To address the low accuracy and stability when applying classical control theory in distribution networks with distributed generation,a control method involving flexible multistate switches(FMSs)is proposed in this st...To address the low accuracy and stability when applying classical control theory in distribution networks with distributed generation,a control method involving flexible multistate switches(FMSs)is proposed in this study.This approach is based on an improved double-loop recursive fuzzy neural network(DRFNN)sliding mode,which is intended to stably achieve multiterminal power interaction and adaptive arc suppression for single-phase ground faults.First,an improved DRFNN sliding mode control(SMC)method is proposed to overcome the chattering and transient overshoot inherent in the classical SMC and reduce the reliance on a precise mathematical model of the control system.To improve the robustness of the system,an adaptive parameter-adjustment strategy for the DRFNN is designed,where its dynamic mapping capabilities are leveraged to improve the transient compensation control.Additionally,a quasi-continuous second-order sliding mode controller with a calculus-driven sliding mode surface is developed to improve the current monitoring accuracy and enhance the system stability.The stability of the proposed method and the convergence of the network parameters are verified using the Lyapunov theorem.A simulation model of the three-port FMS with its control system is constructed in MATLAB/Simulink.The simulation result confirms the feasibility and effectiveness of the proposed control strategy based on a comparative analysis.展开更多
Benefiting from the abrupt phase changes within subwavelength thicknesses,metasurfaces have been widely applied for lightweight and compact optical systems.Simultaneous broadband and high-efficiency characteristics ar...Benefiting from the abrupt phase changes within subwavelength thicknesses,metasurfaces have been widely applied for lightweight and compact optical systems.Simultaneous broadband and high-efficiency characteristics are highly attractive for the practical implementation of metasurfaces.However,current metasurface devices mostly adopt discrete micro/nano structures,which rarely realize both merits simultaneously.In this paper,dielectric metasurfaces composed of quasi-continuous nanostrips are proposed to overcome this limitation.Via quasi-continuous nanostrips metasurface,a normal focusing metalens and a superoscillatory lens overcoming the diffraction limit are designed and experimentally demonstrated.The quasi-continuous metadevices can operate in a broadband wavelength ranging from 450 nm to 1000nm and keep a high power efficiency.The average efficiency of the fabricated metalens reaches 54.24%,showing a significant improvement compared to the previously reported metalenses with the same thickness.The proposed methodology can be easily extended to design other metadevices with the advantages of broadband and high-efficiency in practical optical systems.展开更多
Improving the transfer hydrogenation of N-heteroarenes is of key importance for various industrial pro-cesses and remains a challenge so far.We reported here a microcapsule-pyrolysis strategy to quasi-continuous synth...Improving the transfer hydrogenation of N-heteroarenes is of key importance for various industrial pro-cesses and remains a challenge so far.We reported here a microcapsule-pyrolysis strategy to quasi-continuous synthesis S,N co-doped carbon supported Co single atom catalysts(Co/SNC),which was used for transfer hydrogenation of quinoline with formic acid as the hydrogen donor.Given the unique ge-ometric and electronic properties of the Co single atoms,the excellent catalytic activity,selectivity and stability were observed.Benefiting from the quasi-continuous synthesis method,the as-obtained cata-lysts provide a reference for the large-scale preparation of single atom catalysts without amplification ef-fect.Highly catalytic performances and quasi-continuous preparation process,demonstrating a new and promising approach to rational design of atomically dispersed catalysts with maximum atomic efficiency in industrial.展开更多
Strong law of large numbers is a fundamental theory in probability and statistics. When the measure tool is nonadditive, this law is very different from additive case. In 2010 Chen investigated the strong law of large...Strong law of large numbers is a fundamental theory in probability and statistics. When the measure tool is nonadditive, this law is very different from additive case. In 2010 Chen investigated the strong law of large numbers under upper probabilityVby assumingVis continuous. This assumption is very strong. Upper probabilities may not be continuous. In this paper we prove the strong law of large numbers for an upper probability without the continuity assumption whereby random variables are quasi-continuous and the upper probability is generated by a weakly compact family of probabilities on a complete and separable metric sample space.展开更多
The lower Ordovician mid-assemblage Formations in the central Ordos Basin of China host prolific gas resources,and most hydrocarbon reserves are stored in naturally-fractured reservoirs.Thus,fracture pathway systems m...The lower Ordovician mid-assemblage Formations in the central Ordos Basin of China host prolific gas resources,and most hydrocarbon reserves are stored in naturally-fractured reservoirs.Thus,fracture pathway systems may have a significant impact on reservoir performance.This article focuses on the core-and laboratory-based characterization of fractures.Through the developmental degrees,extended scale,output state and filling characteristics of various types of fractures,the results show that there are three distinct fracture types:1)nearly vertical fractures,2)oblique fractures,and 3)horizontal fractures.Based on a systematic study of the characterization of reservoir space,the main geologic setting of natural gas accumulation and the regional tectonic background,type 1 is mainly driven by the tectonic formation mechanism,and type 3 and parts of low-angle fractures in type 2 are induced by the diagenetic formation mechanism.While recovered paleopressure for methane-rich aqueous inclusions trapped in fracture-filling cement indicates that the fracture opening and growth are consistent with gas maturation and charge and such high-angle fractures in type 2 are caused by the compound formation mechanism.The fractures to hydrocarbon accumulation may play a more significant role in improving the quality of reservoir porosity.Furthermore,connected fractures,dissolved pores and cavities together constitute the three-dimensional pore-cave-fracture network pathway systems,with faults serving as the dominant charge pathways of highly pressurized gas in the study area.Our results demonstrate that protracted growth of a pervasive fracture system is not only the consequence of various formation mechanisms but also intrinsic to quasi-continuous accumulation reservoirs.展开更多
Based on the extensive studies of conventional and unconventional hydrocarbon accumulations,the concept,classification and formation as well as distribution of petroleum reservoirs are discussed.The revised concept de...Based on the extensive studies of conventional and unconventional hydrocarbon accumulations,the concept,classification and formation as well as distribution of petroleum reservoirs are discussed.The revised concept defined the petroleum reservoir as a continuous hydrocarbon accumulation in a single or a set of reservoirs with an independent or uniform pressure system.In terms of the pattern of hydrocarbon accumulation and distribution,the hydrocarbon accumulations are classified into three basic types,i.e.,the continuous accumulation,the quasi-continuous accumulation and the discontinuous accumulation.The hydrocarbon accumulation was demonstrated as a process from continuous accumulation to discontinuous accumulation,and therefore these three basic types of hydrocarbon accumulations were identified.The continuous hydrocarbon accumulation is principally formed in source rocks,and typical examples are shale hydrocarbon reservoirs and coal-bed methane reservoirs;it is mainly characterized by tight-ultra tight reservoirs with permeability of nanodarcy to millidarcy;the hydrocarbons occurred in free,adsorbed or dissolved state;a continuous accumulation comprises actually only a single reservoir,and hydrocarbons are extensively and continuously distributed within the scope of effective source rocks;the accumulation has neither defined boundaries nor bottom or edge water;oil and gas mainly accumulate in situ or near the generation of hydrocarbons with no prominent migration;this hydrocarbon accumulation process is basically not controlled by traps.The quasicontinuous hydrocarbon accumulation mostly occurs in the tight reservoirs adjacent to source rocks,and typical examples are most of tight hydrocarbon reservoirs;the hydrocarbons are distributed quasicontinuously in large areas,and each quasi-continuous hydrocarbon accumulation includes numerous adjacent small-to medium-size reservoirs;reservoirs of this kind of hydrocarbon accumulation have no defined boundaries,no or only local edge and bottom water distribution,and 展开更多
基金the Natural Science Foundation of Fujian,China(No.2021J01633).
文摘To address the low accuracy and stability when applying classical control theory in distribution networks with distributed generation,a control method involving flexible multistate switches(FMSs)is proposed in this study.This approach is based on an improved double-loop recursive fuzzy neural network(DRFNN)sliding mode,which is intended to stably achieve multiterminal power interaction and adaptive arc suppression for single-phase ground faults.First,an improved DRFNN sliding mode control(SMC)method is proposed to overcome the chattering and transient overshoot inherent in the classical SMC and reduce the reliance on a precise mathematical model of the control system.To improve the robustness of the system,an adaptive parameter-adjustment strategy for the DRFNN is designed,where its dynamic mapping capabilities are leveraged to improve the transient compensation control.Additionally,a quasi-continuous second-order sliding mode controller with a calculus-driven sliding mode surface is developed to improve the current monitoring accuracy and enhance the system stability.The stability of the proposed method and the convergence of the network parameters are verified using the Lyapunov theorem.A simulation model of the three-port FMS with its control system is constructed in MATLAB/Simulink.The simulation result confirms the feasibility and effectiveness of the proposed control strategy based on a comparative analysis.
基金the financial support by National Natural Science Foundation of China under contract No.61905031,61905073National Key R&D Program of China under contract No.2020YFC1522900Natural Science Foundation of Chongqing under contract No.CSTB2023NSCQMSX0992。
文摘Benefiting from the abrupt phase changes within subwavelength thicknesses,metasurfaces have been widely applied for lightweight and compact optical systems.Simultaneous broadband and high-efficiency characteristics are highly attractive for the practical implementation of metasurfaces.However,current metasurface devices mostly adopt discrete micro/nano structures,which rarely realize both merits simultaneously.In this paper,dielectric metasurfaces composed of quasi-continuous nanostrips are proposed to overcome this limitation.Via quasi-continuous nanostrips metasurface,a normal focusing metalens and a superoscillatory lens overcoming the diffraction limit are designed and experimentally demonstrated.The quasi-continuous metadevices can operate in a broadband wavelength ranging from 450 nm to 1000nm and keep a high power efficiency.The average efficiency of the fabricated metalens reaches 54.24%,showing a significant improvement compared to the previously reported metalenses with the same thickness.The proposed methodology can be easily extended to design other metadevices with the advantages of broadband and high-efficiency in practical optical systems.
基金financial support from the National Natural Science Foundation of China(Nos.22078371,21938001,21961160741)Guangdong Provincial Key R&D Programme(No.2019B110206002)+4 种基金Special fund for Local Science and Technology Development by the Central Government,Local Innovative and Research Teams Project of Guangdong Pearl River Talents Pro-gram(No.2017BT01C102)the NSF of Guang-dong Province(No.2020A1515011141)the National key Research and Development Program Nanotechnology Specific Project(No.2020YFA0210900)the Science and Technology Key Project of Guangdong Province,China(No.2020B010188002)The Project Supported by Guangdong Natural Science Foundation(No.2021A1515010163).
文摘Improving the transfer hydrogenation of N-heteroarenes is of key importance for various industrial pro-cesses and remains a challenge so far.We reported here a microcapsule-pyrolysis strategy to quasi-continuous synthesis S,N co-doped carbon supported Co single atom catalysts(Co/SNC),which was used for transfer hydrogenation of quinoline with formic acid as the hydrogen donor.Given the unique ge-ometric and electronic properties of the Co single atoms,the excellent catalytic activity,selectivity and stability were observed.Benefiting from the quasi-continuous synthesis method,the as-obtained cata-lysts provide a reference for the large-scale preparation of single atom catalysts without amplification ef-fect.Highly catalytic performances and quasi-continuous preparation process,demonstrating a new and promising approach to rational design of atomically dispersed catalysts with maximum atomic efficiency in industrial.
文摘Strong law of large numbers is a fundamental theory in probability and statistics. When the measure tool is nonadditive, this law is very different from additive case. In 2010 Chen investigated the strong law of large numbers under upper probabilityVby assumingVis continuous. This assumption is very strong. Upper probabilities may not be continuous. In this paper we prove the strong law of large numbers for an upper probability without the continuity assumption whereby random variables are quasi-continuous and the upper probability is generated by a weakly compact family of probabilities on a complete and separable metric sample space.
基金Project (2011ZX05007-004) supported by the National Sciences and Technologies,ChinaProject (41502132) supported by the National Natural Science Foundation of China
文摘The lower Ordovician mid-assemblage Formations in the central Ordos Basin of China host prolific gas resources,and most hydrocarbon reserves are stored in naturally-fractured reservoirs.Thus,fracture pathway systems may have a significant impact on reservoir performance.This article focuses on the core-and laboratory-based characterization of fractures.Through the developmental degrees,extended scale,output state and filling characteristics of various types of fractures,the results show that there are three distinct fracture types:1)nearly vertical fractures,2)oblique fractures,and 3)horizontal fractures.Based on a systematic study of the characterization of reservoir space,the main geologic setting of natural gas accumulation and the regional tectonic background,type 1 is mainly driven by the tectonic formation mechanism,and type 3 and parts of low-angle fractures in type 2 are induced by the diagenetic formation mechanism.While recovered paleopressure for methane-rich aqueous inclusions trapped in fracture-filling cement indicates that the fracture opening and growth are consistent with gas maturation and charge and such high-angle fractures in type 2 are caused by the compound formation mechanism.The fractures to hydrocarbon accumulation may play a more significant role in improving the quality of reservoir porosity.Furthermore,connected fractures,dissolved pores and cavities together constitute the three-dimensional pore-cave-fracture network pathway systems,with faults serving as the dominant charge pathways of highly pressurized gas in the study area.Our results demonstrate that protracted growth of a pervasive fracture system is not only the consequence of various formation mechanisms but also intrinsic to quasi-continuous accumulation reservoirs.
基金This work was supported by National Science and Technology Major Project of China(Grant No.2011ZX05007-004 and Grant No.2011ZX05018001-004)National Natural Science Foundation of China(Grant No.41402121 and Grant No.41502132)+1 种基金Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2013JM5007)Shaanxi Provincial Natural Science Foundation of China(Grant No.2013JQ503).
文摘Based on the extensive studies of conventional and unconventional hydrocarbon accumulations,the concept,classification and formation as well as distribution of petroleum reservoirs are discussed.The revised concept defined the petroleum reservoir as a continuous hydrocarbon accumulation in a single or a set of reservoirs with an independent or uniform pressure system.In terms of the pattern of hydrocarbon accumulation and distribution,the hydrocarbon accumulations are classified into three basic types,i.e.,the continuous accumulation,the quasi-continuous accumulation and the discontinuous accumulation.The hydrocarbon accumulation was demonstrated as a process from continuous accumulation to discontinuous accumulation,and therefore these three basic types of hydrocarbon accumulations were identified.The continuous hydrocarbon accumulation is principally formed in source rocks,and typical examples are shale hydrocarbon reservoirs and coal-bed methane reservoirs;it is mainly characterized by tight-ultra tight reservoirs with permeability of nanodarcy to millidarcy;the hydrocarbons occurred in free,adsorbed or dissolved state;a continuous accumulation comprises actually only a single reservoir,and hydrocarbons are extensively and continuously distributed within the scope of effective source rocks;the accumulation has neither defined boundaries nor bottom or edge water;oil and gas mainly accumulate in situ or near the generation of hydrocarbons with no prominent migration;this hydrocarbon accumulation process is basically not controlled by traps.The quasicontinuous hydrocarbon accumulation mostly occurs in the tight reservoirs adjacent to source rocks,and typical examples are most of tight hydrocarbon reservoirs;the hydrocarbons are distributed quasicontinuously in large areas,and each quasi-continuous hydrocarbon accumulation includes numerous adjacent small-to medium-size reservoirs;reservoirs of this kind of hydrocarbon accumulation have no defined boundaries,no or only local edge and bottom water distribution,and
