Effect of mischmetal addition on the cast microstructure of 6063 alloys has been investigated by means of optical microscopy, TEM and anode filming etc. The results show that there is a critical content of fining dend...Effect of mischmetal addition on the cast microstructure of 6063 alloys has been investigated by means of optical microscopy, TEM and anode filming etc. The results show that there is a critical content of fining dendrite structure by adding mischmetal to 6063 alloys. This critical mischmetal content is about 0.15%. Only when the mischmetal content is above 0.15%, the secondary dendrite arm spacing decreased and eutectic structure fined. The cast grain is obviously refined when the content of mischmetal is lower. Consideration from the cast structure, the suitable mischmetal content in 6063 alloys is 0.20%.展开更多
Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship betw...Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship between configuration and electromagnetic(EM)loss mechanism has remained elusive.Herein,drawing inspiration from the DNA transcription process,we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability.Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N4–C configuration,along with cross polarization generated by the helical structure,endow the helical converters with enhanced EM loss.As a result,HMC-8 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.13 dB at an ultralow thickness of 1.29 mm.Through precise tuning of the graphite domain size,HMC-7 achieves an effective absorption bandwidth(EAB)of 6.08 GHz at 2.02 mm thickness.Furthermore,constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm,with the maximum radar cross section reduction value reaching 36.4 dB m2.This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA,thus contributing to the development of EMWA mechanisms and applications.展开更多
We theoretically investigate the electronic structure of cylindrical magnetic topological insulator quantum wires in MnBi_(2)Te_(4).Our study reveals the emergence of topological surface states in the ferromagnetic ph...We theoretically investigate the electronic structure of cylindrical magnetic topological insulator quantum wires in MnBi_(2)Te_(4).Our study reveals the emergence of topological surface states in the ferromagnetic phase,characterized by spin-polarized subbands resulting from intrinsic magnetization.In the antiferromagnetic phase,we identify the coexistence of three distinct types of topological states,encompassing both surface states and central states.展开更多
In order to clarify the influence of liquid sulfur deposition and adsorption to high-H2S gas reservoirs,three types of natural cores with typical carbonate pore structures were selected for high-temperature and high-p...In order to clarify the influence of liquid sulfur deposition and adsorption to high-H2S gas reservoirs,three types of natural cores with typical carbonate pore structures were selected for high-temperature and high-pressure core displacement experiments.Fine quantitative characterization of the cores in three steady states(original,after sulfur injection,and after gas flooding)was carried out using the nuclear magnetic resonance(NMR)transverse relaxation time spectrum and imaging,X-ray computer tomography(CT)of full-diameter cores,basic physical property testing,and field emission scanning electron microscopy imaging.The loss of pore volume caused by sulfur deposition and adsorption mainly comes from the medium and large pores with sizes bigger than 1000μm.Liquid sulfur has a stronger adsorption and deposition ability in smaller pore spaces,and causes greater damage to reservoirs with poor original pore structures.The pore structure of the three types of carbonate reservoirs shows multiple fractal characteristics.The worse the pore structure,the greater the change of internal pore distribution caused by liquid sulfur deposition and adsorption,and the stronger the heterogeneity.Liquid sulfur deposition and adsorption change the pore size distribution,pore connectivity,and heterogeneity of the rock,which further changes the physical properties of the reservoir.After sulfur injection and gas flooding,the permeability of TypeⅠreservoirs with good physical properties decreased by 16%,and that of TypesⅡandⅢreservoirs with poor physical properties decreased by 90%or more,suggesting an extremely high damage.This indicates that the worse the initial physical properties,the greater the damage of liquid sulfur deposition and adsorption.Liquid sulfur is adsorbed and deposited in different types of pore space in the forms of flocculence,cobweb,or retinitis,causing different changes in the pore structure and physical property of the reservoir.展开更多
A series of direct numerical simulations of the fully developed plane Couette flow at a Reynolds number of 6000（based on the relative wall speed and half the channel height h） with different streamwise and spanwise ...A series of direct numerical simulations of the fully developed plane Couette flow at a Reynolds number of 6000（based on the relative wall speed and half the channel height h） with different streamwise and spanwise lengths are conducted to investigate the effects of the computational box sizes on the secondary flow（SF）. Our focuses are the number of counter-rotating vortex pairs and its relationship to the statistics of the mean flow and the SF in the small and moderate computational box sizes. Our results show that the number of vortex pairs is sensitive to the computational box size, and so are the slope parameter, the rate of the turbulent kinetic energy contributed by the SF, and the ratio of the kinetic energy of the SF to the total kinetic energy. However, the averaged spanwise width of each counter-rotating vortex pair in the plane Couette flow is found, for the first time, within 4（1 ± 0.25）h despite the domain sizes.展开更多
The distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression have been systematically studied. We investigated sedimentary facies and carried ...The distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression have been systematically studied. We investigated sedimentary facies and carried out a comprehensive analy-sis of the vast amount of data from casting thin sections, scanning electron microscope and physical data. Then we analyzed the pore types, pore evolution, distribution and genesis of secondary pores in our study area and discussed the factors controlling the distribution of secondary pores. The results show that pores in the study area are largely composed of intergranular dissolution pores and constituent dissolved pores. Three secondary pore zones were developed in the study area at depths of 2800~3400 m, 3600~4200 m and 4500~4800 m. Secondary pores have been formed mainly because carbonate cement, feldspar, clastic debris and other plastic substances were dissolved by organic acid, released during the evolution of organic matter and acid water formed by CO2. The development and distribution of secondary pores are vertically controlled by the maturity time of source rocks and hori-zontally by the distribution of acid water. As well, this distribution was affected by the sedimentary facies belt and the development of fault zones.展开更多
Structural damage from sample preparation processes such as cutting and polishing may change the pore structure of rocks.However,changes in pore structure caused by this structural damage from crushing and its effect ...Structural damage from sample preparation processes such as cutting and polishing may change the pore structure of rocks.However,changes in pore structure caused by this structural damage from crushing and its effect on marine continental transitional shale have not been well documented.The changes of microscopic pore structure in marine continental transitional shale during the sample preparation have important research value for subsequent exploration and development of shale gas.In this study,the pore structures of transitional shale samples from the Shanxi-Taiyuan Formation of the Southern North China Basin under different degrees of damage were analyzed through low-temperature N;adsorption experiments,combined with X-ray diffraction,total organic carbon,vitrinite reflectance analysis,and scanning electron microscopy.The results showed that(1)With increasing structural damage,the specific surface area(SSA)changed within relatively tight bounds,while the pore volume(PV)varied significantly,and the growth rate(maximum)exhibited a certain critical value with the crushing mesh number increasing from 20 to 200.(2)The ratio of SSA to PV can be used as a potential proxy for evaluating the influence of changes in the pore structure.(3)Correlation analysis revealed that the microscopic pore structure of marine continental transitional shale from the Shanxi-Taiyuan Formations is mainly controlled by organic matter and clay minerals.Clay minerals play a leading role in the development of microscopic pores and changes in pore structure.展开更多
The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearl...The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearly increase with the increase of the In composition, which are in good agreement with the available experimental results. The calculated band structures with the modified Becke-Johnson potential show that all solid solutions are direct gap conductors. The band gap decreases linearly with In composition increasing. Based on the electronic structure calculated, we investigate the thermoelectric properties by the semi-classical Boltzmann transport theory. The results suggest that when Ga is replaced by In, the bipolar effect of Seebeck coefficient S becomes very obvious. The Seebeck coefficient even changes its sign from positive to negative for p-type doping at low carrier concentrations. The optimal p-type doping concentrations have been estimated based on the predicted maximum values of the power factor divided by the scattering time.展开更多
This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional t...This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory （DFT）.The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands（CBs） for Sr2NbxTi1-xO4 with x=0.125 and the system shows n-type degenerate semiconductor features. Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2Nb0.125Ti0.875O4.展开更多
8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-deso...8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-desorption, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-visible diffuse reflectance spectroscopy （DRS） and scanning transmission electron microscopy-high-angle annular dark field （STEM HAADF）. The results of STEM HAADF showed that WO3 species were not uniformly distributed on the SiO2 support. The experimental results of 8wt%WO3/SiO2 performance in ethene/decene metathesis revealed that the catalytic effect of 8wt%WO3/SiO2 catalyst and coke formation over it were closely related to the support pore structure： The 8wt%WO3/SiO2 catalyst with a more complicated pore structure showed better catalytic performance but the coke deposition rate was also faster.展开更多
Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivit...Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivity and large current density.Here,we report a Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructured electrocatalyst embedded in accordion-like N-doped carbon through a simple molten salt annealing strategy.The optimal Ni_(4)N/Ni_(3)ZnC_(0.7)electrocatalyst achieves a high CO Faraday efficiency of 92.3%and a large total current density of-15.8 m A cm^(-2)at-0.8 V versus reversible hydrogen electrode,together with a long-term stability about 30 h.Density functional theory results reveal that the energy barrier for*COOH intermediate formation largely decreased on Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructure compared with Ni_(4)N and Ni_(3)ZnC_(0.7),thus giving rise to enhanced activity and selectivity.A rechargeable Zn-CO_(2)battery is further assembled with Ni_(4)N/Ni_(3)ZnC_(0.7)catalyst as the cathode,which shows a maximum power density of 0.85 mW cm^(-2)and excellent stability.展开更多
The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method.We find that the N substituting O（1） atom is the most sta...The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method.We find that the N substituting O（1） atom is the most stable structure for the smallest formation energy.After N-doping,the charge density distribution significantly changes,and the acceptor impurity level is introduced above the valence band and intersects with the Fermi level.The impurity absorption edges appear to shift toward longer wavelengths with an increase in N-doping concentration.The complex refractive index shows metallic characteristics in the N-doped β-Ga2O3.展开更多
In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/...In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/composition. The determined rock type is roughly similar to palynofacies of Combaz , whereas it is "rock maceral facies (for coal viz. coal facies)" in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research . This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral’s geochemical parameters. So, it is considered as genetic classification. The "rock maceral facies" may be transformed to sedimentary organic facies , which is used as quantitative evaluation means if research being perfect.Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, whatever coal or kerogen ought be polymer, then we follow Combaz’s thought and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly. Here, we use the time of flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz’s models from three to five. They are also models for coal.展开更多
Tris(trimethylsilyl)borate(TMSB) has been intensively studied to improve the performances of lithiumion batteries. However, it is still an interesting issue needed to be resolved for the research on the Li^(+) solvati...Tris(trimethylsilyl)borate(TMSB) has been intensively studied to improve the performances of lithiumion batteries. However, it is still an interesting issue needed to be resolved for the research on the Li^(+) solvation structure affected by TMSB additive. Herein, the electrochemical tests, quantum chemistry calculations, potential-resolved in-situ electrochemical impedance spectroscopy measurements and surface analyses were used to explore the effects of Li^(+) solvation structure with TMSB additive on the formation of the cathode electrolyte interface(CEI) film in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)/Li half cells. The results reveal that the TMSB additive is easy to complex with Li^(+) ion, thus weaken the intermolecular force between Li^(+) ions and ethylene carbonate solvent, which is benefit for the cycle performance. Besides, the changed Li^(+) solvation structure results in a thin and dense CEI film containing compounds with Si–O and B–O bonds which is favorable to the transfer of Li^(+) ions. As a result, the performances of the LNCM811/Li half cells are effectively improved. This research provides a new idea to construct a high-performance CEI film by adjusting the Li^(+) solvation structures.展开更多
In biological systems, conformational transformations of nucleic acids play critical roles in genetic regulation. However, it remains a tricky task to design and optimize specific labeling strategies to track these ch...In biological systems, conformational transformations of nucleic acids play critical roles in genetic regulation. However, it remains a tricky task to design and optimize specific labeling strategies to track these changes.In this study, we exploited an intercalating fluorescent dye,GelRed, to characterize different DNA structures. We studied the correlation between fluorescence intensity and DNA structural properties. We showed that single-stranded DNAs with predicted self-folded secondary structures show much stronger fluorescence than those without such structures. For double-stranded DNAs, we observed that fluorescence intensity is positively correlated to their GCcontent. We also demonstrated that GelRed can be used to monitor DNA conformational changes upon temperature variations in real time. Based on these findings, we concluded that the fluorescence intensity of a GelRed-stained DNA structure has a good correlation with its thermostability in the form of a change in Gibbs free energy.展开更多
A new theoretical model of the triatomic molecular wake effect is proposed and applied to molecular ions D^＋3 and HD^＋2 while passing through a solid. The wake effects resulting from the reactions of the two similar...A new theoretical model of the triatomic molecular wake effect is proposed and applied to molecular ions D^＋3 and HD^＋2 while passing through a solid. The wake effects resulting from the reactions of the two similar ions with thin carbon foil are also investigated by using the Coulomb explosion technique. The experimental results are in good agreement with theoretical estimates and the molecular structure of HD^＋2 is determined by using the model.展开更多
The title compound (p-methylphenylbis(4, 4-dimethyl-6-hydroxycyclohexene-1-one-2-yl)methane) has been synthesized by the reaction of 4-methylbenzaldehyde and 5, 5-dimethyl-1, 3-cyclohexanedione in N,N-dimethylformamid...The title compound (p-methylphenylbis(4, 4-dimethyl-6-hydroxycyclohexene-1-one-2-yl)methane) has been synthesized by the reaction of 4-methylbenzaldehyde and 5, 5-dimethyl-1, 3-cyclohexanedione in N,N-dimethylformamide. Its structure was determined by single crystal X-ray diffraction. The Crystal is monoclinic, space group P21/a, a=0. 9304 (2)nm, b=1. 1754 (2)nm, c=2. 0134 (4)nm, β=102. 40(2)°, Mr= 382. 50, V=2. 1505 (7)nm3, Dc = 1. 181g/cm3, Z=4, μ(MoKα) = 0. 79cm-1, F(000) = 856.The structure was solved by direct methods, and refined by full-matris least-Squares method to a final R =0. 042 and Rw = 0. 045. The crystal structure shows that there are two conjugated enol form in the molecule.展开更多
The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and...The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional （3D） structural configurations of Cu2＋/His complexes at different pH values （2.5, 6.5, and 8.5） are quantitatively determined by x-ray absorption near-edge structure （XANES）. Generally Cu2＋/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2＋. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxy1, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2＋/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5.展开更多
Abstract： The shortest path problem in a network G is to find shortest paths between some specified source vertices and terminal vertices when the lengths of edges are given. The structure of the optimal solutions se...Abstract： The shortest path problem in a network G is to find shortest paths between some specified source vertices and terminal vertices when the lengths of edges are given. The structure of the optimal solutions set on the shortest paths is studied in this paper. First, the conditions of having unique shortest path between two distinguished vertices 8 and t in a network G are discussed; Second, the structural properties of 2-transformation ^-G graph G on the shortest-paths for G are presented heavily.展开更多
In order to obtain enhanced plasma parameters a complete new tokamak HL-2M is now under construction in Southwestern Institute of Physics. To assure the structural safety of the device for the entire operation cycle, ...In order to obtain enhanced plasma parameters a complete new tokamak HL-2M is now under construction in Southwestern Institute of Physics. To assure the structural safety of the device for the entire operation cycle, one of the most important issues is the lifetime-limiting effects due to the pulsed operation mode. Fatigue is one of the major failure modes to be considered in mechanical design, and pulsed operation imposes stress with significant alternating components on the support structure （SS）. Therefore, the reliability of the whole device is strongly affected by the stress and fatigue characteristic of the SS as the interface structure. This article introduces the SS design and details the fatigue life calculation methods based on the different characteristics of the sub-structures. The fatigue life in hazardous areas of the toroidal field coils anti-torque structure （TFCs-ATs） has been determined by non-linear analysis results. And with the stress- time history data of the vacuum vessel ＆ poloidal field coils support structure （VV＆PFCs SS）, the fatigue analysis of the hot spots has been completed based on rain-flow counting method and linear cumulative damage method. The calculated minimum fatigue life on TFCs-ATs and VVSzPFCs SS is 4.743E＋05 and 1.805E＋06 cycles, respectively. And the calculated fatigue life on sub-structures can meet the required life for HL-2M tokamak： 1.0E＋05 cycles.展开更多
文摘Effect of mischmetal addition on the cast microstructure of 6063 alloys has been investigated by means of optical microscopy, TEM and anode filming etc. The results show that there is a critical content of fining dendrite structure by adding mischmetal to 6063 alloys. This critical mischmetal content is about 0.15%. Only when the mischmetal content is above 0.15%, the secondary dendrite arm spacing decreased and eutectic structure fined. The cast grain is obviously refined when the content of mischmetal is lower. Consideration from the cast structure, the suitable mischmetal content in 6063 alloys is 0.20%.
基金supported by the National Natural Science Foundation of China(22265021)the Aeronautical Science Foundation of China(2020Z056056003)Jiangxi Provincial Natural Science Foundation(20232BAB212004).
文摘Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship between configuration and electromagnetic(EM)loss mechanism has remained elusive.Herein,drawing inspiration from the DNA transcription process,we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability.Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N4–C configuration,along with cross polarization generated by the helical structure,endow the helical converters with enhanced EM loss.As a result,HMC-8 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.13 dB at an ultralow thickness of 1.29 mm.Through precise tuning of the graphite domain size,HMC-7 achieves an effective absorption bandwidth(EAB)of 6.08 GHz at 2.02 mm thickness.Furthermore,constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm,with the maximum radar cross section reduction value reaching 36.4 dB m2.This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA,thus contributing to the development of EMWA mechanisms and applications.
基金Project sponsored by the Natural Science Foundation of Chongqing,China(Grant No.CSTB2024NSCQMSX0736)the Special Project of Chongqing Technology Innovation and Application Development(Major Project)(Grant No.CSTB2024TIAD-STX0035)the Research Foundation of Institute for Advanced Sciences of CQUPT(Grant No.E011A2022328)。
文摘We theoretically investigate the electronic structure of cylindrical magnetic topological insulator quantum wires in MnBi_(2)Te_(4).Our study reveals the emergence of topological surface states in the ferromagnetic phase,characterized by spin-polarized subbands resulting from intrinsic magnetization.In the antiferromagnetic phase,we identify the coexistence of three distinct types of topological states,encompassing both surface states and central states.
基金Supported by the National Natural Science Foundation of China(U19B6003)Sinopec Technology Research Project(P20077kxjgz)。
文摘In order to clarify the influence of liquid sulfur deposition and adsorption to high-H2S gas reservoirs,three types of natural cores with typical carbonate pore structures were selected for high-temperature and high-pressure core displacement experiments.Fine quantitative characterization of the cores in three steady states(original,after sulfur injection,and after gas flooding)was carried out using the nuclear magnetic resonance(NMR)transverse relaxation time spectrum and imaging,X-ray computer tomography(CT)of full-diameter cores,basic physical property testing,and field emission scanning electron microscopy imaging.The loss of pore volume caused by sulfur deposition and adsorption mainly comes from the medium and large pores with sizes bigger than 1000μm.Liquid sulfur has a stronger adsorption and deposition ability in smaller pore spaces,and causes greater damage to reservoirs with poor original pore structures.The pore structure of the three types of carbonate reservoirs shows multiple fractal characteristics.The worse the pore structure,the greater the change of internal pore distribution caused by liquid sulfur deposition and adsorption,and the stronger the heterogeneity.Liquid sulfur deposition and adsorption change the pore size distribution,pore connectivity,and heterogeneity of the rock,which further changes the physical properties of the reservoir.After sulfur injection and gas flooding,the permeability of TypeⅠreservoirs with good physical properties decreased by 16%,and that of TypesⅡandⅢreservoirs with poor physical properties decreased by 90%or more,suggesting an extremely high damage.This indicates that the worse the initial physical properties,the greater the damage of liquid sulfur deposition and adsorption.Liquid sulfur is adsorbed and deposited in different types of pore space in the forms of flocculence,cobweb,or retinitis,causing different changes in the pore structure and physical property of the reservoir.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11221061,11272013,and 11302006)
文摘A series of direct numerical simulations of the fully developed plane Couette flow at a Reynolds number of 6000（based on the relative wall speed and half the channel height h） with different streamwise and spanwise lengths are conducted to investigate the effects of the computational box sizes on the secondary flow（SF）. Our focuses are the number of counter-rotating vortex pairs and its relationship to the statistics of the mean flow and the SF in the small and moderate computational box sizes. Our results show that the number of vortex pairs is sensitive to the computational box size, and so are the slope parameter, the rate of the turbulent kinetic energy contributed by the SF, and the ratio of the kinetic energy of the SF to the total kinetic energy. However, the averaged spanwise width of each counter-rotating vortex pair in the plane Couette flow is found, for the first time, within 4（1 ± 0.25）h despite the domain sizes.
基金Financial support for this study by the National Basic Research Program of China (973) (No.2006CB 202300) is gratefully acknowledged
文摘The distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression have been systematically studied. We investigated sedimentary facies and carried out a comprehensive analy-sis of the vast amount of data from casting thin sections, scanning electron microscope and physical data. Then we analyzed the pore types, pore evolution, distribution and genesis of secondary pores in our study area and discussed the factors controlling the distribution of secondary pores. The results show that pores in the study area are largely composed of intergranular dissolution pores and constituent dissolved pores. Three secondary pore zones were developed in the study area at depths of 2800~3400 m, 3600~4200 m and 4500~4800 m. Secondary pores have been formed mainly because carbonate cement, feldspar, clastic debris and other plastic substances were dissolved by organic acid, released during the evolution of organic matter and acid water formed by CO2. The development and distribution of secondary pores are vertically controlled by the maturity time of source rocks and hori-zontally by the distribution of acid water. As well, this distribution was affected by the sedimentary facies belt and the development of fault zones.
基金the financial support by the National Natural Science Foundation of China(Grant No.41927801)。
文摘Structural damage from sample preparation processes such as cutting and polishing may change the pore structure of rocks.However,changes in pore structure caused by this structural damage from crushing and its effect on marine continental transitional shale have not been well documented.The changes of microscopic pore structure in marine continental transitional shale during the sample preparation have important research value for subsequent exploration and development of shale gas.In this study,the pore structures of transitional shale samples from the Shanxi-Taiyuan Formation of the Southern North China Basin under different degrees of damage were analyzed through low-temperature N;adsorption experiments,combined with X-ray diffraction,total organic carbon,vitrinite reflectance analysis,and scanning electron microscopy.The results showed that(1)With increasing structural damage,the specific surface area(SSA)changed within relatively tight bounds,while the pore volume(PV)varied significantly,and the growth rate(maximum)exhibited a certain critical value with the crushing mesh number increasing from 20 to 200.(2)The ratio of SSA to PV can be used as a potential proxy for evaluating the influence of changes in the pore structure.(3)Correlation analysis revealed that the microscopic pore structure of marine continental transitional shale from the Shanxi-Taiyuan Formations is mainly controlled by organic matter and clay minerals.Clay minerals play a leading role in the development of microscopic pores and changes in pore structure.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2012M511603)
文摘The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearly increase with the increase of the In composition, which are in good agreement with the available experimental results. The calculated band structures with the modified Becke-Johnson potential show that all solid solutions are direct gap conductors. The band gap decreases linearly with In composition increasing. Based on the electronic structure calculated, we investigate the thermoelectric properties by the semi-classical Boltzmann transport theory. The results suggest that when Ga is replaced by In, the bipolar effect of Seebeck coefficient S becomes very obvious. The Seebeck coefficient even changes its sign from positive to negative for p-type doping at low carrier concentrations. The optimal p-type doping concentrations have been estimated based on the predicted maximum values of the power factor divided by the scattering time.
基金Project supported by the Natural Science Foundation of ShaanXi Province of China (Grant No 2005F06)Northwest University(NWU) Graduate Innovation and Creativity Funds (Grant No 08YZZ47)
文摘This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory （DFT）.The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands（CBs） for Sr2NbxTi1-xO4 with x=0.125 and the system shows n-type degenerate semiconductor features. Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2Nb0.125Ti0.875O4.
文摘8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-desorption, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-visible diffuse reflectance spectroscopy （DRS） and scanning transmission electron microscopy-high-angle annular dark field （STEM HAADF）. The results of STEM HAADF showed that WO3 species were not uniformly distributed on the SiO2 support. The experimental results of 8wt%WO3/SiO2 performance in ethene/decene metathesis revealed that the catalytic effect of 8wt%WO3/SiO2 catalyst and coke formation over it were closely related to the support pore structure： The 8wt%WO3/SiO2 catalyst with a more complicated pore structure showed better catalytic performance but the coke deposition rate was also faster.
基金financially supported by the National Key Research and Development Program,China(2018YFB1502503)the 2021 Talent Introduction Project of Chongqing Medical and Pharmaceutical College(ygz2021104)。
文摘Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivity and large current density.Here,we report a Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructured electrocatalyst embedded in accordion-like N-doped carbon through a simple molten salt annealing strategy.The optimal Ni_(4)N/Ni_(3)ZnC_(0.7)electrocatalyst achieves a high CO Faraday efficiency of 92.3%and a large total current density of-15.8 m A cm^(-2)at-0.8 V versus reversible hydrogen electrode,together with a long-term stability about 30 h.Density functional theory results reveal that the energy barrier for*COOH intermediate formation largely decreased on Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructure compared with Ni_(4)N and Ni_(3)ZnC_(0.7),thus giving rise to enhanced activity and selectivity.A rechargeable Zn-CO_(2)battery is further assembled with Ni_(4)N/Ni_(3)ZnC_(0.7)catalyst as the cathode,which shows a maximum power density of 0.85 mW cm^(-2)and excellent stability.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10974077)the Natural Science Foundation of Shandong Province,China (Grant No. 2009ZRB01702)the Shandong Provincial Higher Educational Science and Technology Program,China (Grant No. J10LA08)
文摘The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method.We find that the N substituting O（1） atom is the most stable structure for the smallest formation energy.After N-doping,the charge density distribution significantly changes,and the acceptor impurity level is introduced above the valence band and intersects with the Fermi level.The impurity absorption edges appear to shift toward longer wavelengths with an increase in N-doping concentration.The complex refractive index shows metallic characteristics in the N-doped β-Ga2O3.
基金National Natural Science Foundation of China(4 9672 13 1)
文摘In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/composition. The determined rock type is roughly similar to palynofacies of Combaz , whereas it is "rock maceral facies (for coal viz. coal facies)" in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research . This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral’s geochemical parameters. So, it is considered as genetic classification. The "rock maceral facies" may be transformed to sedimentary organic facies , which is used as quantitative evaluation means if research being perfect.Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, whatever coal or kerogen ought be polymer, then we follow Combaz’s thought and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly. Here, we use the time of flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz’s models from three to five. They are also models for coal.
基金supported by the National Natural Science Foundation of China(51962019)the Natural Science Foundation of Gansu Province(20JR5RA469)+1 种基金the Education Department of Gansu Province:"Star of Innovation"Project for Outstanding Graduate Students(2021CXZX-455)the Lanzhou University of Technology Hongliu First-class Discipline Construction Program。
文摘Tris(trimethylsilyl)borate(TMSB) has been intensively studied to improve the performances of lithiumion batteries. However, it is still an interesting issue needed to be resolved for the research on the Li^(+) solvation structure affected by TMSB additive. Herein, the electrochemical tests, quantum chemistry calculations, potential-resolved in-situ electrochemical impedance spectroscopy measurements and surface analyses were used to explore the effects of Li^(+) solvation structure with TMSB additive on the formation of the cathode electrolyte interface(CEI) film in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)/Li half cells. The results reveal that the TMSB additive is easy to complex with Li^(+) ion, thus weaken the intermolecular force between Li^(+) ions and ethylene carbonate solvent, which is benefit for the cycle performance. Besides, the changed Li^(+) solvation structure results in a thin and dense CEI film containing compounds with Si–O and B–O bonds which is favorable to the transfer of Li^(+) ions. As a result, the performances of the LNCM811/Li half cells are effectively improved. This research provides a new idea to construct a high-performance CEI film by adjusting the Li^(+) solvation structures.
基金supported by the National Natural Science Foundation of China(Nos.U1532119,21775157,21675167,and 31571014)the Instrument Developing Project of the Chinese Academy of Sciences(Develop the Microsystems for Single Particle Tracking)
文摘In biological systems, conformational transformations of nucleic acids play critical roles in genetic regulation. However, it remains a tricky task to design and optimize specific labeling strategies to track these changes.In this study, we exploited an intercalating fluorescent dye,GelRed, to characterize different DNA structures. We studied the correlation between fluorescence intensity and DNA structural properties. We showed that single-stranded DNAs with predicted self-folded secondary structures show much stronger fluorescence than those without such structures. For double-stranded DNAs, we observed that fluorescence intensity is positively correlated to their GCcontent. We also demonstrated that GelRed can be used to monitor DNA conformational changes upon temperature variations in real time. Based on these findings, we concluded that the fluorescence intensity of a GelRed-stained DNA structure has a good correlation with its thermostability in the form of a change in Gibbs free energy.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10574095 and 10675087)
文摘A new theoretical model of the triatomic molecular wake effect is proposed and applied to molecular ions D^＋3 and HD^＋2 while passing through a solid. The wake effects resulting from the reactions of the two similar ions with thin carbon foil are also investigated by using the Coulomb explosion technique. The experimental results are in good agreement with theoretical estimates and the molecular structure of HD^＋2 is determined by using the model.
文摘The title compound (p-methylphenylbis(4, 4-dimethyl-6-hydroxycyclohexene-1-one-2-yl)methane) has been synthesized by the reaction of 4-methylbenzaldehyde and 5, 5-dimethyl-1, 3-cyclohexanedione in N,N-dimethylformamide. Its structure was determined by single crystal X-ray diffraction. The Crystal is monoclinic, space group P21/a, a=0. 9304 (2)nm, b=1. 1754 (2)nm, c=2. 0134 (4)nm, β=102. 40(2)°, Mr= 382. 50, V=2. 1505 (7)nm3, Dc = 1. 181g/cm3, Z=4, μ(MoKα) = 0. 79cm-1, F(000) = 856.The structure was solved by direct methods, and refined by full-matris least-Squares method to a final R =0. 042 and Rw = 0. 045. The crystal structure shows that there are two conjugated enol form in the molecule.
基金supported by the National Natural Science Foundation of China(Grant No.11205186)
文摘The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional （3D） structural configurations of Cu2＋/His complexes at different pH values （2.5, 6.5, and 8.5） are quantitatively determined by x-ray absorption near-edge structure （XANES）. Generally Cu2＋/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2＋. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxy1, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2＋/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5.
文摘Abstract： The shortest path problem in a network G is to find shortest paths between some specified source vertices and terminal vertices when the lengths of edges are given. The structure of the optimal solutions set on the shortest paths is studied in this paper. First, the conditions of having unique shortest path between two distinguished vertices 8 and t in a network G are discussed; Second, the structural properties of 2-transformation ^-G graph G on the shortest-paths for G are presented heavily.
基金supported by National Magnetic Confinement Fusion Science Program of China(No.2013GB113001)
文摘In order to obtain enhanced plasma parameters a complete new tokamak HL-2M is now under construction in Southwestern Institute of Physics. To assure the structural safety of the device for the entire operation cycle, one of the most important issues is the lifetime-limiting effects due to the pulsed operation mode. Fatigue is one of the major failure modes to be considered in mechanical design, and pulsed operation imposes stress with significant alternating components on the support structure （SS）. Therefore, the reliability of the whole device is strongly affected by the stress and fatigue characteristic of the SS as the interface structure. This article introduces the SS design and details the fatigue life calculation methods based on the different characteristics of the sub-structures. The fatigue life in hazardous areas of the toroidal field coils anti-torque structure （TFCs-ATs） has been determined by non-linear analysis results. And with the stress- time history data of the vacuum vessel ＆ poloidal field coils support structure （VV＆PFCs SS）, the fatigue analysis of the hot spots has been completed based on rain-flow counting method and linear cumulative damage method. The calculated minimum fatigue life on TFCs-ATs and VVSzPFCs SS is 4.743E＋05 and 1.805E＋06 cycles, respectively. And the calculated fatigue life on sub-structures can meet the required life for HL-2M tokamak： 1.0E＋05 cycles.
