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| 1 | Tribological properties of nanometer cerium oxide as additives in lithium grease显示文摘This paper presents a comparative study of the influence of nanometer-CeO_2(nano-CeO_2) and temperature on tribological and lubricating properties of lithium grease. The morphology and structure of nanocrystals were characterized by means of transmission electron microscopy(TEM) and X-ray diffraction(XRD), respectively. Friction and wear tests were conducted on the friction and wear tester.Results show that the lithium grease with addition of nanometer-CeO_2 has much better friction-reducing and anti-wear performance than that of base grease. When the additive in grease is 0.6 wt%, the friction coefficient(COF) and wear scar diameter(WSD) decrease by 28% and 13% comparing with base grease,respectively. The base grease and grease with 0.6 wt% nanometer-CeO_2 both possess the lowest average COF and wear width at 50 ℃. The worn surface morphology after friction test was analyzed by scanning electron microscopy(SEM) and NANOVEA three-dimensional profilometer. Under the lubrication of the lithium grease containing 0.6 wt% nano-CeO_2. few shallow furrows can be observed on the quite smoothed surface and the WSD decreased. Moreover, It was found that the nano-CeO_2 has been incorporated into the surface protective and lubricious layer by energy dispersive spectrometer(EDS) analysis. | Qiang He Anling Li Yachen Guo Songfeng Liu Yong Zhang Linghao Kong | 2018 | Journal of Rare Earths2018，36，2： | 6 |
| 2 | Assessing IGS GPS/Galileo/BDS-2/BDS-3 phase bias products with PRIDE PPP-AR显示文摘Ambiguity Resolution in Precise Point Positioning (PPP-AR) is important to achieving high-precision positioning in wide areas. The International GNSS (Global Navigation Satellite System) Service (IGS) and some other academic organizations have begun to provide phase bias products to enable PPP-AR, such as the integer-clock like products by Centre National d’Etudes Spatials (CNES), Wuhan University (WUM) and the Center for Orbit Determination in Europe (CODE), as well as the Uncalibrated Phase Delay (UPD) products by School of Geodesy and Geomatics (SGG). To evaluate these disparate products, we carry out Global Positioning System (GPS)/Galileo Navigation Satellite System (Galileo) and BeiDou Navigation Satellite System (BDS-only) PPP-AR using 30 days of data in 2019. In general, over 70% and 80% of GPS and Galileo ambiguity residuals after wide-lane phase bias corrections fall in ± 0.1 cycles, in contrast to less than 50% for BeiDou Navigation Satellite (Regional) System (BDS-2);moreover, around 90% of GPS/Galileo narrow-lane ambiguity residuals are within ± 0.1 cycles, while the percentage drops to about 55% in the case of BDS products. GPS/Galileo daily PPP-AR can usually achieve a positioning precision of 2, 2 and 6 mm for the east, north and up components, respectively, for all phase bias products except those based on German Research Centre for Geosciences (GBM) rapid satellite orbits and clocks. Due to the insufficient number of BDS satellites during 2019, the BDS phase bias products perform worse than the GPS/Galileo products in terms of ambiguity fixing rates and daily positioning precisions. BDS-2 daily positions can only reach a precision of about 10 mm in the horizontal and 20 mm in the vertical components, which can be slightly improved after PPP-AR. However, for the year of 2020, BDS-2/BDS-3 (BDS-3 Navigation Satellite System) PPP-AR achieves about 50% better precisions for all three coordinate components. | Jianghui Geng Songfeng Yang Jiang Guo | 2021 | Satellite Navigation2021，2，1： | 3 |
| 3 | Degradation mechanism analysis of LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2) single crystal cathode materials through machine learning显示文摘LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)has become one of the most popular cathode materials for current lithium-ion batteries due to its high-energy density and cost performance.However,the rapid capacity fading of NCM severely hinders its development and applications.Here,the single crystal NCM523 materials under different degradation states are characterized using scanning transmission electron microscopy(STEM).Then we developed a neural network model with a two-sequential attention block to recognize the crystal structure and locate defects in STEM images.The number of point defects in NCM523 is observed to experience a trend of increasing first and then decreasing in the degradation process.The space between the transition metal columns shrinks obviously,inducing dramatic capacity decay.This analysis sheds light on the defect evolution and chemical transformation correlated with layered material degradation.It also provides interesting hints for researchers to regenerate the electrochemical capacity and design better battery materials with longer life. | Wuxin Sha Yaqing Guo Danpeng Cheng Qigao Han Ping Lou Minyuan Guan Shun Tang Xinfang Zhang Songfeng Lu Shijie Cheng Yuan-Cheng Cao | 2022 | npj Computational Materials2022，，1： | 1 |
| 4 | Investigation on the thermal conductivity of HDPE/MWCNT composites by laser pulse method显示文摘Thermal conductivity (TC) of high density polyethylene/multiwall carbon nanotube (HDPE/MWCNT) composite films was measured by laser pulse method. It is found that the TC increased quickly with the increase of MWCNT fraction when the volume fraction of MWCNT was below 3.35%. However,as the volume fraction of MWCNT was over 3.35%,the increasing rate became slow. A new percolation model was proposed based on the effect of MWCNT network to simulate the TC of HDPE/MWCNT composite films. The simulation result was in good agreement the experimental data well. In addition,the relationship of TC with the increase of temperature was also discussed. | CHEN XinGui HE GuanHu DU JinHong PEI SongFeng GUO JingDong | 2009 | Science China(Technological Sciences)2009，52，9： | 1 |
| 5 | Machine learning in polymer informatics显示文摘Polymers have been widely used in energy storage,construction,medicine,aerospace,and so on.However,the complexity of chemical composition and morphology of polymers has brought challenges to their development.Thanks to the integration of machine leaming algorithms and large data resources,the data-driven methods have opened up a new road for the development of poly-mer science and engineering.The emerging polymer informatics attempts to accelerate the performance prediction and process optimization of new poly-mers by using machine learning models based on reliable data.With the grad-ual supplement of currently available databases,the emergence of new databases and the continuous improvement of machine learning algorithms,the research paradigm of polymer informatics will be more efficient and widely used.Based on these points,this paper reviews the development trends of machine learning assisted polymer informatics and provides a simple introduc-tion for researchers in materials,artificial intelligence,and other fields. | Wuxin Sha Yan Li Shun Tang Jie Tian Yuming Zhao Yaqing Guo Weixin Zhang Xinfang Zhang Songfeng Lu Yuan-Cheng Cao Shijie Cheng | 2021 | InfoMat2021，3，4： | 1 |
| 6 | Experimental Research on Supercritical Carbon Dioxide Fracturing of Sedimentary Rock:A Critical Review显示文摘Supercritical carbon dioxide(ScCO_(2))fracturing has great advantages and prospects in both shale gas exploitation and CO_(2)storage.This paper reviews current laboratory experimental methods and results for sedimentary rocks fractured by ScCO_(2).The breakdown pressure,fracture parameters,mineral composition,bedding plane angle and permeability are discussed.We also compare the differences between sedimentary rock and granite fractured by ScCO_(2),ultimately noting problems and suggesting solutions and strategies for the future.The analysis found that the breakdown pressure of ScCO_(2)was reduced 6.52%–52.31%compared with that of using water.ScCO_(2)tends to produce a complex fracture morphology with significantly higher permeability.When compared with water,the fracture aperture of ScCO_(2)was decreased by 4.10%–72.33%,the tortuosity of ScCO_(2)was increased by 5.41%–70.98%and the fractal dimension of ScCO_(2)was increased by 4.55%–8.41%.The breakdown pressure of sandstone is more sensitive to the nature of the fracturing fluid,but fracture aperture is less sensitive to fracturing fluid than for shale and coal.Compared with granite,the tortuosity of sedimentary rock is more sensitive to the fracturing fluid and the fracture fractal dimension is less sensitive to the fracturing fluid.Existing research shows that ScCO_(2)has the advantages of low breakdown pressure,good fracture creation and environmental protection.It is recommended that research be conducted in terms of sample terms,experimental conditions,effectiveness evaluation and theoretical derivation in order to promote the application of ScCO_(2)reformed reservoirs in the future. | ZHENG Bowen QI Shengwen LU Wei GUO Songfeng WANG Zan YU Xin ZHANG Yan | 2023 | Acta Geologica Sinica(English Edition)2023，97，3： | 0 |
| 7 | Geological evaluation for the carbon dioxide geological utilization and storage(CGUS)site:A review显示文摘Carbon dioxide(CO_(2))geological utilization and storage(CGUS)is the key link of CO_(2)capture,utilization,and storage(CCUS).The accurate characterization of the geological body structure is a vital prerequisite of CGUS.This paper gives a review of the multi-scale three-dimensional geological structure characterization and site selection of CO_(2)storage.It shows that there is a lack of systematic and high-precision methods for transparency characterization of multi-scale three-dimensional engineering geological structure and hydrogeological structure of a CO_(2)storage site.There is no clear understanding of the fracture evolution and gas-liquid migration process of multi-scale geological body structure under the disturbance of CO_(2)injection.There is a lack of sufficient quantitative methods for the dynamic evaluation of CO_(2)geological storage potential.The geological suitability evaluation method for site selection of CO_(2)storage is rough and has poor applicability,which is difficult to satisfy the urgent needs of CGUS site selection in the whole process of CO_(2)sequestration industrialization in the future.Thus,it is required to conduct studies on the transparency characterization of geological body structure and intelligent site selection for CO_(2)storage,which is of great importance for CGUS engineering practice. | Shengwen QI Bowen ZHENG Zan WANG Haijun ZHAO Zhendong CUI Tianming HUANG Songfeng GUO Lei FU Pingchuan DONG | 2023 | Science China Earth Sciences2023，66，9： | 0 |
| 8 | Investigation on the Deformation and Failure Patterns of Loess Cut Slope Based on the Unsaturated Triaxial Test in Yan'an,China显示文摘The large-scale implementation of the Gully Stabilization and Land Reclamation(GSLR)project induces various failures of loess slopes due to excavation in Yan'an,China.However,the deformation and failure behavior of these excavated loess slopes have not been fully understood.In this study,field investigation was undertaken for analyzing the distributions and failure features of excavation-induced loess slope failures.It is found that plastic failure mainly occurs in Q_(3) loess layers and brittle failure in Q_(2).To understand the underlying failure mechanism,a series of triaxial shear tests were conducted on intact Q_(3) and Q_(2) loess samples that with different water contents,namely natural water content(natural),dry side of the natural value(drying 5%),and wet side(wetting 5%).The characteristics of stress-strain curves and failure modes of the samples were analyzed.Results show that the stress-strain curves of Q_(2) samples are dominated by strain-softening characteristics,while Q_(3) samples mainly exhibit strain-harden features except in the drying state.Correspondingly,shear failures of Q_(3) specimens are mainly caused by shear crack planes(single,X or V-shaped).For Q_(2) loess,the dominance of tensile cracks is observed on the surface of damaged specimens.These disclose the different failure modes of excavated slopes located in different strata,that is,the arc sliding failure of Q_(3) loess slopes and the stepped tensile failure of Q_(2) loess slopes,and are helpful in the design and management of the ongoing GSLR projects in the Loess Plateau. | Lina Ma Shengwen Qi Songfeng Guo Qiangbing Huang Xiaokun Hou | 2024 | Journal of Earth Science2024，35，1： | 0 |
| 9 | Shear mechanical properties and energy evolution of rock-like samples containing multiple combinations of non-persistent joints显示文摘Discontinuities are often considered as important factors responsible for the instability caused by shear failure in engineering rock mass,and energy-driven instability is the root cause of rock failure.However,few studies focus on the energy evolution during the failure process using a three-dimensional(3D)numerical model.In this study,a series of laboratory direct shear tests on rock-like samples is numer-ically simulated using bonded particle models(BPMs)with multiple combinations of discontinuous in the particle flow code(PFC3D),in which the location and size of the particles conform to the uniform distribution.The effects of joint row number and inclination on the stress-strain characteristics and failure mode of rock were studied from the perspective of microcrack growth and energy evolution.The results showed that,when the number of joint rows Nr>1,the shear failure region does not change with the increase of Nr for the type B(2-columnn multiple-row at center)and the type C(2-column multiple-row at edge)as compared to the type A(1-column multiple-row at center)joint models.Notably,joints significantly increase the post-peak energy dissipation but have little effect on the proportion of energy before the peak.Friction consumes most of the energy while kinetic energy accounts for less than 1%of total energy during the shear process.Peak elastic strain energy follows the variation trend of peak shear displacement.The development and accumulation of microcracks directly affect the energy dissipation,and there is a significant linear relationship between the cumulative number of critical microcracks and the critical dissipated energy at the failure,when the dip direction of joints is opposite to the shear direction,more microcracks will be accumulated at the peak time,resulting in more energy dissipation.The results contribute to deeply understanding the shear failure process of non-persistent jointed mass. | Daping Tai Shengwen Qi Bowen Zheng Chonglang Wang Songfeng Guo Guangming Luo | 2023 | Journal of Rock Mechanics and Geotechnical Engineering2023，15，7： | 0 |
| 10 | Damage evolution of rock-encased-backfill structure under stepwise cyclic triaxial loading显示文摘Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations. | Xin Yu Yuye Tan Weidong Song John Kemeny Shengwen Qi Bowen Zheng Songfeng Guo | 2024 | Journal of Rock Mechanics and Geotechnical Engineering2024，16，2： | 0 |
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