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Effect of confining pressure on rock breaking by high-pressure waterjet-assisted TBM

Underground Space 2024年第5期18卷 151-161页

作者： Chen Xu Yujie Zhu Xiaoli Liu Fei Chen Min Zhu Enzhi Wang Sijing Wang school of Resource and environment engineering Wuhan University of TechnologyWuhan 430070China Changjiang Institute of Survey PlanningDesign and ResearchWuhan 430010China State Key Laboratory of Hydroscience and engineering Tsinghua UniversityBeijing 100084China Key Laboratory of Geotechnical Mechanics and engineering of Ministry of Water resources Wuhan 430010China

High-pressure waterjet-assisted tunnel boring machine(WTBM)is an efficient method for improving the tunneling performance of a tunnel boring machine(TBM)and reducing the wear of its disc cutters in hard rock with high *** pressure directly affects the efficiency of rock breaking and the configuration of the disc *** this study,we evaluated the effect of confining pressure on WTBM rock breaking by developing a self-designed and manufactured experimental system,including confining pressure loading,TBM disc-cutter penetration,and high-pressure *** macro fracture,acoustic emission(AE),peak normal force drop,and specific energy(SE)were analyzed for four different confining pressures(10,20,30,and 35 MPa).The results showed that the cutting depth of the waterjet increased linearly as the waterjet pressure increased and decreased with the gradual increase in the nozzle moving *** expansion and development of cracks formed rock debris,and the size of the rock fragments decreased with an increase in confining *** the waterjet pressure was 280 MPa,the nozzle moving velocity was 800 mm/min and the kerf space was 75 mm,which indicated that the confining pressure,which was 23.16 MPa,minimized the cutting SE under this ***,regardless of the confining pressure,the maximum normal force of WTBM was less than that of a TBM,whereas the SE of WTBM was less than that of complete TBM cutting mode(CTCM).The average force drop and average drop rate of SE were approximately 25%,and 80%,*** results of this study can inspire the design and mechanism of a TBM assisted by a high-pressure waterjet.

关键词： Waterjet Tunnel boring machine(TBM) Confining pressure Specific energy Force drop

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Hydrothermal liquefaction of biomass for jet fuel precursors:A review

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Chinese Chemical Letters 2024年第8期35卷 36-49页

作者： Shengfei Dong Ziyu Liu Xiaoyi Yang school of Energy and Power engineering Energy and Environment International CentreBeihang UniversityBeijing 100191China school of Aeronautic Science and engineering Beihang UniversityBeijing 100191China

Climate change is an important issue facing the world today and carbon reduction has become the fo-cus of attention for all *** bio-fuels are an important means to achieve carbon emis-sion *** production of jet fuel precursors from biomass by hydrothermal liquefaction(HTL)has received a lot of attention due to its mild conditions and environmental *** biomass and algal biomass are considered as the second and the third generation biomasses as promising raw materials for alternative fuel *** them,lignocellulosic biomass has been extensively studied due to its wide range of sources and can be divided into one-step HTL and stepwise HTL accord-ing to the process *** biomass has been extensively studied experimentally due to its short growth cycle and the fact that it can sequester large amounts of carbon without taking up arable *** this paper,the feedstock composition of different biomasses is reviewed for the HTL of biomass.A detailed review of the process characteristics,reaction pathways and influencing factors for the HTL pro-duction of jet fuel precursors from lignocellulosic biomass and algal biomass is also *** references are provided for further process optimization and bio-crude quality upgrading.

关键词： Hydrothermal liquefaction(HTL) Lignocellulosic biomass Microalgae Bio-crude Jet fuel precursors

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Thermal decomposition mechanism and kinetics of bastnaesite in suspension roasting process:A comparative study in N_(2) and air atmospheres

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Journal of Rare Earths 2024年第9期42卷 1809-1816,I0006页

作者： Wenbo Li Jijia Chen Shaokai Cheng Junyan Sun Xiaolong Zhang school of resources and Civil engineering Northeastern UniversityShenyang110819China National-Local Joint engineering Research Center of High-Efficient Exploitation Technology for Refractory Iron Ore resources Shenyang110819China

To investigate the thermal decomposition behavior and reaction kinetics of bastnaesite in suspension roasting,the gas and solid products of bastnaesite roasted in N2 and air atmospheres were examined using a gas analyzer,X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometry(EDS).Subsequently,the kinetic parameters of bastnaesite in the suspension roasting process were derived and calculated using the isothermal *** results show that the decomposition product of bastnaesite in N_(2) is ***,once the roasting temperature exceeds 600℃,CO is generated in addition to CO_(2),and all the XRD diffraction peaks of CeOF are shifted to the right,indicating that CO_(2) can oxidize CeOF and lead to the transformation of Ce(Ⅲ) into Ce(Ⅳ).When roasted in air,the decomposition product CeOF can be completely converted to CeF3 and Ce_(7)O_(12) as it easily ***,the reaction rate of bastnaesite in air is higher than that of N_(2),and the starting reaction temperature is lower than that of N_(2).A large number of irregular cracks and holes appear on the surface of solid-phase products following suspension roasting,which are due to the thermal decomposition of bastnaesite that produces CO_(2) as well as the reconstruction of the lattice of the solid-phase *** reaction kinetic model of bastnaesite roasted in N_(2)(temperature range 600-750℃) and air(temperatu re range 500-575℃) confo rms to the A_(3/2) model with the mechanism function G(α)=-ln(1-α)^(2/3),and the reaction activation energy is 59.78 kj/mol and lnA is 1.65 s^(-1) in N_(2) *** air,the reaction activation energy is 100.30 kj/mol and lnA is 9.63 s^(-1).

关键词： Rare earths Bastnaesite Suspension roasting Thermal decomposition mechanism Reaction kinetics

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Promoting environmental Risk Assessment and Control of Emerging Contaminants in China

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engineering 2024年第6期37卷 13-17页

作者： Bin Wang Qian Sui Huijuan Liu Gang Yu Jiuhui Qu school of environment Tsinghua UniversityBeijing 100084China school of resources and environmental engineering East China University of Science and TechnologyShanghai 200237China Advanced Interdisciplinary Institute of environmental and Ecology Beijing Normal UniversityZhuhai 519000China

*** In recent years,China has carried out an extensive preventative battle against air,water,and soil pollution,and the nation’s environmental quality-as reflected by conventional pollutant indicators—has significantly *** the same time,the issue of emerging contaminants(ECs)is beginning to receive increasing *** generally refer to newly discovered or noticeable pollutants that pose risks to the ecological environment or human *** they have not been included in environmental management,or existing management measures are insufficient to effectively prevent and control their *** ECs of greatest concern generally include persistent organic pollutants(POPs),endocrine-disrupting chemicals(EDCs),pharmaceuticals and personal care products(PPCPs),and *** four categories of ECs are not entirely separate,as they interrelate with each other(Fig.1).Chemical production and product usage are the main sources of *** is the world’s largest producer and consumer of bulk chemicals,and the production value of China’s chemical industry is predicted to reach 50%of the global total by 2030[1].Scientific control of ECs based on their environmental risk assessment is a necessary way to support the prevention and legal governance of ECs.

关键词： legal entirely prevention

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Crystal phase control and ignition properties of HNS/CL-20 composite microspheres prepared by microfluidics combined with emulsification techniques

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Particuology 2024年第2期85卷 241-251页

作者： Yi Liu Yunyan Guo Rui Zhu Jinqiang Zhou Zhengxu Lin Kai Han Chongwei An Jingyu Wang Bidong Wu school of environment and Safety engineering North University of ChinaTaiyuan030051China school of engineering Beijing Institute of TechnologyBeijing100081China Shanxi Province Ultrafine Powder engineering Technology Research Center Taiyuan030051China

Improved controllability and energy density of ignition agents are of great significance for the devel-opment of energetic composite *** this study,droplet microfluidics and emulsification tech-niques were combined to prepare HNS/CL-20 composite microspheres with polyglycidyl azide polymer(GAP)as the *** influence of binder content on the morphology of microspheres was investi-gated,and the microspheres were characterized and tested for particle size,crystal structure,thermal decomposition,dispersibility,mechanical sensitivity,combustion behavior and detonation *** results showed that microspheres prepared with a binder content of 3%had higher sphericity and particle size *** microspheres retained the crystal structure of both HNS and CL-20(ε-type).Compared with raw HNS,the microspheres had higher apparent activation energy,better safety per-formance,and good *** ignition experiments and detonation performance tests show that HNS/CL-20 composite microspheres have excellent ignition performance,obvious combustion flame,and significant energy release effects,which are expected to achieve high energy and high-speed response of the igniter,thus improving the ignition reliability in special environments or systems.

关键词： Droplet microfluidics Emulsification technology Energetic materials Composite microspheres Crystal phase control Ignition

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Precise regulation of the phase transformation for pyrolusite during the reduction roasting process

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 81-90页

作者： Ruofeng Wang Peng Gao Shuai Yuan Yanjun Li Yingzhi Liu Cheng Huang school of resources and Civil engineering Northeastern UniversityShenyang 110819China National-Local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang 110819China

The mechanism involved in the phase transformation process of pyrolusite (MnO_(2)) during roasting in a reducing atmosphere was systematically elucidated in this study,with the aim of effectively using low-grade complex manganese ore *** to single-factor experiment results,the roasted product with a divalent manganese (Mn^(2+)) distribution rate of 95.30% was obtained at a roasting time of 25 min,a roasting temperature of 700℃,a CO concentration of 20at%,and a total gas volume of 500 mL·min^(-1),in which the manganese was mainly in the form of manganosite (MnO).Scanning electron microscopy and Brunauer–Emmett–Teller theory demonstrated the microstructural evolution of the roasted product and the gradual reduction in the pyrolusite ore from the surface to the core Thermodynamic calculations,X-ray photoelectron spectroscopy,and X-ray diffractometry analyses determined that the phase transformation of pyrolusite followed the order of MnO_(2)→Mn_(2)O_(3)→Mn_(3)O_(4)→MnO phase by phase,and the reduction of manganese oxides in each valence state proceeded simultaneously.

关键词： pyrolusite phase transformation reduction roasting microstructural evolution reaction mechanism

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Recent process developments in beneficiation and metallurgy of rare earths:A review

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Journal of Rare Earths 2024年第4期42卷 629-642页

作者： Shaokai Cheng Wenbo Li Yuexin Han Yongsheng Sun Peng Gao Xiaolong Zhang school of resources and Civil engineering Northeastern UniversityShenyang110819China National-local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang110819China

Rare earth elements(REEs)are irreplaceable materials supporting low-carbon technology and equip-ment,and their commercial demand and strategic position are becoming increasingly *** the continuous depletion of rare earth(RE)resources,developing high-efficiency beneficiation and eco-friendly metallurgical processes has attracted widespread *** paper reviews the major minerals exploited for RE production and their deposits,as well as the beneficiation and metallurgical processes of RE ***,monazite,mixed RE ores,and ion-adsorption clays are the main raw materials in the world to ***-bearing ores(except ion-adsorption minerals)are generally beneficiated by flotation,gravity and magnetic separation *** mainstream metallurgical processes for bastnaesite,monazite and mixed RE concentrates are oxidation roasting-HCl leaching,caustic soda decomposition and high-temperature concentrated sulfuric acid roasting,***-adsorption clays are directly processed by in situ leaching-precipitation/solvent *** achieve the sustainable development of RE resources,it is essential to further explore innovative techniques to achievecomprehensive utilization and cleaner production.

关键词： Rare earths Beneficiation processes Metallurgical processes Cleaner production

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Dynamic COVID Zero Strategy triggered a significant increase of chlorine-based disinfectant

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Frontiers of environmental Science & engineering 2024年第8期18卷 73-80页

作者： Xuhao Wang Mai Su Chunyan Wang Yi Liu school of environment Tsinghua UniversityBeijing 100084China

Chlorine-based disinfectants(CBDs)have been widely used to prevent and control the spread of the COVID-19,which may lead to the formation of carcinogenic *** China,strict disinfection strategies by local governments/communities or volunteering by residents have been implemented to meet the Dynamic COVID Zero(DCZ)***,the amount of CBDs used has not been *** author proposed an urban-scale disinfectant consumption estimation(ALICE)model to quantify weekly CBD *** results show that the CBD consumption for the urban region of Beijing during the DCZ strategy was 3704.0 t(0.43 kg/(cap-yr)),equivalent to a monthly increase of 15 g/cap(70.5%)in CBD consumption compared with that in *** to the scenario analysis,a stricter strategy with a shorter response time toward new cases will decrease the total CBD consumption by 1.2% compared with the baseline estimation.A more precise prevention strategy with a smaller delineation of risk area and a less stringent strategy with a longer response time will lower the total CBD consumption by 0.42% and 0.35%,***,the more precise prevention strategy will reduce CBD consumption of close off and lockdown area(COLD area)by 16.9%,and the stricter strategy will reduce this consumption by 37.7%.This study highlights the impact of pandemic prevention and control strategies on chlorine-based disinfectant consumption and some implications for future environmental pollution and risk assessments.

关键词： COVID-19 Dynamic COVID Zero Strategy Disinfectants consumption Bottom-up approach Scenario analysis

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Iron-induced NaTi（PO）with regulated electronic structure enables freshwater harvesting based on rocking-chair desalination battery

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Science China Chemistry 2024年

作者： Yuliang Wu Chen Ling Chaolin Li Wenhui Wang school of Civil and environmental engineering Harbin Institute of Technology school of environment and resources Taiyuan University of Science and Technology State Key Laboratory of Urban Water Resource and environment Harbin Institute of Technology

Despite the promising potential of NaTi2（PO4）3as desalination battery electrode,its mediocre seawater desalination capacity and durability fail to meet the requirements of practical ***,the substitution of Ti by Fe in NaTi2（PO4）3(NT2-xFxP),which possesses a stronger electronegativity relative to Ti,can regulate the electronic structure,thus facilitating charge transfer and ion diffusion during the desalination *** kinetic and thermodynamic facilitation of NT2-xFxP is clarified by the electrochemical analyses and DFT ***,the additional redox center and solid-solution reaction mechanism induced by Fe-dopant further contribute to a superior desalination performance of NT2-xFxP in different seawater *** from the multifunctional effect of Fe-dopant,the optimal NT1.7F0.3P delivers a large salt removal capacity(173.6 mg g-1) with an ultrahigh salt removal rate (8.48 mg g-1min-1),and maintains 96.6%of desalination capacity after 500cycles in natural ***,the assembled NT1.7F0.3P||NaFeHCF rocking-chair desalination battery （RCDB） demonstrates a higher desalination performance than that of reported RCDB systems,and can desalinate natural seawater to freshwater standards under continuous desalination mode for the first time in RCDB *** work provides a facile but effective strategy to modulate the electronic structure of NaTi2（PO4）3for RCDB,and exploits a new perspective for developing scalable RCDB devices for continuous desalinating real seawater to freshwater.

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Energy evolution and structural health monitoring of coal under different failure modes:An experimental study

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 917-928页

作者： Yarong Xue Xueqiu He Dazhao Song Zhenlei Li Majid Khan Taoping Zhong Fei Yang school of Civil and resources engineering University of Science and Technology BeijingBeijing 100083China Zhong-an Academy of Safety engineering Beijing 100083China

Structural instability in underground engineering,especially in coal-rock structures,poses significant safety ***,the development of an accurate monitoring method for the health of coal-rock bodies is *** focus of this work is on understanding energy evolution patterns in coal-rock bodies under complex conditions by using shear,splitting,and uniaxial compression *** examine the changes in energy parameters during various loading stages and the effects of various failure modes,resulting in an innovative energy dissipation-based health evaluation technique for *** results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading,indicated by fluctuations in elastic energy and dissipation energy *** tensile failure,the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak *** the other hand,shear failure is described by “high accumulation and low dissipation” in energy *** failure modes correlate with an accelerated increase in the dissipation energy before destabilization,and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples.A novel mathematical and statistical approach is developed,establishing a dissipation energy anomaly index,W,which categorizes the structural health of coal into different danger *** method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments,contributing to the development of structural health monitoring technology.

关键词： energy dissipation structural health monitoring early warning coal-rock mechanics failure mode

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