In the heterogeneous reservoirs,CO_(2) flooding easily leads to CO_(2) gas channeling,which can seriously affect sweeping efficiency and reduce oil recovery.After thoroughly investigating the advantages and shortcomin...In the heterogeneous reservoirs,CO_(2) flooding easily leads to CO_(2) gas channeling,which can seriously affect sweeping efficiency and reduce oil recovery.After thoroughly investigating the advantages and shortcomings of various CO_(2) plugging technologies,this paper focuses on the feasibility of improving conventional water-alternating gas(WAG)through CO_(2)-responsive gel materials.Based on the different chemical reaction mechanisms between the unique chemical structure and CO_(2),changes in the material’s physical and chemical properties can respond to CO_(2).The feasibility of utilizing these property changes for CO_(2)-responsive plugging is explored.Various CO_(2)-responsive gels and gel nanoparticles have been extensively researched in different fields,such as energy,medicine,and biology.This paper surveys the molecular structures,chemical compositions,response mechanisms,and changes of these CO_(2)-responsive gels,aiming to draw insights into the carbon dioxide-enhanced oil recovery(CO_(2)-EOR)field.Finally,the key issues and future development direction of CO_(2)-responsive plugging gels were analyzed.展开更多
Undesirable gas channeling always occurs along the high-permeability layers in heterogeneous oil reservoirs during water-alternating-CO_(2)(WAG)flooding,and conventional polymer gels used for blocking the“channeling...Undesirable gas channeling always occurs along the high-permeability layers in heterogeneous oil reservoirs during water-alternating-CO_(2)(WAG)flooding,and conventional polymer gels used for blocking the“channeling”paths usually suffer from either low injectivity or poor gelation control.Herein,we for the first time developed an in-situ high-pressure CO_(2)-triggered gel system based on a smart surfactant,N-erucamidopropyl-N,N-dimethylamine(UC22AMPM),which was introduced into the aqueous slugs to control gas channeling inWAG processes.The water-like,low-viscosity UC22AMPM brine solution can be thickened by high-pressure CO_(2) owing to the formation of wormlike micelles(WLMs),as well as their growth and shear-induced structure buildup under shear flow.The thickening power can be further potentiated by the generation of denser WLMs resulting from either surfactant concentration augmentation or a certain range of heating,and can be impaired via pressurization above the critical pressure of CO_(2) because of its soaring solvent power.Core flooding tests using heterogeneous cores demonstrated that gas channeling was alleviated by plugging of high-capacity channels due to the in-situ gelation of UC22AMPM slugs upon their reaction with the pre-or post-injected CO_(2) slugs under shear flow,thereupon driving chase fluids into unrecovered low-permeability areas and producing an 8.0% higher oil recovery factor than the conventional WAG mode.This smart surfactant enabled high injectivity and satisfactory gelation control,attributable to low initial viscosity and the combined properties of one component and CO_(2)-triggered gelation,respectively.This work could provide a guide towards designing gels for reducing CO_(2) spillover and reinforcing the CO_(2) sequestration effect during CO_(2) enhanced oil recovery processes.展开更多
Current methods for the analysis of channeling-path phenomena in reservoirs cannot account for the influence of time and space on the actual seepage behavior.In the present study,this problem is addressed considering ...Current methods for the analysis of channeling-path phenomena in reservoirs cannot account for the influence of time and space on the actual seepage behavior.In the present study,this problem is addressed considering actual production data and dynamic characteristic parameters quantitatively determined in the near wellbore area by fitting the water-cut curve of the well.Starting from the dynamic relationship between injection and production data,the average permeability is determined and used to obtain a real-time quantitative characterization of the seepage behavior of the channeling-path in the far wellbore area.For the considered case study(Jidong oilfield),it is found that the seepage capacity of the channeling-path in the far wellbore area is far less(10 times smaller)than that of the channeling-path in the near wellbore area.The present study and the proposed model(combining near wellbore area and far wellbore area real-time data)have been implemented to support the definition of relevant adjustment measures to ultimately improve oil recovery.展开更多
CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technol...CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of "thief zones". Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system (modified polyacry- lamide-methenamine-resorcinol gel system) to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were con- ducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indi- cate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guideli- nes for the deployment of theCO2-sensitive gel system for field applications.展开更多
A combined PIXE-RBS channeling measurement system to examine Ⅲ-Ⅴ compound semiconductors has been established. Preliminary results on studying Si+ and Te+ implanted GaAs have been presented and discussed.
Laser focused atomic deposition is a unique and effective way to fabricate highly accurate pitch standards in nanometrology.However,the stability and repeatability of the atom lithography fabrication process remains a...Laser focused atomic deposition is a unique and effective way to fabricate highly accurate pitch standards in nanometrology.However,the stability and repeatability of the atom lithography fabrication process remains a challenging problem for massive production.Based on the atom-light interaction theory,channeling is utilized to improve the stability and repeatability.From the comparison of three kinds of atom-light interaction models,the optimal parameters for channeling are obtained based on simulation.According to the experimental observations,the peak to valley height of Cr nano-gratings keeps stable when the cutting proportion changes from 15%to 50%,which means that the channeling shows up under this condition.The channeling proves to be an effective method to optimize the stability and repeatability of laser focused Cr atomic deposition.展开更多
Combining the charged particle activation analysis (CPAA) and the (?)hanneling technique, partial concentrations of carbon on different crystal lattice locations of GaAs were calculated. The results show that at lower...Combining the charged particle activation analysis (CPAA) and the (?)hanneling technique, partial concentrations of carbon on different crystal lattice locations of GaAs were calculated. The results show that at lower total concentration (≈0.3 ppm), carbon atoms occupy principally the octahedral and displaced octahedral interstitial positions, but at higher total concentration (≈2 ppm), the substitutional carbon plays a principal role.展开更多
We show our new channeling measurement results on ZnSe/Zns and GaSb/AlSb superlattices,which are different from the channeling results on strained-layer superlattices in the early publications.A new concept of“effect...We show our new channeling measurement results on ZnSe/Zns and GaSb/AlSb superlattices,which are different from the channeling results on strained-layer superlattices in the early publications.A new concept of“effective channel”,and a calculation formula of“effective channel geometry width”have been presented and derived,the theoretical analysis is in good agreement with the experiment results.展开更多
We investigate the interactions of charged particles with straight and bent single-walled carbon nanotubes (SWNTs) under channeling conditions in the presence of dynamic polarization of the valence electrons in carb...We investigate the interactions of charged particles with straight and bent single-walled carbon nanotubes (SWNTs) under channeling conditions in the presence of dynamic polarization of the valence electrons in carbon, This polarization is described by a cylindrical, two-fluid hydrodynamic model with the parameters taken from the recent modelling of several independent experiments on electron energy loss spectroscopy of carbon nano-structures. We use the hydrodynamic model to calculate the image potential for protons moving through four types of SWNTs at a speed of 3 atomic units. The image potential is then combined with the Doyle-Turner atomic potential to obtain the total potential in the bent carbon nanotubes. Using that potential, we also compute the spatial and angular distributions of protons channeled through the bent carbon nanotubes, and compare the results with the distributions obtained without taking into account the image potential.展开更多
An Al0.2Ga0.8N/AlN/Al0.2Ga0.8N heterostructure was grown by metalorganic chemical vapor deposition on a sapphire (0001) substrate with a thick (〉 1 μm) GaN intermediate layer. The Al composition was determined b...An Al0.2Ga0.8N/AlN/Al0.2Ga0.8N heterostructure was grown by metalorganic chemical vapor deposition on a sapphire (0001) substrate with a thick (〉 1 μm) GaN intermediate layer. The Al composition was determined by Rutherford backscattering (RBS). Using the channeling scan around an off-normal [1213] axis in the (1010) plane of the Al0.2Ga0.8N layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, is investigated. The results show that eT in the high-quality Al0.2Ga0.8N layer is dramatically released by the AIN interlayer from 0.66% to 0.27%.展开更多
Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-wel...Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-well connectivity and considers the flow characteristics and related channeling terms.The Lorentz curve is drawn to qualitatively discern the geological type of the low-permeability fractured reservoir and determine the channeling direction and size.The practical application of such an approach to a sample oilfield shows that it can accurately identify the channeling paths of the considered low-permeability fractured reservoir and predict production performances according to the inter-well connectivity model.As a result,early detection of water channeling becomes possible,paving the way to real-time production system optimization in low-permeability fractured reservoirs.展开更多
A 240-nm thick Al0.4In0.02Ga0.58N layer is grown by metal organic chemical vapour deposition, with an over 1-μm thick GaN layer used as a buffer layer on a substrate of sapphire (0001). Rutherford backscattering an...A 240-nm thick Al0.4In0.02Ga0.58N layer is grown by metal organic chemical vapour deposition, with an over 1-μm thick GaN layer used as a buffer layer on a substrate of sapphire (0001). Rutherford backscattering and channeling are used to characterize the microstructure of AlInGaN. The results show a good crystalline quality of AIInGaN (χmin = 1.5%) with GaN buffer layer. The channeling angular scan around an off-normal {1213} axis in the {1010} plane of the AlInGaN layer is used to determine tetragonal distortion eT, which is caused by the elastic strain in the AIInGaN. The resulting AlInGaN is subjected to an elastic strain at interracial layer, and the strain decreases gradually towards the near-surface layer. It is expected that an epitaxial AlInGaN thin film with a thickness of 850 nm will be fully relaxed (^eT = 0).展开更多
A new method is proposed here aiming at designing a shielding wall with the efficiency significantly higher than that of traditional designs. This new design arises from the idea of using channeling in multilayered sh...A new method is proposed here aiming at designing a shielding wall with the efficiency significantly higher than that of traditional designs. This new design arises from the idea of using channeling in multilayered shielding wall structure, each layer composed of bent crystallites distributed in a way that each layer covers a small section of 2π angular range of which wall is exposed. Part of the incident charged particles will get channeled in bent crystallites in each layer. Bending of channeled particles in bent crystallites will change their directions in the wall increasing their path lengths in the wall which would enhance its shielding efficiency for charged particle radiations. Proposed design is useful for radiation shielding in fission power plants, future fusion reactors and air travel.展开更多
Focused ion beam(FIB)processing with low-energy ions has become a standard technique for the manipulation of nanostructures.Many underlying ion beam effects that deviate from conventional high-energy ion irradiation o...Focused ion beam(FIB)processing with low-energy ions has become a standard technique for the manipulation of nanostructures.Many underlying ion beam effects that deviate from conventional high-energy ion irradiation of bulk systems are considered today;however,ion channeling with its consequence of significant deeper penetration depth has been only theoretically investigated in this regime.We present here an experimental approach to determine the channeling of low-energy ions in crystalline nanoparticles by measuring the sputter yield derived from scanning electron microscopy(SEM)images taken after irradiation under various incident ion angles.Channeling maps of 30 and 20 keV Ga+ions in Ag nanocubes have been identified and fit well with the theory.Indeed,channeling has a significant impact on the transport of energetic ions in crystals due to the large critical angle at low ion energies,thus being relevant for any FIB-application.Consequently,the obtained sputter yield clearly differs from amorphous materials;therefore,it is recommended not to rely only on,e.g.,ion distribution depths predicted by standard Monte-Carlo(MC)algorithms for amorphous materials.展开更多
Identification of the ice channel is the basic technology for developing intelligent ships in ice-covered waters,which is important to ensure the safety and economy of navigation.In the Arctic,merchant ships with low ...Identification of the ice channel is the basic technology for developing intelligent ships in ice-covered waters,which is important to ensure the safety and economy of navigation.In the Arctic,merchant ships with low ice class often navigate in channels opened up by icebreakers.Navigation in the ice channel often depends on good maneuverability skills and abundant experience from the captain to a large extent.The ship may get stuck if steered into ice fields off the channel.Under this circumstance,it is very important to study how to identify the boundary lines of ice channels with a reliable method.In this paper,a two-staged ice channel identification method is developed based on image segmentation and corner point regression.The first stage employs the image segmentation method to extract channel regions.In the second stage,an intelligent corner regression network is proposed to extract the channel boundary lines from the channel region.A non-intelligent angle-based filtering and clustering method is proposed and compared with corner point regression network.The training and evaluation of the segmentation method and corner regression network are carried out on the synthetic and real ice channel dataset.The evaluation results show that the accuracy of the method using the corner point regression network in the second stage is achieved as high as 73.33%on the synthetic ice channel dataset and 70.66%on the real ice channel dataset,and the processing speed can reach up to 14.58frames per second.展开更多
Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear ...Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear precoding such as Tomlinson-Harashima precoding(THP)algorithm has been proved to be a promising technology to solve this problem,which has smaller noise amplification effect compared with linear precoding.However,the similarity of different user channels(defined as channel correlation)will degrade the performance of THP algorithm.In this paper,we qualitatively analyze the inter-beam interference in the whole process of LEO satellite over a specific coverage area,and the impact of channel correlation on Signal-to-Noise Ratio(SNR)of receivers when THP is applied.One user grouping algorithm is proposed based on the analysis of channel correlation,which could decrease the number of users with high channel correlation in each precoding group,thus improve the performance of THP.Furthermore,our algorithm is designed under the premise of co-frequency deployment and orthogonal frequency division multiplexing(OFDM),which leads to more users under severe inter-beam interference compared to the existing research on geostationary orbit satellites broadcasting systems.Simulation results show that the proposed user grouping algorithm possesses higher channel capacity and better bit error rate(BER)performance in high SNR conditions relative to existing works.展开更多
Due to the interdependency of frame synchronization(FS)and channel estimation(CE),joint FS and CE(JFSCE)schemes are proposed to enhance their functionalities and therefore boost the overall performance of wireless com...Due to the interdependency of frame synchronization(FS)and channel estimation(CE),joint FS and CE(JFSCE)schemes are proposed to enhance their functionalities and therefore boost the overall performance of wireless communication systems.Although traditional JFSCE schemes alleviate the influence between FS and CE,they show deficiencies in dealing with hardware imperfection(HI)and deterministic line-of-sight(LOS)path.To tackle this challenge,we proposed a cascaded ELM-based JFSCE to alleviate the influence of HI in the scenario of the Rician fading channel.Specifically,the conventional JFSCE method is first employed to extract the initial features,and thus forms the non-Neural Network(NN)solutions for FS and CE,respectively.Then,the ELMbased networks,named FS-NET and CE-NET,are cascaded to capture the NN solutions of FS and CE.Simulation and analysis results show that,compared with the conventional JFSCE methods,the proposed cascaded ELM-based JFSCE significantly reduces the error probability of FS and the normalized mean square error(NMSE)of CE,even against the impacts of parameter variations.展开更多
The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein...The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein,we construct a lithium nitrate(LiNO_(3))-implanted electroactiveβphase polyvinylidene fluoride-co-hexafluoropropylene(PVDF-HFP)crystalline polymorph layer(PHL).The electronegatively charged polymer chains attain lithium ions on the surface to form lithium-ion charged channels.These channels act as reservoirs to sustainably release Li ions to recompense the ionic flux of electrolytes,decreasing the growth of lithium dendrites.The stretched molecular channels can also accelerate the transport of Li ions.The combined effects enable a high Coulombic efficiency of 97.0%for 250 cycles in lithium(Li)||copper(Cu)cell and a stable symmetric plating/stripping behavior over 2000 h at 3 mA cm^(-2)with ultrahigh Li utilization of 50%.Furthermore,the full cell coupled with PHL-Cu@Li anode and Li Fe PO_(4) cathode exhibits long-term cycle stability with high-capacity retention of 95.9%after 900 cycles.Impressively,the full cell paired with LiNi_(0.87)Co_(0.1)Mn_(0.03)O_(2)maintains a discharge capacity of 170.0 mAh g^(-1)with a capacity retention of 84.3%after 100 cycles even under harsh condition of ultralow N/P ratio of 0.83.This facile strategy will widen the potential application of LiNO_(3)in ester-based electrolyte for practical high-voltage LMBs.展开更多
基金Supported by the Open Fund Project of Hubei Key Laboratory of Oil and Gas Drilling and Production Engineering(YQZC202105)Yangtze University Student Innovation Program(Yz2022018).
文摘In the heterogeneous reservoirs,CO_(2) flooding easily leads to CO_(2) gas channeling,which can seriously affect sweeping efficiency and reduce oil recovery.After thoroughly investigating the advantages and shortcomings of various CO_(2) plugging technologies,this paper focuses on the feasibility of improving conventional water-alternating gas(WAG)through CO_(2)-responsive gel materials.Based on the different chemical reaction mechanisms between the unique chemical structure and CO_(2),changes in the material’s physical and chemical properties can respond to CO_(2).The feasibility of utilizing these property changes for CO_(2)-responsive plugging is explored.Various CO_(2)-responsive gels and gel nanoparticles have been extensively researched in different fields,such as energy,medicine,and biology.This paper surveys the molecular structures,chemical compositions,response mechanisms,and changes of these CO_(2)-responsive gels,aiming to draw insights into the carbon dioxide-enhanced oil recovery(CO_(2)-EOR)field.Finally,the key issues and future development direction of CO_(2)-responsive plugging gels were analyzed.
基金Financial support from the Natural Science Foundation of Sichuan Province(2022NSFSC0030)National Natural Science Foundation of China(U1762218)is gratefully acknowledged.
文摘Undesirable gas channeling always occurs along the high-permeability layers in heterogeneous oil reservoirs during water-alternating-CO_(2)(WAG)flooding,and conventional polymer gels used for blocking the“channeling”paths usually suffer from either low injectivity or poor gelation control.Herein,we for the first time developed an in-situ high-pressure CO_(2)-triggered gel system based on a smart surfactant,N-erucamidopropyl-N,N-dimethylamine(UC22AMPM),which was introduced into the aqueous slugs to control gas channeling inWAG processes.The water-like,low-viscosity UC22AMPM brine solution can be thickened by high-pressure CO_(2) owing to the formation of wormlike micelles(WLMs),as well as their growth and shear-induced structure buildup under shear flow.The thickening power can be further potentiated by the generation of denser WLMs resulting from either surfactant concentration augmentation or a certain range of heating,and can be impaired via pressurization above the critical pressure of CO_(2) because of its soaring solvent power.Core flooding tests using heterogeneous cores demonstrated that gas channeling was alleviated by plugging of high-capacity channels due to the in-situ gelation of UC22AMPM slugs upon their reaction with the pre-or post-injected CO_(2) slugs under shear flow,thereupon driving chase fluids into unrecovered low-permeability areas and producing an 8.0% higher oil recovery factor than the conventional WAG mode.This smart surfactant enabled high injectivity and satisfactory gelation control,attributable to low initial viscosity and the combined properties of one component and CO_(2)-triggered gelation,respectively.This work could provide a guide towards designing gels for reducing CO_(2) spillover and reinforcing the CO_(2) sequestration effect during CO_(2) enhanced oil recovery processes.
基金supported by Bohai Oilfield Efficient Development Demonstration Project(2016ZX05058-003-011).
文摘Current methods for the analysis of channeling-path phenomena in reservoirs cannot account for the influence of time and space on the actual seepage behavior.In the present study,this problem is addressed considering actual production data and dynamic characteristic parameters quantitatively determined in the near wellbore area by fitting the water-cut curve of the well.Starting from the dynamic relationship between injection and production data,the average permeability is determined and used to obtain a real-time quantitative characterization of the seepage behavior of the channeling-path in the far wellbore area.For the considered case study(Jidong oilfield),it is found that the seepage capacity of the channeling-path in the far wellbore area is far less(10 times smaller)than that of the channeling-path in the near wellbore area.The present study and the proposed model(combining near wellbore area and far wellbore area real-time data)have been implemented to support the definition of relevant adjustment measures to ultimately improve oil recovery.
基金financial support from the National Basic Research Program of China(2015CB251201)the Fundamental Research Funds for the Central Universities(15CX06024A)the Program for Changjiang Scholars and Innovative Research Team in University(IRT1294 and IRT1086)
文摘CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of "thief zones". Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system (modified polyacry- lamide-methenamine-resorcinol gel system) to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were con- ducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indi- cate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guideli- nes for the deployment of theCO2-sensitive gel system for field applications.
文摘A combined PIXE-RBS channeling measurement system to examine Ⅲ-Ⅴ compound semiconductors has been established. Preliminary results on studying Si+ and Te+ implanted GaAs have been presented and discussed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0200902)Science and Technology Commission of Shanghai Municipality,China(Grant No.17JC1400801)Young Scientists Fund of the National Natural Science Foundation of China(Grant No.51705369).
文摘Laser focused atomic deposition is a unique and effective way to fabricate highly accurate pitch standards in nanometrology.However,the stability and repeatability of the atom lithography fabrication process remains a challenging problem for massive production.Based on the atom-light interaction theory,channeling is utilized to improve the stability and repeatability.From the comparison of three kinds of atom-light interaction models,the optimal parameters for channeling are obtained based on simulation.According to the experimental observations,the peak to valley height of Cr nano-gratings keeps stable when the cutting proportion changes from 15%to 50%,which means that the channeling shows up under this condition.The channeling proves to be an effective method to optimize the stability and repeatability of laser focused Cr atomic deposition.
基金The Project Supported partly by Natural Science Foundation of China and Electronic Science Academy
文摘Combining the charged particle activation analysis (CPAA) and the (?)hanneling technique, partial concentrations of carbon on different crystal lattice locations of GaAs were calculated. The results show that at lower total concentration (≈0.3 ppm), carbon atoms occupy principally the octahedral and displaced octahedral interstitial positions, but at higher total concentration (≈2 ppm), the substitutional carbon plays a principal role.
基金Supported in part by the Natural Science Foundation of Jiangxi Provincethe General Theory Research Foundation of Nanchang University.
文摘We show our new channeling measurement results on ZnSe/Zns and GaSb/AlSb superlattices,which are different from the channeling results on strained-layer superlattices in the early publications.A new concept of“effective channel”,and a calculation formula of“effective channel geometry width”have been presented and derived,the theoretical analysis is in good agreement with the experiment results.
基金supported by the Funds from the Ministry of EducationScience and Technological Development of the Republic of Serbia(Grant No.45005)Natural Sciences and Engineering Research Council of Canada for Finacial Support
文摘We investigate the interactions of charged particles with straight and bent single-walled carbon nanotubes (SWNTs) under channeling conditions in the presence of dynamic polarization of the valence electrons in carbon, This polarization is described by a cylindrical, two-fluid hydrodynamic model with the parameters taken from the recent modelling of several independent experiments on electron energy loss spectroscopy of carbon nano-structures. We use the hydrodynamic model to calculate the image potential for protons moving through four types of SWNTs at a speed of 3 atomic units. The image potential is then combined with the Doyle-Turner atomic potential to obtain the total potential in the bent carbon nanotubes. Using that potential, we also compute the spatial and angular distributions of protons channeled through the bent carbon nanotubes, and compare the results with the distributions obtained without taking into account the image potential.
基金supported by the National Natural Science Foundation of China(Grant No.91226202)
文摘An Al0.2Ga0.8N/AlN/Al0.2Ga0.8N heterostructure was grown by metalorganic chemical vapor deposition on a sapphire (0001) substrate with a thick (〉 1 μm) GaN intermediate layer. The Al composition was determined by Rutherford backscattering (RBS). Using the channeling scan around an off-normal [1213] axis in the (1010) plane of the Al0.2Ga0.8N layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, is investigated. The results show that eT in the high-quality Al0.2Ga0.8N layer is dramatically released by the AIN interlayer from 0.66% to 0.27%.
文摘Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-well connectivity and considers the flow characteristics and related channeling terms.The Lorentz curve is drawn to qualitatively discern the geological type of the low-permeability fractured reservoir and determine the channeling direction and size.The practical application of such an approach to a sample oilfield shows that it can accurately identify the channeling paths of the considered low-permeability fractured reservoir and predict production performances according to the inter-well connectivity model.As a result,early detection of water channeling becomes possible,paving the way to real-time production system optimization in low-permeability fractured reservoirs.
基金Project supported by the National Natural Science Foundation of China(Grant No.10875004)the National Basic Research Program of China(Grant No.2010CB832904)
文摘A 240-nm thick Al0.4In0.02Ga0.58N layer is grown by metal organic chemical vapour deposition, with an over 1-μm thick GaN layer used as a buffer layer on a substrate of sapphire (0001). Rutherford backscattering and channeling are used to characterize the microstructure of AlInGaN. The results show a good crystalline quality of AIInGaN (χmin = 1.5%) with GaN buffer layer. The channeling angular scan around an off-normal {1213} axis in the {1010} plane of the AlInGaN layer is used to determine tetragonal distortion eT, which is caused by the elastic strain in the AIInGaN. The resulting AlInGaN is subjected to an elastic strain at interracial layer, and the strain decreases gradually towards the near-surface layer. It is expected that an epitaxial AlInGaN thin film with a thickness of 850 nm will be fully relaxed (^eT = 0).
文摘A new method is proposed here aiming at designing a shielding wall with the efficiency significantly higher than that of traditional designs. This new design arises from the idea of using channeling in multilayered shielding wall structure, each layer composed of bent crystallites distributed in a way that each layer covers a small section of 2π angular range of which wall is exposed. Part of the incident charged particles will get channeled in bent crystallites in each layer. Bending of channeled particles in bent crystallites will change their directions in the wall increasing their path lengths in the wall which would enhance its shielding efficiency for charged particle radiations. Proposed design is useful for radiation shielding in fission power plants, future fusion reactors and air travel.
基金We thank the Deutsche Forschungsgemeinschaft(DFG)for financial support through the project Ro1198/22-1“Energy induced nanoparticle substrate interactions”.
文摘Focused ion beam(FIB)processing with low-energy ions has become a standard technique for the manipulation of nanostructures.Many underlying ion beam effects that deviate from conventional high-energy ion irradiation of bulk systems are considered today;however,ion channeling with its consequence of significant deeper penetration depth has been only theoretically investigated in this regime.We present here an experimental approach to determine the channeling of low-energy ions in crystalline nanoparticles by measuring the sputter yield derived from scanning electron microscopy(SEM)images taken after irradiation under various incident ion angles.Channeling maps of 30 and 20 keV Ga+ions in Ag nanocubes have been identified and fit well with the theory.Indeed,channeling has a significant impact on the transport of energetic ions in crystals due to the large critical angle at low ion energies,thus being relevant for any FIB-application.Consequently,the obtained sputter yield clearly differs from amorphous materials;therefore,it is recommended not to rely only on,e.g.,ion distribution depths predicted by standard Monte-Carlo(MC)algorithms for amorphous materials.
基金financially supported by the National Key Research and Development Program(Grant No.2022YFE0107000)the General Projects of the National Natural Science Foundation of China(Grant No.52171259)the High-Tech Ship Research Project of the Ministry of Industry and Information Technology(Grant No.[2021]342)。
文摘Identification of the ice channel is the basic technology for developing intelligent ships in ice-covered waters,which is important to ensure the safety and economy of navigation.In the Arctic,merchant ships with low ice class often navigate in channels opened up by icebreakers.Navigation in the ice channel often depends on good maneuverability skills and abundant experience from the captain to a large extent.The ship may get stuck if steered into ice fields off the channel.Under this circumstance,it is very important to study how to identify the boundary lines of ice channels with a reliable method.In this paper,a two-staged ice channel identification method is developed based on image segmentation and corner point regression.The first stage employs the image segmentation method to extract channel regions.In the second stage,an intelligent corner regression network is proposed to extract the channel boundary lines from the channel region.A non-intelligent angle-based filtering and clustering method is proposed and compared with corner point regression network.The training and evaluation of the segmentation method and corner regression network are carried out on the synthetic and real ice channel dataset.The evaluation results show that the accuracy of the method using the corner point regression network in the second stage is achieved as high as 73.33%on the synthetic ice channel dataset and 70.66%on the real ice channel dataset,and the processing speed can reach up to 14.58frames per second.
基金supported by the Key R&D Project of the Ministry of Science and Technology of China(2020YFB1808005)。
文摘Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear precoding such as Tomlinson-Harashima precoding(THP)algorithm has been proved to be a promising technology to solve this problem,which has smaller noise amplification effect compared with linear precoding.However,the similarity of different user channels(defined as channel correlation)will degrade the performance of THP algorithm.In this paper,we qualitatively analyze the inter-beam interference in the whole process of LEO satellite over a specific coverage area,and the impact of channel correlation on Signal-to-Noise Ratio(SNR)of receivers when THP is applied.One user grouping algorithm is proposed based on the analysis of channel correlation,which could decrease the number of users with high channel correlation in each precoding group,thus improve the performance of THP.Furthermore,our algorithm is designed under the premise of co-frequency deployment and orthogonal frequency division multiplexing(OFDM),which leads to more users under severe inter-beam interference compared to the existing research on geostationary orbit satellites broadcasting systems.Simulation results show that the proposed user grouping algorithm possesses higher channel capacity and better bit error rate(BER)performance in high SNR conditions relative to existing works.
基金supported in part by the Sichuan Science and Technology Program(Grant No.2023YFG0316)the Industry-University Research Innovation Fund of China University(Grant No.2021ITA10016)+1 种基金the Key Scientific Research Fund of Xihua University(Grant No.Z1320929)the Special Funds of Industry Development of Sichuan Province(Grant No.zyf-2018-056).
文摘Due to the interdependency of frame synchronization(FS)and channel estimation(CE),joint FS and CE(JFSCE)schemes are proposed to enhance their functionalities and therefore boost the overall performance of wireless communication systems.Although traditional JFSCE schemes alleviate the influence between FS and CE,they show deficiencies in dealing with hardware imperfection(HI)and deterministic line-of-sight(LOS)path.To tackle this challenge,we proposed a cascaded ELM-based JFSCE to alleviate the influence of HI in the scenario of the Rician fading channel.Specifically,the conventional JFSCE method is first employed to extract the initial features,and thus forms the non-Neural Network(NN)solutions for FS and CE,respectively.Then,the ELMbased networks,named FS-NET and CE-NET,are cascaded to capture the NN solutions of FS and CE.Simulation and analysis results show that,compared with the conventional JFSCE methods,the proposed cascaded ELM-based JFSCE significantly reduces the error probability of FS and the normalized mean square error(NMSE)of CE,even against the impacts of parameter variations.
基金the financial support from the National Natural Science Foundation of China(Nos.22205191 and 52002346)the Science and Technology Innovation Program of Hunan Province(No.2021RC3109)+1 种基金the Natural Science Foundation of Hunan Province,China(No.2022JJ40446)Guangxi Key Laboratory of Low Carbon Energy Material(No.2020GXKLLCEM01)。
文摘The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein,we construct a lithium nitrate(LiNO_(3))-implanted electroactiveβphase polyvinylidene fluoride-co-hexafluoropropylene(PVDF-HFP)crystalline polymorph layer(PHL).The electronegatively charged polymer chains attain lithium ions on the surface to form lithium-ion charged channels.These channels act as reservoirs to sustainably release Li ions to recompense the ionic flux of electrolytes,decreasing the growth of lithium dendrites.The stretched molecular channels can also accelerate the transport of Li ions.The combined effects enable a high Coulombic efficiency of 97.0%for 250 cycles in lithium(Li)||copper(Cu)cell and a stable symmetric plating/stripping behavior over 2000 h at 3 mA cm^(-2)with ultrahigh Li utilization of 50%.Furthermore,the full cell coupled with PHL-Cu@Li anode and Li Fe PO_(4) cathode exhibits long-term cycle stability with high-capacity retention of 95.9%after 900 cycles.Impressively,the full cell paired with LiNi_(0.87)Co_(0.1)Mn_(0.03)O_(2)maintains a discharge capacity of 170.0 mAh g^(-1)with a capacity retention of 84.3%after 100 cycles even under harsh condition of ultralow N/P ratio of 0.83.This facile strategy will widen the potential application of LiNO_(3)in ester-based electrolyte for practical high-voltage LMBs.