This paper assesses the structure and ability of Local Seismological Gravity Monitoring Network (LSGMN) in China main tectonic zone and China Seismological Gravity Monitoring System (CSGMS) which formed after the proj...This paper assesses the structure and ability of Local Seismological Gravity Monitoring Network (LSGMN) in China main tectonic zone and China Seismological Gravity Monitoring System (CSGMS) which formed after the project of 'China Crustal Movement Observation Network (CCMON)' has been performed. The main conclusions drawn are as follows: ①LSGMN has good monitoring and prediction ability for the earthquake of M_s about 5. But it lacks ability to monitor and predict the strong earthquake of M_s>6 because of the little range of the observation network;②CSGMS has good ability to monitor and predict the earthquake of M_s>7, but the resolving power is not enough for the earthquake magnitude from M_s=6 to M_s=7 because the observation stations are too sparse.展开更多
In this study, the types of micropores in a reservoir are analyzed using casting thin section(CTS) observation and scanning electron microscopy(SEM) experiments. The high-pressure mercury injection(HPMI) and constant-...In this study, the types of micropores in a reservoir are analyzed using casting thin section(CTS) observation and scanning electron microscopy(SEM) experiments. The high-pressure mercury injection(HPMI) and constant-rate mercury injection(CRMI) experiments are performed to study the micropore structure of the reservoir. Nuclear magnetic resonance(NMR), gas-water relative seepage, and gas-water two-phase displacement studies are performed to examine the seepage ability and parameters of the reservoir, and further analyses are done to confirm the controlling effects of reservoir micropore structures on seepage ability. The experimental results show that Benxi, Taiyuan, Shanxi, and Shihezi formations in the study area are typical ultra-low porosity and ultra-low permeability reservoirs. Owing to compaction and later diagenetic transformation, they contain few primary pores. Secondary pores are the main pore types of reservoirs in the study area. Six main types of secondary pores are: intergranular dissolved pores, intragranular dissolved pores, lithic dissolved pores, intercrystalline dissolved pores, micropores, and microfracture. The results show that reservoirs with small pore-throat radius, medium displacement pressure, and large differences in pore-throat structures are present in the study area. The four types of micropore structures observed are: lower displacement pressure and fine pores with medium-fine throats, low displacement pressure and fine micropores with fine throats, medium displacement pressure and micropores with micro-fine throats, and high displacement pressure and micropores with micro throats. The micropore structure is complex, and the reservoir seepage ability is poor in the study areas. The movable fluid saturation, range of the gas-water two-phase seepage zone, and displacement types are the three parameters that well represent the reservoir seepage ability. According to the characteristic parameters of microscopic pore structure and seepage characteristics, the reservoirs in the study area are classified into four types(Ⅰ–Ⅳ), and types Ⅰ, Ⅱ, and Ⅲ are the main types observed. From type Ⅰ to type Ⅳ, the displacement pressure increases, and the movable fluid saturation and gas-water two-phase seepage zone decrease, and the displacement type changes from the reticulation-uniform displacement to dendritic and snake like.展开更多
Synthesis and characterization of lanthanum-doped yttrium iro n garnet(YIG)in the compositional se ries of Y_(3-x)La_(x)Fe_(5)O_(12)(x=0.0,0.1,0.3,and 0.5)were carried out.All compositions were made by using solid sta...Synthesis and characterization of lanthanum-doped yttrium iro n garnet(YIG)in the compositional se ries of Y_(3-x)La_(x)Fe_(5)O_(12)(x=0.0,0.1,0.3,and 0.5)were carried out.All compositions were made by using solid state reaction method with ball-milling technique.The phase formation,surface morphology,magnetic properties,and microwave absorbing ability of all compositions were characterized by using an X-ray diffractometer,a scanning electron microscope,a vibrating sample magnetometer,and a Vector network analyzer.The results reveal that all compositions are crystallized into Y_(3)Fe_(5)O_(12)phase(space group la-3d(230).It was observed that the lattice constant is increased from 1.2373 to 1.2421 nm with the increase of lanthanum substitution level from x=0.0-0.5.The crystallite size of Y_(3-x)La_(x)Fe_(5)O_(12)series calculated by Scherrer method is found to decrease from 78 nm in x=0.0-63 nm in x=0.5.The particle size distribution from the surface morphology image analysis is shifted to lower-range number with the increase of lanthanum substitution level from x=0.0 to 0.5.The substitution process also affects the lattice distortion in La-doped samples and changes the bond angles and bond lengths of the YIG structure.As the results,a linear correlation between the Fe'-O-Fe bond angle with magnetic properties parameters of saturation magnetization(M_(s))and remanence magnetization(M_(r))was studied.Due to the lanthanum substitution process,all La^(3+)-doped samples possess higher M_(s)and M_(r)values compared to the original composition.The results of Vector network analyzer show that the improvement of the M_(s)and M_(r)plays an important role in enhancing the microwave absorbing ability of the materials.The minimum RL changes from-8.22 dB(~85.22%microwave absorption)in x=0.0 to-14.21 dB(~96.25%microwave absorption)in x=0.5.The enhancement is mainly ascribed to the natural magnetic resonance loss and dipoIe-polarization loss due to the substitution process.The decreasing particle size also enhances the microwave absorbing ability of the La-doped samples via multiple-reflections mechanism.展开更多
The biological performance of Ti-6Al-4V implant is primarily determined by their surface properties.However,traditional surface modification methods,such as acid etching,hardly make improvement in their osseointegrati...The biological performance of Ti-6Al-4V implant is primarily determined by their surface properties.However,traditional surface modification methods,such as acid etching,hardly make improvement in their osseointegration ability and antibacterial capacity.In this study,we prepared a multi-scale composite structure coated with zinc oxide(ZnO)on Ti-6Al-4V implant by an innovative technology of two-step laser processing combined with solution-assistant.Compared with the acid etching method,the physicochemical properties of surface significantly improved.The in vitro results showed that the particular dimension of micro-nano structure and the multifaceted nature of ZnO synergistically affected MC3T3-E1 osteogenesis and bacterial activities:(1)The surface morphology showed a‘contact guidance'effect on cell arrangement,which was conducive to the adhesion of filopodia and cell spreading,and the osteogenesis level of MC3T3-E1 was enhanced due to the release of zinc ions(Zn^(2+));(2)the characterization of bacterial response revealed that periodic nanostructures and Zn^(2+)released could cause damage to the cell wall of E.coli and reduce the adhesion and aggregation of S.aureus.In conclusion,the modified surface showed a synergistic effect of physical topography and chemical composition,making this a promising method and providing new insight into bone defect repairment.展开更多
A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calc...A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calculation on this model deduces a parameter describing the glass forming ability of metallic alloys:α_c=(1-2.08/Φ_m)T_g/T_m,where T_g is gass transition temperature,T_m is the melting temperature,and Φ_m is entralpy change of melting.It is believed that easy glass forming alloy systems have larger values of a_c.This new criterion of GFA not only provides the theoretical background for several GFA criteria in the literature cited,but also can predict the GFA of many alloy systems more reasonably and accurately.展开更多
This study utilizes mediation analysis and bootstrapping to analyze the mediating effect of capital structure on the association between managerial ability and firm performance.The dataset consists of 6384 firm-year o...This study utilizes mediation analysis and bootstrapping to analyze the mediating effect of capital structure on the association between managerial ability and firm performance.The dataset consists of 6384 firm-year observations from the Taiwan Residents electronics industry during 2005–2018.Our results indicate that(1)low(high)levels of debt are likely observed in firms with CEOs with high(low)ability,(2)managerial ability positively affects firm performance,and(3)capital structure mediates the positive relationship between managerial ability and firm performance.Overall,the findings may have limited generalizability due to the specific sample characteristics and provide convincing support for the importance of capital structure as a mediator in the managerial ability-firm performance nexus.Specifically,this study highlights the need for examining the effect of managerial ability on firm performance through a mediator.展开更多
Despite its significance in both fundamental science and industrial applications,the glass-forming transition in the Al_(2)O_(3)-Y_(2)O_(3)(AY)refractory system is not yet fully understood due to the elusive structure...Despite its significance in both fundamental science and industrial applications,the glass-forming transition in the Al_(2)O_(3)-Y_(2)O_(3)(AY)refractory system is not yet fully understood due to the elusive structure evolution upon cooling.Here,atomic-scale structural changes in AY-bearing melts with different compositions and temperatures are tracked by employing in situ high-energy synchrotron X-ray diffraction and empirical potential structure refinement simulation.We find that the glass-forming abilities(GFA)of AY-bearing melts are intriguingly correlated with the dependence of melt structure on temperature.In the case of the Al_(2)O_(3)and Y_(3)A_(l5)O_(12)(YAG),the observed large structural changes from superheating to under-cooling melt(i.e.,higher temperature susceptibility)correspond to a low GFA.Conversely,the 74Al_(2)O_(3)-26Y_(2)O_(3)(AY26)melt,with the smallest temperature susceptibility,exhibits the highest GFA.Simulation models illustrate that the temperature susceptibility of melt is associated with its atomic arrangement,especially the stability of cation-cation pairs.A balanced network(in AY26 melt),where the unsteady OAl3 tri-clusters are minimized and steady apex-to-apex connections between adjacent network units are abundant,contributes to stabilizing cationic interactions.This,in turn,fosters the formation of largesized Al-O-Al rings,which topologically facilitates the subsequent glass-forming transition.Our findings provide new structural insight into the GFA of AY-bearing melts and may expand to other unconventional glass-forming systems to accelerate glassy materials design.展开更多
The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the...The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the addition of specific minor elements can greatly enhance the GFA of parent alloys,yet the underlying mechanism remains unclear.In this study,we use the ZrCuAl system as a model to explore how the addition of minor Al influences the crystallization rate by modulating the properties of the crystal-liquid interface,thereby affecting the GFA.The results reveal that the minor addition of Al significantly reduces the crystal growth rate,a phenomenon not governed by particle density fluctuations at the interface.The impact of minor element additions extends beyond a modest increase in crystal-unfavorable motifs in the bulk supercooled liquid.More importantly,it leads to a significant enrichment of these motifs at the crystal-supercooled liquid interface,forming a dense topological network of crystal-unfavorable structures that effectively prevent the growth of the crystalline interface and enhance GFA.Our results provide valuable insights for the design and development of high-performance metallic glasses.展开更多
Molecular dynamics(MD) simulations were performed to investigate the glass forming ability(GFA) and microscopic structural properties of liquid Cu-Zr alloys.Based on the analysis of composition dependences of the redu...Molecular dynamics(MD) simulations were performed to investigate the glass forming ability(GFA) and microscopic structural properties of liquid Cu-Zr alloys.Based on the analysis of composition dependences of the reduced glass transition temperatures and the excess volume,we found that the Cu-Zr glasses have the largest GFA at Cu65Zr35 composition.To get more detailed information of local structure,we calculated the pair correlation functions,partial pair correlation functions,the excess entropy,chemical order parameter,coordination number,and Voronoi index of Cu-Zr liquids.We found that there exists an obvious and close relationship among the GFA,the excess entropy calculated using the total pair correlation functions,chemical order parameters,and some Cu centered cluster with Voronoi index <0,2,8,1> and Zr centered cluster with Voronoi index <0,3,6,4>,which all have nonlinear dependences on Cu/Zr concentration and have extreme values at liquid Cu65Zr35 composition.展开更多
The effects of Y and Nb addition on thermal stability,glass-forming ability(GFA),and magnetic softness of Co75B25 metallic glass(MG)were comprehensively investigated.The experimental results indicated that the thermal...The effects of Y and Nb addition on thermal stability,glass-forming ability(GFA),and magnetic softness of Co75B25 metallic glass(MG)were comprehensively investigated.The experimental results indicated that the thermal stability,GFA,and magnetic softness of the studied MGs increase in the order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25).The structural origins of the improved properties were revealed by ab initio molecular dynamics(AIMD)simulations and density functional theory(DFT)calculations.Results showed that the B-centered prism units are the primary structure-forming units of the four MGs,connect through vertex-,edge-,and face-shared(VS,ES,and FS)atoms,and Co-centered units tend to connect with Co/B-centered units via the intercross-shared(IS)atoms.The addition of Y and Nb not only plays the role of connecting atoms but also enhances both bond strengths and the fractions of icosahedral-like units in increasing order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25),which is conducive to the enhancement of the structural stability,atomic packing density,and viscosity,thereby improving thermal stability and GFA.In addition,the improvement of structural stability and homogeneity leads to enhanced magnetic softness.展开更多
The work addresses to the study of the molecular and crystal structure and properties of a new energyintensive compound 3,6-bis(2,2,2-trinitroethylnitramino)-1,2,4,5-tetrazine(NBTAT),first obtained by the authors in 2...The work addresses to the study of the molecular and crystal structure and properties of a new energyintensive compound 3,6-bis(2,2,2-trinitroethylnitramino)-1,2,4,5-tetrazine(NBTAT),first obtained by the authors in 2020.NBTAT compound crystallizes in the monoclinic system,space group P2(1)/n,density at room temperature 1.939 g/cm^(3).The energies of crystal packing and pairwise intermolecular interactions in NBTAT and its unnitrated analogue BTAT were calculated,and their comparative analysis was carried out.The enthalpy of formation of NBTAT molecules was calculated by quantum-chemical methods using Gaussian 09,and the enthalpy of formation of NBTAT in the solid phase(618 kJ/mol)was estimated.The energy capabilities of NBTAT as an oxidizer of solid composite propellants are estimated.It is shown that in metal-free compositions NBTAT is significantly superior to ammonium perchlorate(AP),dinitramide ammonium salt(ADN),HMX,BTAT at all stages of rocket systems,and is comparable to the superdense CL-20 yielding to the latter at the lower stages and slightly winning at the upper stages.展开更多
Cognitive ability is important component of competitive ability of athletes,an important content of winning elements in sports,and an important topic of modern sports training and scientific research.These problems wi...Cognitive ability is important component of competitive ability of athletes,an important content of winning elements in sports,and an important topic of modern sports training and scientific research.These problems will restrict the improvement of athletes’cognitive ability and mental level.Based on the theory of psychology,use multiple hierarchical thinking,research cognitive theory of sports and the characteristics of cognitive ability of elite athletes,research the structure element system of cognitive ability,construct a two-level structure model of the cognitive ability of excellent athletes,summarize specific characteristics of the first level elements,and apply psychological cognitive theory to the training of modern Olympic Games mobilization,so as to provide valuable cognitive training,psychological training,and intelligence training for athletes theoretical guidance.展开更多
Among students' abilities,the important one is the ability of studying independently.It is the teachers' indispensable task to foster students' ability of studying independently.This essay deals with the p...Among students' abilities,the important one is the ability of studying independently.It is the teachers' indispensable task to foster students' ability of studying independently.This essay deals with the problem that how a teacher can foster the ability of student self-study,especially English study,from these perspectives:the nature,the characteristics,the conditions and the structure of the ability of independent study.The appropriate methods that the teacher should take in the process of fostering the ability are discussed in the last part of this essay.展开更多
Electric pulse modification （EPM） is a novel technique that reduces grain size by altering the structure of a melt. It was investigated that the response of the casting structure of high pure aluminum to EPM in diff...Electric pulse modification （EPM） is a novel technique that reduces grain size by altering the structure of a melt. It was investigated that the response of the casting structure of high pure aluminum to EPM in different superheated melts. The results indicate that the grain refining effect of a given pulse electric field holds an optimal temperature range, moreover, a lower or higher superheated temperature will both disadvantage the improvements of casting structure. It essentially lies in the cooperative action between the distorted absorption of clusters and the activated capability of atoms in the aluminum melt.展开更多
Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Ther...Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter （DSC） indicate that the glass-forming ability （GFA） of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction （XRD） and transmission electron microscope （TEM） show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.展开更多
In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infi...In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.展开更多
The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA)are studied via molecular dynamics simulations.Pair distribution function and the largest...The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA)are studied via molecular dynamics simulations.Pair distribution function and the largest standard cluster(LSC)are adopted to characterize the local atomic structures in the(Zr_(50)Cu_(50))_(100-x)Al_(x)systems.The[12/555]icosahedra and their medium-range order(IMRO)play an important role in forming(Zr_(50)Cu_(50))_(100-x)Al_(x)metallic glasses(MGs).The fraction of[12/555],the number of IMRO,and the maximum size of IMRO in MGs increase significantly with increasing x.A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids.No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity.Instead,a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr_(50)Cu_(50)alloys.展开更多
The rare earth based hydrogen storage alloys MmxM1 1 - x ( Ni3.55 Co0.75 Mn0.4 A10.3 ) ( x = 0 ～ 0.5 ) were investigated in this work.Adjusted Ml: Mm ratio to change the content of La,Ce,Pr and Nd in the alloys and t...The rare earth based hydrogen storage alloys MmxM1 1 - x ( Ni3.55 Co0.75 Mn0.4 A10.3 ) ( x = 0 ～ 0.5 ) were investigated in this work.Adjusted Ml: Mm ratio to change the content of La,Ce,Pr and Nd in the alloys and then to change the phase structure, the influences of phase structure on the electrochemical properties were analyzed.The results indicate that the main phase of all alloys is LaNi5 with CaCu5 type structure and the crystal lattices constants of LaNi5 are changed with increasing x value, i.e, decreased a-axis, increased c-axis and axis ratio and nonlinear decreased crystal volume.The crystal volume of the alloy with x = 0.3 is larger than others.There is second phase A1LaNi4 in alloys when x≥0.3, which decrease the discharge capacity, but increase the cycling stability and high rate discharge ability.Compared comprehensively, the alloy with x = 0.3 shows the higher discharge capacity and the better cycling stability.展开更多
Three types of blue-violet light-emitting devices based on an excito n- confined structure have been prepared, in which different materials were used as emitting layers and hole-transporting layers. They had structur...Three types of blue-violet light-emitting devices based on an excito n- confined structure have been prepared, in which different materials were used as emitting layers and hole-transporting layers. They had structures of ITO/CuPc/ NPB/CPB/TPBi/Alq 3/LiF/Al(D NC), ITO/CuPc/J03/CBP/TPBi/Alq 3/LiF/Al(D JC) and ITO /CuPc/J03/FNPD/TPBi/Alq 3/LiF/Al(D JF). Here copper phthaloc yan ine (CuPc) acted as hole-injecting layer(HIL), N,N-bis-(1-naphthyl)-N,N-di phenyl-1.1bipheny1-4-4-diamine(NPB) and J03 hole-transporting layers (HTLs) , 4,4'-dicarbazolyl-1,1'-biphenyl (CBP) and FNPD as emitting layers(EMLs), N, arylbenzimidazoles (TPBi) as hole-blocking layer(HBL), and tris(8-quinolinolat o) aluminium complex(Alq 3) as electron-transporting layer(ETL). TPBi applied her e is a good confinement to both charges and excitons, which make the devices emit blue-violet light or iginating from the emitter, CBP and FNPD. Their characteristics have also been i nvestigated. The result shows that the device D NC based on NPB/CBP has the best performance among the three devices. The excellence of D NC is attrib uted to the better hole-transporting ability of NPB as compared with J03, and t he better emitting ability of CBP as compared with FNPD, although the best match ing of energy levels is found in the hole-transporting layer and emitting layer of the device D JF.展开更多
Crystals of the title compound C22H12N62HCl?H2O (DAA稨Cl) were obtained from a HCl aqueous solution of 4, 5-diazafluorene-9-one azine. The crystal belongs to monoclinic, space group P21/c with a = 5.203(3), b = 8.991(...Crystals of the title compound C22H12N62HCl?H2O (DAA稨Cl) were obtained from a HCl aqueous solution of 4, 5-diazafluorene-9-one azine. The crystal belongs to monoclinic, space group P21/c with a = 5.203(3), b = 8.991(3), c = 22.17(1) , b = 92.13(4), V = 1036.2(9) 3, Z = 2, C22H18N6O2Cl2, Mr = 468.1, Dc = 1.503 g/cm3, F(000) = 484, m(MoKa) = 0.344 mm-1, R = 0.052 and wR = 0.056 for 755 observed reflections. The Cl…N(2) distance of 2.999(6) ?and Cl…HN(2) angle of 160.8(8)o imply the existence of a stronger H-bond between Cl and DAA. And both the rather longer ClH distance of 1.814(2) ?and the unexpected shorter N(2)H distance of 1.236(6) ?suggest the protonation of DAA molecule and explain the weak coordination ability of DAA to a metal center in the acidic solution.展开更多
基金The State Natural Science Foundation!(49974019)State Climb Plan
文摘This paper assesses the structure and ability of Local Seismological Gravity Monitoring Network (LSGMN) in China main tectonic zone and China Seismological Gravity Monitoring System (CSGMS) which formed after the project of 'China Crustal Movement Observation Network (CCMON)' has been performed. The main conclusions drawn are as follows: ①LSGMN has good monitoring and prediction ability for the earthquake of M_s about 5. But it lacks ability to monitor and predict the strong earthquake of M_s>6 because of the little range of the observation network;②CSGMS has good ability to monitor and predict the earthquake of M_s>7, but the resolving power is not enough for the earthquake magnitude from M_s=6 to M_s=7 because the observation stations are too sparse.
基金the National Natural Science Foundation of China(Grant No.41390451,41172101)the National Key Research Project of China(No.2016YFC0601003).
文摘In this study, the types of micropores in a reservoir are analyzed using casting thin section(CTS) observation and scanning electron microscopy(SEM) experiments. The high-pressure mercury injection(HPMI) and constant-rate mercury injection(CRMI) experiments are performed to study the micropore structure of the reservoir. Nuclear magnetic resonance(NMR), gas-water relative seepage, and gas-water two-phase displacement studies are performed to examine the seepage ability and parameters of the reservoir, and further analyses are done to confirm the controlling effects of reservoir micropore structures on seepage ability. The experimental results show that Benxi, Taiyuan, Shanxi, and Shihezi formations in the study area are typical ultra-low porosity and ultra-low permeability reservoirs. Owing to compaction and later diagenetic transformation, they contain few primary pores. Secondary pores are the main pore types of reservoirs in the study area. Six main types of secondary pores are: intergranular dissolved pores, intragranular dissolved pores, lithic dissolved pores, intercrystalline dissolved pores, micropores, and microfracture. The results show that reservoirs with small pore-throat radius, medium displacement pressure, and large differences in pore-throat structures are present in the study area. The four types of micropore structures observed are: lower displacement pressure and fine pores with medium-fine throats, low displacement pressure and fine micropores with fine throats, medium displacement pressure and micropores with micro-fine throats, and high displacement pressure and micropores with micro throats. The micropore structure is complex, and the reservoir seepage ability is poor in the study areas. The movable fluid saturation, range of the gas-water two-phase seepage zone, and displacement types are the three parameters that well represent the reservoir seepage ability. According to the characteristic parameters of microscopic pore structure and seepage characteristics, the reservoirs in the study area are classified into four types(Ⅰ–Ⅳ), and types Ⅰ, Ⅱ, and Ⅲ are the main types observed. From type Ⅰ to type Ⅳ, the displacement pressure increases, and the movable fluid saturation and gas-water two-phase seepage zone decrease, and the displacement type changes from the reticulation-uniform displacement to dendritic and snake like.
基金Project supported by the Ministry of Finance Indonesia for the research grant through the competitive research program of RISPRO Kompetisi(PRJ-45/LPDP/2020)。
文摘Synthesis and characterization of lanthanum-doped yttrium iro n garnet(YIG)in the compositional se ries of Y_(3-x)La_(x)Fe_(5)O_(12)(x=0.0,0.1,0.3,and 0.5)were carried out.All compositions were made by using solid state reaction method with ball-milling technique.The phase formation,surface morphology,magnetic properties,and microwave absorbing ability of all compositions were characterized by using an X-ray diffractometer,a scanning electron microscope,a vibrating sample magnetometer,and a Vector network analyzer.The results reveal that all compositions are crystallized into Y_(3)Fe_(5)O_(12)phase(space group la-3d(230).It was observed that the lattice constant is increased from 1.2373 to 1.2421 nm with the increase of lanthanum substitution level from x=0.0-0.5.The crystallite size of Y_(3-x)La_(x)Fe_(5)O_(12)series calculated by Scherrer method is found to decrease from 78 nm in x=0.0-63 nm in x=0.5.The particle size distribution from the surface morphology image analysis is shifted to lower-range number with the increase of lanthanum substitution level from x=0.0 to 0.5.The substitution process also affects the lattice distortion in La-doped samples and changes the bond angles and bond lengths of the YIG structure.As the results,a linear correlation between the Fe'-O-Fe bond angle with magnetic properties parameters of saturation magnetization(M_(s))and remanence magnetization(M_(r))was studied.Due to the lanthanum substitution process,all La^(3+)-doped samples possess higher M_(s)and M_(r)values compared to the original composition.The results of Vector network analyzer show that the improvement of the M_(s)and M_(r)plays an important role in enhancing the microwave absorbing ability of the materials.The minimum RL changes from-8.22 dB(~85.22%microwave absorption)in x=0.0 to-14.21 dB(~96.25%microwave absorption)in x=0.5.The enhancement is mainly ascribed to the natural magnetic resonance loss and dipoIe-polarization loss due to the substitution process.The decreasing particle size also enhances the microwave absorbing ability of the La-doped samples via multiple-reflections mechanism.
基金supported by the National Natural Science Foundation of China(51975336)Key Research and Development Program of Shandong Province(2020JMRH0202)+1 种基金the National Natural Science Foundation of China(52172282)China Postdoctoral Science Foundation(2021M690106)。
文摘The biological performance of Ti-6Al-4V implant is primarily determined by their surface properties.However,traditional surface modification methods,such as acid etching,hardly make improvement in their osseointegration ability and antibacterial capacity.In this study,we prepared a multi-scale composite structure coated with zinc oxide(ZnO)on Ti-6Al-4V implant by an innovative technology of two-step laser processing combined with solution-assistant.Compared with the acid etching method,the physicochemical properties of surface significantly improved.The in vitro results showed that the particular dimension of micro-nano structure and the multifaceted nature of ZnO synergistically affected MC3T3-E1 osteogenesis and bacterial activities:(1)The surface morphology showed a‘contact guidance'effect on cell arrangement,which was conducive to the adhesion of filopodia and cell spreading,and the osteogenesis level of MC3T3-E1 was enhanced due to the release of zinc ions(Zn^(2+));(2)the characterization of bacterial response revealed that periodic nanostructures and Zn^(2+)released could cause damage to the cell wall of E.coli and reduce the adhesion and aggregation of S.aureus.In conclusion,the modified surface showed a synergistic effect of physical topography and chemical composition,making this a promising method and providing new insight into bone defect repairment.
文摘A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calculation on this model deduces a parameter describing the glass forming ability of metallic alloys:α_c=(1-2.08/Φ_m)T_g/T_m,where T_g is gass transition temperature,T_m is the melting temperature,and Φ_m is entralpy change of melting.It is believed that easy glass forming alloy systems have larger values of a_c.This new criterion of GFA not only provides the theoretical background for several GFA criteria in the literature cited,but also can predict the GFA of many alloy systems more reasonably and accurately.
基金Funding was provided by Universiti Malaysia Pahang(Grant No.RDU1903110).
文摘This study utilizes mediation analysis and bootstrapping to analyze the mediating effect of capital structure on the association between managerial ability and firm performance.The dataset consists of 6384 firm-year observations from the Taiwan Residents electronics industry during 2005–2018.Our results indicate that(1)low(high)levels of debt are likely observed in firms with CEOs with high(low)ability,(2)managerial ability positively affects firm performance,and(3)capital structure mediates the positive relationship between managerial ability and firm performance.Overall,the findings may have limited generalizability due to the specific sample characteristics and provide convincing support for the importance of capital structure as a mediator in the managerial ability-firm performance nexus.Specifically,this study highlights the need for examining the effect of managerial ability on firm performance through a mediator.
基金supported by the National Natural Science Foundation of China-Key Program(No.52234010)National Natural Science Foundation of China(No.51971138)+2 种基金National Natural Science Foundation of China-Distinguished Young Scholars(No.52325407)National Key Basic Research Program of China(No.2020YFA0406101)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202102).
文摘Despite its significance in both fundamental science and industrial applications,the glass-forming transition in the Al_(2)O_(3)-Y_(2)O_(3)(AY)refractory system is not yet fully understood due to the elusive structure evolution upon cooling.Here,atomic-scale structural changes in AY-bearing melts with different compositions and temperatures are tracked by employing in situ high-energy synchrotron X-ray diffraction and empirical potential structure refinement simulation.We find that the glass-forming abilities(GFA)of AY-bearing melts are intriguingly correlated with the dependence of melt structure on temperature.In the case of the Al_(2)O_(3)and Y_(3)A_(l5)O_(12)(YAG),the observed large structural changes from superheating to under-cooling melt(i.e.,higher temperature susceptibility)correspond to a low GFA.Conversely,the 74Al_(2)O_(3)-26Y_(2)O_(3)(AY26)melt,with the smallest temperature susceptibility,exhibits the highest GFA.Simulation models illustrate that the temperature susceptibility of melt is associated with its atomic arrangement,especially the stability of cation-cation pairs.A balanced network(in AY26 melt),where the unsteady OAl3 tri-clusters are minimized and steady apex-to-apex connections between adjacent network units are abundant,contributes to stabilizing cationic interactions.This,in turn,fosters the formation of largesized Al-O-Al rings,which topologically facilitates the subsequent glass-forming transition.Our findings provide new structural insight into the GFA of AY-bearing melts and may expand to other unconventional glass-forming systems to accelerate glassy materials design.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.T2325004 and 52161160330)the support from the Hong Kong Institute of Advanced Studies through the materials cluster project。
文摘The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the addition of specific minor elements can greatly enhance the GFA of parent alloys,yet the underlying mechanism remains unclear.In this study,we use the ZrCuAl system as a model to explore how the addition of minor Al influences the crystallization rate by modulating the properties of the crystal-liquid interface,thereby affecting the GFA.The results reveal that the minor addition of Al significantly reduces the crystal growth rate,a phenomenon not governed by particle density fluctuations at the interface.The impact of minor element additions extends beyond a modest increase in crystal-unfavorable motifs in the bulk supercooled liquid.More importantly,it leads to a significant enrichment of these motifs at the crystal-supercooled liquid interface,forming a dense topological network of crystal-unfavorable structures that effectively prevent the growth of the crystalline interface and enhance GFA.Our results provide valuable insights for the design and development of high-performance metallic glasses.
基金Funded by the National Natural Science Foundation of China (Grant Nos. 11074253,10874182 and 50803066)the Foundation of the Education Committee of Anhui Province,China (Grant Nos. KJ2010A031 and KJ2010A012)
文摘Molecular dynamics(MD) simulations were performed to investigate the glass forming ability(GFA) and microscopic structural properties of liquid Cu-Zr alloys.Based on the analysis of composition dependences of the reduced glass transition temperatures and the excess volume,we found that the Cu-Zr glasses have the largest GFA at Cu65Zr35 composition.To get more detailed information of local structure,we calculated the pair correlation functions,partial pair correlation functions,the excess entropy,chemical order parameter,coordination number,and Voronoi index of Cu-Zr liquids.We found that there exists an obvious and close relationship among the GFA,the excess entropy calculated using the total pair correlation functions,chemical order parameters,and some Cu centered cluster with Voronoi index <0,2,8,1> and Zr centered cluster with Voronoi index <0,3,6,4>,which all have nonlinear dependences on Cu/Zr concentration and have extreme values at liquid Cu65Zr35 composition.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.51871039)the Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province),the Supercomputing Center of Dalian University of Technology,and the Global Institute for Materials Research Tohoku Program,Tohoku University,Japan。
文摘The effects of Y and Nb addition on thermal stability,glass-forming ability(GFA),and magnetic softness of Co75B25 metallic glass(MG)were comprehensively investigated.The experimental results indicated that the thermal stability,GFA,and magnetic softness of the studied MGs increase in the order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25).The structural origins of the improved properties were revealed by ab initio molecular dynamics(AIMD)simulations and density functional theory(DFT)calculations.Results showed that the B-centered prism units are the primary structure-forming units of the four MGs,connect through vertex-,edge-,and face-shared(VS,ES,and FS)atoms,and Co-centered units tend to connect with Co/B-centered units via the intercross-shared(IS)atoms.The addition of Y and Nb not only plays the role of connecting atoms but also enhances both bond strengths and the fractions of icosahedral-like units in increasing order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25),which is conducive to the enhancement of the structural stability,atomic packing density,and viscosity,thereby improving thermal stability and GFA.In addition,the improvement of structural stability and homogeneity leads to enhanced magnetic softness.
基金The Ministry of Science and Higher Education of the Russian Federation(Agreement with Zelinsky Institute of Organic Chemistry RAS No 075-15-2020-803).
文摘The work addresses to the study of the molecular and crystal structure and properties of a new energyintensive compound 3,6-bis(2,2,2-trinitroethylnitramino)-1,2,4,5-tetrazine(NBTAT),first obtained by the authors in 2020.NBTAT compound crystallizes in the monoclinic system,space group P2(1)/n,density at room temperature 1.939 g/cm^(3).The energies of crystal packing and pairwise intermolecular interactions in NBTAT and its unnitrated analogue BTAT were calculated,and their comparative analysis was carried out.The enthalpy of formation of NBTAT molecules was calculated by quantum-chemical methods using Gaussian 09,and the enthalpy of formation of NBTAT in the solid phase(618 kJ/mol)was estimated.The energy capabilities of NBTAT as an oxidizer of solid composite propellants are estimated.It is shown that in metal-free compositions NBTAT is significantly superior to ammonium perchlorate(AP),dinitramide ammonium salt(ADN),HMX,BTAT at all stages of rocket systems,and is comparable to the superdense CL-20 yielding to the latter at the lower stages and slightly winning at the upper stages.
基金Thanks to Professor Korobeynikov Georgiy of National University of Physical Education and Sports of Ukraine.Thanks to Professor Chen Jinsong of Jiangsu Ocean University of Chinathanks for your support and help.
文摘Cognitive ability is important component of competitive ability of athletes,an important content of winning elements in sports,and an important topic of modern sports training and scientific research.These problems will restrict the improvement of athletes’cognitive ability and mental level.Based on the theory of psychology,use multiple hierarchical thinking,research cognitive theory of sports and the characteristics of cognitive ability of elite athletes,research the structure element system of cognitive ability,construct a two-level structure model of the cognitive ability of excellent athletes,summarize specific characteristics of the first level elements,and apply psychological cognitive theory to the training of modern Olympic Games mobilization,so as to provide valuable cognitive training,psychological training,and intelligence training for athletes theoretical guidance.
文摘Among students' abilities,the important one is the ability of studying independently.It is the teachers' indispensable task to foster students' ability of studying independently.This essay deals with the problem that how a teacher can foster the ability of student self-study,especially English study,from these perspectives:the nature,the characteristics,the conditions and the structure of the ability of independent study.The appropriate methods that the teacher should take in the process of fostering the ability are discussed in the last part of this essay.
基金This work was financially supported by the National Natural Science Foundation of China (No.50174028).
文摘Electric pulse modification （EPM） is a novel technique that reduces grain size by altering the structure of a melt. It was investigated that the response of the casting structure of high pure aluminum to EPM in different superheated melts. The results indicate that the grain refining effect of a given pulse electric field holds an optimal temperature range, moreover, a lower or higher superheated temperature will both disadvantage the improvements of casting structure. It essentially lies in the cooperative action between the distorted absorption of clusters and the activated capability of atoms in the aluminum melt.
基金Project supported by the National Science Foundation for 0utstanding Young Scientists of China （Grant No 50125101）.
文摘Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter （DSC） indicate that the glass-forming ability （GFA） of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction （XRD） and transmission electron microscope （TEM） show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.
基金supported by the National Natural Science Foundation of China(No.51772310)National Natural Science Foundation of China(No.52222202)+3 种基金Chinese Academy of Sciences Key Research Program of Frontier Sciences(No.QYZDYSSWJSC031)Key Deployment Projects of the Chinese Academy of Sciences(No.ZDRW-CN2019-01)Shanghai Sailing Program(No.21YF1454600)Outstanding Chinese and Foreign Youth Exchange Program of China Association of Science and Technology.
文摘In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.
基金the National Natural Science Foundation of China(Grant No.51701071)the Natural Science Foundation of Hunan Province,China(Grant Nos.2018JJ3100 and 2018JJ2078)the Project of the Hunan Educational Department,China(Grant No.19B122)。
文摘The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA)are studied via molecular dynamics simulations.Pair distribution function and the largest standard cluster(LSC)are adopted to characterize the local atomic structures in the(Zr_(50)Cu_(50))_(100-x)Al_(x)systems.The[12/555]icosahedra and their medium-range order(IMRO)play an important role in forming(Zr_(50)Cu_(50))_(100-x)Al_(x)metallic glasses(MGs).The fraction of[12/555],the number of IMRO,and the maximum size of IMRO in MGs increase significantly with increasing x.A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids.No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity.Instead,a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr_(50)Cu_(50)alloys.
文摘The rare earth based hydrogen storage alloys MmxM1 1 - x ( Ni3.55 Co0.75 Mn0.4 A10.3 ) ( x = 0 ～ 0.5 ) were investigated in this work.Adjusted Ml: Mm ratio to change the content of La,Ce,Pr and Nd in the alloys and then to change the phase structure, the influences of phase structure on the electrochemical properties were analyzed.The results indicate that the main phase of all alloys is LaNi5 with CaCu5 type structure and the crystal lattices constants of LaNi5 are changed with increasing x value, i.e, decreased a-axis, increased c-axis and axis ratio and nonlinear decreased crystal volume.The crystal volume of the alloy with x = 0.3 is larger than others.There is second phase A1LaNi4 in alloys when x≥0.3, which decrease the discharge capacity, but increase the cycling stability and high rate discharge ability.Compared comprehensively, the alloy with x = 0.3 shows the higher discharge capacity and the better cycling stability.
基金Project supported by the National Natural Science Foundation of China ( Grant Nos. 60077020 90201034) and the Foundation of National High Technology Research and Development Program (Grant No.2001AA313070)
文摘Three types of blue-violet light-emitting devices based on an excito n- confined structure have been prepared, in which different materials were used as emitting layers and hole-transporting layers. They had structures of ITO/CuPc/ NPB/CPB/TPBi/Alq 3/LiF/Al(D NC), ITO/CuPc/J03/CBP/TPBi/Alq 3/LiF/Al(D JC) and ITO /CuPc/J03/FNPD/TPBi/Alq 3/LiF/Al(D JF). Here copper phthaloc yan ine (CuPc) acted as hole-injecting layer(HIL), N,N-bis-(1-naphthyl)-N,N-di phenyl-1.1bipheny1-4-4-diamine(NPB) and J03 hole-transporting layers (HTLs) , 4,4'-dicarbazolyl-1,1'-biphenyl (CBP) and FNPD as emitting layers(EMLs), N, arylbenzimidazoles (TPBi) as hole-blocking layer(HBL), and tris(8-quinolinolat o) aluminium complex(Alq 3) as electron-transporting layer(ETL). TPBi applied her e is a good confinement to both charges and excitons, which make the devices emit blue-violet light or iginating from the emitter, CBP and FNPD. Their characteristics have also been i nvestigated. The result shows that the device D NC based on NPB/CBP has the best performance among the three devices. The excellence of D NC is attrib uted to the better hole-transporting ability of NPB as compared with J03, and t he better emitting ability of CBP as compared with FNPD, although the best match ing of energy levels is found in the hole-transporting layer and emitting layer of the device D JF.
基金The project was supported by the National Natural Science Foundation (29973036) of China
文摘Crystals of the title compound C22H12N62HCl?H2O (DAA稨Cl) were obtained from a HCl aqueous solution of 4, 5-diazafluorene-9-one azine. The crystal belongs to monoclinic, space group P21/c with a = 5.203(3), b = 8.991(3), c = 22.17(1) , b = 92.13(4), V = 1036.2(9) 3, Z = 2, C22H18N6O2Cl2, Mr = 468.1, Dc = 1.503 g/cm3, F(000) = 484, m(MoKa) = 0.344 mm-1, R = 0.052 and wR = 0.056 for 755 observed reflections. The Cl…N(2) distance of 2.999(6) ?and Cl…HN(2) angle of 160.8(8)o imply the existence of a stronger H-bond between Cl and DAA. And both the rather longer ClH distance of 1.814(2) ?and the unexpected shorter N(2)H distance of 1.236(6) ?suggest the protonation of DAA molecule and explain the weak coordination ability of DAA to a metal center in the acidic solution.
