检索结果-南通市图书馆

Paleobiological significance of the James Ross Basin

在线全文

学校读者我要写书评

暂无评论

Advances in Polar Science 2019年第3期30卷 186-198页

作者： J.Alistair CRAME British Antarctic Survey High CrossMadingley RoadCambridge CB3 0ETUK

The extensive Late Mesozoic–Early Cenozoic sedimentary succession exposed within the James Ross Basin,Antarctica has huge potential to enhance paleobiological investigations into both the marine and terrestrial fossil *** excess of 7 km in total thickness and spanning the Early Cretaceous(Aptian)–Late Eocene in age,it represents an invaluable high-latitude(~65°S)site for comparison with lower latitude,tropical ones in an essentially greenhouse *** Early Cretaceous(Aptian–Albian)sequence is deep-water but there are indications of shallowing to inner shelf depths in both the Turonian and Coniacian *** first prolific shallow-water marine fauna occurs in the Santonian–Campanian Santa Marta Formation and this is followed by repeated occurrences through the later Campanian,Maastrichtian,Danian and Middle Eocene(Lutetian).In this study an attempt has been made to compare these Antarctic faunas directly with the well-known ones of the same age from the US Gulf *** comparisons made for three time slices,Late Maastrichtian,Danian and Middle Eocene,indicate that the Antarctic is characterised by both low taxonomic diversity and high levels of *** James Ross Basin is providing important evidence to indicate that the highest southern latitudes have always been characterised by a distinctive temperate biota,even on a pre-glacial *** roots of at least some elements of the modern Southern Ocean biota can be traced back to a Late Mesozoic–Early Cenozoic austral realm.

关键词： James Ross Basin biostratigraphy molluscan faunas US Gulf Coast biodiversity patterns evolutionof temperate biotas

Stability analyses of vertically exposed cemented backfill:A revisit to Mitchell's physical model tests

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2016年第6期26卷 1135-1144页

作者： Liu Guangsheng Li Li Yang Xiaocong Guo Lijie School of Civil and environmental Engineering University of Science and Technology BeijingBeijing 100083China Department of Civil Geological and Mining EngineeringEcole Polytechnique de MontrealMontreal H3C3A7Canada Beijing General research Institute of Mining and Metallurgy Beijing 100160China

Mitchell's solution is commonly used to determine the required strength of vertically exposed cemented backfill in mines. Developed for drained backfill, Mitchell model assumed a zero friction angle for the backfill. Physical model tests were performed. Good agreements were obtained between the required strengths predicted by the analytical solution and experimental results. However, it is well-known that zero friction angle can only be possible in terms of total stresses when geomaterials are submitted to unconsolidated and undrained conditions. A revisit to Mitchell's physical model tests reveals that both the laboratory tests performed for obtaining the shear strength parameters of the cemented backfill and the box stability tests were conducted under a condition close to undrained condition. This explains well the good agreement between Mitchell's solution and experimental results. Good agreements are equally obtained between Mitchell's experimental results and FLAC3 D numerical modeling of shortterm stability analyses of exposed cemented backfill.

关键词： Cemented backfill Required strength Mitchell Physical model tests Numerical modeling FLAC3D

Potential application of electron work function in analyzing fracture toughness of materials

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2017年第10期33卷 1128-1133页

作者： Hao Lu Chenxin Ouyang Xianguo Yan Jian Wang Guomin Hua Reinaldo Chung D.Y.Li Department of Chemical and Materials Engineering University of Alberta Edmonton. Alberta T6G 1H9 Canada College of Materials Science and Engineering Donghua University Shanghai 201620 China School of Mechanical Engineering Taiyuan University of Science and Technology Taiyuan 030024 China Extraction Reliability Engineering Suncor Energy Inc. Fort McMurray Alberta Canada

Fracture toughness determines materials＇ resistance to fracture, which is measured often using impact or bending tests. However, it is difficult to evaluate fracture toughness of coatings and small *** this article, using white irons as sample materials, we explore a possible approach of using electron work function（EWF） as an indicator in evaluating fracture toughness of hard metallic materials. This parameter is promising for being utilized to analyze toughness of protective coatings and small objects as well as bulk materials. Through comparison with results obtained from impact tests and elastic modulus measurement, effectiveness of this EWF approach is demonstrated.

关键词： Fracture toughness Elastic modulus Electron work function

An analytical solution to estimate the settlement of tailings or backfill slurry by considering the sedimentation and consolidation

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2021年第3期31卷 463-471页

作者： Jiahao Qin Jian Zheng Li Li research Institute of Mining and environment(RIME UQAT-Polytechnique) Department of CivilGeological and Mining EngineeringMontréalQuébec H3C 3A7Canada

A common and important task in mining industry is to estimate the settlement or final volume of the tailings or backfill associated with sedimentation and self-weight consolidation. Up to now however, most existing analytical solutions were developed by only considering the settlement induced by consolidation. In this paper, the process of shrinkage tests has been compared with those of sedimentation and consolidation. It was shown that the pore water and particles movement in the sedimentation are very similar to that in the normal shrinkage. The void ratio at the end of sedimentation is thus for the first time considered to be equal to the void ratio at desaturation onset of shrinkage tests. An analytical solution was then proposed to estimate the settlement of tailings or backfill by considering the sedimentation and consolidation. To validate the proposed analytical solution, tailing deposition tests were conducted in two molds to simulate the tailings impoundment and underground mine stope. The required parameters were obtained through shrinkage and consolidation tests. Good agreements were obtained between the measured settlements and those calculated by the proposed solution. The proposed solution can thus be considered as validated and used to evaluate the settlement of tailings or backfill slurry.

关键词： Shrinkage Sedimentation Consolidation Settlement Tailings Backfill

Air entrainment in a vertical dropshaft with limited air supply

在线全文

学校读者我要写书评

暂无评论

Theoretical & Applied Mechanics Letters 2018年第5期8卷 315-319,362页

作者： Qiang Ding Yiyi Ma David Z.Zhu Department of Civil Engineering Zhejiang University Department of Civil and environmental Engineering University of Alberta

Dropshafts are vertical structures widely used in urban drainage systems and buildings for water *** this paper,a physical model study was conducted to investigate the air entrainment in the dropshaft under various flow regimes with and without air *** from the experiments,the air entrainment mechanisms varied with the water flow regimes in the *** there was no water plug formed in the dropshaft,air could be supplied directly from *** the water plug was formed,while without venting,the air was replenished only from downstream intermittently and then in the form of large air bubble traveling upwards to the airspace at the top;while with venting,air was mainly replenished from the dropshaft top and no large air bubble was *** experimental results also showed that the amount of entrained air in the dropshaft with venting was greater than that without venting.

关键词： Air entrainment Air supply Bubble Flow regime Dropshaft

Encapsulation of selenium sulfide in double-layered hollow carbon spheres as advanced electrode material for lithium storage

在线全文

学校读者我要写书评

暂无评论

Nano research 2016年第12期9卷 3725-3734页

作者： Hongwei Zhang Liang Zhou Xiaodan Huang Hao Song Chengzhong Yu Australian Institute for Bioengineering and Nanotechnology The University of Queensland Brisbane QLD 4072 Australia State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Selenium sulfide/double-layered hollow carbon sphere （SeS2/DLHC） composites have been designed as high-performance cathode materials for novel Li-SeS2 batteries. In the constructed composite, SeS2 is predominantly encapsulated in the interlayer space of DLHCs with a high loading of 75% （weight percentage） and serves as the active component for lithium storage. The presence of Se in the composite and the carbon framework not only alleviate the shuttling of polysulfide, but also improve the conductivity of electrodes. Migration of active materials from the interlayer void to the hollow cavity of DLHCs after cycling, which further mitigates the loss of active materials and the shuttle effect, is observed. As a result, the SeS2/DLHC composite delivers a high specific capacity （930 mA.h.g-1 at 0.2 C） and outstanding rate capability （400 mA.h.g-1 at 6 C）, which is much better than those of SeS2/single-layered hollow carbon sphere, Se/DLHC, and S/DLHC composites. Notably, the SeS2/DLHC composite shows an ultralong cycle life with 89% capacity retention over 900 cycles at 1 C, or only 0.012% capacity decay per cycle. Our study reveals that both SeS2 and the double-layered structures are responsible for the excellent electrochemical performance.

关键词： selenium sulfide double-layered hollowcarbon cathode materials lithium storage

Observations on the application of artificial neural network to predicting ground motion measures

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Earthquake Science 2012年第2期25卷 161-175页

作者： Hanping Hong Taojun Liu Chien-Shen Lee Department of Civil and environmental Engineering University of Western Ontario London Ontario N6A 5B9 Canada

Application of the artificial neural network （ANN） to predict pseudospectral acceleration or peak ground acceleration is explored in the study. The training of ANN model is carried out using feed-forward backpropagation method and about 600 records from 39 California earthquakes. The statistics of the residuals or modeling error for the trained ANN-based models are almost the same as those for the parametric ground motion prediction equations, derived through regression analysis; the residual or modeling error can be modeled as a normal variate. The similarity and differences between the predictions by these two approaches are shown. The trained ANN-based models, however, are not robust because the models with almost identical mean square errors do not always lead to the same predictions. This undesirable behaviour for predicting the ground motion measures has not been shown or discussed in the literature; the presented results, at least, serve to raise questions and caution on this problem. A practical approach to ameliorate this problem, perhaps, is to consider several trained ANN models, and to take the average of the predicted values from the trained ANN models as the predicted ground motion measure.

关键词： neural network peak ground acceleration pseudospectral acceleration seismic ground motion measures uncertainty

Modeling mass transfer of CO_2 in brine at high pressures by chemical potential gradient

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2013年第6期56卷 821-830页

作者： JI YuanHui JI XiaoYan LU XiaoHua TU YongMing Division of Energy Science Lule University of Technology State Key Laboratory of Materials-Oriented Chemical Engineering Nanjing University of Technology Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education Southeast University Division of Structural Engineering and Bridges Royal Institute of Technology (KTH)

To investigate long-term CO2 behavior in geological formations and quantification of possible CO2 leaks, it is crucial to inves- tigate the potential mobility of CO2 dissolved in brines over a wide range of spatial and temporal scales and density distribu- tions in geological media. In this work, the mass transfer of aqueous CO2 in brines has been investigated by means of a chemi- cal potential gradient model based on non-equilibrium thermodynamics in which the statistical associating fluid theory equa- tion of state was used to calculate the fugacity coefficient of CO2 in brine. The investigation shows that the interracial concen- tration of aqueous CO2 and the corresponding density both increase with increasing pressure and decreasing temperature; the effective diffusion coefficients decrease initially and then increase with increasing pressure; and the density of the CO2-disolved brines increases with decreasing CO2 pressure in the CO2 dissolution process. The aqueous CO2 concentration profiles obtained by the chemical potential gradient model are considerably different from those obtained by the concentration gradient model, which shows the importance of considering non-ideality, especially when the pressure is high.

关键词： C02 geological sequestration dissolution non-equilibrium thermodynamics mass transport diffusion density SAFTEoS

Enhanced helium ion irradiation tolerance in a Fe-Co-Ni-Cr-Al-Ti high-entropy alloy with L12 nanoparticles

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第12期143卷 169-177页

作者： Y.L.Zhao F.L.Meng T.Yang J.H.Luan S.F.Liu G.M.Yeli W.T.Lin W.H.Liu X.J.Liu C.T.Liu J.J.Kai School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China School of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Department of Materials Science and Engineering Mechanical Behavior Division of Shenyang National Laboratory for Materials ScienceCity University of Hong KongHong KongChina Department of Mechanical Engineering City University of Hong KongHong KongChina Institute of Nuclear&New Energy Technology Tsinghua UniversityBeijing 100084China

L12-strengthened high entropy alloys(HEAs)with excellent room and high-temperature mechanical prop-erties have been proposed as promising candidates as structural materials for advanced nuclear ***,knowledge about their radiation response is fairly *** the present work,a novel HEA with a high density of L12 nanoparticles was irradiated with He ion at 500°*** electron microscope(TEM)and atom probe tomography(APT)were employed to study the evolution of mi-crostructural stability and radiation-induced *** to the single-phase FeCoNiCr HEA,the main microstructural features were numerous large faulted dislocation loops and helium *** the irradiation resistance of the present L12-strengthened HEA is much improved in terms of reduced bubble size,which could be attributed to the considerable He trapping efficiency of the coherent pre-cipitate/matrix interface and the enhanced capability of the interface for damage elimination when the matrix channel width is *** analysis revealed that an inverse-Kirkendall-mechanism-dominated radiation-induced segregation(RIS)occurs around bubbles,where a significant Co enrichment and Ni de-pletion can be clearly *** addition,the competing dynamics of ballistic mixing and elemental clustering that raised from the irradiation-enhanced diffusion in a highly supersaturated matrix,along with the low precipitation nucleation barrier due to the small lattice misfit,lead to a dynamical pre-cipitation dissolution and re-precipitation appears under *** a promising phenomenon is expected to promote a potential self-healing effect and could in turn provide a sustainable irradiation tolerance over the operational lifetime of a reactor.

关键词： L12 nanoparticles High-entropy alloy Helium bubble Phase stability Radiation-induced segregation