Network autoregression and factor model are effective methods for modeling network time series data.In this study,we propose a network autoregression model with a factor structure that incorporates a latent group stru...Network autoregression and factor model are effective methods for modeling network time series data.In this study,we propose a network autoregression model with a factor structure that incorporates a latent group structure to address nodal heterogeneity within the network.An iterative algorithm is employed to minimize a least-squares objective function,allowing for simultaneous estimation of both the parameters and the group structure.To determine the unknown number of groups and factors,a PIC criterion is introduced.Additionally,statistical inference of the estimated parameters is presented.To assess the validity of the proposed estimation and inference procedures,we conduct extensive numerical studies.We also demonstrate the utility of our model using a stock dataset obtained from the Chinese A-Share stock market.展开更多
Group activities are commonly used in second language classroom in recent years mostly because they encourage students to work together,helping each other.However,it is of great importance for teachers to notice the g...Group activities are commonly used in second language classroom in recent years mostly because they encourage students to work together,helping each other.However,it is of great importance for teachers to notice the group structures so that this class activity could play its important role in the classroom.展开更多
Based on the long period digital surface wave data recorded by 11 CDSN stations and 11 IRIS stations, the dispersion curves of the group velocities of fundamental mode Rayleigh waves along 647 paths, with the periods ...Based on the long period digital surface wave data recorded by 11 CDSN stations and 11 IRIS stations, the dispersion curves of the group velocities of fundamental mode Rayleigh waves along 647 paths, with the periods from 10 s to 92 s, were measured by multi-filter. Their distribution at 25 central periods within the region of 18((54(N, 70(~140(E was inverted by Dimtar-Yanovskaya method. Within the period from 10 s to 15.9 s, the group velocity distribution is laterally inhomogeneous and is closely related to geotectonic units, with two low velocity zones located in the Tarim basin and the East China Sea and its north regions, respectively. From 21 s to 33 s, the framework of tectonic blocks is revealed. From 36.6 s to 40 s, the lithospheric subdivision of the Chinese mainland is obviously uncovered, with distinct boundaries among the South-North seismic belt, the Tibetan plateau, the North China, the South China and the Northeast China. Four cross-sections of group velocity distribution with period along 30(N, 38(N, 90(E and 120(E, are discussed, respectively, which display the basic features of the crust and upper mantle of the Chinese mainland and its neighboring regions. There are distinguished velocity differences among the different tectonic blocks. There are low-velocity-zones (LVZ) in the middle crust of the eastern Tibetan plateau, high velocity featured as stable platform in the Tarim basin and the Yangtze platform, shallow and thick low-velocity-zone in the upper mantle of the North China. The upper mantle LVZ in the East China Sea and the Japan Sea is related to the frictional heat from the subduction of the Philippine slab and the strong extension since the Himalayan orogenic period.展开更多
Pore distribution and micro pore-throat structure characteristics are significant for tight oil reservoir evaluation, but their relationship remains unclear. This paper selects the tight sandstone reservoir of the Cha...Pore distribution and micro pore-throat structure characteristics are significant for tight oil reservoir evaluation, but their relationship remains unclear. This paper selects the tight sandstone reservoir of the Chang 7 member of the Xin’anbian Block in the Ordos Basin as the research object and analyzes the pore size distribution and micro pore-throat structure using field emission scanning electron microscopy(FE-SEM), high-pressure mercury injection(HPMI), highpressure mercury injection, and nuclear magnetic resonance(NMR) analyses. The study finds that:(1) Based on the pore size distribution, the tight sandstone reservoir is characterized by three main patterns with different peak amplitudes. The former peak corresponds to the nanopore scale, and the latter peak corresponds to the micropore scale. Then, the tight sandstone reservoir is categorized into three types: type 1 reservoir contains more nanopores with a nanopore-to-micropore volume ratio of 82:18;type 2 reservoir has a nanopore-to-micropore volume ratio of 47:53;and type 3 reservoir contains more micropores with a nanopore-to-micropore volume ratio of 35:65.(2) Affected by the pore size distribution, the throat radius distributions of different reservoir types are notably offset. The type 1 reservoir throat radius distribution curve is weakly unimodal, with a relatively dispersed distribution and peak ranging from 0.01 μm to 0.025 μm. The type 2 reservoir’s throat radius distribution curve is single-peaked with a wide distribution range and peak from 0.1 μm to 0.25 μm. The type 3 reservoir’s throat radius distribution curve is single-peaked with a relatively narrow distribution and peak from 0.1 μm to 0.25 μm. With increasing micropore volume, pore-throat structure characteristics gradually improve.(3) The correlation between micropore permeability and porosity exceeds that of nanopores, indicating that the development of micropores notably influences the seepage capacity. In the type 1 reservoir, only the mean radius and effective porosity have suitable correlations with the nanopore and micropore porosities. The pore-throat structure parameters of the type 2 and 3 reservoirs have reasonable correlations with the nanopore and micropore porosities, indicating that the development of these types of reservoirs is affected by the pore size distribution. This study is of great significance for evaluating lacustrine tight sandstone reservoirs in China. The research results can provide guidance for evaluating tight sandstone reservoirs in other regions based on pore size distribution.展开更多
Background:This study examined the determinants of loan repayment among microcredit finance group members in Delta State,Nigeria.Methods:To capture the determinants of loan repayment in the study area,a total of 48 mi...Background:This study examined the determinants of loan repayment among microcredit finance group members in Delta State,Nigeria.Methods:To capture the determinants of loan repayment in the study area,a total of 48 microcredit groups and 300 microcredit group members were randomly selected through a multi-stage random sampling technique.The study data was collected by questionnaire.Statistical tools such as simple descriptive statistics(table,frequency,percentage and mean)and a multiple regression analysis were used to examine the data.Results:The results indicate that females form a greater proportion of the study area microcredit group members at 70%,moreover 73%of the respondents have a household size of between 6 to 10 persons.These findings revealed that the groups had a mean 8 years of existence with a mean membership size of 13 persons.Further,an average interest rate of 40 percent per annum was charged on loans,with mean loan duration of 6 months.The regression’s result demonstrated that the determinants of the group member’s loan repayment included the group member’s age,household size,house income,and educational level,the amount of credit received,length of stay in their locality,distance to the credit source,supervision and disbursement lag.Conclusion:Therefore it was suggested that the various agricultural microcredit finance groups should carefully examine the significant determinants of loan repayment for the approach’s viability and sustainability and for optimum repayment performance.展开更多
<正> This article considers the coset structure of spin group via analyzing the expression of its representation.One example is also given to take a closer look at what the coset and the subgroup are.
This paper describes a shake table test study on the seismic response of low-cap pile groups and a bridge structure in liquefiable ground.The soil profile,contained in a large-scale laminar shear box,consisted of a ho...This paper describes a shake table test study on the seismic response of low-cap pile groups and a bridge structure in liquefiable ground.The soil profile,contained in a large-scale laminar shear box,consisted of a horizontally saturated sand layer overlaid with a silty clay layer,with the simulated low-cap pile groups embedded.The container was excited in three E1 Centra earthquake events of different levels.Test results indicate that excessive pore pressure(EPP) during slight shaking only slightly accumulated,and the accumulation mainly occurred during strong shaking.The EPP was gradually enhanced as the amplitude and duration of the input acceleration increased.The acceleration response of the sand was remarkably influenced by soil liquefaction.As soil liquefaction occurred,the peak sand displacement gradually lagged behind the input acceleration;meanwhile,the sand displacement exhibited an increasing effect on the bending moment of the pile,and acceleration responses of the pile and the sand layer gradually changed from decreasing to increasing in the vertical direction from the bottom to the top.A jump variation of the bending moment on the pile was observed near the soil interface in all three input earthquake events.It is thought that the shake table tests could provide the groundwork for further seismic performance studies of low-cap pile groups used in bridges located on liquefiable groun.展开更多
By using solvothermal method, two new main group metal coordination polymers based on 2,5-furandicarboxylic acid(H2FDA) ligand, [Sr2(FDA)2(H2O)5]n(1) and [Ba4(FDA)4(H2O)10]n(2), were produced and characterized by sing...By using solvothermal method, two new main group metal coordination polymers based on 2,5-furandicarboxylic acid(H2FDA) ligand, [Sr2(FDA)2(H2O)5]n(1) and [Ba4(FDA)4(H2O)10]n(2), were produced and characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR, and powder X-ray diffraction. Compound 1 crystallizes in monoclinic, space group C2/c with a = 13.454(3), b = 13.426(3), c = 20.166(4), β = 107.06(3)°, V = 3482.4(13) 3, Dc = 2.188 g/cm3, C12H14Sr2O15, Mr = 573.47, F(000) = 2256, μ(Mo Kα)= 6.21 mm–1, Z = 8, R = 0.0522 and w R = 0.1229 for 2493 observed reflections(I > 2σ(I)), and R = 0.0689 and w R = 0.1324 for all data. Compound 2 crystallizes in triclinic, space group P1 with a = 6.8382(14), b = 10.932(2), c = 25.571(5), α = 94.64(3), β = 95.41(3), γ = 107.83(3)o, V = 1799.4(6) 3, Dc = 2.484 g/cm3, C24H28Ba4O30, Mr = 1345.82, F(000) = 1272, μ(Mo Kα) = 4.43 mm–1, Z = 2, R = 0.0485 and w R = 0.0906 for 5020 observed reflections(I > 2σ(I)), and R = 0.0706 and w R = 0.0991 for all data. In 1, the trinuclear clusters Sr3 are connected with adjacent four clusters by a carboxylate group to produce a two-dimensional(2D) sheet, which is extended by a FDA-based pillar into a 3D framework. In 2, neighbouring trinuclear clusters Ba3 are linked through two-O–C–O- of FDA2-ligands to form one-dimensional(1D) chains, which are connected by a FDA-based pillar to construct a 2D framework. The thermal stabilities of 1 and 2 are also investigated.展开更多
Molecular management is a promising technology to face challenges in the refining industry, such as more stringent requirements for product oil and heavier crude oil, and to maximize the value of every molecule in pet...Molecular management is a promising technology to face challenges in the refining industry, such as more stringent requirements for product oil and heavier crude oil, and to maximize the value of every molecule in petroleum fractions. To achieve molecular management in refining processes, a novel model that is based on structure oriented lumping(SOL) and group contribution(GC) methods was proposed in this study. SOL method was applied to describe a petroleum fraction with structural increments, and GC method aimed to estimate molecular properties. The latter was achieved by associating rules between SOL structural increments and GC structures. A three-step reconstruction algorithm was developed to build a representative set of molecules from partial analytical data. First, structural distribution parameters were optimized with several properties. Then, a molecular library was created by using the optimized parameters. In the final step, maximum information entropy(MIE) method was applied to obtain a molecular fraction. Two industrial samples were used to validate the method, and the simulation results of the feedstock properties agreed well with the experimental data.展开更多
The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the str...The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the structure factors are retrieved from the fcf, and such simulated data are used in the revision of the space groups of several incorrectly-refined crystal structures. Two cases, a P1 to P1 revision and a chemically-incorrect structure that is refined in a correct space group, are discussed.展开更多
As a novel type of foundation in beach and shallow sea, the bucket structure is especially suitable for complex conditions such as soft clay ground and the worse types of sea environments. In this paper, the bearing c...As a novel type of foundation in beach and shallow sea, the bucket structure is especially suitable for complex conditions such as soft clay ground and the worse types of sea environments. In this paper, the bearing capacity of a multi-bucket structure is studied by experiments with a single bucket and four-bucket foundation in a saturated sand layer. Based on the experimental data and numerical analysis results, the bearing capacity behavior and the bucket group effect are compared and analyzed. Furthermore, some influential factors, such as the soil type, the ratio of length to diameter L/D, the ratio of the bucket spacing to the bucket diameter S/D, and the bucket number are introduced and their effects on the multi-bucket structural capacity are investigated. The vertical static capacity adjustment factor is introduced to evaluate the bucket group effects of the multi-bucket foundation.展开更多
Cast thin section observation, scanning electron microscopy(SEM), high-pressure mercury injection(HPMI), and nuclear magnetic resonance(NMR) were used to examine the microstructure of tight carbonate reservoirs in the...Cast thin section observation, scanning electron microscopy(SEM), high-pressure mercury injection(HPMI), and nuclear magnetic resonance(NMR) were used to examine the microstructure of tight carbonate reservoirs in the Lower Jurassic Da’anzhai Member, the central Sichuan Basin. The pore space in the Da’anzhai Member is classified into 2 types and 17 subtypes, with nano-scale pore throats of ‘O’, ‘S’, ‘Z’, and ‘I’ shapes. Poorly sorted pore throats vary greatly in diameter;thus, it is difficult for fluid flow to pass through these pore throats. There are three classes of pore throats in carbonate reservoirs, i.e. isolated pores, pores coexisting with fractures, and large pores and fractures. Isolated pores may provide some pore space, but the permeability is low. Pores and fractures coexisting in the reservoir may have a great impact on porosity and permeability;they are the major pore space in the reservoir. Large pores and fractures have a great impact on reservoir properties, but they only account for a limited proportion of total pore space. The microstructure of Da’anzhai reservoirs, which dominates fluid mobility, is dependent on sedimentary environment, diagenesis, and tectonic process. Pore structure is related to sedimentary environment. The occurrence of microfractures, which may improve reservoir properties, is dependent on tectonic process. Diageneses are of utmost importance to pore evolution, cementation and growth of minerals have played an important role in destroying reservoir microstructure.展开更多
Haitaite-(La),(La,Ce)(U^(4+),U6^(+),Fe^(2+))(Fe^(3+),Al)2(Ti,Fe^(2+),Fe^(3+))18O38,is a new member of the crichtonite group.It is named after the Haita Village in the Miyi County of Sichuan Province,China,where the mi...Haitaite-(La),(La,Ce)(U^(4+),U6^(+),Fe^(2+))(Fe^(3+),Al)2(Ti,Fe^(2+),Fe^(3+))18O38,is a new member of the crichtonite group.It is named after the Haita Village in the Miyi County of Sichuan Province,China,where the mineral was discovered.The mineral occurs as black opaque centimeter-sized aggregates in the external contact zone between the Neoproterozoic(~800 Ma)alkali feldspar granite and the Mesoproterozoic(~1700 Ma)micaschist.In the studied sample,haitaite-(La)is associated with other minerals,including ilmenite,magnetite,rutile,zircon,brannerite and uraninite.The new mineral is a black,metallic phase and has a Mohs hardness of 6,with a density of 4.99 g/cm3(calculated)and 5.03 g/cm^(3)(measured).Haitaite-(La)is opaque in transmitted light and grayish-white under reflected light,with a reflectivity between 22.5%and 16.42%in the 400–700 nm band(SiC,in the air).The compositions of the mineral were measured by EPMA,the U4+/U6+ratio was determined by X-ray photoelectron spectroscopy and the Fe^(2+)/Fe^(3+)ratio was determined by Mössbauer spectroscopy.Haitaite-(La)is trigonal,belongs to R3¯and has unit-cell parameters a=10.3678(5)Å,c=20.8390(11)Å,V=1939.9(2)Å3,Z=3.The crystalline structure is composed of octahedra with 9 layers of close-packed octahedra(M1,M3,M4,M5),tetrahedra(M2)and contains large 12-coordinated M0 sites.展开更多
Key frame extraction based on sparse coding can reduce the redundancy of continuous frames and concisely express the entire video.However,how to develop a key frame extraction algorithm that can automatically extract ...Key frame extraction based on sparse coding can reduce the redundancy of continuous frames and concisely express the entire video.However,how to develop a key frame extraction algorithm that can automatically extract a few frames with a low reconstruction error remains a challenge.In this paper,we propose a novel model of structured sparse-codingbased key frame extraction,wherein a nonconvex group log-regularizer is used with strong sparsity and a low reconstruction error.To automatically extract key frames,a decomposition scheme is designed to separate the sparse coefficient matrix by rows.The rows enforced by the nonconvex group log-regularizer become zero or nonzero,leading to the learning of the structured sparse coefficient matrix.To solve the nonconvex problems due to the log-regularizer,the difference of convex algorithm(DCA)is employed to decompose the log-regularizer into the difference of two convex functions related to the l1 norm,which can be directly obtained through the proximal operator.Therefore,an efficient structured sparse coding algorithm with the group log-regularizer for key frame extraction is developed,which can automatically extract a few frames directly from the video to represent the entire video with a low reconstruction error.Experimental results demonstrate that the proposed algorithm can extract more accurate key frames from most Sum Me videos compared to the stateof-the-art methods.Furthermore,the proposed algorithm can obtain a higher compression with a nearly 18% increase compared to sparse modeling representation selection(SMRS)and an 8% increase compared to SC-det on the VSUMM dataset.展开更多
Piles supporting marine structures such as jetties, relieving platforms, quay walls and fixed offshore structures are subjected to lateral loads due to berthing and mooring forces, wind, waves, storm surges and curren...Piles supporting marine structures such as jetties, relieving platforms, quay walls and fixed offshore structures are subjected to lateral loads due to berthing and mooring forces, wind, waves, storm surges and current forces. This paper presents some factors that affect the design of pile groups supporting marine structures founded in cohesionless soils. Some main aspects that should be considered in the pile group design are addressed such as pile batter angle, pile group arrangement, pile spacing, pile slenderness ratio and magnitude of lateral static loading. Numerical analyses were conducted to investigate these design aspects with and without impact of scour. Different scour depths were considered to cover the possible root causes of scour around pile groups such as waves, current and ship propeller jets. The study revealed that scour has greater impact on lateral loading of pile groups compared to its impact on single piles. Pile groups with side-by-side arrangement exposed to scour are more critical than single piles and piles groups with tandem arrangement due to the combined effect of scour and pile-soil-pile interaction. It is also concluded that scour protection is not always required. More attention and considerations should be given to scour protection around piles especially if the piles are closely spaced, arranged side-by-side and if slenderness ratio is less than 12.5.展开更多
Based on the qualitative study of microscopic reservoir features using core analysis,cast and fluorescence thin sections inspection,scanning electron microscope(SEM)and field emission scanning electron microscope(FESE...Based on the qualitative study of microscopic reservoir features using core analysis,cast and fluorescence thin sections inspection,scanning electron microscope(SEM)and field emission scanning electron microscope(FESEM)and quantitative examination of pore size and geometry using mercury injection,nano-CT and nitrogen adsorption,reservoir rock of Da’anzhai Member were divided into 9 types,while storage spaces were divided into 4 types and 14 sub-types.The study shows that sparry coquina is the most promising reservoir type.Pores that smaller than 1μm in diameter contribute 91.27%of storage space volume.Most of them exhibit slot-like geometry with good connectivity.By building up storage space models,it was revealed that micron scale storage spaces mainly composed of fractures and nanometer scale pores and fractures form multi-scale dual porosity system.Low resource abundance,small single well controlled reserve,and low production are related to the nano-scale pore space in Da’anzhai Memer,whereas the dual-porosity system composed of pores and fractures makes for long-term oil yield.Due to the existence of abundant slot-like pore space and fractures,economic tight oil production was achieved without stimulations.展开更多
The Group of Nuclear Structure Research at IMP has devoted much effort to the lifetime measurements of lowlying excited states via ?? fast timing coincidence. Two experiments were performed in 2015 at the radioactive ...The Group of Nuclear Structure Research at IMP has devoted much effort to the lifetime measurements of lowlying excited states via ?? fast timing coincidence. Two experiments were performed in 2015 at the radioactive beam line RIBLL[1] and gas-filled recoil separator SHANS[2].展开更多
A subgroup H of a group G is said to be primitive if it is a proper subgroup of the intersection of all subgroups of G containing H as its proper subgroup. The purpose of this note is to go further into the influence ...A subgroup H of a group G is said to be primitive if it is a proper subgroup of the intersection of all subgroups of G containing H as its proper subgroup. The purpose of this note is to go further into the influence of primitive subgroups on the structure of finite groups. Some new results are obtained.展开更多
A novel D-π-A type α-cyanostilbenzene derivative,(Z)-2-(4-aminophenyl)-3-(4-bromophenyl)-acrylonitrile(ABAN), was designed and synthesized, by introducing an electrondonating amino group and a heavy atom. The struct...A novel D-π-A type α-cyanostilbenzene derivative,(Z)-2-(4-aminophenyl)-3-(4-bromophenyl)-acrylonitrile(ABAN), was designed and synthesized, by introducing an electrondonating amino group and a heavy atom. The structure of ABAN was confirmed by FT-IR, 1H NMR, 13 C NMR spectra and single-crystal X-ray diffraction analysis. The ABAN is of orthorhombic system, space group P212121, with a = 8.6100(14), b = 9.6923(16), c = 15.705(3) ?, Mr = 299.17, V = 1310.6(4) ?3, Z = 4, Dc = 1.516 g/cm-3, μ = 3.119 mm-1, F(000) = 600, Rint = 0.038, R(I > 2σ(I)) = 0.0276, w R(I > 2σ(I)) = 0.0628, R(all data) = 0.0324, wR(all data) = 0.0646, completeness to theta = 25.00 was 99.8% and GOOF = 1.04. In the crystal structure, ABAN molecules were linked with each other through intermolecular C–H···π interactions and N–H···N hydrogen bonds, by which the 1D chain, 2D plane and 3D stacking structures were constructed. The photophysical properties and calculation results confirmed that ABAN possessed an intramolecular charge transfer(ICT) process. ABAN could be applied into the optoelectronic material field due to good solvent-tuned photophysical properties and highly thermal stability.展开更多
The technique for order performance by similarity to ideal solution (TOPSIS) is one of the major techniques in dealing with multiple criteria decision making (MCDM) problems, and the belief structure (BS) model has be...The technique for order performance by similarity to ideal solution (TOPSIS) is one of the major techniques in dealing with multiple criteria decision making (MCDM) problems, and the belief structure (BS) model has been used successfully for uncertain MCDM with incompleteness, impreciseness or ignorance. In this paper, the TOPSIS method with BS model is proposed to solve group belief MCDM problems. Firstly, the group belief MCDM problem is structured as a belief decision matrix in which the judgments of each decision maker are described as BS models, and then the evidential reasoning approach is used for aggregating the multiple decision makers judgments. Subsequently, the positive and negative ideal belief solutions are defined with the principle of TOPSIS. To measure the separation from ideal solutions, the concept and algorithm of belief distance measure are defined, which can be used for comparing the difference between BS models. Finally, the relative closeness and ranking index are calculated for ranking the alternatives. A numerical example is given to illustrate the proposed method.展开更多
基金Supported by National Natural Science Foundation of China(72222009,71991472)。
文摘Network autoregression and factor model are effective methods for modeling network time series data.In this study,we propose a network autoregression model with a factor structure that incorporates a latent group structure to address nodal heterogeneity within the network.An iterative algorithm is employed to minimize a least-squares objective function,allowing for simultaneous estimation of both the parameters and the group structure.To determine the unknown number of groups and factors,a PIC criterion is introduced.Additionally,statistical inference of the estimated parameters is presented.To assess the validity of the proposed estimation and inference procedures,we conduct extensive numerical studies.We also demonstrate the utility of our model using a stock dataset obtained from the Chinese A-Share stock market.
文摘Group activities are commonly used in second language classroom in recent years mostly because they encourage students to work together,helping each other.However,it is of great importance for teachers to notice the group structures so that this class activity could play its important role in the classroom.
基金Climb Project Continental Dynamics of East Asia and Joint Seismological Science Foundation of China (9507413).
文摘Based on the long period digital surface wave data recorded by 11 CDSN stations and 11 IRIS stations, the dispersion curves of the group velocities of fundamental mode Rayleigh waves along 647 paths, with the periods from 10 s to 92 s, were measured by multi-filter. Their distribution at 25 central periods within the region of 18((54(N, 70(~140(E was inverted by Dimtar-Yanovskaya method. Within the period from 10 s to 15.9 s, the group velocity distribution is laterally inhomogeneous and is closely related to geotectonic units, with two low velocity zones located in the Tarim basin and the East China Sea and its north regions, respectively. From 21 s to 33 s, the framework of tectonic blocks is revealed. From 36.6 s to 40 s, the lithospheric subdivision of the Chinese mainland is obviously uncovered, with distinct boundaries among the South-North seismic belt, the Tibetan plateau, the North China, the South China and the Northeast China. Four cross-sections of group velocity distribution with period along 30(N, 38(N, 90(E and 120(E, are discussed, respectively, which display the basic features of the crust and upper mantle of the Chinese mainland and its neighboring regions. There are distinguished velocity differences among the different tectonic blocks. There are low-velocity-zones (LVZ) in the middle crust of the eastern Tibetan plateau, high velocity featured as stable platform in the Tarim basin and the Yangtze platform, shallow and thick low-velocity-zone in the upper mantle of the North China. The upper mantle LVZ in the East China Sea and the Japan Sea is related to the frictional heat from the subduction of the Philippine slab and the strong extension since the Himalayan orogenic period.
基金the National Natural Science Foundation of China(Grant No.41625009)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA14010404)The authors also extend their thanks to the editors and reviewers for their positive and constructive comments and suggestions.
文摘Pore distribution and micro pore-throat structure characteristics are significant for tight oil reservoir evaluation, but their relationship remains unclear. This paper selects the tight sandstone reservoir of the Chang 7 member of the Xin’anbian Block in the Ordos Basin as the research object and analyzes the pore size distribution and micro pore-throat structure using field emission scanning electron microscopy(FE-SEM), high-pressure mercury injection(HPMI), highpressure mercury injection, and nuclear magnetic resonance(NMR) analyses. The study finds that:(1) Based on the pore size distribution, the tight sandstone reservoir is characterized by three main patterns with different peak amplitudes. The former peak corresponds to the nanopore scale, and the latter peak corresponds to the micropore scale. Then, the tight sandstone reservoir is categorized into three types: type 1 reservoir contains more nanopores with a nanopore-to-micropore volume ratio of 82:18;type 2 reservoir has a nanopore-to-micropore volume ratio of 47:53;and type 3 reservoir contains more micropores with a nanopore-to-micropore volume ratio of 35:65.(2) Affected by the pore size distribution, the throat radius distributions of different reservoir types are notably offset. The type 1 reservoir throat radius distribution curve is weakly unimodal, with a relatively dispersed distribution and peak ranging from 0.01 μm to 0.025 μm. The type 2 reservoir’s throat radius distribution curve is single-peaked with a wide distribution range and peak from 0.1 μm to 0.25 μm. The type 3 reservoir’s throat radius distribution curve is single-peaked with a relatively narrow distribution and peak from 0.1 μm to 0.25 μm. With increasing micropore volume, pore-throat structure characteristics gradually improve.(3) The correlation between micropore permeability and porosity exceeds that of nanopores, indicating that the development of micropores notably influences the seepage capacity. In the type 1 reservoir, only the mean radius and effective porosity have suitable correlations with the nanopore and micropore porosities. The pore-throat structure parameters of the type 2 and 3 reservoirs have reasonable correlations with the nanopore and micropore porosities, indicating that the development of these types of reservoirs is affected by the pore size distribution. This study is of great significance for evaluating lacustrine tight sandstone reservoirs in China. The research results can provide guidance for evaluating tight sandstone reservoirs in other regions based on pore size distribution.
文摘Background:This study examined the determinants of loan repayment among microcredit finance group members in Delta State,Nigeria.Methods:To capture the determinants of loan repayment in the study area,a total of 48 microcredit groups and 300 microcredit group members were randomly selected through a multi-stage random sampling technique.The study data was collected by questionnaire.Statistical tools such as simple descriptive statistics(table,frequency,percentage and mean)and a multiple regression analysis were used to examine the data.Results:The results indicate that females form a greater proportion of the study area microcredit group members at 70%,moreover 73%of the respondents have a household size of between 6 to 10 persons.These findings revealed that the groups had a mean 8 years of existence with a mean membership size of 13 persons.Further,an average interest rate of 40 percent per annum was charged on loans,with mean loan duration of 6 months.The regression’s result demonstrated that the determinants of the group member’s loan repayment included the group member’s age,household size,house income,and educational level,the amount of credit received,length of stay in their locality,distance to the credit source,supervision and disbursement lag.Conclusion:Therefore it was suggested that the various agricultural microcredit finance groups should carefully examine the significant determinants of loan repayment for the approach’s viability and sustainability and for optimum repayment performance.
基金The project supported by National Key Basic Research Project of China under Grant No. 2004CB318000 and National Natural Science Foundation of China under Grant Nos. 10375038 and 90403018. The authors would like to express their thanks to Moningside Center, The Chinese Academy of Sciences. Part of the work was done when we were joining the Workshop on Mathematical Physics there.Acknowledgments We are deeply grateful to Profs. Qi-Keng Lu, Han-Ying Guo, and Shi-Kun Wang for their valuable discussions, which essentially stimulate us to write down this work.
文摘<正> This article considers the coset structure of spin group via analyzing the expression of its representation.One example is also given to take a closer look at what the coset and the subgroup are.
基金Major Research Plan of National Natural Science Foundation of China Under Grant No.90815009National Natural Science Foundation of China Under Grant No.50378031 and 50178027Western Transport Construction Technology Projects Under Grant No.2009318000100
文摘This paper describes a shake table test study on the seismic response of low-cap pile groups and a bridge structure in liquefiable ground.The soil profile,contained in a large-scale laminar shear box,consisted of a horizontally saturated sand layer overlaid with a silty clay layer,with the simulated low-cap pile groups embedded.The container was excited in three E1 Centra earthquake events of different levels.Test results indicate that excessive pore pressure(EPP) during slight shaking only slightly accumulated,and the accumulation mainly occurred during strong shaking.The EPP was gradually enhanced as the amplitude and duration of the input acceleration increased.The acceleration response of the sand was remarkably influenced by soil liquefaction.As soil liquefaction occurred,the peak sand displacement gradually lagged behind the input acceleration;meanwhile,the sand displacement exhibited an increasing effect on the bending moment of the pile,and acceleration responses of the pile and the sand layer gradually changed from decreasing to increasing in the vertical direction from the bottom to the top.A jump variation of the bending moment on the pile was observed near the soil interface in all three input earthquake events.It is thought that the shake table tests could provide the groundwork for further seismic performance studies of low-cap pile groups used in bridges located on liquefiable groun.
基金supported by URT program of Beijing Institute of Petrochemical Technology(2015J00058 and 2015J00056)
文摘By using solvothermal method, two new main group metal coordination polymers based on 2,5-furandicarboxylic acid(H2FDA) ligand, [Sr2(FDA)2(H2O)5]n(1) and [Ba4(FDA)4(H2O)10]n(2), were produced and characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR, and powder X-ray diffraction. Compound 1 crystallizes in monoclinic, space group C2/c with a = 13.454(3), b = 13.426(3), c = 20.166(4), β = 107.06(3)°, V = 3482.4(13) 3, Dc = 2.188 g/cm3, C12H14Sr2O15, Mr = 573.47, F(000) = 2256, μ(Mo Kα)= 6.21 mm–1, Z = 8, R = 0.0522 and w R = 0.1229 for 2493 observed reflections(I > 2σ(I)), and R = 0.0689 and w R = 0.1324 for all data. Compound 2 crystallizes in triclinic, space group P1 with a = 6.8382(14), b = 10.932(2), c = 25.571(5), α = 94.64(3), β = 95.41(3), γ = 107.83(3)o, V = 1799.4(6) 3, Dc = 2.484 g/cm3, C24H28Ba4O30, Mr = 1345.82, F(000) = 1272, μ(Mo Kα) = 4.43 mm–1, Z = 2, R = 0.0485 and w R = 0.0906 for 5020 observed reflections(I > 2σ(I)), and R = 0.0706 and w R = 0.0991 for all data. In 1, the trinuclear clusters Sr3 are connected with adjacent four clusters by a carboxylate group to produce a two-dimensional(2D) sheet, which is extended by a FDA-based pillar into a 3D framework. In 2, neighbouring trinuclear clusters Ba3 are linked through two-O–C–O- of FDA2-ligands to form one-dimensional(1D) chains, which are connected by a FDA-based pillar to construct a 2D framework. The thermal stabilities of 1 and 2 are also investigated.
基金Supported by the National Natural Science Foundation of China(U1462206)
文摘Molecular management is a promising technology to face challenges in the refining industry, such as more stringent requirements for product oil and heavier crude oil, and to maximize the value of every molecule in petroleum fractions. To achieve molecular management in refining processes, a novel model that is based on structure oriented lumping(SOL) and group contribution(GC) methods was proposed in this study. SOL method was applied to describe a petroleum fraction with structural increments, and GC method aimed to estimate molecular properties. The latter was achieved by associating rules between SOL structural increments and GC structures. A three-step reconstruction algorithm was developed to build a representative set of molecules from partial analytical data. First, structural distribution parameters were optimized with several properties. Then, a molecular library was created by using the optimized parameters. In the final step, maximum information entropy(MIE) method was applied to obtain a molecular fraction. Two industrial samples were used to validate the method, and the simulation results of the feedstock properties agreed well with the experimental data.
文摘The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the structure factors are retrieved from the fcf, and such simulated data are used in the revision of the space groups of several incorrectly-refined crystal structures. Two cases, a P1 to P1 revision and a chemically-incorrect structure that is refined in a correct space group, are discussed.
文摘As a novel type of foundation in beach and shallow sea, the bucket structure is especially suitable for complex conditions such as soft clay ground and the worse types of sea environments. In this paper, the bearing capacity of a multi-bucket structure is studied by experiments with a single bucket and four-bucket foundation in a saturated sand layer. Based on the experimental data and numerical analysis results, the bearing capacity behavior and the bucket group effect are compared and analyzed. Furthermore, some influential factors, such as the soil type, the ratio of length to diameter L/D, the ratio of the bucket spacing to the bucket diameter S/D, and the bucket number are introduced and their effects on the multi-bucket structural capacity are investigated. The vertical static capacity adjustment factor is introduced to evaluate the bucket group effects of the multi-bucket foundation.
基金the China National Science and Technology Major Project(2016ZX05046-003,2017ZX05001001-002)Petro-China Innovation Foundation(2018D-5007-0105)Scientific Research Starting Project of SWPU(2017QHZ005).
文摘Cast thin section observation, scanning electron microscopy(SEM), high-pressure mercury injection(HPMI), and nuclear magnetic resonance(NMR) were used to examine the microstructure of tight carbonate reservoirs in the Lower Jurassic Da’anzhai Member, the central Sichuan Basin. The pore space in the Da’anzhai Member is classified into 2 types and 17 subtypes, with nano-scale pore throats of ‘O’, ‘S’, ‘Z’, and ‘I’ shapes. Poorly sorted pore throats vary greatly in diameter;thus, it is difficult for fluid flow to pass through these pore throats. There are three classes of pore throats in carbonate reservoirs, i.e. isolated pores, pores coexisting with fractures, and large pores and fractures. Isolated pores may provide some pore space, but the permeability is low. Pores and fractures coexisting in the reservoir may have a great impact on porosity and permeability;they are the major pore space in the reservoir. Large pores and fractures have a great impact on reservoir properties, but they only account for a limited proportion of total pore space. The microstructure of Da’anzhai reservoirs, which dominates fluid mobility, is dependent on sedimentary environment, diagenesis, and tectonic process. Pore structure is related to sedimentary environment. The occurrence of microfractures, which may improve reservoir properties, is dependent on tectonic process. Diageneses are of utmost importance to pore evolution, cementation and growth of minerals have played an important role in destroying reservoir microstructure.
基金supported by China Nuclear Geology(Grant No.202137-3)the National Natural Science Foundation of China(Grant No.42002044)the CNNC Science Fund for Talented Young Scholars(Grant No.QNYC2020-2).
文摘Haitaite-(La),(La,Ce)(U^(4+),U6^(+),Fe^(2+))(Fe^(3+),Al)2(Ti,Fe^(2+),Fe^(3+))18O38,is a new member of the crichtonite group.It is named after the Haita Village in the Miyi County of Sichuan Province,China,where the mineral was discovered.The mineral occurs as black opaque centimeter-sized aggregates in the external contact zone between the Neoproterozoic(~800 Ma)alkali feldspar granite and the Mesoproterozoic(~1700 Ma)micaschist.In the studied sample,haitaite-(La)is associated with other minerals,including ilmenite,magnetite,rutile,zircon,brannerite and uraninite.The new mineral is a black,metallic phase and has a Mohs hardness of 6,with a density of 4.99 g/cm3(calculated)and 5.03 g/cm^(3)(measured).Haitaite-(La)is opaque in transmitted light and grayish-white under reflected light,with a reflectivity between 22.5%and 16.42%in the 400–700 nm band(SiC,in the air).The compositions of the mineral were measured by EPMA,the U4+/U6+ratio was determined by X-ray photoelectron spectroscopy and the Fe^(2+)/Fe^(3+)ratio was determined by Mössbauer spectroscopy.Haitaite-(La)is trigonal,belongs to R3¯and has unit-cell parameters a=10.3678(5)Å,c=20.8390(11)Å,V=1939.9(2)Å3,Z=3.The crystalline structure is composed of octahedra with 9 layers of close-packed octahedra(M1,M3,M4,M5),tetrahedra(M2)and contains large 12-coordinated M0 sites.
基金supported in part by the National Natural Science Foundation of China(61903090,61727810,62073086,62076077,61803096,U191140003)the Guangzhou Science and Technology Program Project(202002030289)Japan Society for the Promotion of Science(JSPS)KAKENHI(18K18083)。
文摘Key frame extraction based on sparse coding can reduce the redundancy of continuous frames and concisely express the entire video.However,how to develop a key frame extraction algorithm that can automatically extract a few frames with a low reconstruction error remains a challenge.In this paper,we propose a novel model of structured sparse-codingbased key frame extraction,wherein a nonconvex group log-regularizer is used with strong sparsity and a low reconstruction error.To automatically extract key frames,a decomposition scheme is designed to separate the sparse coefficient matrix by rows.The rows enforced by the nonconvex group log-regularizer become zero or nonzero,leading to the learning of the structured sparse coefficient matrix.To solve the nonconvex problems due to the log-regularizer,the difference of convex algorithm(DCA)is employed to decompose the log-regularizer into the difference of two convex functions related to the l1 norm,which can be directly obtained through the proximal operator.Therefore,an efficient structured sparse coding algorithm with the group log-regularizer for key frame extraction is developed,which can automatically extract a few frames directly from the video to represent the entire video with a low reconstruction error.Experimental results demonstrate that the proposed algorithm can extract more accurate key frames from most Sum Me videos compared to the stateof-the-art methods.Furthermore,the proposed algorithm can obtain a higher compression with a nearly 18% increase compared to sparse modeling representation selection(SMRS)and an 8% increase compared to SC-det on the VSUMM dataset.
文摘Piles supporting marine structures such as jetties, relieving platforms, quay walls and fixed offshore structures are subjected to lateral loads due to berthing and mooring forces, wind, waves, storm surges and current forces. This paper presents some factors that affect the design of pile groups supporting marine structures founded in cohesionless soils. Some main aspects that should be considered in the pile group design are addressed such as pile batter angle, pile group arrangement, pile spacing, pile slenderness ratio and magnitude of lateral static loading. Numerical analyses were conducted to investigate these design aspects with and without impact of scour. Different scour depths were considered to cover the possible root causes of scour around pile groups such as waves, current and ship propeller jets. The study revealed that scour has greater impact on lateral loading of pile groups compared to its impact on single piles. Pile groups with side-by-side arrangement exposed to scour are more critical than single piles and piles groups with tandem arrangement due to the combined effect of scour and pile-soil-pile interaction. It is also concluded that scour protection is not always required. More attention and considerations should be given to scour protection around piles especially if the piles are closely spaced, arranged side-by-side and if slenderness ratio is less than 12.5.
基金Supported by the China National Science and Technology Major Project(2016ZX05046-001)
文摘Based on the qualitative study of microscopic reservoir features using core analysis,cast and fluorescence thin sections inspection,scanning electron microscope(SEM)and field emission scanning electron microscope(FESEM)and quantitative examination of pore size and geometry using mercury injection,nano-CT and nitrogen adsorption,reservoir rock of Da’anzhai Member were divided into 9 types,while storage spaces were divided into 4 types and 14 sub-types.The study shows that sparry coquina is the most promising reservoir type.Pores that smaller than 1μm in diameter contribute 91.27%of storage space volume.Most of them exhibit slot-like geometry with good connectivity.By building up storage space models,it was revealed that micron scale storage spaces mainly composed of fractures and nanometer scale pores and fractures form multi-scale dual porosity system.Low resource abundance,small single well controlled reserve,and low production are related to the nano-scale pore space in Da’anzhai Memer,whereas the dual-porosity system composed of pores and fractures makes for long-term oil yield.Due to the existence of abundant slot-like pore space and fractures,economic tight oil production was achieved without stimulations.
文摘The Group of Nuclear Structure Research at IMP has devoted much effort to the lifetime measurements of lowlying excited states via ?? fast timing coincidence. Two experiments were performed in 2015 at the radioactive beam line RIBLL[1] and gas-filled recoil separator SHANS[2].
文摘A subgroup H of a group G is said to be primitive if it is a proper subgroup of the intersection of all subgroups of G containing H as its proper subgroup. The purpose of this note is to go further into the influence of primitive subgroups on the structure of finite groups. Some new results are obtained.
基金Supported by the Educational Commission of Anhui Province(KJ2014ZD02)the National Natural Science Foundation of China(51432001)
文摘A novel D-π-A type α-cyanostilbenzene derivative,(Z)-2-(4-aminophenyl)-3-(4-bromophenyl)-acrylonitrile(ABAN), was designed and synthesized, by introducing an electrondonating amino group and a heavy atom. The structure of ABAN was confirmed by FT-IR, 1H NMR, 13 C NMR spectra and single-crystal X-ray diffraction analysis. The ABAN is of orthorhombic system, space group P212121, with a = 8.6100(14), b = 9.6923(16), c = 15.705(3) ?, Mr = 299.17, V = 1310.6(4) ?3, Z = 4, Dc = 1.516 g/cm-3, μ = 3.119 mm-1, F(000) = 600, Rint = 0.038, R(I > 2σ(I)) = 0.0276, w R(I > 2σ(I)) = 0.0628, R(all data) = 0.0324, wR(all data) = 0.0646, completeness to theta = 25.00 was 99.8% and GOOF = 1.04. In the crystal structure, ABAN molecules were linked with each other through intermolecular C–H···π interactions and N–H···N hydrogen bonds, by which the 1D chain, 2D plane and 3D stacking structures were constructed. The photophysical properties and calculation results confirmed that ABAN possessed an intramolecular charge transfer(ICT) process. ABAN could be applied into the optoelectronic material field due to good solvent-tuned photophysical properties and highly thermal stability.
基金supported by National Natural Science Foundation of China (No.70971131, 70901074)
文摘The technique for order performance by similarity to ideal solution (TOPSIS) is one of the major techniques in dealing with multiple criteria decision making (MCDM) problems, and the belief structure (BS) model has been used successfully for uncertain MCDM with incompleteness, impreciseness or ignorance. In this paper, the TOPSIS method with BS model is proposed to solve group belief MCDM problems. Firstly, the group belief MCDM problem is structured as a belief decision matrix in which the judgments of each decision maker are described as BS models, and then the evidential reasoning approach is used for aggregating the multiple decision makers judgments. Subsequently, the positive and negative ideal belief solutions are defined with the principle of TOPSIS. To measure the separation from ideal solutions, the concept and algorithm of belief distance measure are defined, which can be used for comparing the difference between BS models. Finally, the relative closeness and ranking index are calculated for ranking the alternatives. A numerical example is given to illustrate the proposed method.
