检索结果-南通市图书馆

Multifractal estimation of NMR T_(2) cut-off value in low-permeability rocks considering spectrum kurtosis: SMOTE-based oversampling integrated with machine learning

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2023年第6期20卷 3411-3427页

作者： Xiao-Jun Chen Rui-Xue Zhang Xiao-Bo Zhao Jun-Wei Yang Zhang-jian Lan Cheng-fei Luo jian-Chao cai MOE Key Laboratory of Tectonics and Petroleum Resources Wuhan430074HubeiChina Department of Chemical Engineering and Analytical Science The University of ManchesterManchesterM139PLUK jianghan Oilfied SINOPECQianjiang430063HubeiChina Hainan Branch of CNOOC Ltd Haikou570311HainanChina CNOOC EnerTech-Drilling&Production Co.CNOOC Central Laboratory(Zhanjiang) Zhanjiang524057GuangdongChina National Key Laboratory of Petroleum Resources and Engineering China University of PetroleumBeijing102249China

The transverse relaxation time (T_(2)) cut-off value plays a crucial role in nuclear magnetic resonance for identifying movable and immovable boundaries, evaluating permeability, and determining fluid saturation in petrophysical characterization of petroleum reservoirs. This study focuses on the systematic analysis of T_(2) spectra and T_(2) cut-off values in low-permeability reservoir rocks. Analysis of 36 low-permeability cores revealed a wide distribution of T_(2) cut-off values, ranging from 7 to 50 ms. Additionally, the T_(2) spectra exhibited multimodal characteristics, predominantly displaying unimodal and bimodal morphologies, with a few trimodal morphologies, which are inherently influenced by different pore types. Fractal characteristics of pore structure in fully water-saturated cores were captured through the T_(2) spectra, which were calculated using generalized fractal and multifractal theories. To augment the limited dataset of 36 cores, the synthetic minority oversampling technique was employed. Models for evaluating the T_(2) cut-off value were separately developed based on the classified T_(2) spectra, considering the number of peaks, and utilizing generalized fractal dimensions at the weight 0. The primary objective of this work is to gain insights into the relationship between the kurtosis of the T_(2) spectrum and pore types, as well as to predict the T_(2) cut-off value of low-permeability rocks using machine learning and data augmentation techniques.

关键词： Nuclear magnetic resonance Low-permeability porous media T_(2)cut-off value Fractal and multifractal Data augmentation Machine learning

Dynamical brane creation and annihilation via a background flux

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 24-29页

作者： Yi-fei Chen jian-Xin Lu Interdisciplinary Center for Theoretical Study University of Science and Technology of ChinaPeng Huanwu Center for Fundamental TheoryHefei 230026China

We study the dynamical Myers effect by allowing the fuzzy(or the dynamical dielectric brane)coordinates to be time *** find three novel kinds of the dynamical spherical dielectric branes depending on their respective excess *** first represents a dynamical spherical brane carrying a negative excess energy(having a lower bound)with its radius oscillating periodically between two given non-zero *** second is the one with zero excess energy and whose time dependence can be expressed in terms of a simple *** particular dynamical spherical configuration represents the dielectric brane creation and/or annihilation like a photon in the presence of a background creating an electron-position pair and then annihilating back to a *** third is the one carrying positive excess energy and the radius can also oscillate periodically between two non-zero values but,unlike the first kind,it passes zero twice for each *** of the above can also be interpreted as the time evolution of a semi-spherical D-brane–anti semi-spherical D-brane system.

关键词： dynamical Myers effect D-branes string/M-theory

Red/orange dual-emissive carbon dots for pH sensing and cell imaging

在线全文

学校读者我要写书评

暂无评论

Nano Research 2019年第4期12卷 815-821页

作者： Miaoran Zhang Rigu Su jian Zhong Ling fei Wei cai Qingwen Guan Weijun Li Neng Li Yusheng Chen Lulu cai Quan Xu State Key Laboratory of Heavy Oil Processing Beijing Key Laboratory of Biogas Upgrading Utilization China University of Petroleum (Beijing) Beijing 102249 China Personalized Drug Therapy Key Laboratory of Sichuan Province Department of Pharmacy Sichuan Provincial People's Hospital University of Electronic Science and Technology of China Chengdu 611731 China School of Pharmacy North Sichuan Medical College Nanchong 637000 China Chemical Engineering Department University of Louisiana at Lafayette Lafayette LA 70504 USA State Key Laboratory of Silicate Materials for Architectures Wuhan University of Technology Wuhan 430070 China Department of Chemistry University of Akron Akron OH 44325 USA

The dual-emissive N,S co-doped carbon dots (N,S-CDs) with a long emission wavelength were synthesized via solvothermal *** N,S-CDs possess relatively high photoluminescence (PL) quantum yield (QY) (35.7%) towards near-infrared fluorescent peak up to 648 *** the advanced characterization techniques including X-ray photoelectron spectroscopy (XPS),Fourier transform infrared spectroscopy (FTIR),*** is found that the doped N,S elements play an important role in the formation of high QY *** N,S-CDs exist distinct pH-sensitive feature with reversible fluorescence in a good linear relationship with pH values in the range of *** is more,N,S-CDs can be used as an ultrasensitive Ag+ probe sensor with the resolution up to 0.4 μ*** finding will expand the application of as prepared N,S-CDs in sensing and environmental fields.

关键词： carbon cell imaging dual-emissive photoluminescence pH-sensitive Ag^+ probe

Density Functional Theory Study on Interaction between Catechin and Thymine

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

Chinese Journal of Chemical Physics 2012年第6期25卷 642-648,I0003页

作者： Wan-fei cai Yan Zheng Lai-cai Li An-min Tian Departement of Chemistry and Material Science Sichuan Normal University Chengdu 510065China Departement of Chemistry Sichuan University Chengdu 510054 China

The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke＇s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional （B3LYP） method by 6-31＋G＊ basis set. Thirteen stable structures for the catechin-thymine complexes have been found which form two hydrogen bonds at least. The vibrational frequencies are also studied at the same level to analyze these complexes. The results indicated that catechin interacted with thynfine by three different hydrogen bonds as N-H…O, C-H…O, O-H…O and the complexes are mainly stabilized by the hydrogen bonding interactions. Theories of atoms in molecules and natural bond orbital have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error, which are from -18.15 k J/mol to -32.99 kJ/mol. The results showed that the hydrogen bonding contribute to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the inonomer, which is in agreement with experimental results.

关键词： Density functional theory Thymine Hydrogen bond Catechin

Sediment dynamics in an offshore tidal channel in the southern Yellow Sea

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

International Journal of Sediment Research 2014年第2期29卷 246-259页

作者： Wen-fei NI Ya-ping WANG Xin-qing ZOU Ji-cai ZHANG jian-hua GAO School of Geographic and Oceanographic Sciences Nanjing University Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology Ministry of Land and Resources School of Geographic and Oceanographic Sciences Nanjing University

The geomorphology of the southern Yellow Sea(SYS) is characterized by offshore radial sand ridges(RSR).An offshore tidal channel(KSY Channel) is located perpendicular to the coast,comprised of a main and a tributary channel separated by a submarine sand ridge(KSY Sand Ridge) extending *** order to investigate the interactions among water flow,sediment transport,and topography,current velocity and suspended sediment concentration(SSC) were observed at 11 anchor stations along KSY Channel in RSR during a spring tide *** resolution bottom topography was also *** currents and tidally averaged suspended sediment fluxes were calculated and analyzed by using the decomposition *** suggested that the water currents became stronger landward but with asymmetrical current speed and temporal duration of flood and ebb *** currents showed landward water transport in the nearshore channel and a clockwise circulation around the KSY Sand ***-averaged SSC also increased landward along the *** main mechanisms controlling SSC variations were resuspension and horizontal advection,with spatial and temporal variations in the channel,which also contributed to sediment redistribution between channels and sand *** flow transport and the tidal pumping effect dominated the suspended sediment flux in the KSY *** KSY Sand Ridge had a potential southward migration due to the interaction between water flow,sediment transport,and topography.

关键词： Tidal channel Sand ridge Suspended sediment concentration Flux decomposition Southern Yellow Sea

Consensus model of social network group decision-making based on trust relationship among experts and expert reliability

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2023年第6期34卷 1576-1588页

作者： WANG Ya cai Mei jian Xinglian School of Management Science and Engineering Nanjing University of Information Science and TechnologyNanjing 210044China

Due to people’s increasing dependence on social networks,it is essential to develop a consensus model considering not only their own factors but also the interaction between *** external trust relationship among experts and the internal reliability of experts are important factors in *** paper focuses on improving the scientificity and effectiveness of decision-making and presents a consensus model combining trust relationship among experts and expert reliability in social network group decision-making(SN-GDM).A concept named matching degree is proposed to measure expert ***,linguistic information is applied to manage the imprecise and vague *** degree is expressed by a 2-tuple linguistic model,and experts’preferences are measured by a probabilistic linguistic term set(PLTS).Subsequently,a hybrid weight is explored to weigh experts’importance in a *** a consensus measure is introduced and a feedback mechanism is developed to produce some personalized recommendations with higher group ***,a comparative example is provided to prove the scientificity and effectiveness of the proposed consensus model.

关键词： social network group decision-making(SN-GDM) trust relationship expert reliability consensus model probabilistic linguistic term set(PLTS).

FLOW REGIMES BELOW AERATORS FOR DISCHARGE TUNNELS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2012年第3期24卷 378-382页

作者： MA fei WU jian-hua College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

The flow regimes below an aerator influence directly the air entrainment and the cavitation damage control. Based on the theoretical considerations, the experiments of the aerator for a discharge tunnel were conducted, and the relationships between the flow regime and hydraulic and geometric parameters were investigated. The results showed that, there are two kinds of threshold values for the flow regime conversions. One is Fr1-2 standing for the conversion from the fully filled cavity to the partially filled cavity, and the other is Fr2-3 which shows the change from the partially filled cavity to the net air cavity. Two empirical expressions were obtained for the conversions of the flow regimes, which can be used in the designs of the aerators.

关键词： aerator discharge tunnel flow regime filling water jet length

Efficient hydrolysis of hemicellulose to furfural by novel superacid SO_4H-functionalized ionic liquids

在线全文

学校读者我要写书评

暂无评论

Green Energy & Environment 2019年第1期4卷 49-55页

作者： Wei Hui Yan Zhou Yan Dong Zhi-Jun Cao fei-Qiang He Min-Zhong cai Duan-jian Tao College of Chemistry and Chemical Engineering Institute of Advanced Materials Jiangxi Normal University

Novel superacid SO_4H-functionalized ionic liquids(SFILs) were designed and prepared in this work. The catalytic activities of SFILs were evaluated in xylan hydrolysis and xylose dehydration to produce furfural. Combined with the results of acid strength of SFILs characterized by solid-state ^(31)P MAS NMR, it was found that the catalytic performance of SFILs was positively correlated to their acid strength. The superacid SFIL [Ch-SO_4H][CF_3SO_3] displayed the best catalytic performance with more than 80% yield of furfural, and it was also obviously superior to usual SO_3H-functionalized acidic ILs, mineral liquid acids, and acidic resin Amberlyst-15 catalysts in catalytic activity under optimized conditions. In addition, the superacid SFIL [Ch-SO_4H][CF_3SO_3] could be easily separated from reaction system and reused at least five times without obvious decrease.

关键词： Superacid Ionic liquids Hemicellulose Hydrolysis Furfural

Hand-eye calibration with a new linear decomposition algorithm

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第10期9卷 1363-1368页

作者： Rong-hua LIANG jian-fei MAO College of Information Engineering Zhejiang University of Technology Hangzhou 310032 China

To solve the homogeneous transformation equation of the form AX=XB in hand-eye calibration, where X represents an unknown transformation from the camera to the robot hand, and A and B denote the known movement transformations associated with the robot hand and the camera, respectively, this paper introduces a new linear decomposition algorithm which consists of singular value decomposition followed by the estimation of the optimal rotation matrix and the least squares equation to solve the rotation matrix of X. Without the requirements of traditional methods that A and B be rigid transformations with the same rotation angle, it enables the extension to non-rigid transformations for A and B. The details of our method are given, together with a short discussion of experimental results, showing that more precision and robustness can be achieved.

关键词： Homogeneous transformation equation Singular value decomposition (SVD) Optimal rotation matrix Rigid transformations