped functional porous materials have been becoming one of the most representative EWS catalysts,which can not only achieve the dispersion and adjustment for active Ru sites,but also simultaneously solve the problems of mass transfer and catalytic conversion in *** this review,the design and preparation strategies of Ru-doped functional porous materials toward EWS in recent years are summarized,including Ru-doped metal organic frameworks(MOFs),Ru-doped porous organic polymers(POPs),and their ***,detailed structure–activity relationships induced by the tuned geometric/electronic structures of Ru-doped functional porous materials are further depicted in this *** but not least,the challenges and perspectives of Ru-doped functional porous materials catalysts are reasonably proposed to provide fresh ideas for the design of Ru-based EWS catalysts.

关键词： Ru-based catalyst functional porous materials electrolytic water splitting oxygen evolution reaction hydrogen evolution reaction

Radial growth in Qinghai spruce is most sensitive to severe drought in the Qilian Mountains of Northwest China

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Journal of Forestry Research 2024年第3期35卷 73-86页

作者： Xuge Wang Liang jiao Ruhong Xue Peng zhang Dashi Du Mengyuan Wei Qian Li College of Geography and Environmental Science Northwest Normal UniversityNo.967Anning East RoadLanzhou 730070People's Republic of China Key Laboratory of Resource Environment and Sustainable Development of Oasis Northwest Normal UniversityLanzhou 730070Gansu ProvincePeople's Republicof China

Global warming and frequent extreme drought events lead to tree death and extensive forest decline,but the underlying mechanism is not *** drought years,cambial development is more sensitive to climate change,but in different phenological stages,the response rela-tionship is ***,the dynamic relationship between tree radial growth and climatic/environmental fac-tors needs to be *** thus continuously monitored radial growth of Qinghai spruce(Picea crassifolia Kom.)and environmental factors from January 2021 to November 2022 using point dendrometers and portable meteorological weather stations in the central area of the Qilian *** relationship and stability between the radial growth of Qinghai spruce and environmental factors were compared for different levels of drought in 2021 and *** year 2022 had higher temperatures and less precipitation and was drier than *** with 2021,the growing period in 2022 for Qinghai spruce was 10 days shorter,maximum growth rate(Grmax)was 4.5μm·d^(-1) slower,and the initiation of growth was 6 days *** of Qinghai spruce was always restricted by drought,and the stem radial increment(SRI)was more sensitive to precipitation and air relative *** changes in cumulative radial growth were divided into four phenological stages according to the time of growth onset,cessation,and maximum growth rate(Grmax)of Qinghai *** responses of SRI to climate change were stronger in Stage 3 and Stage 4 of 2021 and stronger in Stage 1(initiation growth stage)and Stage 3 of *** results provide important information on the growth of the trees in response to drought and for specific managing forests as the climate warms.

关键词： Picea crassifolia Radial growth dynamics Severe drought Response stability Point dendrometer

Design of an aircraft autonomous traction taxiing system based on hydraulic secondary control

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Chinese Journal of Aeronautics 2024年第6期37卷 348-359页

作者： Xiaochao LIU Zhongyi QIU Hao zhang Pengyuan QI Zhenyu WANG Yaoxing SHANG Zongxia jiao Research Institute for Frontier Science Beihang UniversityBeijing 100083China School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China Ningbo Institute of Technology Beihang UniversityNingbo 315800China tianmushan Laboratory Xixi Octagon CityYuhang DistrictHangzhou 310023China Science and Technology on Aircraft Control Laboratory Beihang UniversityBeijing 100083China Beijing tianma Intelligent Control Technology Co. Ltd.Beijing 101399China China Coal Research Institute Beijing 100013China

At present,aircraft taxiing at ground airports needs to be provided with a thrust by the main *** taxiing process is inefficient,has high fuel consumption and serious pollution,and is prone to safety *** this paper,a new configuration of aircraft autonomous traction taxiing system is proposed based on the principle of hydraulic secondary control,in which a hydraulic motor drive device is installed at the front wheels of the aircraft to drive the wheels to rotate forward or *** on this,autonomous taxiing can be realized without relying on the main engines,thus greatly improving airport operation ***,this paper analyzes the influencing factors of the autonomous traction taxiing process,and investigates the parameter matching design of the new configuration ***,this paper develops the ground principle prototype,designs the aircraft longitudinal bonding force observer and the aircraft wheel disturbance moment observer,and proposes the speed control method of the aircraft front wheel autonomous traction taxiing by considering the ground bonding force saturation ***,the ground taxiing test is conducted,and the results show that the new configuration proposed in this paper presents a new solution for aircraft autonomous traction taxiing.

关键词： Autonomous traction taxi-ing Hydraulic secondary control Hydraulic motors Saturation characteristics Disturbance observation Speed control

Ultralow-phase-noise and broadband frequency-hopping coupled optoelectronic oscillator under quiet point operation

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Photonics Research 2024年第8期12卷 1785-1793页

作者： HUI LIU MINGYANG GUO tian zhang JIAN DAI KUN XU State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and TelecommunicationsBeijing 100876China School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

Advancements in microwave photonics have yielded novel approaches for generating high-purity microwave *** these,optoelectronic oscillators(OEOs)and coupled optoelectronic oscillators(COEOs)have demonstrated the capability to generate frequency-independent microwaves with exceptionally low phase ***,the tunability of the oscillators is rather limited due to the necessity for narrowband electronic bandpass filters,presenting challenges in achieving both wide and rapid tuning ***,we present a COEO featuring ultralow phase noise,flexible tuning capability,and high *** is achieved through a quiet point(QP)-operated harmonic mode-locked fiber laser,which effectively mitigates optical amplifier noise and supermode competition,thus significantly diminishing the necessity for ultra-narrow electronic *** to the liberated tuning ability,we present an oscillator that can be tuned from 2 GHz to 18 GHz,with phase noise as low as-140 d Bc/Hz at 10 k Hz under the QP *** then illustrate the practical application of the proposed oscillator in generating frequency-hopping signals with consistent spurious modes less than-85 d Bc,absolute phase noise below-135 d Bc/Hz at 10 k Hz,hopping resolution of 1.25 MHz,and fractional frequency stability below 6.1×10^(-12)at 1 s averaging time when locked to a *** presented COEO structure emerges as a compelling solution for agile and low-noise microwave sources in advanced wireless communication and radar systems.

关键词： optoelectronic tuning amplifier

Numerical simulation of flow field deposition and erosion characteristics around bridge-road transition section

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Journal of Mountain Science 2024年第5期21卷 1491-1508页

作者： zhang Kai WANG Zhenghui WANG Tao tian Jianjin zhang Hailong LIU Yonghe College of Civil Engineering Lanzhou Jiaotong UniversityLanzhou 730000China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Wind-sand flow generates erosion and deposition around obstacles such as bridges and roadbeds, resulting in sand damage and endangering railway systems in sandy regions. Previous studies have mainly focused on the flow field around roadbeds, overlooking detailed examinations of sand particle erosion and deposition patterns near bridges and roadbeds. This study employs numerical simulations to analyze the influence of varying heights and wind speeds on sand deposition and erosion characteristics at different locations: the bridge-road transition section(side piers), middle piers, and roadbeds. The results show that the side piers, experience greater accumulation than the middle piers. Similarly, the leeward side of the roadbed witnesses more deposition compared to the windward side. Another finding reveals a reduced sand deposition length as the vertical profile, in alignment with the wind direction, moves further from the bridge abutments at the same clearance height. As wind speeds rise, there’s a decline in sand deposition and a marked increase in erosion around the side piers, middle piers and roadbeds. In conclusion, a bridge clearance that’s too low can cause intense sand damage near the side piers, while an extremely high roadbed may lead to extensive surface sand deposition. Hence, railway bridges in areas prone to sandy winds should strike a balance in clearance height. This research provides valuable guidelines for determining the most suitable bridge and roadbed heights in regions affected by wind and sand.

关键词： Sandstorm Flow field Bridge-road transition section Sedimentation erosion Numerical simulation

Ni-catalyzed highly regio- and stereo-selective diborylative cyclization of 1,6-enynes with diboron reagent

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Science China Chemistry 2024年第3期67卷 981-989页

作者： Qitao Guan Zhen Shen Yiqiang tian Genping Huang Chun zhang Institute of Molecular Plus Tianjin Key Laboratory of Molecular Optoelectronic ScienceDepartment of ChemistrySchool of SciencesTianjin UniversityTianjin 300072China State Key Laboratory of Elemento-Organic Chemistry Nankai UniversityTianjin 300071China

The Ni-catalyzed highly selective diborylative cyclization of 1,6-enynes with diboron reagent has been developed. When pinB-Bdan was used, multiple types of boron-containing functional groups could be installed into organic molecule with great chemoselectivity and regioselectivity though this reaction. Meanwhile, if B_2pai_2 was employed, the asymmetric diborylative cyclization could be well induced by using strategy of dynamic kinetic resolution. Importantly, the above reactions could afford desired product with 100% atomic economy, and could be compatible with different series of substituents. The studies of further transformation well illustrated that different type products could serve diverse synthetic strategy. Notably, the reaction mechanism was intensively studied by density functional theory(DFT) calculations, which could reveal the mechanism of regio- and enantio-selective control.

关键词： nickel-catalyzed organoboron cyclization regioselectivity enantioselectivity

C_(60) as a metal-free catalyst for lithium-oxygen batteries

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Nano Research 2024年第5期17卷 3982-3987页

作者： Xinxin zhang Jiaming tian Yu Wang Shaohua Guo Yafei Li Jiangsu Collaborative Innovation Centre of Biomedical Functional Materials School of Chemistry and Materials ScienceNanjing Normal UniversityNanjing 210023China College of Engineering and Applied Sciences Jiangsu Key Laboratory of Artificial Functional MaterialsNational Laboratory of Solid State MicrostructuresCollaborative Innovation Center of Advanced MicrostructuresFrontiers Science Center for Critical Earth Material CyclingNanjing UniversityNanjing 210023China

Carbon materials have shown significant potential as catalysts for lithium-oxygen batteries(LOBs).However,the intrinsic carbon sites are typically inert,necessitating extensive modifications and resulting in a limited density of active *** we present C_(60) as a metal-free cathode catalyst for LOBs,using density functional theory calculations and experimental *** lithiation reactions on the pristine carbon sites of C_(60) are energetically favorable due to its curvedπ-conjugation over the pentagon-hexagon *** kinetic analysis specifically reveals low energy barriers for Li_(2)O_(2) decomposition and Li diffusion on C_(60).Consequently,C_(60) exhibits significantly higher catalytic activity than typical carbon materials such as graphene and carbon *** electrochemical measurements validate the predictions,notably demonstrating that the intrinsic activity of C_(60) is comparable to that of noble metals.

关键词： lithium-oxygen batteries C_(60) density functional theory(DFT)calculations metal-free cathode