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Three dimensional discrete element modelling of the conventional compression behavior of gas hydrate bearing coal

International Journal of Coal Science & Technology 2024年第1期11卷 61-77页

作者： xia Gao Nannan Wang Baoyong Zhang Qiqi Lin Qiang Wu Wei Meng xia Liu Department of Architecture and Civil Engineering Heilongjiang University of Science and TechnologyHarbin150022China School of Qilu Transportation Shandong UniversityJinan250061China Department of Safety Engineering Heilongjiang University of Science and TechnologyHarbin150022China Jining Hongxiang Highway Survey Design and Research Institute Co.Ltd Jining272000China

To analyze the relationship between macro and meso parameters of the gas hydrate bearing coal(GHBC)and to calibrate the meso-parameters,the numerical tests were conducted to simulate the laboratory triaxial compression tests by PFC3D,with the parallel bond model employed as the particle contact constitutive ***,twenty simulation tests were conducted to quantify the relationship between the macro–meso ***,nine orthogonal simulation tests were performed using four meso-mechanical parameters in a three-level to evaluate the sensitivity of the meso-mechanical ***,the calibration method of the meso-parameters were then ***,the contact force chain,the contact force and the contact number were examined to investigate the saturation effect on the meso-mechanical behavior of *** results show that:(1)The elastic modulus linearly increases with the bonding stiffness ratio and the friction coefficient while exponentially increasing with the normal bonding strength and the bonding radius *** failure strength increases exponentially with the increase of the friction coefficient,the normal bonding strength and the bonding radius coefficient,and remains constant with the increase of bond stiffness ratio;(2)The friction coefficient and the bond radius coefficient are most sensitive to the elastic modulus and the failure strength;(3)The number of the force chains,the contact force,and the bond strength between particles will increase with the increase of the hydrate saturation,which leads to the larger failure strength.

关键词： Gas hydrate bearing coal Discrete element method Triaxial compression test Macro-meso mechanical propertie

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A super sandstorm altered the abundance and composition of airborne bacteria in Beijing

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Journal of Environmental Sciences 2024年第10期144卷 35-44页

作者： Fanxuan xia Zhuo Chen Enze Tian Jinhan Mo Beijing Key Laboratory of Indoor Air Quality Evaluation and Control Department of Building ScienceTsinghua UniversityBeijing 100084China Songshan Lake Materials Laboratory Dongguan 523808China Institute of Physics Chinese Academy of SciencesBeijing 100190China College of Civil and Transportation Engineering Shenzhen UniversityShenzhen 518060China Key Laboratory of Coastal Urban Resilient Infrastructures(Shenzhen University) Ministry of EducationShenzhen 518060China Key Laboratory of Eco Planning&Green Building(Tsinghua University) Ministry of EducationBeijing 100084China

Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built ***,few studies have examined the change of airborne bacteria during severe sandstorm *** this work,we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia onMarch 15th,2021,which affected large areas of China and *** characteristics of the sandstorm were compared with those of the subsequent clean and haze *** composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction(qPCR)and high-throughput sequencing *** the sandstorm,the particulate matter(PM)concentration and bacterial richnesswere extremely high(PM2.5:207μg/m3;PM10:1630μg/m3;5700 amplicon sequence variants/m3).In addition,the sandstorm brought 10 pathogenic bacterial genera to the atmosphere,posing a grave hazard to human *** the sandstorm subsided,small bioaerosols(0.65–1.1μm)with a similar bacterial community remained suspended in the atmosphere,bringing possible long-lasting health risks.

关键词： Airborne bacteria Sandstorm Bioaerosol Haze Pathogen

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Intelligent Reflecting Surface-Aided Secure and Covert Communications

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China Communications 2024年第9期21卷 1-10页

作者： Zhou xiaobo Jiang Yong xia Tingting xia Guiyang Shen Tong School of Information and Artificial Intelligence Anhui Agricultural UniversityAnhui 230036China

This work employs intelligent reflecting surface(IRS)to enhance secure and covert communication *** formulate an optimization problem to jointly design both the reflection beamformer at IRS and transmit power at transmitter Alice in order to optimize the achievable secrecy rate at Bob subject to a covertness *** first develop a Dinkelbach-based algorithm to achieve an upper bound performance and a high-quality *** reducing the overhead and computational complexity of the Dinkelbach-based scheme,we further conceive a low-complexity algorithm in which analytical expression for the IRS reflection beamforming is derived at each *** result shows that the devised low-complexity algorithm is able to achieve similar secrecy rate performance as the Dinkelbach-based *** examination also shows that introducing an IRS into the considered system can significantly improve the secure and covert communication performance relative to the scheme without IRS.

关键词： covert communications intelligent reflecting surface physical layer security reflection beamforming

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mtDNA-triggered pH response signal-amplified fluorescent probe for multiple cell discrimination

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Chinese Chemical Letters 2024年第3期35卷 363-368页

作者： Tianping xia Yanxian Hou Zhuoran xia Gengwen Chen Peichen Tang Jiangli Fan xiaojun Peng State Key Laboratory of Fine Chemicals Frontiers Science Center for Smart Materials Oriented Chemical EngineeringDalian University of TechnologyDalian 116024China Hematology Reagent R&D Department Mindray Bio-medical Electronics Co.Ltd.Shenzhen 518132China Research Institute of Dalian University of Technology in Shenzhen Shenzhen 518057China

Developing fluorescence probes with multiple responses has vital significance but remains ***,for the first time,we present a mitochondrial DNA(mtDNA)-triggered pH response signalamplified fluorescent probe(QCY-DBT)for multiple cell *** probe exhibited a large stokes shift(229 nm),excellent DNA selectivity over RNA,and ultrasensitivity of detection limit(DL;74.0 ng/mL).Thus,QCY-DBT was successfully applied to analyze multiple human peripheral blood cells and visualize mtDNA in healthy and apoptotic *** the tumor acidic environment(pH 6.0–7.0),the absorbance of QCY-DBT at 436 nm increased,and the fluorescence signal(665 nm)was amplified by mtDNA,which enabled the direct observation of tumor *** study provides help in designing smart probes with multiple responses for efficient abnormal cell detection.

关键词： Fluorescence probe Mitochondrial DNA pH response Peripheral blood cells Multiple cell detection

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Performance Enhancement of Single-Phase Immersion Liquid-Cooled Data Center Servers

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Journal of Thermal Science 2024年第5期33卷 1757-1772页

作者： GE Junlei xia Feifan ZHANG Chengbin HUANG Yongping School of Energy and Environment Southeast UniversityNanjing 210096China Wuhan Digital Engineering Research Institute Wuhan 430205China

As the promising cooling method for the next generation of data centers,the internal heat transport mechanism and enhancement mechanism of single-phase immersion liquid-cooled(SPILC)systems are not yet well *** address this,a steady-state three-dimensional numerical model is constructed herein to analyze flow and thermal transport capacities in servers using SPILC and traditional air-cooling ***,this paper emphasizes the influence of component positioning,and underscores the benefits of optimizing coolant flow distribution using *** results indicate that the SPILC system outperforms the traditional air-cooling approach at the same inlet Reynolds number(Re).When Re=10000,the SPILC method reduces the maximum temperature by up to 70.13%,increases the average convective heat transfer coefficient by287.5%,and provides better overall thermal uniformity in data center ***,placing devices downstream of high-power components creates"thermal barriers"and degrades thermal transport for upstream devices due to increased flow *** spacing between high-power devices can lead to the formation of bypass channels,further deteriorating heat ***,the addition of baffles in the inlet section of SPILC systems effectively enhances heat dissipation *** maximize the heat dissipation capacity,minimizing bypass channels and optimizing the flow distribution of coolants are crucial.

关键词： single-phase immersion liquid-cooled performance enhancement data center

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Numerical insight into heat transfer enhancement by granules inner-migration in a moving bed:A performance comparison between slanted-stick and plow-shaped agitator

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Particuology 2024年第6期89卷 109-116页

作者： Binfan Jiang Hao Pei Dehong xia Haiyang Wang School of Energy and Environmental Engineering University of Science and Technology BeijingBeijing 100083China Shunde Graduate School of University of Science and Technology Beijing Guangdong 528399China Jianlong Group&USTB Joint Laboratory Beijing 100083China

Waste heat recovery of high-temperature granules is one of the most promising sustainable energy supply and carbon reduction ways for industry.A moving bed indirect heat exchanger(MBIHE)with inner-migration was proposed for granular heat *** migration and the enhanced heat transfer induced by two types of agitators(i.e.,agitator with slanted stick A_(s)and with plow-shaped surface A_(p))in the MBIHE are analyzed based on DEM coupled with *** to the effective agitation,the average heat transfer coefficient in the granule side is enhanced to∼3 times compared to that without *** heat recovery efficiency in the moving bed reached more than 70%with the agitations of either A_(s)or A_(p).The heat efficiency of A_(s)is∼7%higher than that of A_(p),but with at least 60%greater rotational *** ensure reliable agitation,the A_(p)is suggested to be adopted in the MBIHE to induce granule migration.

关键词： Waste heat recovery High-temperature granule Granule migration Heat transfer enhancement Industry energy saving

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Elliptical encirclement control capable of reinforcing performances for UAVs around a dynamic target

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Defence Technology（防务技术） 2024年第2期32卷 104-119页

作者： Fei Zhang Xingling Shao Yi xia Wendong Zhang National Key Laboratory for Electronic Measurement Technology School of Instrument and ElectronicsNorth University of ChinaTaiyuan030051China

Most researches associated with target encircling control are focused on moving along a circular orbit under an ideal environment free from external ***,elliptical encirclement with a time-varying observation radius,may permit a more flexible and high-efficacy enclosing solution,whilst the non-orthogonal property between axial and tangential speed components,non-ignorable environmental perturbations,and strict assignment requirements empower elliptical encircling control to be more challenging,and the relevant investigations are still *** this line,an appointed-time elliptical encircling control rule capable of reinforcing circumnavigation performances is developed to enable Unmanned Aerial Vehicles(UAVs)to move along a specified elliptical path within a predetermined reaching *** remarkable merits of the designed strategy are that the relative distance controlling error can be guaranteed to evolve within specified regions with a designer-specified convergence ***,wind perturbations can be online counteracted based on an unknown system dynamics estimator(USDE)with only one regulating parameter and high computational *** tool demonstrates that all involved error variables are ultimately limited,and simulations are implemented to confirm the usability of the suggested control algorithm.

关键词： Elliptical encirclement Reinforced performances Wind perturbations UAVs

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DEM investigation of strength and critical state behaviours of granular materials under true triaxial loadings

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Particuology 2024年第2期85卷 198-212页

作者： Minyi Zhu Guobin Gong Jun xia Stephen Wilkinson Department of Civil Engineering Xi'an Jiaotong-Liverpool UniversityChina Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Engineering and Information Sciences University of Wollongong in DubaiUnited Arab Emirates

This paper investigates the strength and critical state(CS)behaviours of granular materials via DEM simulations of true triaxial drained tests under three different loading modes including constant b(in-termediate stress ratio)tests with constantσ'1(major principal stress),constant p(mean pressure)and constantσ'3(minor principal stress)*** this end,a series of samples are generated with the same particle size distribution,and with the confining stresses ranging from 100 kPa to 900 *** CS is achieved for all *** the macroscopic behaviours and the microscopic behaviours are examined and compared considering different loading modes,confining stresses and intermediate stress ratios(b).The critical state lines(CSLs)are found to be unique and independent of the loading modes,but dependent on the b *** CSLs with b=0 and b=1 form the two boundaries of CSLs respectively beyond which CSLs under all other b tests cannot go *** different strength criteria are examined and compared in terms of both peak and CS *** Mohr-Coulomb strength criterion is found to be only suitable for axisymmetric loading *** Lade-Duncan criterion is only suitable for describing peak strengths,which is dependent on the loading modes and confining *** Satake criterion and Matsuoka-Nakai criterion are the more appropriate strength criteria for describing CS failures,indicating that the CS values of both the Satake parameter and the Matsuoka-Nakai parameter describe an inherent property that characterizes the CS failure for a given type of *** CS mechanical coordination number is fitted by a curved line for a given b value,which is unique regardless of the loading *** peak and CS values of both major and minor principal fabric tensors decrease with increasing b values,while they increase with increasing b values for the intermediate principal fabric tensor.

关键词： Discrete element method Intermediate stress ratio Dilation Critical state Failure criterion

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Classification and spectrum optimization method of grease based on infrared spectrum

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Friction 2024年第6期12卷 1154-1164页

作者： Xin FENG Yanqiu xia Peiyuan XIE xiaohe LI School of Energy Power and Mechanical Engineering North China Electric Power UniversityBeijing 102206China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

The infrared(IR)absorption spectral data of 63 kinds of lubricating greases containing six different types of thickeners were obtained using the IR *** Kohonen neural network algorithm was used to identify the type of the lubricating *** results show that this machine learning method can effectively eliminate the interference fringes in the IR spectrum,and complete the feature selection and dimensionality reduction of the high-dimensional spectral *** 63 kinds of greases exhibit spatial clustering under certain IR spectrum recognition spectral bands,which are linked to characteristic peaks of lubricating greases and improve the recognition accuracy of these *** model achieved recognition accuracy of 100.00%,96.08%,94.87%,100.00%,and 87.50%for polyurea grease,calcium sulfonate composite grease,aluminum(Al)-based grease,bentonite grease,and lithium-based grease,*** on the different IR absorption spectrum bands produced by each kind of lubricating grease,the three-dimensional spatial distribution map of the lubricating grease drawn also verifies the accuracy of classification while recognizing the *** paper demonstrates fast recognition speed and high accuracy,proving that the Kohonen neural network algorithm has an efficient recognition ability for identifying the types of the lubricating grease.

关键词： grease infrared(IR)spectroscopy layered Kohonen network species recognition spectrum band optimization

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Efficient energy transfer from self-trapped excitons to Mn^(2+) dopants in CsCdCl_(3):Mn^(2+) perovskite nanocrystals

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International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1456-1461页

作者： Anran Zhang Xinquan Zhou Ranran Gu Zhiguo xia State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied TechniquesSchool of Materials Science and EngineeringSouth China University of TechnologyGuangzhou 510641China School of Physics and Optoelectronics South China University of TechnologyGuangzhou 510641China

Mn^(2+)doping has been adopted as an efficient approach to regulating the luminescence properties of halide perovskite nano-crystals(NCs).However,it is still difficult to understand the interplay of Mn^(2+)luminescence and the matrix self-trapped exciton(STE)emission *** this study,Mn^(2+)-doped CsCdCl_(3) NCs are prepared by hot injection,in which CsCdCl_(3) is selected because of its unique crystal structure suitable for STE *** blue emission at 441 nm of undoped CsCdCl_(3) NCs originates from the defect states in the ***^(2+)doping promotes lattice distortion of CsCdCl_(3) and generates bright orange-red light emission at 656 *** en-ergy transfer from the STEs of CsCdCl_(3) to the excited levels of the Mn^(2+)ion is confirmed to be a significant factor in achieving efficient luminescence in CsCdCl_(3):Mn^(2+)*** work highlights the crucial role of energy transfer from STEs to Mn^(2+)dopants in Mn^(2+)-doped halide NCs and lays the groundwork for modifying the luminescence of other metal halide perovskite NCs.

关键词： perovskite nanocrystals self-trapped excitons luminescence energy transfer

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