We mapped and analyzed the microsatellites throughout 284295605 base pairs ofthe unambiguously assembled sequence scaffolds along 19 chromosomes of the haploid poplargenome.Totally,we found 150985 SSRs with repeat uni...We mapped and analyzed the microsatellites throughout 284295605 base pairs ofthe unambiguously assembled sequence scaffolds along 19 chromosomes of the haploid poplargenome.Totally,we found 150985 SSRs with repeat unit lengths between 2 and 5 bp.The establishedmicrosatellite physical map demonstrated tr at SSRs were distributed relatively evenly across thegenome of Populus.On average,These SSRs occurred every 1883 bp within the poplar genome and the SSRdensities in intergenic regions,introns,exons and UTRs were 85.4%,10.7%,2.7% and1.2%,respectively.We took di-,tri-,tetra-and pentamers as the four classes of repeat units and foundthat the density of each class of SSRs decreased with the repeat unit lengths except for thetetranucleotide repeats.It was noteworthy that the length diversification of microsatellitesequences was negatively correlated with their repeat unit length and the SSRs with shorter repeatunits gained repeats faster than the SSRs with longer repeat units.We also found that the GC contentof poplar sequence significantly correlated with densities of SSRs with uneven repeat unit lengths(tri-and penta-),but had no significant correlation with densities of SSRs with even repeat unitlengths (di-and tetra-).In poplar genome,there were evidences that the occurrence of differentmicrosatellites was under selection and the GC content in SSR sequences was found to significantlyrelate to the functional importance of microsatellites.展开更多
A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change sin...A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change since 16.7 cal. ka BP. Fossil pollen assem-blages and lithology indicate that the study area was dominated by desert. The desert had extremely arid climate and lower effec-tive moisture during 16.7–7.9 cal. ka BP, especially from 16.7 to 8.9 cal. ka BP when the lake maybe dried up. During 8.9–7.9 cal. ka BP, the environment gradually recovered in this area. It was then followed by the optimum period from 7.9 to 4.3 cal. Ka BP, when the effective moisture obviously increased. It was characterized by the typical desert-steppe/steppe vegetation and was ac-companied with several patch-birch woodlands around the lake. After that, a short but extremely arid climatic event occurred during 4.3–3.8 cal. ka BP, and the vegetation quickly changed from desert-steppe/steppe to desert. It was a relatively optimum period from 3.8 to 0.53 cal. ka BP showing typical desert-steppe/meadow-steppe landscape. Since 0.53 cal. ka BP, the climate has shown signs of deteriorating again. Furthermore, regional comparison shows that the characteristics of climatic and environmental evolution in this area were clearly different from East Asia monsoonal area during the last 16.7 cal. ka BP. It was characterized by the arid climate during the late-glacial and early Holocene, and relatively wet during the mid-late Holocene.展开更多
Salix suchowensis is an early-flowering shrub willow that provides a desirable system for studies on the basic biology of woody plants.The current reference genome of S.suchowensis was assembled with 454 sequencing re...Salix suchowensis is an early-flowering shrub willow that provides a desirable system for studies on the basic biology of woody plants.The current reference genome of S.suchowensis was assembled with 454 sequencing reads.Here,we report a chromosome-scale assembly of S.suchowensis generated by combining PacBio sequencing with Hi-C technologies.The obtained genome assemblies covered a total length of 356 Mb.The contig N50 of these assemblies was 263,908 bp,which was~65-fold higher than that reported previously.The contiguity and completeness of the genome were significantly improved.By applying Hi-C data,339.67 Mb(95.29%)of the assembled sequences were allocated to the 19 chromosomes of haploid willow.With the chromosome-scale assembly,we revealed a series of major chromosomal fissions and fusions that explain the genome divergence between the sister genera of Salix and Populus.The more complete and accurate willow reference genome obtained in this study provides a fundamental resource for studying many genetic and genomic characteristics of woody plants.展开更多
Oil, protein and starch are key chemical components of maize kernels. A population of 245 recombinant inbred lines(RILs) derived from a cross between a high-oil inbred line, By804, and a regular inbred line, B73, was ...Oil, protein and starch are key chemical components of maize kernels. A population of 245 recombinant inbred lines(RILs) derived from a cross between a high-oil inbred line, By804, and a regular inbred line, B73, was used to dissect the genetic interrelationships among oil, starch and protein content at the individual QTL level by unconditional and conditional QTL mapping. Combined phenotypic data over two years with a genetic linkage map constructed using 236 markers, nine, five and eight unconditional QTL were detected for oil, protein and starch content, respectively. Some QTL for oil, protein and starch content were clustered in the same genomic regions and the direction of their effects was consistent with the sign of their correlation. In conditional QTL mapping, 37(29/8) unconditional QTL were not detected or showed reduced effects, four QTL demonstrated similar effects under unconditional and conditional QTL mapping, and 17 additional QTL were identified by conditional QTL mapping. These results imply that there is a strong genetic relationship among oil, protein and starch content in maize kernels. The information generated in the present investigation could be helpful in marker-assisted breeding for maize varieties with desirable kernel quality traits.展开更多
Wind energy is a promising renewable energy source for a low-carbon society.This study is to develop a fully packaged vortexinduced vibration triboelectric nanogenerator(VIV-TENG)for scavenging wind energy.The VIV-TEN...Wind energy is a promising renewable energy source for a low-carbon society.This study is to develop a fully packaged vortexinduced vibration triboelectric nanogenerator(VIV-TENG)for scavenging wind energy.The VIV-TENG consists of a wind vane,internal power generation unit,an external frame,four springs,a square cylinder and a circular turntable.The internal power generation unit consists of polytetrafluoroethylene(PTFE)balls,a honeycomb frame and two copper electrodes.Different from most of the previous wind energy harvesting TENGs,the bouncing PTFE balls are fully packaged in the square cylinder.The distinct design separates the process of contact electrification from the external environment,and at the same time avoids the frictional wear of the ordinary wind energy harvesting TENGs.The corresponding VIV parameters are investigated to evaluate their influence on the vibration behaviors and the energy output.Resonant state of the VIV-TENG corresponds to the high output performance from the VIV-TENG.The distinct,robust structure ensures the full-packaged VIV-TENG can harvest wind energy from arbitrary directions and even in undesirable weather conditions.The study proposes a novel TENG configuration for harvesting wind energy and the VIV-TENG proves promising powering micro-electro-mechanical appliances.展开更多
During the past decade, significant advances have been made in refinements for regenerative therapies following human spinal cord injury （SCI）. Positive results have been achieved with different types of cells in va...During the past decade, significant advances have been made in refinements for regenerative therapies following human spinal cord injury （SCI）. Positive results have been achieved with different types of cells in various clinical studies of SCI. In this review, we summarize recently-completed clinical trials using cell- mediated regenerative therapies for human SCI, together with ongoing trials using neural stem cells. Specifically, clinical studies published in Chinese journals are included. These studies show that current transplantation therapies are relatively safe, and have provided varying degrees of neurological recovery. However, many obstacles exist, hindering the introduction of a specific clinical therapy, including complications and their causes, selection of the target population, and optimization of transplantation material. Despite these and other challenges, with the collaboration of research groups and strong support from various organizations, cell-mediated regenerative therapies will open new perspectives for SCI treatment.展开更多
The perceptual effect of the phase information in speech has been studied by auditorysubjective tests. On the condition that the phase spectrum in speech is changed while amplitudespectrum is unchanged, the tests show...The perceptual effect of the phase information in speech has been studied by auditorysubjective tests. On the condition that the phase spectrum in speech is changed while amplitudespectrum is unchanged, the tests show that: (1) If the envelop of the reconstructed speech signalis unchanged, there is indistinctive auditory perception between the original speech and thereconstructed speech; (2) The auditory perception effect of the reconstructed speech mainly lieson the amplitude of the derivative of the additive phase; (3) td is the maximum relative time shiftbetween different frequency components of the reconstructed speech signal. The speech qualityis excellent while td ＜10ms; good while 10ms＜ td ＜20ms; common while 20ms＜ td ＜35ms, andpoor while td ＞35ms.展开更多
Bi- and Y-codoped TiO2 photocatalysts were synthesized through a sol-gel method, and they were applied in the photocatalytic reduction of CO2 to formic acid under visible light irradiation. The results revealed that, ...Bi- and Y-codoped TiO2 photocatalysts were synthesized through a sol-gel method, and they were applied in the photocatalytic reduction of CO2 to formic acid under visible light irradiation. The results revealed that, after doping Bi and Y, the surface area of TiO2 was increased from 5.4 to 93.1 m2/g when the mole fractions of doping Bi and Y were 1.0% and 0.5%, respectively, and the lattice structures of the photocatalysts changed and the oxygen vacancies on the surface of the photocatalysts formed, which would act as the electron capture centers and slow down the recombination of pho- to-induced electron and hole. The photocurrent spectra also proved that the photocatalysts had better electronic transmission capacities. The HCOOH yield in CO2 photocatalytic reduction was 747.82 μmol/gcat by using 1% Bi-0.5% Y-TiO2 as a photocatalyst. The HCOOH yield was 1.17 times higher than that by using 1% Bi-TiO2, and 2.23 times higher than that by using pure TiO2. Furthermore, the 1% Bi-0.5% Y-TiO2 showed the highest apparent quantum efficiency （AQE） of 4.45%.展开更多
The high-resolution DEM-IMB-LBM model can accurately describe pore-scale fluid-solid interactions,but its potential for use in geotechnical engineering analysis has not been fully unleashed due to its prohibitive comp...The high-resolution DEM-IMB-LBM model can accurately describe pore-scale fluid-solid interactions,but its potential for use in geotechnical engineering analysis has not been fully unleashed due to its prohibitive computational costs.To overcome this limitation,a message passing interface(MPI)parallel DEM-IMB-LBM framework is proposed aimed at enhancing computation efficiency.This framework utilises a static domain decomposition scheme,with the entire computation domain being decomposed into multiple subdomains according to predefined processors.A detailed parallel strategy is employed for both contact detection and hydrodynamic force calculation.In particular,a particle ID re-numbering scheme is proposed to handle particle transitions across sub-domain interfaces.Two benchmarks are conducted to validate the accuracy and overall performance of the proposed framework.Subsequently,the framework is applied to simulate scenarios involving multi-particle sedimentation and submarine landslides.The numerical examples effectively demonstrate the robustness and applicability of the MPI parallel DEM-IMB-LBM framework.展开更多
Understanding the underlying mechanisms and links between genome evolution and adaptive innovations stands as a key goal in evolutionary studies.Poplars,among the world’s most widely distributed and cultivated trees,...Understanding the underlying mechanisms and links between genome evolution and adaptive innovations stands as a key goal in evolutionary studies.Poplars,among the world’s most widely distributed and cultivated trees,exhibit extensive phenotypic diversity and environmental adaptability.In this study,we present a genus-level super-pangenome comprising 19 Populus genomes,revealing the likely pivotal role of private genes in facilitating local environmental and climate adaptation.Through the integration of pangenomes with transcriptomes,methylomes,and chromatin accessibility mapping,we unveil that the evolutionary trajectories of pangenes and duplicated genes are closely linked to local genomic landscapes of regulatory and epigenetic architectures,notably CG methylation in gene-body regions.Further comparative genomic analyses have enabled the identification of 142202 structural variants across species that intersect with a significant number of genes and contribute substantially to both phenotypic and adaptive divergence.We have experimentally validated a∼180-bp presence/absence variant affecting the expression of the CUC2 gene,crucial for leaf serration formation.Finally,we developed a user-friendly web-based tool encompassing the multi-omics resources associated with the Populus super-pangenome(http://www.populus-superpangenome.com).Together,the present pioneering super-pangenome resource in forest trees not only aids in the advancement of breeding efforts of this globally important tree genus but also offers valuable insights into potential avenues for comprehending tree biology.展开更多
One objective of developing machine learning(ML)-based material models is to integrate them with well-established numerical methods to solve boundary value problems(BVPs).In the family of ML models,recurrent neural ne...One objective of developing machine learning(ML)-based material models is to integrate them with well-established numerical methods to solve boundary value problems(BVPs).In the family of ML models,recurrent neural networks(RNNs)have been extensively applied to capture history-dependent constitutive responses of granular materials,but these multiple-step-based neural networks are neither sufficiently efficient nor aligned with the standard finite element method(FEM).Single-step-based neural networks like the multi-layer perceptron(MLP)are an alternative to bypass the above issues but have to introduce some internal variables to encode complex loading histories.In this work,one novel Frobenius norm-based internal variable,together with the Fourier layer and residual architectureenhanced MLP model,is crafted to replicate the history-dependent constitutive features of representative volume element(RVE)for granular materials.The obtained ML models are then seamlessly embedded into the FEM to solve the BVP of a biaxial compression case and a rigid strip footing case.The obtained solutions are comparable to results from the FEM-DEM multiscale modelling but achieve significantly improved efficiency.The results demonstrate the applicability of the proposed internal variable in enabling MLP to capture highly nonlinear constitutive responses of granular materials.展开更多
The classical deviatoric hardening models are capable of characterizing the mechanical response of granular materials for a broad range of degrees of compaction.This work finds that it has limitations in accurately pr...The classical deviatoric hardening models are capable of characterizing the mechanical response of granular materials for a broad range of degrees of compaction.This work finds that it has limitations in accurately predicting the volumetric deformation characteristics under a wide range of confining/consolidation pressures.The issue stems from the pressure independent hardening law in the classical deviatoric hardening model.To overcome this problem,we propose a refined deviatoric hardening model in which a pressure-dependent hardening law is developed based on experimental observations.Comparisons between numerical results and laboratory triaxial tests indicate that the improved model succeeds in capturing the volumetric deformation behavior under various confining/consolidation pressure conditions for both dense and loose sands.Furthermore,to examine the importance of the improved deviatoric hardening model,it is combined with the bounding surface plasticity theory to investigate the mechanical response of loose sand under complex cyclic loadings and different initial consolidation pressures.It is proved that the proposed pressure-dependent deviatoric hardening law is capable of predicting the volumetric deformation characteristics to a satisfactory degree and plays an important role in the simulation of complex deformations for granular geomaterials.展开更多
The shape and color of rice leaves are important agronomic traits that directly influence the proportion of sunlight energy utilization and ultimately affect the yield and quality.A new mutant exhibiting stable inheri...The shape and color of rice leaves are important agronomic traits that directly influence the proportion of sunlight energy utilization and ultimately affect the yield and quality.A new mutant exhibiting stable inheritance was identified as derived from ethyl methane sulfonate(EMS)-treated restorer Jinhui 10,tentatively named as narrow and striped leaf 1(nsl1).The nsl1 displayed pale white leaves at the seeding stage and then white striped leaves in parallel to the main vein at the jointing stage.Meanwhile,its leaf blades are significantly narrower than the control group of Jinhui 10.The chloroplast structures of cells in the white striped area of the nsl1 mutant break down,and the photosynthetic pigments are significantly lower than that of the wild type.Moreover,fluorescence parameters,such as F0,F v/F m,U psII,qp,and ETR,in the nsl1 mutant are significantly lower than those of the wild type,and the photosynthetic efficiency is also significantly decreased.These changes in leaf color and shape,together with physiological changes in the nsl1,result in smaller plant height and a decrease in the most important agronomic traits,such as the number of grains per panicle,grain weight,etc.Genetic analysis shows that the narrow and striped traits of the nsl1 mutant are controlled by a single recessive nuclear gene,which is located between InDel 16and InDel 12 in chromosome 3.The physical distance is204 kb.So far,no similar genes of such leaf color and shape in this area have been reported.This study has laid a solid foundation for the gene cloning and function analysis of NSL1.展开更多
Water spewing and muck plugging often occur during earth pressure balance(EPB)shield machines tunnelling in water-rich sandy strata,even though the conventional foam has been employed to condition sandy soils.In this ...Water spewing and muck plugging often occur during earth pressure balance(EPB)shield machines tunnelling in water-rich sandy strata,even though the conventional foam has been employed to condition sandy soils.In this study,a novel thickened foaming agent suitable for EPB shield tunnelling in water-rich sandy strata is developed.In contrast to conventional foam-conditioned sands,the thickened foam-conditioned sand has a low permeability due to the consistent filling of soil pores with the thickened foam,and the initial permeability coefficient decreases by approximately two orders of magnitude.It also exhibits a suitable workability,which is attributed to the enhanced capability of the thickened foam to condition sandy soils.In addition,the effect of concentration on the stability of the foam is explained by the Gibbs-Marangoni effect,and conditioning mechanisms for the thickened foam on sands are discussed from the evolution of foam bubbles.展开更多
As an important technology in fine chemical production,the selective hydrogenation ofα,β-unsaturated aldehydes has attracted much attention in recent years.In the process ofα,β-unsaturated aldehyde hydrogenation,a...As an important technology in fine chemical production,the selective hydrogenation ofα,β-unsaturated aldehydes has attracted much attention in recent years.In the process ofα,β-unsaturated aldehyde hydrogenation,a conjugated system is formed between>C=C<and>C=O,leading to hydrogenation at both ends of the conjugated system,which competes with each other and results in more complex products.Therefore,improving the reaction selectivity is also difficult in industrial fields.Recently,many researchers have reported that surface-active sites on catalysts play a crucial role inα,β-unsaturated aldehyde hydrogenation.This review attempts to summarize recent advances in understanding the effects of surface-active sites(SASs)over metal catalysts for enhancing the process of hydrogenation.The construction strategies and roles of SASs for hydrogenation catalysts are summarized.Particular attention has been given to the adsorption configuration and transformation mechanism ofα,β-unsaturated aldehydes on catalysts,which contributes to understanding the relationship between SASs and hydrogenation activity.In addition,recent advances in metal-supported catalysts for the selective hydrogenation ofα,β-unsaturated aldehydes to understand the role of SASs in hydrogenation are briefly reviewed.Finally,the opportunities and challenges will be highlighted for the future development of the precise construction of SASs.展开更多
The shear strength of sand-foam mixtures plays a crucial role in ensuring successful earth pressure balance(EPB)shield tunneling.Since the sand-foam mixtures are constantly sheared by the cutterhead and the screw conv...The shear strength of sand-foam mixtures plays a crucial role in ensuring successful earth pressure balance(EPB)shield tunneling.Since the sand-foam mixtures are constantly sheared by the cutterhead and the screw conveyor with varied rotation speeds during tunneling,it is non-trivial to investigate the effect of shear rates on the undrained shear strength of sand-foam mixtures under chamber pressures to extend the understanding on the tunneling process.This study conducted a series of pressurized vane shear tests to investigate the role of shear rates on the peak and residual strengths of sand-foam mixtures at different pore states.Different from the shear-rate characteristics of natural sands or clay,the results showed that the peak strength of sand-foam mixtures under high vertical total stress(σ_(v)≥200 kPa)and low foam injection ratio(FIR30%)decreased with the increase in shear rate.Otherwise,the peak strength was not measurably affected by shear rates.The sand-foam mixtures in the residual state resembled low-viscous fluid with yield stress and the residual strength increased slightly with shear rates.In addition,the peak and residual strengths were approximately linear with vertical effective stress regardless of the total stress and FIR.The peak effective internal friction angle remained almost invariant in a low shear rate(γ′<0.25 s1)but decreased when the shear rate continued increasing.The residual effective internal friction angle was lower than the peak counterpart and insensitive to shear rates.This study unveiled the role of shear rates in the undrained shear strength of sand-foam mixtures with various FIRs and vertical total stresses.The findings can extend the understanding of the rate-dependent shear characteristics of conditioned soils and guide the decision-making of soil conditioning schemes in the EPB shield tunneling practice.展开更多
Energy shortages have hindered global economic development.By utilizing waste as a substrate for microbial fermentation,hydrogen production can transform waste into a valuable resource,significantly reducing the cost ...Energy shortages have hindered global economic development.By utilizing waste as a substrate for microbial fermentation,hydrogen production can transform waste into a valuable resource,significantly reducing the cost of hydrogen production and addressing a significant hurdle in achieving large-scale production of microbial hydrogen.This approach has significant potential for future hydrogen-production applications.Two-stage indirect photohydrolysis has recently emerged as a promising and efficient method for hydrogen production using cyanobacteria and green algae.However,this method cannot be directly applied to organic wastewater for hydrogen production.In contrast,dark fermentation by bacteria,particularly ethanol-type fermentation,is highly efficient for producing hydrogen.Therefore,the combination of the indirect photohydrolysis of algae and dark fermentation by bacteria is expected to significantly enhance the hydrogen-production capacity of organic wastewater,laying the groundwork for future large-scale microbial hydrogen production.This study reviews the main types and technical principles of microbial hydrogen production from waste,available waste types,research progress in the microbial hydrogen-production process,strategies to improve the hydrogen-production rate,and challenges faced during industrialization.Future research directions for microbial-waste hydrogen production are also proposed.The aim of this study is to provide a valuable reference for large-scale biological hydrogen-production research.展开更多
Although organellar genomes(including chloroplast and mitochondrial genomes)are smaller than nuclear genomes in size and gene number,organellar genomes are very important for the investigation of plant evolution and m...Although organellar genomes(including chloroplast and mitochondrial genomes)are smaller than nuclear genomes in size and gene number,organellar genomes are very important for the investigation of plant evolution and molecular ecology mechanisms.Few studies have focused on the organellar genomes of horticultural plants.Approximately 1193 chloroplast genomes and 199 mitochondrial genomes of land plants are available in the National Center for Biotechnology Information(NCBI),of which only 39 are from horticultural plants.In this paper,we report an innovative and efficient method for high-quality horticultural organellar genome assembly from next-generation sequencing(NGS)data.Sequencing reads were first assembled by Newbler,Amos,and Minimus software with default parameters.The remaining gaps were then filled through BLASTN search and PCR.The complete DNA sequence was corrected based on Illumina sequencing data using BWA(Burrows–Wheeler Alignment tool)software.The advantage of this approach is that there is no need to isolate organellar DNA from total DNA during sample preparation.Using this procedure,the complete mitochondrial and chloroplast genomes of an ornamental plant,Salix suchowensis,and a fruit tree,Ziziphus jujuba,were identified.This study shows that horticultural plants have similar mitochondrial and chloroplast sequence organization to other seed plants.Most horticultural plants demonstrate a slight bias toward A+T rich features in the mitochondrial genome.In addition,a phylogenetic analysis of 39 horticultural plants based on 15 protein-coding genes showed that some mitochondrial genes are horizontally transferred from chloroplast DNA.Our study will provide an important reference for organellar genome assembly in other horticultural plants.Furthermore,phylogenetic analysis of the organellar genomes of horticultural plants could accurately clarify the unanticipated relationships among these plants.展开更多
The polyurethane foam(PU)compressible layer is a viable solution to the problem of damage to the secondary lining in squeezing tunnels.Nevertheless,the mechanical behaviour of the multi-layer yielding supports has not...The polyurethane foam(PU)compressible layer is a viable solution to the problem of damage to the secondary lining in squeezing tunnels.Nevertheless,the mechanical behaviour of the multi-layer yielding supports has not been thoroughly investigated.To fill this gap,large-scale model tests were conducted in this study.The synergistic load-bearing mechanics were analyzed using the convergenceconfinement method.Two types of multi-layer yielding supports with different thicknesses(2.5 cm,3.75 cm and 5 cm)of PU compressible layers were investigated respectively.Digital image correlation(DIC)analysis and acoustic emission(AE)techniques were used for detecting the deformation fields and damage evolution of the multi-layer yielding supports in real-time.Results indicated that the loaddisplacement relationship of the multi-layer yielding supports could be divided into the crack initiation,crack propagation,strain-hardening,and failure stages.Compared with those of the stiff support,the toughness,deformability and ultimate load of the yielding supports were increased by an average of 225%,61%and 32%,respectively.Additionally,the PU compressible layer is positioned between two primary linings to allow the yielding support to have greater mechanical properties.The analysis of the synergistic bearing effect suggested that the thickness of PU compressible layer and its location significantly affect the mechanical properties of the yielding supports.The use of yielding supports with a compressible layer positioned between the primary and secondary linings is recommended to mitigate the effects of high geo-stress in squeezing tunnels.展开更多
This study presents an AI-based constitutive modelling framework wherein the prediction model directly learns from triaxial testing data by combining discrete element modelling(DEM)and deep learning.A constitutive lea...This study presents an AI-based constitutive modelling framework wherein the prediction model directly learns from triaxial testing data by combining discrete element modelling(DEM)and deep learning.A constitutive learning strategy is proposed based on the generally accepted frame-indifference assumption in constructing material constitutive models.The low-dimensional principal stress-strain sequence pairs,measured from discrete element modelling of triaxial testing,are used to train recurrent neural networks,and then the predicted principal stress sequence is augmented to other high-dimensional or general stress tensor via coordinate transformation.Through detailed hyperparameter investigations,it is found that long short-term memory(LSTM)and gated recurrent unit(GRU)networks have similar prediction performance in constitutive modelling problems,and both satisfactorily predict the stress responses of granular materials subjected to a given unseen strain path.Furthermore,the unique merits and ongoing challenges of data-driven constitutive models for granular materials are discussed.展开更多
基金Supported by Program for New Century Excellent Talents in University (Grant No. NCET-04-0516)Fok Ying Tung Education Foundation, and the National Natural Science Foundation of China (Grant No. 30200224)
文摘We mapped and analyzed the microsatellites throughout 284295605 base pairs ofthe unambiguously assembled sequence scaffolds along 19 chromosomes of the haploid poplargenome.Totally,we found 150985 SSRs with repeat unit lengths between 2 and 5 bp.The establishedmicrosatellite physical map demonstrated tr at SSRs were distributed relatively evenly across thegenome of Populus.On average,These SSRs occurred every 1883 bp within the poplar genome and the SSRdensities in intergenic regions,introns,exons and UTRs were 85.4%,10.7%,2.7% and1.2%,respectively.We took di-,tri-,tetra-and pentamers as the four classes of repeat units and foundthat the density of each class of SSRs decreased with the repeat unit lengths except for thetetranucleotide repeats.It was noteworthy that the length diversification of microsatellitesequences was negatively correlated with their repeat unit length and the SSRs with shorter repeatunits gained repeats faster than the SSRs with longer repeat units.We also found that the GC contentof poplar sequence significantly correlated with densities of SSRs with uneven repeat unit lengths(tri-and penta-),but had no significant correlation with densities of SSRs with even repeat unitlengths (di-and tetra-).In poplar genome,there were evidences that the occurrence of differentmicrosatellites was under selection and the GC content in SSR sequences was found to significantlyrelate to the functional importance of microsatellites.
基金sup-ported by the National Natural Science Foundation of China (90502008, 40871006 and 40721061)the Program for New Century Excellent Talents in University
文摘A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change since 16.7 cal. ka BP. Fossil pollen assem-blages and lithology indicate that the study area was dominated by desert. The desert had extremely arid climate and lower effec-tive moisture during 16.7–7.9 cal. ka BP, especially from 16.7 to 8.9 cal. ka BP when the lake maybe dried up. During 8.9–7.9 cal. ka BP, the environment gradually recovered in this area. It was then followed by the optimum period from 7.9 to 4.3 cal. Ka BP, when the effective moisture obviously increased. It was characterized by the typical desert-steppe/steppe vegetation and was ac-companied with several patch-birch woodlands around the lake. After that, a short but extremely arid climatic event occurred during 4.3–3.8 cal. ka BP, and the vegetation quickly changed from desert-steppe/steppe to desert. It was a relatively optimum period from 3.8 to 0.53 cal. ka BP showing typical desert-steppe/meadow-steppe landscape. Since 0.53 cal. ka BP, the climate has shown signs of deteriorating again. Furthermore, regional comparison shows that the characteristics of climatic and environmental evolution in this area were clearly different from East Asia monsoonal area during the last 16.7 cal. ka BP. It was characterized by the arid climate during the late-glacial and early Holocene, and relatively wet during the mid-late Holocene.
基金supported by the National Key Research and Development Plan of China(2016YFD0600101)supported by the PAPD(Priority Academic Program Development)program at Nanjing Forestry University.
文摘Salix suchowensis is an early-flowering shrub willow that provides a desirable system for studies on the basic biology of woody plants.The current reference genome of S.suchowensis was assembled with 454 sequencing reads.Here,we report a chromosome-scale assembly of S.suchowensis generated by combining PacBio sequencing with Hi-C technologies.The obtained genome assemblies covered a total length of 356 Mb.The contig N50 of these assemblies was 263,908 bp,which was~65-fold higher than that reported previously.The contiguity and completeness of the genome were significantly improved.By applying Hi-C data,339.67 Mb(95.29%)of the assembled sequences were allocated to the 19 chromosomes of haploid willow.With the chromosome-scale assembly,we revealed a series of major chromosomal fissions and fusions that explain the genome divergence between the sister genera of Salix and Populus.The more complete and accurate willow reference genome obtained in this study provides a fundamental resource for studying many genetic and genomic characteristics of woody plants.
基金supported by the National High Technology Research Program of China (No. 2012AA101104)
文摘Oil, protein and starch are key chemical components of maize kernels. A population of 245 recombinant inbred lines(RILs) derived from a cross between a high-oil inbred line, By804, and a regular inbred line, B73, was used to dissect the genetic interrelationships among oil, starch and protein content at the individual QTL level by unconditional and conditional QTL mapping. Combined phenotypic data over two years with a genetic linkage map constructed using 236 markers, nine, five and eight unconditional QTL were detected for oil, protein and starch content, respectively. Some QTL for oil, protein and starch content were clustered in the same genomic regions and the direction of their effects was consistent with the sign of their correlation. In conditional QTL mapping, 37(29/8) unconditional QTL were not detected or showed reduced effects, four QTL demonstrated similar effects under unconditional and conditional QTL mapping, and 17 additional QTL were identified by conditional QTL mapping. These results imply that there is a strong genetic relationship among oil, protein and starch content in maize kernels. The information generated in the present investigation could be helpful in marker-assisted breeding for maize varieties with desirable kernel quality traits.
基金The work was supported by the National Natural Science Foundation of China(Nos.51879022,51979045,52101400,52101382,and 52101345)China Scholarship Council(CSC No.202006570022)+2 种基金the Fundamental Research Funds for the Central Universities,China(Nos.3132019330,3132021340)Science and Technology Innovation Foundation of Dalian(No.2021JJ12GX028)Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.311021013).
文摘Wind energy is a promising renewable energy source for a low-carbon society.This study is to develop a fully packaged vortexinduced vibration triboelectric nanogenerator(VIV-TENG)for scavenging wind energy.The VIV-TENG consists of a wind vane,internal power generation unit,an external frame,four springs,a square cylinder and a circular turntable.The internal power generation unit consists of polytetrafluoroethylene(PTFE)balls,a honeycomb frame and two copper electrodes.Different from most of the previous wind energy harvesting TENGs,the bouncing PTFE balls are fully packaged in the square cylinder.The distinct design separates the process of contact electrification from the external environment,and at the same time avoids the frictional wear of the ordinary wind energy harvesting TENGs.The corresponding VIV parameters are investigated to evaluate their influence on the vibration behaviors and the energy output.Resonant state of the VIV-TENG corresponds to the high output performance from the VIV-TENG.The distinct,robust structure ensures the full-packaged VIV-TENG can harvest wind energy from arbitrary directions and even in undesirable weather conditions.The study proposes a novel TENG configuration for harvesting wind energy and the VIV-TENG proves promising powering micro-electro-mechanical appliances.
基金supported by grants from the National Natural Science Foundation of China (81271003)he National Basic Research Development Program (973 Program) of China (2010CB945500,2012CB966300,2009CB941100)
文摘During the past decade, significant advances have been made in refinements for regenerative therapies following human spinal cord injury （SCI）. Positive results have been achieved with different types of cells in various clinical studies of SCI. In this review, we summarize recently-completed clinical trials using cell- mediated regenerative therapies for human SCI, together with ongoing trials using neural stem cells. Specifically, clinical studies published in Chinese journals are included. These studies show that current transplantation therapies are relatively safe, and have provided varying degrees of neurological recovery. However, many obstacles exist, hindering the introduction of a specific clinical therapy, including complications and their causes, selection of the target population, and optimization of transplantation material. Despite these and other challenges, with the collaboration of research groups and strong support from various organizations, cell-mediated regenerative therapies will open new perspectives for SCI treatment.
基金the National Natural Science Foundation of China (No.60071029)
文摘The perceptual effect of the phase information in speech has been studied by auditorysubjective tests. On the condition that the phase spectrum in speech is changed while amplitudespectrum is unchanged, the tests show that: (1) If the envelop of the reconstructed speech signalis unchanged, there is indistinctive auditory perception between the original speech and thereconstructed speech; (2) The auditory perception effect of the reconstructed speech mainly lieson the amplitude of the derivative of the additive phase; (3) td is the maximum relative time shiftbetween different frequency components of the reconstructed speech signal. The speech qualityis excellent while td ＜10ms; good while 10ms＜ td ＜20ms; common while 20ms＜ td ＜35ms, andpoor while td ＞35ms.
基金This work was supported by the National Natural Science Foundation of China （No. 213660044）, Guangxi Natural Science Foundation （No. 2016GXNSFFA380015）, and the Dean Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology （Nos. 2016Z003 and 2017K008）.
文摘Bi- and Y-codoped TiO2 photocatalysts were synthesized through a sol-gel method, and they were applied in the photocatalytic reduction of CO2 to formic acid under visible light irradiation. The results revealed that, after doping Bi and Y, the surface area of TiO2 was increased from 5.4 to 93.1 m2/g when the mole fractions of doping Bi and Y were 1.0% and 0.5%, respectively, and the lattice structures of the photocatalysts changed and the oxygen vacancies on the surface of the photocatalysts formed, which would act as the electron capture centers and slow down the recombination of pho- to-induced electron and hole. The photocurrent spectra also proved that the photocatalysts had better electronic transmission capacities. The HCOOH yield in CO2 photocatalytic reduction was 747.82 μmol/gcat by using 1% Bi-0.5% Y-TiO2 as a photocatalyst. The HCOOH yield was 1.17 times higher than that by using 1% Bi-TiO2, and 2.23 times higher than that by using pure TiO2. Furthermore, the 1% Bi-0.5% Y-TiO2 showed the highest apparent quantum efficiency （AQE） of 4.45%.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.12072217 and 42077254)the Natural Science Foundation of Hunan Province,China(Grant No.2022JJ30567).
文摘The high-resolution DEM-IMB-LBM model can accurately describe pore-scale fluid-solid interactions,but its potential for use in geotechnical engineering analysis has not been fully unleashed due to its prohibitive computational costs.To overcome this limitation,a message passing interface(MPI)parallel DEM-IMB-LBM framework is proposed aimed at enhancing computation efficiency.This framework utilises a static domain decomposition scheme,with the entire computation domain being decomposed into multiple subdomains according to predefined processors.A detailed parallel strategy is employed for both contact detection and hydrodynamic force calculation.In particular,a particle ID re-numbering scheme is proposed to handle particle transitions across sub-domain interfaces.Two benchmarks are conducted to validate the accuracy and overall performance of the proposed framework.Subsequently,the framework is applied to simulate scenarios involving multi-particle sedimentation and submarine landslides.The numerical examples effectively demonstrate the robustness and applicability of the MPI parallel DEM-IMB-LBM framework.
基金supported by the National Key Research and Development Program of China(2022YFD2201200 to J.W.and 2021YFD2200202 to T.Y.and J.L.)National Natural Science Foundation of China(32371695 and 31971567 to J.W.)Fundamental Research Funds for the Central Universities(2023SCUNL105 and SCU2022D003 to J.W.).
文摘Understanding the underlying mechanisms and links between genome evolution and adaptive innovations stands as a key goal in evolutionary studies.Poplars,among the world’s most widely distributed and cultivated trees,exhibit extensive phenotypic diversity and environmental adaptability.In this study,we present a genus-level super-pangenome comprising 19 Populus genomes,revealing the likely pivotal role of private genes in facilitating local environmental and climate adaptation.Through the integration of pangenomes with transcriptomes,methylomes,and chromatin accessibility mapping,we unveil that the evolutionary trajectories of pangenes and duplicated genes are closely linked to local genomic landscapes of regulatory and epigenetic architectures,notably CG methylation in gene-body regions.Further comparative genomic analyses have enabled the identification of 142202 structural variants across species that intersect with a significant number of genes and contribute substantially to both phenotypic and adaptive divergence.We have experimentally validated a∼180-bp presence/absence variant affecting the expression of the CUC2 gene,crucial for leaf serration formation.Finally,we developed a user-friendly web-based tool encompassing the multi-omics resources associated with the Populus super-pangenome(http://www.populus-superpangenome.com).Together,the present pioneering super-pangenome resource in forest trees not only aids in the advancement of breeding efforts of this globally important tree genus but also offers valuable insights into potential avenues for comprehending tree biology.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.12072217).
文摘One objective of developing machine learning(ML)-based material models is to integrate them with well-established numerical methods to solve boundary value problems(BVPs).In the family of ML models,recurrent neural networks(RNNs)have been extensively applied to capture history-dependent constitutive responses of granular materials,but these multiple-step-based neural networks are neither sufficiently efficient nor aligned with the standard finite element method(FEM).Single-step-based neural networks like the multi-layer perceptron(MLP)are an alternative to bypass the above issues but have to introduce some internal variables to encode complex loading histories.In this work,one novel Frobenius norm-based internal variable,together with the Fourier layer and residual architectureenhanced MLP model,is crafted to replicate the history-dependent constitutive features of representative volume element(RVE)for granular materials.The obtained ML models are then seamlessly embedded into the FEM to solve the BVP of a biaxial compression case and a rigid strip footing case.The obtained solutions are comparable to results from the FEM-DEM multiscale modelling but achieve significantly improved efficiency.The results demonstrate the applicability of the proposed internal variable in enabling MLP to capture highly nonlinear constitutive responses of granular materials.
基金the funding support from Basic Science Center Program for Multiphase Media Evolution in Hypergravity of the National Natural Science Foundation of China(Grant No.51988101).
文摘The classical deviatoric hardening models are capable of characterizing the mechanical response of granular materials for a broad range of degrees of compaction.This work finds that it has limitations in accurately predicting the volumetric deformation characteristics under a wide range of confining/consolidation pressures.The issue stems from the pressure independent hardening law in the classical deviatoric hardening model.To overcome this problem,we propose a refined deviatoric hardening model in which a pressure-dependent hardening law is developed based on experimental observations.Comparisons between numerical results and laboratory triaxial tests indicate that the improved model succeeds in capturing the volumetric deformation behavior under various confining/consolidation pressure conditions for both dense and loose sands.Furthermore,to examine the importance of the improved deviatoric hardening model,it is combined with the bounding surface plasticity theory to investigate the mechanical response of loose sand under complex cyclic loadings and different initial consolidation pressures.It is proved that the proposed pressure-dependent deviatoric hardening law is capable of predicting the volumetric deformation characteristics to a satisfactory degree and plays an important role in the simulation of complex deformations for granular geomaterials.
基金supported by Key Scientific Programs of Chongqing City(CSTC2012ggC 80002)
文摘The shape and color of rice leaves are important agronomic traits that directly influence the proportion of sunlight energy utilization and ultimately affect the yield and quality.A new mutant exhibiting stable inheritance was identified as derived from ethyl methane sulfonate(EMS)-treated restorer Jinhui 10,tentatively named as narrow and striped leaf 1(nsl1).The nsl1 displayed pale white leaves at the seeding stage and then white striped leaves in parallel to the main vein at the jointing stage.Meanwhile,its leaf blades are significantly narrower than the control group of Jinhui 10.The chloroplast structures of cells in the white striped area of the nsl1 mutant break down,and the photosynthetic pigments are significantly lower than that of the wild type.Moreover,fluorescence parameters,such as F0,F v/F m,U psII,qp,and ETR,in the nsl1 mutant are significantly lower than those of the wild type,and the photosynthetic efficiency is also significantly decreased.These changes in leaf color and shape,together with physiological changes in the nsl1,result in smaller plant height and a decrease in the most important agronomic traits,such as the number of grains per panicle,grain weight,etc.Genetic analysis shows that the narrow and striped traits of the nsl1 mutant are controlled by a single recessive nuclear gene,which is located between InDel 16and InDel 12 in chromosome 3.The physical distance is204 kb.So far,no similar genes of such leaf color and shape in this area have been reported.This study has laid a solid foundation for the gene cloning and function analysis of NSL1.
基金The financial support from the National Natural Science Foundation of China(Grant No.52022112)the Fundamental Research Funds for the Central South University(Grant No.2023ZZTS0366)are acknowledged and appreciated.The authors are also grateful for the help from Dr.Ji Zhao of China University of Mining and Technology.
文摘Water spewing and muck plugging often occur during earth pressure balance(EPB)shield machines tunnelling in water-rich sandy strata,even though the conventional foam has been employed to condition sandy soils.In this study,a novel thickened foaming agent suitable for EPB shield tunnelling in water-rich sandy strata is developed.In contrast to conventional foam-conditioned sands,the thickened foam-conditioned sand has a low permeability due to the consistent filling of soil pores with the thickened foam,and the initial permeability coefficient decreases by approximately two orders of magnitude.It also exhibits a suitable workability,which is attributed to the enhanced capability of the thickened foam to condition sandy soils.In addition,the effect of concentration on the stability of the foam is explained by the Gibbs-Marangoni effect,and conditioning mechanisms for the thickened foam on sands are discussed from the evolution of foam bubbles.
基金supported by the National Natural Science Foundation of China (Grant No.21968007)the Guangxi Natural Science Foundation (Grant No.2020GXNSFDA297007)+1 种基金the Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology (Grant No.2023K002)Special funding for‘Guangxi Bagui Scholars’.
文摘As an important technology in fine chemical production,the selective hydrogenation ofα,β-unsaturated aldehydes has attracted much attention in recent years.In the process ofα,β-unsaturated aldehyde hydrogenation,a conjugated system is formed between>C=C<and>C=O,leading to hydrogenation at both ends of the conjugated system,which competes with each other and results in more complex products.Therefore,improving the reaction selectivity is also difficult in industrial fields.Recently,many researchers have reported that surface-active sites on catalysts play a crucial role inα,β-unsaturated aldehyde hydrogenation.This review attempts to summarize recent advances in understanding the effects of surface-active sites(SASs)over metal catalysts for enhancing the process of hydrogenation.The construction strategies and roles of SASs for hydrogenation catalysts are summarized.Particular attention has been given to the adsorption configuration and transformation mechanism ofα,β-unsaturated aldehydes on catalysts,which contributes to understanding the relationship between SASs and hydrogenation activity.In addition,recent advances in metal-supported catalysts for the selective hydrogenation ofα,β-unsaturated aldehydes to understand the role of SASs in hydrogenation are briefly reviewed.Finally,the opportunities and challenges will be highlighted for the future development of the precise construction of SASs.
基金the National Outstanding Youth Science Fund Project of the National Natural Science Foundation of China(Grant No.52022112)the Hunan Provincial Innovation Foundation for Postgraduate of China(Grant No.2020zzts152)are acknowledged.
文摘The shear strength of sand-foam mixtures plays a crucial role in ensuring successful earth pressure balance(EPB)shield tunneling.Since the sand-foam mixtures are constantly sheared by the cutterhead and the screw conveyor with varied rotation speeds during tunneling,it is non-trivial to investigate the effect of shear rates on the undrained shear strength of sand-foam mixtures under chamber pressures to extend the understanding on the tunneling process.This study conducted a series of pressurized vane shear tests to investigate the role of shear rates on the peak and residual strengths of sand-foam mixtures at different pore states.Different from the shear-rate characteristics of natural sands or clay,the results showed that the peak strength of sand-foam mixtures under high vertical total stress(σ_(v)≥200 kPa)and low foam injection ratio(FIR30%)decreased with the increase in shear rate.Otherwise,the peak strength was not measurably affected by shear rates.The sand-foam mixtures in the residual state resembled low-viscous fluid with yield stress and the residual strength increased slightly with shear rates.In addition,the peak and residual strengths were approximately linear with vertical effective stress regardless of the total stress and FIR.The peak effective internal friction angle remained almost invariant in a low shear rate(γ′<0.25 s1)but decreased when the shear rate continued increasing.The residual effective internal friction angle was lower than the peak counterpart and insensitive to shear rates.This study unveiled the role of shear rates in the undrained shear strength of sand-foam mixtures with various FIRs and vertical total stresses.The findings can extend the understanding of the rate-dependent shear characteristics of conditioned soils and guide the decision-making of soil conditioning schemes in the EPB shield tunneling practice.
基金Supported by the Natural Science Basic Research Program of Shaanxi Province(S2021-JC-LHJJXMLH-QY-SM-0119).
文摘Energy shortages have hindered global economic development.By utilizing waste as a substrate for microbial fermentation,hydrogen production can transform waste into a valuable resource,significantly reducing the cost of hydrogen production and addressing a significant hurdle in achieving large-scale production of microbial hydrogen.This approach has significant potential for future hydrogen-production applications.Two-stage indirect photohydrolysis has recently emerged as a promising and efficient method for hydrogen production using cyanobacteria and green algae.However,this method cannot be directly applied to organic wastewater for hydrogen production.In contrast,dark fermentation by bacteria,particularly ethanol-type fermentation,is highly efficient for producing hydrogen.Therefore,the combination of the indirect photohydrolysis of algae and dark fermentation by bacteria is expected to significantly enhance the hydrogen-production capacity of organic wastewater,laying the groundwork for future large-scale microbial hydrogen production.This study reviews the main types and technical principles of microbial hydrogen production from waste,available waste types,research progress in the microbial hydrogen-production process,strategies to improve the hydrogen-production rate,and challenges faced during industrialization.Future research directions for microbial-waste hydrogen production are also proposed.The aim of this study is to provide a valuable reference for large-scale biological hydrogen-production research.
基金This study was supported by the National Key Research and Development Plan of China(2016YFD0600101)2017 Graduate Research and Innovation Program Projects in Jiangsu Province(KYCY17_0827)+3 种基金the Fundamental Research Funds for the Central Non-Profit Research Institution of CAF(CAFYBB2014QB015)the National Natural Science Foundation of China(31570662,31500533,and 61401214)the Jiangsu Provincial Department of Housing and Urban-Rural Development(2016ZD44)the PAPD(Priority Academic Program Development)program at Nanjing Forestry University.
文摘Although organellar genomes(including chloroplast and mitochondrial genomes)are smaller than nuclear genomes in size and gene number,organellar genomes are very important for the investigation of plant evolution and molecular ecology mechanisms.Few studies have focused on the organellar genomes of horticultural plants.Approximately 1193 chloroplast genomes and 199 mitochondrial genomes of land plants are available in the National Center for Biotechnology Information(NCBI),of which only 39 are from horticultural plants.In this paper,we report an innovative and efficient method for high-quality horticultural organellar genome assembly from next-generation sequencing(NGS)data.Sequencing reads were first assembled by Newbler,Amos,and Minimus software with default parameters.The remaining gaps were then filled through BLASTN search and PCR.The complete DNA sequence was corrected based on Illumina sequencing data using BWA(Burrows–Wheeler Alignment tool)software.The advantage of this approach is that there is no need to isolate organellar DNA from total DNA during sample preparation.Using this procedure,the complete mitochondrial and chloroplast genomes of an ornamental plant,Salix suchowensis,and a fruit tree,Ziziphus jujuba,were identified.This study shows that horticultural plants have similar mitochondrial and chloroplast sequence organization to other seed plants.Most horticultural plants demonstrate a slight bias toward A+T rich features in the mitochondrial genome.In addition,a phylogenetic analysis of 39 horticultural plants based on 15 protein-coding genes showed that some mitochondrial genes are horizontally transferred from chloroplast DNA.Our study will provide an important reference for organellar genome assembly in other horticultural plants.Furthermore,phylogenetic analysis of the organellar genomes of horticultural plants could accurately clarify the unanticipated relationships among these plants.
基金supported by the National Key Research and Development Program of China (Grant No.2021YFB2600800)the National Key Research and Development 451 Program of China (Grant No.2021YFC3100803)the Guangdong Innovative and Entrepreneurial Research Team Program (Grant No.2016ZT06N340).
文摘The polyurethane foam(PU)compressible layer is a viable solution to the problem of damage to the secondary lining in squeezing tunnels.Nevertheless,the mechanical behaviour of the multi-layer yielding supports has not been thoroughly investigated.To fill this gap,large-scale model tests were conducted in this study.The synergistic load-bearing mechanics were analyzed using the convergenceconfinement method.Two types of multi-layer yielding supports with different thicknesses(2.5 cm,3.75 cm and 5 cm)of PU compressible layers were investigated respectively.Digital image correlation(DIC)analysis and acoustic emission(AE)techniques were used for detecting the deformation fields and damage evolution of the multi-layer yielding supports in real-time.Results indicated that the loaddisplacement relationship of the multi-layer yielding supports could be divided into the crack initiation,crack propagation,strain-hardening,and failure stages.Compared with those of the stiff support,the toughness,deformability and ultimate load of the yielding supports were increased by an average of 225%,61%and 32%,respectively.Additionally,the PU compressible layer is positioned between two primary linings to allow the yielding support to have greater mechanical properties.The analysis of the synergistic bearing effect suggested that the thickness of PU compressible layer and its location significantly affect the mechanical properties of the yielding supports.The use of yielding supports with a compressible layer positioned between the primary and secondary linings is recommended to mitigate the effects of high geo-stress in squeezing tunnels.
基金This work is partially supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.41606213,51639004 and 12072217).
文摘This study presents an AI-based constitutive modelling framework wherein the prediction model directly learns from triaxial testing data by combining discrete element modelling(DEM)and deep learning.A constitutive learning strategy is proposed based on the generally accepted frame-indifference assumption in constructing material constitutive models.The low-dimensional principal stress-strain sequence pairs,measured from discrete element modelling of triaxial testing,are used to train recurrent neural networks,and then the predicted principal stress sequence is augmented to other high-dimensional or general stress tensor via coordinate transformation.Through detailed hyperparameter investigations,it is found that long short-term memory(LSTM)and gated recurrent unit(GRU)networks have similar prediction performance in constitutive modelling problems,and both satisfactorily predict the stress responses of granular materials subjected to a given unseen strain path.Furthermore,the unique merits and ongoing challenges of data-driven constitutive models for granular materials are discussed.
