Photothermal synergistic catalytic systems for treating volatile organic compounds(VOCs)have attracted signif-icant attention due to their energy efficiency and potential to reduce carbon emissions.However,the mechani...Photothermal synergistic catalytic systems for treating volatile organic compounds(VOCs)have attracted signif-icant attention due to their energy efficiency and potential to reduce carbon emissions.However,the mechanism underlying the synergistic reaction remains a critical issue.This study introduces a photothermal synergistic system for the removal of ethyl acetate(EA)by synthesizing Cu-doped OMS-2(denoted as Cu-OMS-2).Under ultraviolet-visible(UV–Vis)irradiation in a flow system,the Cu-OMS-2 catalyst exhibited significantly enhanced performance in the EA degradation process,nearly doubling the effectiveness of pure OMS-2,and increasing carbon dioxide yield by 20%.This exceptional performance is attributed to the synergistic effect of increased oxygen vacancies(OV)at OMS-2 active sites and Cu doping,as confirmed by H2-TPR,O_(2)-TPD,and CO consump-tion measurements.This study clarifies the catalytic mechanism of light-assisted thermocatalysis and offers a novel strategy for designing photothermal catalysts with homogeneous Cu-doped nanorods for VOC removal.展开更多
The first 2^(+)excited states of the nucleus directly reflect the interaction between the shell structure and the nucleus,providing insights into the validity of the shell model and nuclear structure characteristics.A...The first 2^(+)excited states of the nucleus directly reflect the interaction between the shell structure and the nucleus,providing insights into the validity of the shell model and nuclear structure characteristics.Although the features of the first 2^(+)excited states can be measured for stable nuclei and calculated using nuclear models,significant uncertainty remains.This study employs a machine learning model based on a light gradient boosting machine(LightGBM)to investigate the first 2^(+)excited states.Specifically,the training of the LightGBM algorithm and the prediction of the first 2^(+)properties of 642 nuclei are presented.Furthermore,detailed comparisons of the LightGBM predictions were performed with available experimental data,shell model calculations,and Bayesian neural network predictions.The results revealed that the average difference between the LightGBM predictions and the experimental data was 18 times smaller than that obtained by the shell model and only 70%of the BNN prediction results.Considering Mg,Ca,Kr,Sm,and Pb isotopes as examples,it was also observed that LightGBM can effectively reproduce the magic number mutation caused by shell effects,with the energy being as low as 0.04 MeV due to shape coexistence.Therefore,we believe that leveraging LightGBM-based machine learning can profoundly enhance our insights into nuclear structures and provide new avenues for nuclear physics research.展开更多
Electrocatalytic CO_(2) reduction(ECR)is a promising approach for achieving carbon neutrality due to its ability to convert CO_(2) to valuable chemicals.Recent advances have significantly enhanced the ECR performance ...Electrocatalytic CO_(2) reduction(ECR)is a promising approach for achieving carbon neutrality due to its ability to convert CO_(2) to valuable chemicals.Recent advances have significantly enhanced the ECR performance of various catalysts by tuning their oxidation states,particularly for Cu-based catalysts that can reduce CO_(2) to multiple products.However,the oxidation state of copper(OSCu),especially Cu+,changes during the reaction process,posing significant challenges for both catalyst characterization and performance.In this review,the current understanding of the effect of oxidation states on product selectivity was first discussed.A comprehensive overview of in situ/operando characterization techniques,used to monitor the dynamic evolution of oxidation states during ECR,was then provided.Various strategies for stabilizing oxidation states through modification of catalysts and manipulation of external conditions were discussed.This review aimed to deepen the understanding of oxidation states in ECR and enlighten the development of more efficient electrocatalysts.展开更多
Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ ...Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method.The NaBH_(4) regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n(V^(4+))/n(V^(5+))ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7μmol/(g×h)and apparent quantum efficiency of 1.148%at 420 nm without any sacrificial agent,which is 11 times than that of V-Zn(O,S).The Vo acts as the active site to trap and activate N_(2) molecules and to trap and activate H_(2)O to produce the H for N_(2) molecules photocatalytic reduction.The rich Vo defects can also reduce the competitive adsorption of H_(2)O and N_(2) molecules on the surface active site of the catalyst.The heterovalent vanadium states act as the photogenerated electrons,quickly hopping between V^(4+)and V^(5+)to transfer for the photocatalytic N_(2) reduction reaction.Additionally,the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination.These synergistic effects collectively boost the photocatalytic nitrogen fixation activity.This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N_(2) fixation under mild conditions.展开更多
Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction tem...Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 ℃ and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 ℃, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA.h/g at a rate of 0.1C （1C=148 mA/g） and a good rate capability at high rates, even up to 50C.展开更多
This paper presents a three-dimensional, three-phase compositional model considering CO2 phase equilibrium between water and oil. In this model, CO2 is mutually soluble in aqueous and hydrocarbon phases, while other c...This paper presents a three-dimensional, three-phase compositional model considering CO2 phase equilibrium between water and oil. In this model, CO2 is mutually soluble in aqueous and hydrocarbon phases, while other components, except water,exist in hydrocarbon phase. The Peng–Robinson(PR) equation of state and the Wong–Sandler mixing rule with non-random two-liquid parameters are used to calculate CO2 fugacity in the aqueous phase. One-dimensional and three-dimensional CO2 flooding examples show that a significant amount of injected CO2 is dissolved in water. Our simulation shows 7% of injected CO2 can be dissolved in the aqueous phase, which delays oil recovery by 4%. The gas rate predicted by the model is smaller than the conventional model as long as water is undersaturated by CO2, which can be considered as 'lost' in the aqueous phase. The model also predicts that the delayed oil can be recovered after the gas breakthrough, indicating that delayed oil is hard to recover in field applications. A three-dimensional example reveals that a highly stratified reservoir causes uneven displacement and serious CO2 breakthrough. If mobility control measures like water alternating gas are undertaken, the solubility e ects will be more pronounced than this example.展开更多
High valence state species are significant in the energy-relevant electrochemical oxidation reactions.Herein,the high active state of Ni^(3+)formation induced by Mo^(6+)and their efficient synergism in NiS_(2)-MoS_(2)...High valence state species are significant in the energy-relevant electrochemical oxidation reactions.Herein,the high active state of Ni^(3+)formation induced by Mo^(6+)and their efficient synergism in NiS_(2)-MoS_(2)hetero-nanorods powder catalyst with the rough layered structure are demonstrated,as proof of concept,for the urea-assisted water electrolysis.This catalyst can be derived from the sulfidation of NiMoO_(4) nanorods that can realize individual metal sulfides sufficiently mixing at a domain size in the nanoscale which creates lots of active sites and nanointerfaces.The high valence state of Mo^(6+)and Ni^(3+)formation and increased conductive phase of 1 T MoS_(2)in the hetero-nanorods compared to the counterpart pure phases are revealed by spectral study and microscopic analysis;high electrochemical surface area and active site exposure are found due to the nano-interface formation and layered rough nanosheets over the surface of nanorods.They show much higher catalytic performance than their pure phases for urea oxidation,including high catalytic activity,stability,charge transfer ability and catalytic kinetics resulting from more active Ni^(3+)species formation and electronic synergism of high valence metals.Transformation of 1 T MoS_(2)to Mo^(6+)and increased amount of Mo^(6+)and Ni^(3+)after stability test indicate their involvement and synergism for the catalysis reaction.The current work offers a novel understanding of the synergistic effect based on the high valence state synergism for heterogeneous catalysts in electrocatalysis.展开更多
A new technology thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al2O3 composite w...A new technology thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al2O3 composite was prepared successfully. The metallographic analysis and performance test show that the microstructure of parts is dense and mechanical properties axe excellent with the volume fraction of Al is 37%. The bend strength and fracture toughness of the composite are about 570- 690 MPa and 8.5-16.8 MPa·m^1/2, respectively. Comparing with reaction in situ and high temperature oxidation technologies the bending strength and fracture toughness are improved greatly. At the same time, it shows that the technology parameters have great influences on the properties. So it is feasible to prepare metal/ceramics composites by the proposed technology.展开更多
In this paper,(500 nm 1%+5μm 3%)bimodal scale Al2O3p/AZ31 composites was fabricated by solid state synthesis and the effect of bimodal scale Al2O3 particulates on its dynamic recrystallization behavior and mechanical...In this paper,(500 nm 1%+5μm 3%)bimodal scale Al2O3p/AZ31 composites was fabricated by solid state synthesis and the effect of bimodal scale Al2O3 particulates on its dynamic recrystallization behavior and mechanical properties was investigated.The optical microscopy,scanning electron microscopy,transmission electron microscopy and electron universal strength tester composites were used to characterize the composites.The results indicate that the grains size of the composites are significantly refined and the mechanical properties are obviously improved.Due to the presence of the bimodal scale Al2o3 particulates,the high-density dislocation zone is formed around nano-Al2o3p and the particle deformation zone is formed near micron-ABOap.These zones are ideal sites for the formation of recrystallization nucleus.Meanwhile,the addition of the bimodal scale Al2o3 particulates may delay or hinder the growth of matrix grain through the pining effect on the grain boundaries,resulting in significantly improving the yield strength and tensile strength of Al2O3p/AZ31 composites.展开更多
Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indica...Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indicating high crystalline and phase purity.The SEM and TEM images reveal that diameter of the spherical-like Na2FePO4F/C particles ranges from 50 to 300 nm,and HRTEM image shows that the surface of Na2FePO4F/C composite is uniformly coated by carbon layer with a average thickness of about 3.6 nm.The carbon coating constrains the growth of the particles and effectively reduces the agglomeration of nanoparticles.Using lithium metal as anode,the composite delivers a discharge capacities of 102.8,96.4 and 90.3 mA·h/g at rates of 0.5C,1C and 2C,respectively.After 100 cycles at 0.5C,a discharge capacity of 98.9 mA·h/g is maintained with capacity retention of 96.2%.The Li+diffusion coefficient(D)of Na2FePO4F/C composite is calculated as 1.71×10^–9 cm^2/s.This study reveals that the simple solid state reaction could be a practical and effective synthetic route for the industrial production of Na2FePO4F/C material.展开更多
Solid-state grinding is a simple and effective method to introduce vip species into the channels of microporous materials through filling.The structure and the surface acidity of the materials were obtained from BET...Solid-state grinding is a simple and effective method to introduce vip species into the channels of microporous materials through filling.The structure and the surface acidity of the materials were obtained from BET isotherms and NH3-TPD,respectively.XRD,UV-vis,UV diffuse-reflectance,and TEM were used to characterize the phases,and the morphology,respectively.The clustered layers of MgO-Al2O3phases were formed in the internal pore surface and were highly dispersed inside the channels of the ZSM-5 host.So the volume of MgO-Al2O3/ZSM-5 composite was larger than the ZSM-5 zeolite itself and some mesoporous channels appeared when Mg/Al species entered the channels.Meanwhile,new acid sites emerged in MgO-Al2O3/ZSM-5 composite and the acid amount of the sample changed.The improved Pt dispersion and the increased acid content would cause the increase of propane conversion and the modification of selectivity during the reaction.展开更多
As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.B...As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.展开更多
We present an experimental determination on the Lande g-factors for the 5 s^2 ^1 S0 and 5 s5 p ^3P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in th...We present an experimental determination on the Lande g-factors for the 5 s^2 ^1 S0 and 5 s5 p ^3P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the ^87Sr optical lattice clock. The Zeeman shift of the 5 s5 p ^3 P0-5 s^2 ^1 S0 forbidden transition is measured with the π-polarized and σ^±-polarized interrogations at different magnetic field strengths. Moreover, in the g-factor measurement with the σ^±-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5 s^2 ^1 S0 g-factor for the ^87Sr atom is-1.306（52） ×10^-4, which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential g-factorδg between the 5 s5 p^3 P0 state and the 5 s^2 ^1 S0 state of the ^87Sr atoms is measured in the experiment as well,which are-7.67（36） ×10^-5 with π-transition spectra and-7.72（43） X 10^-5 with σ^±-transition spectra, in good agreement with the previous report [Phys. Rev. A 76（2007） 022510]. This work can also be used for determining the differential g-factor of the clock states for the optical clocks based on other atoms.展开更多
Dialogue State Tracking(DST)is a critical component of task-oriented spoken dialogue systems(SDS),tasked with maintaining an accurate representation of the conversational state by predicting slots and their correspond...Dialogue State Tracking(DST)is a critical component of task-oriented spoken dialogue systems(SDS),tasked with maintaining an accurate representation of the conversational state by predicting slots and their corresponding values.Recent advances leverage Large Language Models(LLMs)with prompt-based tuning to improve tracking accuracy and efficiency.However,these approaches often incur substantial computational and memory overheads and typically address slot extraction implicitly within prompts,without explicitly modeling the complex dependencies between slots and values.In this work,we propose PUGG,a novel DST framework that constructs schema-driven prompts to fine-tune GPT-2 and utilizes its tokenizer to implement a memory encoder.PUGG explicitly extracts slot values via GPT-2 and employs Graph Attention Networks(GATs)to model and reason over the intricate relationships between slots and their associated values.We evaluate PUGG on four publicly available datasets,where it achieves stateof-the-art performance across multiple evaluation metrics,highlighting its robustness and generalizability in diverse conversational scenarios.Our results indicate that the integration of GPT-2 substantially reduces model complexity and memory consumption by streamlining key processes.Moreover,prompt tuning enhances the model’s flexibility and precision in extracting relevant slot-value pairs,while the incorporation of GATs facilitates effective relational reasoning,leading to improved dialogue state representations.展开更多
基金supported by the Qilu University of Technology(Shandong Academy of Sciences),the Basic Research Project of Science,Education and Industry Integration Pilot Project(No.2022PY047).
文摘Photothermal synergistic catalytic systems for treating volatile organic compounds(VOCs)have attracted signif-icant attention due to their energy efficiency and potential to reduce carbon emissions.However,the mechanism underlying the synergistic reaction remains a critical issue.This study introduces a photothermal synergistic system for the removal of ethyl acetate(EA)by synthesizing Cu-doped OMS-2(denoted as Cu-OMS-2).Under ultraviolet-visible(UV–Vis)irradiation in a flow system,the Cu-OMS-2 catalyst exhibited significantly enhanced performance in the EA degradation process,nearly doubling the effectiveness of pure OMS-2,and increasing carbon dioxide yield by 20%.This exceptional performance is attributed to the synergistic effect of increased oxygen vacancies(OV)at OMS-2 active sites and Cu doping,as confirmed by H2-TPR,O_(2)-TPD,and CO consump-tion measurements.This study clarifies the catalytic mechanism of light-assisted thermocatalysis and offers a novel strategy for designing photothermal catalysts with homogeneous Cu-doped nanorods for VOC removal.
基金supported by the National Key R&D Program of China (No. 2022YFA1603300)the Romanian Ministry of Research,Innovation and Digitalization under Contract PN 23.21.01.06+1 种基金The ELI-RO project with Contract ELI-RORDI-2024-008 (AMAP)a grant from the Romanian Ministry of Research,Innovation and Digitization,CNCS-UEFIS-CDI,with project numbers PN-Ⅲ-P4-PCE-2021-1014, PN-Ⅲ-P4-PCE-2021-0595, and PN-Ⅲ-P1-1.1-TE2021-1464 within PNCDI Ⅲ
文摘The first 2^(+)excited states of the nucleus directly reflect the interaction between the shell structure and the nucleus,providing insights into the validity of the shell model and nuclear structure characteristics.Although the features of the first 2^(+)excited states can be measured for stable nuclei and calculated using nuclear models,significant uncertainty remains.This study employs a machine learning model based on a light gradient boosting machine(LightGBM)to investigate the first 2^(+)excited states.Specifically,the training of the LightGBM algorithm and the prediction of the first 2^(+)properties of 642 nuclei are presented.Furthermore,detailed comparisons of the LightGBM predictions were performed with available experimental data,shell model calculations,and Bayesian neural network predictions.The results revealed that the average difference between the LightGBM predictions and the experimental data was 18 times smaller than that obtained by the shell model and only 70%of the BNN prediction results.Considering Mg,Ca,Kr,Sm,and Pb isotopes as examples,it was also observed that LightGBM can effectively reproduce the magic number mutation caused by shell effects,with the energy being as low as 0.04 MeV due to shape coexistence.Therefore,we believe that leveraging LightGBM-based machine learning can profoundly enhance our insights into nuclear structures and provide new avenues for nuclear physics research.
基金supported by the National Natural Science Foundation of China(No.52221004)the Shenzhen Science and Technology Program(No.RCJC20221008092758099)+1 种基金the Shenzhen Pengrui Young Faculty Program of Shenzhen Pengrui Foundation(No.SZPR2023004)the Guangdong Higher Education Institutions Innovative Research Team of Urban Water Cycle and Ecological Safety(No.2023KCXTD053).
文摘Electrocatalytic CO_(2) reduction(ECR)is a promising approach for achieving carbon neutrality due to its ability to convert CO_(2) to valuable chemicals.Recent advances have significantly enhanced the ECR performance of various catalysts by tuning their oxidation states,particularly for Cu-based catalysts that can reduce CO_(2) to multiple products.However,the oxidation state of copper(OSCu),especially Cu+,changes during the reaction process,posing significant challenges for both catalyst characterization and performance.In this review,the current understanding of the effect of oxidation states on product selectivity was first discussed.A comprehensive overview of in situ/operando characterization techniques,used to monitor the dynamic evolution of oxidation states during ECR,was then provided.Various strategies for stabilizing oxidation states through modification of catalysts and manipulation of external conditions were discussed.This review aimed to deepen the understanding of oxidation states in ECR and enlighten the development of more efficient electrocatalysts.
文摘Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method.The NaBH_(4) regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n(V^(4+))/n(V^(5+))ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7μmol/(g×h)and apparent quantum efficiency of 1.148%at 420 nm without any sacrificial agent,which is 11 times than that of V-Zn(O,S).The Vo acts as the active site to trap and activate N_(2) molecules and to trap and activate H_(2)O to produce the H for N_(2) molecules photocatalytic reduction.The rich Vo defects can also reduce the competitive adsorption of H_(2)O and N_(2) molecules on the surface active site of the catalyst.The heterovalent vanadium states act as the photogenerated electrons,quickly hopping between V^(4+)and V^(5+)to transfer for the photocatalytic N_(2) reduction reaction.Additionally,the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination.These synergistic effects collectively boost the photocatalytic nitrogen fixation activity.This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N_(2) fixation under mild conditions.
基金Project supported by the Research Funds of the Key Laboratory of Fuel Cell Technology of Guangdong Province,ChinaProject(7411793079907)supported by the Guangzhou Special Foundation for Applied Basic Research+1 种基金Project(2013A15GX048)supported by the Dalian Science and Technology Project Foundation,ChinaProject(21376035)supported by the National Natural Science Foundation of China
文摘Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 ℃ and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 ℃, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA.h/g at a rate of 0.1C （1C=148 mA/g） and a good rate capability at high rates, even up to 50C.
基金financially supported by National Natural Science Foundation of China(U1762101)National Science and Technology Major Projects(2017ZX05069)
文摘This paper presents a three-dimensional, three-phase compositional model considering CO2 phase equilibrium between water and oil. In this model, CO2 is mutually soluble in aqueous and hydrocarbon phases, while other components, except water,exist in hydrocarbon phase. The Peng–Robinson(PR) equation of state and the Wong–Sandler mixing rule with non-random two-liquid parameters are used to calculate CO2 fugacity in the aqueous phase. One-dimensional and three-dimensional CO2 flooding examples show that a significant amount of injected CO2 is dissolved in water. Our simulation shows 7% of injected CO2 can be dissolved in the aqueous phase, which delays oil recovery by 4%. The gas rate predicted by the model is smaller than the conventional model as long as water is undersaturated by CO2, which can be considered as 'lost' in the aqueous phase. The model also predicts that the delayed oil can be recovered after the gas breakthrough, indicating that delayed oil is hard to recover in field applications. A three-dimensional example reveals that a highly stratified reservoir causes uneven displacement and serious CO2 breakthrough. If mobility control measures like water alternating gas are undertaken, the solubility e ects will be more pronounced than this example.
基金supported by the National Natural Science Foundation of China(21972124,21603041)the Priority Academic Program Development of Jiangsu Higher Education Institutionthe support of the Six Talent Peaks Project of Jiangsu Province(XCL-070-2018)。
文摘High valence state species are significant in the energy-relevant electrochemical oxidation reactions.Herein,the high active state of Ni^(3+)formation induced by Mo^(6+)and their efficient synergism in NiS_(2)-MoS_(2)hetero-nanorods powder catalyst with the rough layered structure are demonstrated,as proof of concept,for the urea-assisted water electrolysis.This catalyst can be derived from the sulfidation of NiMoO_(4) nanorods that can realize individual metal sulfides sufficiently mixing at a domain size in the nanoscale which creates lots of active sites and nanointerfaces.The high valence state of Mo^(6+)and Ni^(3+)formation and increased conductive phase of 1 T MoS_(2)in the hetero-nanorods compared to the counterpart pure phases are revealed by spectral study and microscopic analysis;high electrochemical surface area and active site exposure are found due to the nano-interface formation and layered rough nanosheets over the surface of nanorods.They show much higher catalytic performance than their pure phases for urea oxidation,including high catalytic activity,stability,charge transfer ability and catalytic kinetics resulting from more active Ni^(3+)species formation and electronic synergism of high valence metals.Transformation of 1 T MoS_(2)to Mo^(6+)and increased amount of Mo^(6+)and Ni^(3+)after stability test indicate their involvement and synergism for the catalysis reaction.The current work offers a novel understanding of the synergistic effect based on the high valence state synergism for heterogeneous catalysts in electrocatalysis.
基金supported by National Natural Science Foundation of China(No50705018)Postdoctoral Foundation of China (No20070420847)
文摘A new technology thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al2O3 composite was prepared successfully. The metallographic analysis and performance test show that the microstructure of parts is dense and mechanical properties axe excellent with the volume fraction of Al is 37%. The bend strength and fracture toughness of the composite are about 570- 690 MPa and 8.5-16.8 MPa·m^1/2, respectively. Comparing with reaction in situ and high temperature oxidation technologies the bending strength and fracture toughness are improved greatly. At the same time, it shows that the technology parameters have great influences on the properties. So it is feasible to prepare metal/ceramics composites by the proposed technology.
基金the National Key Research and Development Program(2019YFB2006500)National Natural Science Foundation of China(51404082).
文摘In this paper,(500 nm 1%+5μm 3%)bimodal scale Al2O3p/AZ31 composites was fabricated by solid state synthesis and the effect of bimodal scale Al2O3 particulates on its dynamic recrystallization behavior and mechanical properties was investigated.The optical microscopy,scanning electron microscopy,transmission electron microscopy and electron universal strength tester composites were used to characterize the composites.The results indicate that the grains size of the composites are significantly refined and the mechanical properties are obviously improved.Due to the presence of the bimodal scale Al2o3 particulates,the high-density dislocation zone is formed around nano-Al2o3p and the particle deformation zone is formed near micron-ABOap.These zones are ideal sites for the formation of recrystallization nucleus.Meanwhile,the addition of the bimodal scale Al2o3 particulates may delay or hinder the growth of matrix grain through the pining effect on the grain boundaries,resulting in significantly improving the yield strength and tensile strength of Al2O3p/AZ31 composites.
基金Projects(51472211,51502256)supported by the National Natural Science Foundation of ChinaProjects(2016GK4005,2016GK4030)supported by the Strategic New Industry of Hunan Province,ChinaProject(13C925)supported by the Research Foundation of Education Bureau of Hunan Province,China
文摘Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indicating high crystalline and phase purity.The SEM and TEM images reveal that diameter of the spherical-like Na2FePO4F/C particles ranges from 50 to 300 nm,and HRTEM image shows that the surface of Na2FePO4F/C composite is uniformly coated by carbon layer with a average thickness of about 3.6 nm.The carbon coating constrains the growth of the particles and effectively reduces the agglomeration of nanoparticles.Using lithium metal as anode,the composite delivers a discharge capacities of 102.8,96.4 and 90.3 mA·h/g at rates of 0.5C,1C and 2C,respectively.After 100 cycles at 0.5C,a discharge capacity of 98.9 mA·h/g is maintained with capacity retention of 96.2%.The Li+diffusion coefficient(D)of Na2FePO4F/C composite is calculated as 1.71×10^–9 cm^2/s.This study reveals that the simple solid state reaction could be a practical and effective synthetic route for the industrial production of Na2FePO4F/C material.
基金the financial supports of the National Natural Science Foundation of China(Grant No.21376051,21106017,21306023 and 51077013)the Natural Science Foundation of Jiangsu(Grant No.BK20131288)+3 种基金the Fund Project for Transformation of Scientific and Technological Achievements of Jiangsu Province of China(Grant No.BA2011086)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20100092120047)the Key Program for the Scientific Research Guiding Fund of Basic Scientific Research Operation Expenditure of Southeast University(Grant No.3207043101)Instrumental Analysis Fund of Southeast University
文摘Solid-state grinding is a simple and effective method to introduce vip species into the channels of microporous materials through filling.The structure and the surface acidity of the materials were obtained from BET isotherms and NH3-TPD,respectively.XRD,UV-vis,UV diffuse-reflectance,and TEM were used to characterize the phases,and the morphology,respectively.The clustered layers of MgO-Al2O3phases were formed in the internal pore surface and were highly dispersed inside the channels of the ZSM-5 host.So the volume of MgO-Al2O3/ZSM-5 composite was larger than the ZSM-5 zeolite itself and some mesoporous channels appeared when Mg/Al species entered the channels.Meanwhile,new acid sites emerged in MgO-Al2O3/ZSM-5 composite and the acid amount of the sample changed.The improved Pt dispersion and the increased acid content would cause the increase of propane conversion and the modification of selectivity during the reaction.
基金funded by the National Natural Science Foundation of China(Grant No.NSFC51374147)the German Society for Petroleum and Coal Science and Technology(Grant No.DGMK680-4)
文摘As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61127901,11404025 and 91536106the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB21030700+1 种基金the Key Research Project of Frontier Science of Chinese Academy of Sciences under Grant No QYZDB-SSW-JSC004the China Postdoctoral Science Foundation under Grant No 2014M560061
文摘We present an experimental determination on the Lande g-factors for the 5 s^2 ^1 S0 and 5 s5 p ^3P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the ^87Sr optical lattice clock. The Zeeman shift of the 5 s5 p ^3 P0-5 s^2 ^1 S0 forbidden transition is measured with the π-polarized and σ^±-polarized interrogations at different magnetic field strengths. Moreover, in the g-factor measurement with the σ^±-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5 s^2 ^1 S0 g-factor for the ^87Sr atom is-1.306（52） ×10^-4, which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential g-factorδg between the 5 s5 p^3 P0 state and the 5 s^2 ^1 S0 state of the ^87Sr atoms is measured in the experiment as well,which are-7.67（36） ×10^-5 with π-transition spectra and-7.72（43） X 10^-5 with σ^±-transition spectra, in good agreement with the previous report [Phys. Rev. A 76（2007） 022510]. This work can also be used for determining the differential g-factor of the clock states for the optical clocks based on other atoms.
基金supported by the MSIT(Ministry of Science and ICT),Republic of Korea,under the ITRC(Information Technology Research Centre)support program(IITP-2024-RS-2024-00437191)supervised by the IITP(Institute for Information&Communications Technology Planning&Evaluation).
文摘Dialogue State Tracking(DST)is a critical component of task-oriented spoken dialogue systems(SDS),tasked with maintaining an accurate representation of the conversational state by predicting slots and their corresponding values.Recent advances leverage Large Language Models(LLMs)with prompt-based tuning to improve tracking accuracy and efficiency.However,these approaches often incur substantial computational and memory overheads and typically address slot extraction implicitly within prompts,without explicitly modeling the complex dependencies between slots and values.In this work,we propose PUGG,a novel DST framework that constructs schema-driven prompts to fine-tune GPT-2 and utilizes its tokenizer to implement a memory encoder.PUGG explicitly extracts slot values via GPT-2 and employs Graph Attention Networks(GATs)to model and reason over the intricate relationships between slots and their associated values.We evaluate PUGG on four publicly available datasets,where it achieves stateof-the-art performance across multiple evaluation metrics,highlighting its robustness and generalizability in diverse conversational scenarios.Our results indicate that the integration of GPT-2 substantially reduces model complexity and memory consumption by streamlining key processes.Moreover,prompt tuning enhances the model’s flexibility and precision in extracting relevant slot-value pairs,while the incorporation of GATs facilitates effective relational reasoning,leading to improved dialogue state representations.
