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A novel box-counting method for quantitative fractal analysis of threedimensional pore characteristics in sandstone

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International Journal of Mining Science and Technology 2024年第4期34卷 479-489页

作者： Huiqing liu Heping Xie Fei Wu Cunbao li Renbo gao State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China School of Resources and Safety Engineering Chongqing UniversityChongqing 400030China Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Shenzhen UniversityShenzhen 518060China Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy College of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China

Fractal theory offers a powerful tool for the precise description and quantification of the complex pore structures in reservoir rocks,crucial for understanding the storage and migration characteristics of media within these *** with the challenge of calculating the three-dimensional fractal dimensions of rock porosity,this study proposes an innovative computational process that directly calculates the three-dimensional fractal dimensions from a geometric *** employing a composite denoising approach that integrates Fourier transform(FT)and wavelet transform(WT),coupled with multimodal pore extraction techniques such as threshold segmentation,top-hat transformation,and membrane enhancement,we successfully crafted accurate digital rock *** improved box-counting method was then applied to analyze the voxel data of these digital rocks,accurately calculating the fractal dimensions of the rock pore *** numerical simulations of permeability experiments were conducted to explore the physical correlations between the rock pore fractal dimensions,porosity,and absolute *** results reveal that rocks with higher fractal dimensions exhibit more complex pore connectivity pathways and a wider,more uneven pore distribution,suggesting that the ideal rock samples should possess lower fractal dimensions and higher effective porosity rates to achieve optimal fluid transmission *** methodology and conclusions of this study provide new tools and insights for the quantitative analysis of complex pores in rocks and contribute to the exploration of the fractal transport properties of media within rocks.

关键词： 3D fractal analysis Fractal dimension Rock pore structure Box-counting method Permeability simulation Computational geosciences

Effect of process parameters on microstructure and mechanical properties of a nickel-aluminum-bronze alloy fabricated by laser powder bed fusion

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Journal of Central South University 2024年第8期31卷 2944-2960页

作者： Han, Chang-jun Zou, Yu-jin Hu, gao-ling Dong, Zhi li, Kai Huang, jin-miao li, Bo-yuan Zhou, Kun Yang, Yong-qiang Wang, Di School of Mechanical and Automotive Engineering South China University of Technology Guangzhou China Singapore Centre for 3D Printing School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore Singapore

This work investigated the effect of process parameters on densification, microstructure, and mechanical properties of a nickel-aluminum-bronze (NAB) alloy fabricated by laser powder bed fusion (LPBF) additive manufacturing. The LPBF-printed NAB alloy samples with relative densities of over 98.5% were obtained under the volumetric energy density range of 200–250 J/mm3. The microstructure of the NAB alloy printed in both horizontal and vertical planes primarily consisted of β′ martensitic phase and banded α phase. In particular, a coarser-columnar grain structure and stronger crystallographic texture were achieved in the vertical plane, where the maximum texture intensity was 30.56 times greater than that of random textures at the (100) plane. Increasing the volumetric energy density resulted in a decrease in the columnar grain size, while increasing the amount of α phase. Notably, β1′ martensitic structures with nanotwins and nanoscale κ-phase precipitates were identified in the microstructure of LPBF-printed NAB samples with a volumetric energy density of 250 J/mm3. Furthermore, under optimal process parameters with a laser power of 350 W and scanning speed of 800 mm/s, significant improvements were observed in the microhardness (HV 386) and ultimate tensile strength (671 MPa), which was attributed to an increase in refined acicular martensite.

关键词： additive manufacturing copper alloy laser powder bed fusion nickel-aluminum-bronze alloy

Prediction of undeformed chip thickness distribution and surface roughness in ultrasonic vibration grinding of inner hole of bearings

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第4期25卷 311-323页

作者： Yanqin li Daohui XIANG Guofu gao Feng JIAO Bo ZHAO School of Mechanical and Power Engineering Henan Polytechnic UniversityJiaozuo 454000China

Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal *** randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and impact the surface roughness of ***,previous studies used iterative method to calculate the unformed chip thickness(UCT),which has low computational *** this study,a symbolic difference method is proposed to calculate the *** UCT distributions are obtained to describe the stochastic interaction characteristics of ultrasonic grinding ***,the UCT distribution characteristics under different machining parameters are ***,a surface roughness prediction model is established based on the UCT ***,the correctness of the model is verified by *** study provides a quick and accurate method for predicting surface roughness in longitudinal ultrasonic vibration grinding.

关键词： Ultrasonic vibration grinding Undeformed chip thickness(UCT) Distribution characteristics Surface roughness

Gelatin-Based Metamaterial Hydrogel Films with High Conformality for Ultra-Soft Tissue Monitoring

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Nano-Micro Letters 2024年第2期16卷 347-364页

作者： Yuewei Chen Yanyan Zhou Zihe Hu Weiying Lu Zhuang li Ning gao Nian liu Yuanrong li jing He Qing gao Zhijian Xie Jiachun li Yong He State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310027People’s Republic of China School of Mechanical Engineering Guizhou UniversityGuiyang 550025People’s Republic of China Stomatology Hospital School of StomatologyZhejiang University School of MedicineClinical Research Center for Oral Diseases of Zhejiang ProvinceKey Laboratory of Oral Biomedical Research of Zhejiang ProvinceCancer Center of Zhejiang UniversityHangzhou 310006People’s Republic of China

Implantable hydrogel-based bioelectronics(IHB)can precisely monitor human health and diagnose ***,achieving biodegradability,biocompatibility,and high conformality with soft tissues poses significant challenges for *** is the most suitable candidate for IHB since it is a collagen hydrolysate and a substantial part of the extracellular matrix found naturally in most *** study used 3D printing ultrafine fiber networks with metamaterial design to embed into ultra-low elastic modulus hydrogel to create a novel gelatin-based conductive film(GCF)with mechanical *** regulation of GCF nearly covers soft tissue mechanics,an elastic modulus from 20 to 420 kPa,and a Poisson’s ratio from-0.25 to *** negative Poisson’s ratio promotes conformality with soft tissues to improve the efficiency of biological *** GCF can monitor heartbeat signals and respiratory rate by determining cardiac deformation due to its high ***,the gelatin characteristics of the biodegradable GCF enable the sensor to monitor and support tissue *** GCF metamaterial design offers a unique idea for bioelectronics to develop implantable sensors that integrate monitoring and tissue repair and a customized method for endowing implanted sensors to be highly conformal with soft tissues.

关键词： Implantable hydrogel-based bioelectronics Conformality 3D printing Metamaterial design

Enhancing performance of low-temperature processed CsPbI2Br all-inorganic perovskite solar cells using polyethylene oxide-modified TiO_(2)

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 786-794页

作者： Xu Zhao Naitao gao Shengcheng Wu Shaozhen li Sujuan Wu School of Electrical and Electronic Engineering Wuhan Polytechnic UniversityWuhan 430023China Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials South China Academy of Advanced OptoelectronicsSouth China Normal UniversityGuangzhou 510006China

CsPbX_(3)-based(X=I,Br,Cl)inorganic perovskite solar cells(PSCs)prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal ***,the high trap state density and serious charge recombination between low-temperature processed TiO_(2)film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic *** a thin polyethylene oxide(PEO)layer is employed to modify TiO_(2)film to passivate traps and promote carrier *** impacts of PEO layer on microstructure and photoelectric characteristics of TiO_(2)film and related devices are systematically *** results suggest that PEO modification can reduce the surface roughness of TiO_(2)film,decrease its average surface potential,and passivate trap *** optimal conditions,the champion efficiency of CsPbI_(2)Br PSCs with PEO-modified TiO_(2)(PEO-PSCs)has been improved to 11.24%from 9.03%of reference ***,the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.

关键词： polyethylene oxide-modified TiO_(2) film low-temperature process CsPbI_(2)Br-based all-inorganic perovskite solar cells photo-voltaic performance

Energy-absorbing porous materials:Bioinspired architecture and fabrication

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Nano Research 2024年第2期17卷 679-690页

作者： Junheng Zhao Meng li Jiewei Chen Weiwei gao Hao Bai State Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310058China Department of Polymer Science and Engineering Zhejiang UniversityHangzhou 310058China

Energy-absorbing materials are widely used in transportations,sports,and the military ***,porous materials,including natural and artificial materials,have attracted tremendous attentions due to their light weight and excellent energy absorption *** review summarizes the recent progresses in the natural and artificial energy-absorbing porous ***,we review the typical natural porous materials including cuttlebone,bighorn sheep horn,pomelo peel,and sunflower stem *** architectures,energy absorption abilities,and mechanisms of these typical natural materials and their bioinspired materials are ***,we provide a review on the fabrication methods of artificial energy-absorbing porous materials,such as conventional foaming and three-dimensional(3D)***,we address the challenges and prospects for the future development of energy-absorbing porous *** importantly,our review provides a direct guidance for the design and fabrication of energy-absorbing porous materials required for various engineering applications.

关键词： energy-absorbing porous materials natural materials natural structures bioinspired materials

New dating indicates intermittent human occupation of the Nwya Devu Paleolithic site on the high-altitude central Tibetan Plateau during the past 45,000 years

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Science China Earth Sciences 2024年第2期67卷 531-551页

作者： Junyi GE Xiaoling ZHANG Shejiang WANG linhui li Wei HE Yingshuai jin Peiqi ZhANG Bing XU Chenglong DENG John WOLSEN Zhengtang GUO Xing gao Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of SciencesBeijing 100044China University of the Chinese Academy of Sciences Beijing 100049China Tibetan Cultural Relics Conservation Institute Lhasa 850000China Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences.Beijing 100029China State Key Laboratory of lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China School of Anthropology University of ArizonaTucson85721USA

The timing and mechanisms of the human occupation of the demanding high-altitude Tibetan Plateau environment are of great ***,we report on our reinvestigations and dating of the Nwya Devu site,located nearly 4600 meters above sea level on the central Tibetan Plateau.A new microblade techno-complex was identified on a lower lake shore at this site,distinct from the previously reported blade tool *** two lithic assemblages were dated to 45.6±2.6 and10.3±0.5 ka using optically stimulated luminescence and accelerator mass spectrometry^(14)C *** represent,respectively,the earliest known Paleolithic and microlithic sites on the interior Tibetan Plateau,indicating multiple occupation episodes of hunter-gatherers during the past 45 *** studies reveal that relatively stable depositional conditions and a paleoenvironment characterized by a comparatively warm climate facilitated these multiple occupations at Nwya *** contemporaneous occurrence of the Upper Paleolithic blade technology on the Tibetan Plateau and most of Eurasia between 50 and 40 ka indicates rapid,large-scale dispersals of humans that profoundly affected human demography on a large *** new archaeological evidence and previously reported genetic data,we conclude that the Tibetan Plateau provided a relatively stable habitat for Upper Paleolithic hunter-gatherers,which may have contributed to the complex and multiple-origin gene pool of present-day Tibetans.

关键词： Tibetan Plateau Paleolithic Nwya Devu High-altitude adaptation Microblade industry Early Upper Paleolithic OSLdating AMS^(14)C dating

Advances in friction of aluminium alloy deep drawing

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Friction 2024年第3期12卷 396-427页

作者： Yiren gao Hongxia li Danyang ZHAO Minjie WANG Xiaobo FAN School of Mechanical Engineering Dalian University of TechnologyDalian 116023China

Broad use of lightweight aluminium alloy parts in automobile manufacturing,aerospace,electronic communication,and rail transit is mainly formed through deep drawing *** drawing friction is a key boundary condition for controlling the forming quality of aluminium alloy ***,due to the oxidation and adhesion tendency of aluminium alloys,the tribological situations of aluminium alloy deep drawing(AADD)system is more complicated than those of traditional deep drawing of steel ***,the study of AADD friction is essential for manufacturing high-performance aluminium alloy ***,aiming to provide a valuable reference for researchers in related fields,a comprehensive review of AADD friction is provided,including friction mechanism,influencing factors,friction measurement,friction model,friction simulation,and lubrication-free friction ***,a brief conclusion and several current challenges were discussed.

关键词： aluminium alloy deep drawing(AADD) influencing factors friction measurement friction model friction control

A brief review of tribological properties for black phosphorus

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Friction 2024年第5期12卷 823-844页

作者： Fanfan LV Wei WANG jinjin li Yuan gao Kuaishe WANG College of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055China State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing10084China

Black phosphorus (BP) is a new class of two-dimensional (2D) layered material, which shows the unanticipated characteristics in many aspects including electronics, transistors, sensors, energy storage, batteries, photocatalysis, and other applications due to its high charge carrier mobility, tunable direct bandgap, and unique in-plane anisotropic structure. In addition, BP has drawn tremendous attention in the field of tribology due to the low shear strength, the layered structure, and the weak connected force between the layers by van der Waals interaction. In recent years, many significant progresses have been made in experimental studies on BP materials as solid lubricants or lubrication additives. This work offers a review of researching regarding the tribological properties of BP. Moreover, the lubrication mechanisms of BP as the lubrication additive including the formation of the tribo-film, micro-bearing effect, and self-repair performance are also summarized. Finally, the current challenges and prospects of BP material as lubricant are proposed.

关键词： black phosphorus(BP) two-dimensional(2D)layered material lubrication additives tribological mechanisms