Log anomaly detection is an important paradigm for system troubleshooting.Existing log anomaly detection based on Long Short-Term Memory(LSTM)networks is time-consuming to handle long sequences.Transformer model is in...Log anomaly detection is an important paradigm for system troubleshooting.Existing log anomaly detection based on Long Short-Term Memory(LSTM)networks is time-consuming to handle long sequences.Transformer model is introduced to promote efficiency.However,most existing Transformer-based log anomaly detection methods convert unstructured log messages into structured templates by log parsing,which introduces parsing errors.They only extract simple semantic feature,which ignores other features,and are generally supervised,relying on the amount of labeled data.To overcome the limitations of existing methods,this paper proposes a novel unsupervised log anomaly detection method based on multi-feature(UMFLog).UMFLog includes two sub-models to consider two kinds of features:semantic feature and statistical feature,respectively.UMFLog applies the log original content with detailed parameters instead of templates or template IDs to avoid log parsing errors.In the first sub-model,UMFLog uses Bidirectional Encoder Representations from Transformers(BERT)instead of random initialization to extract effective semantic feature,and an unsupervised hypersphere-based Transformer model to learn compact log sequence representations and obtain anomaly candidates.In the second sub-model,UMFLog exploits a statistical feature-based Variational Autoencoder(VAE)about word occurrence times to identify the final anomaly from anomaly candidates.Extensive experiments and evaluations are conducted on three real public log datasets.The results show that UMFLog significantly improves F1-scores compared to the state-of-the-art(SOTA)methods because of the multi-feature.展开更多
The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance.Dielectric force microscopy(DFM)has been previously developed to map charge carri...The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance.Dielectric force microscopy(DFM)has been previously developed to map charge carrier concentrations with nanometer-scale spatial resolution.However,it is challenging to quantitatively obtain the charge carrier concentration,since the dielectric force is also affected by the mobility.Here,we quantitative measured the charge carrier concentration at the saturation mobility regime via the rectification effect-dependent gating ratio of DFM.By measuring a series of n-type GaAs and GaN thin films with mobility in the saturation regime,we confirmed the decreased DFM-measured gating ratio with increasing electron concentration.Combined with numerical simulation to calibrate the tip–sample geometry-induced systematic error,the quantitative correlation between the DFM-measured gating ratio and the electron concentration has been established,where the extracted electron concentration presents high accuracy in the range of 4×10^(16)–1×10^(18)cm^(-3).We expect the quantitative DFM to find broad applications in characterizing the charge carrier transport properties of various semiconducting materials and devices.展开更多
Engineering mechanics is as a basic course,and the learning effect of this course directly affects the learning of subsequent professional courses.However,the teaching quality of engineering mechanics in vocational co...Engineering mechanics is as a basic course,and the learning effect of this course directly affects the learning of subsequent professional courses.However,the teaching quality of engineering mechanics in vocational colleges has been subpar for a long time.In this study,we explored the teaching situation of engineering mechanics by using questionnaires,pointing out the challenges faced in the teaching of engineering mechanics and putting forward four targeted suggestions,which include stimulating students’interest and increasing the investment in laboratory equipment,to improve the teaching quality.The findings of this study may provide some reference for the teaching reform of engineering mechanics.展开更多
Geranylgeranyl pyrophosphate synthetase(GGPPS) has gained increasing attention as a key enzyme in terpene analysis.We designed specific primers based on plant GGPPS homologs and used reverse transcription polymerase c...Geranylgeranyl pyrophosphate synthetase(GGPPS) has gained increasing attention as a key enzyme in terpene analysis.We designed specific primers based on plant GGPPS homologs and used reverse transcription polymerase chain reaction(RT-PCR) to obtain and identify Pin GGPPS,a GGPPS gene sequence from Pinus massoniana,using bioinformatics tools.Quantitative PCR analysis of Pin GGPPS expression levels in roots,pine needles,immature stems,and semilignified stems from 6-month-old P.massoniana showed that expression levels of Pin GGPPS were highest in pine needles,followed by immature stems and semilignified stems,and lowest in roots.When we examined the correlation between Pin GGPPS gene expression levels and resin productivity in 20 adult plants for 28 successive days,Pin GGPPS expression levels presented a substantially linear distribution when plotted against their corresponding resin yields.In summary,we characterized the gene Pin GGPPS for the first time in P.massoniana,and established a correlation between Pin GGPPS gene expression levels and resin productivity,suggesting the importance of theory and production practice for P.massoniana.展开更多
We analyzed the fine-scale spatial genetic structure of the individuals of Zelkova schneideriana,which were classified by age using the spatial autocorrelation method,to quantify spatial patterns of genetic variation ...We analyzed the fine-scale spatial genetic structure of the individuals of Zelkova schneideriana,which were classified by age using the spatial autocorrelation method,to quantify spatial patterns of genetic variation within the population and to explore potential mechanisms that determine genetic variation in population. The spatial autocorrelation coefficient( r) at 13 distance classes was determined on the basis of both geographical distance and genetic distance matrix which was derived from co-dominant SSR data using Gen Al Ex software. The results showed that all the individuals of Z. schneideriana exhibited significantly positive spatial genetic structure at distance less than 40 m( the X-intercept was 53. 568),indicating that the average length of the smallest genetic patch for the same genotype clustering of the Z. schneideriana Mailing population was about 50 m. Limited seed dispersal is the main factor that leads to the spatial genetic variation within populations. The individuals in age Class II showed significantly positive spatial genetic structure at distance less than 30 m( the X-intercept was 47. 882),while the individuals in age Class I and age Class III showed no significant spatial genetic structure in any of the spatial distance classes. Z. schneideriana is a long-lived perennial plant; the self-thinning resulted from the cohort competition between individuals in the growing process may lead to this certain spatial structure in age Class III of Z. schneideriana population.展开更多
With the emergence of pre-trained models,current neural networks are able to give task performance that is comparable to humans.However,we know little about the fundamental working mechanism of pre-trained models in w...With the emergence of pre-trained models,current neural networks are able to give task performance that is comparable to humans.However,we know little about the fundamental working mechanism of pre-trained models in which we do not know how they approach such performance and how the task is solved by the model.For example,given a task,human learns from easy to hard,whereas the model learns randomly.Undeniably,difficulty-insensitive learning leads to great success in natural language processing(NLP),but little attention has been paid to the effect of text difficulty in NLP.We propose a human learning matching index(HLM Index)to investigate the effect of text difficulty.Experiment results show:1)LSTM gives more human-like learning behavior than BERT.Additionally,UID-SuperLinear gives the best evaluation of text difficulty among four text difficulty criteria.Among nine tasks,some tasks’performance is related to text difficulty,whereas others are not.2)Model trained on easy data performs best in both easy and medium test data,whereas trained on hard data only performs well on hard test data.3)Train the model from easy to hard,leading to quicker convergence.展开更多
Recent advances in deep sequencing technologies have revealed that,while less than 2%of the human genome is transcribed into mRNA for protein synthesis,over 80%of the genome is transcribed,leading to the production of...Recent advances in deep sequencing technologies have revealed that,while less than 2%of the human genome is transcribed into mRNA for protein synthesis,over 80%of the genome is transcribed,leading to the production of large amounts of noncoding RNAs(ncRNAs).It has been shown that ncRNAs,especially long non-coding RNAs(lncRNAs),may play crucial regulatory roles in gene expression.As one of the first isolated and reported lncRNAs,H19 has gained much attention due to its essential roles in regulating many physiological and/or pathological processes including embryogenesis,development,tumorigenesis,osteogen-esis,and metabolism.Mechanistically,H19 mediates diverse regulatory functions by serving as competing endogenous RNAs(CeRNAs),Igf2/H19 imprinted tandem gene,modular scaffold,cooperating with H19 antisense,and acting directly with other mRNAs or lncRNAs.Here,we summarized the current understanding of H19 in embryogenesis and development,cancer development and progression,mesenchymal stem cell lineage-specific differentiation,and metabolic diseases.We discussed the potential regulatory mechanisms underlying H19’s func-tions in those processes although more in-depth studies are warranted to delineate the exact molecular,cellular,epigenetic,and genomic regulatory mechanisms underlying the physiolog-ical and pathological roles of H19.Ultimately,these lines of investigation may lead to the development of novel therapeutics for human diseases by exploiting H19 functions.展开更多
The development of high-performance solid-state electrolyte(SSE)films is critical to the practical application of all-solid-state Li metal batteries(ASSLMBs).However,developing high-performance free-standing electroly...The development of high-performance solid-state electrolyte(SSE)films is critical to the practical application of all-solid-state Li metal batteries(ASSLMBs).However,developing high-performance free-standing electrolyte films remains a challenging task.In this work,we demonstrate a novel scalable solvent-free process for fabricating high ceramic content composite solid-state electrolyte(HCCSE)films.Specifically speaking,a mixture of ceramic and polymer is dry mixed,fibered,and calendered into a free-standing porous ceramic film,on which polymer precursor is coated and polymerized to bridge the inorganic ceramic particles,resulting in a flexible HCCSE film with a ceramic content of up to 80 wt.%.High ceramic content not only leads to high ionic conductivity but also brings good mechanical properties;while the organic phase enables electrode|electrolyte interfacial stability.When Li_(10)GeP_(2)S_(12)(LGPS)and polymeric ionic liquid-based solid polymer electrolytes(PIL-SPEs)were used as the inorganic and organic phases,respectively,the room temperature ionic conductivity of the resulted HCCSE reaches 0.91 mS·cm−1.Based on this HCCSE,Li||Li symmetric battery cycled stably for more than 2,400 h with ultra-low overpotential,and ASSLMBs with different cathodes(LiFePO4 and sulfurized polyacrylonitrile(PAN-S))present small polarization and decent cyclability at room temperature.This work provides a novel scalable solvent-free strategy for preparing high-performance freestanding composite solid-state electrolyte(CSE)film for room temperature ASSLMBs.展开更多
C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(...C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(x)Hf_(1−x)C–SiC composites still faces some challenges.Furthermore,mechanical properties and thermophysical properties of Ta_(x)Hf_(1−x)C vary with the composition,but not monotonically.In-depth analysis of mechanical behaviors of the C_(f)/Ta_(x)Hf_(1−x)C–SiC composites is extremely important for their development and applications.In this study,the Ta_(x)Hf_(1−x)C powders(x=0.2,0.5,0.8)were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800℃,with a small amount of Si as an additive.Subsequently,the efficient fabrication of 2D-C_(f)/Ta_(x)Hf_(1−x)C–SiC composites was achieved by slurry impregnation and lamination(SIL)combined with precursor infiltration and pyrolysis(PIP).In addition,the mechanical behavior of the composites was investigated systematically.It is demonstrated that the composites present remarkable non-brittle fractures,including a large number of fiber pull out and interphase debonding.Also,the fracture failure involves a complex process of microcrack generation and propagation,matrix cracking,and layer fracture.Moreover,the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4.As a result,C_(f)/Ta_(0.2)Hf_(0.8)C–SiC composites exhibit exceptional flexural strength of 437±19 MPa,improved by 46%compared with C_(f)/Ta_(0.8)Hf_(0.2)C–SiC(299±19 MPa).This study provides a new perception of design and fabrication of ultra-high-temperature ceramic(UHTC)matrix composites with high performance.展开更多
BMP9 mediated osteogenic differentiation mechanisms of MSCs were widely explored, however, mechanisms of BMP9-induced angiogenesis still need to be clarified. We previously characterized that Notch1 promoted BMP9-indu...BMP9 mediated osteogenic differentiation mechanisms of MSCs were widely explored, however, mechanisms of BMP9-induced angiogenesis still need to be clarified. We previously characterized that Notch1 promoted BMP9-induced osteogenesis–angiogenesis coupling process in mesenchymal stem cells (MSCs). Here, we explored the underlying mechanisms of lncRNA H19 (H19) mediated regulation of BMP9-induced angiogenesis through activating Notch1 signaling. We demonstrated that basal expression level of H19 was high in MSCs, and silencing H19 attenuates BMP9-induced osteogenesis and angiogenesis of MSCs both in vitro and in vivo. Meanwhile, we identified that BMP9-induced production of CD31+ cells was indispensable for BMP9-induced bone formation, and silencing H19 dramatically blocked BMP9-induced production of CD31^(+) cells. In addition, we found that down-regulation of H19 inhibited BMP9 mediated blood vessel formation and followed subsequent bone formation in vivo. Mechanistically, we clarified that H19 promoted p53 phosphorylation by direct interacting and phosphorylating binding, and phosphorylated p53 potentiated Notch1 expression and activation of Notch1 targeting genes by binding on the promoter area of Notch1 gene. These findings suggested that H19 regulated BMP9-induced angiogenesis of MSCs by promoting the p53-Notch1 angiogenic signaling axis.展开更多
Ultra-high temperature ceramics(UHTCs)are generally referred to the carbides,nitrides,and borides of the transition metals,with the Group IVB compounds(Zr&Hf)and TaC as the main focus.The UHTCs are endowed with ul...Ultra-high temperature ceramics(UHTCs)are generally referred to the carbides,nitrides,and borides of the transition metals,with the Group IVB compounds(Zr&Hf)and TaC as the main focus.The UHTCs are endowed with ultra-high melting points,excellent mechanical properties,and ablation resistance at elevated temperatures.These unique combinations of properties make them promising materials for extremely environmental structural applications in rocket and hypersonic vehicles,particularly nozzles,leading edges,and engine components,etc.In addition to bulk UHTCs,UHTC coatings and fiber reinforced UHTC composites are extensively developed and applied to avoid the intrinsic brittleness and poor thermal shock resistance of bulk ceramics.Recently,high-entropy UHTCs are developed rapidly and attract a lot of attention as an emerging direction for ultra-high temperature materials.This review presents the state of the art of processing approaches,microstructure design and properties of UHTCs from bulk materials to composites and coatings,as well as the future directions.展开更多
In this work,three-dimensional(3D)Cf/SiBCN composites were fabricated by polymer infiltration and pyrolysis(PIP)with poly(methylvinyl)borosilazane as SiBCN precursor.The 3D microstructure evolution process of the comp...In this work,three-dimensional(3D)Cf/SiBCN composites were fabricated by polymer infiltration and pyrolysis(PIP)with poly(methylvinyl)borosilazane as SiBCN precursor.The 3D microstructure evolution process of the composites was investigated by an advanced X-ray computed tomography(XCT).The effect of dicumyl peroxide(DCP)initiator addition on the crosslinking process,microstructure evolution,and mechanical properties of the composites were uncovered.With the addition of a DCP initiator,the liquid precursor can cross-linking to solid-state at 120℃.Moreover,DCP addition decreases the release of small molecule gas during pyrolysis,leading to an improved ceramic yield 4.67 times higher than that without DCP addition.After 7 PIP cycles,density and open porosity of the final Cf/SiBCN composite with DCP addition are 1.73 g.cm^(-3)and〜10%,respectively,which are 143.0%higher and 30.3%lower compared with the composites without DCP addition.As a result,the flexural strength and elastic modulus of Cf/SiBCN composites with DCP addition(371 MPa and 31 GPa)are 1.74 and 1.60 times higher than that without DCP addition(213 MPa and 19.4 GPa),respectively.展开更多
Eu^(2+)/Sm^(3+)co-doped dual-emitting Sr_(4)La(PO_(4))_(3)O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and ...Eu^(2+)/Sm^(3+)co-doped dual-emitting Sr_(4)La(PO_(4))_(3)O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu^(2+)/Sm^(3+)co-doped Sr_(4)La(PO_(4))_(3)O phosphors were researched and analyzed in detail.The blue emission of Eu^(2+)and the red emission of Sm^(3+)can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(^(3+))phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(3+)phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu^(2+)and Sm^(3+)ions.展开更多
Fiber damage and uniform interphase preparation are the main challenges in conventional short fiber reinforced ceramic matrix composites.In this work,we develop a novel processing route in fabrication of short carbon ...Fiber damage and uniform interphase preparation are the main challenges in conventional short fiber reinforced ceramic matrix composites.In this work,we develop a novel processing route in fabrication of short carbon fiber reinforced ZrB_(2)-SiC composites(C_(sf)/ZrB_(2)-SiC)overcoming the above two issues.At first,C_(sf) preforms with oriented designation and uniform PyC/SiC interphase are fabricated via direct ink writing(DIW)of short carbon fiber paste followed by chemical vapor infiltration.After that,ZrB_(2) and SiC are introduced into the preforms by slurry impregnation and reactive melt infiltration,respectively.Microstructure evolution and optimization of the composites during fabrication are investigated in detail.The as-fabricated C_(sf)/ZrB_(2)-SiC composites have a bulk density of 2.47 g/cm^(3),with uniform weak interphase and without serious fiber damage.Consequently,non-brittle fracture occurs in the C_(sf)/ZrB_(2)-SiC composites with widespread toughening mechanisms such as crack deflection and bridging,interphase debonding,and fiber pull-out.This work provides a new opportunity to the material design and selection of short fiber reinforced composites.展开更多
A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a ...A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.展开更多
Background:The inhibitory microenvironment around spinal cord injury(SCI)severely restricted functional repair after injury.Mitophagy was one of the important measures to maintain cellular homeostasis and ensure the h...Background:The inhibitory microenvironment around spinal cord injury(SCI)severely restricted functional repair after injury.Mitophagy was one of the important measures to maintain cellular homeostasis and ensure the harmonious nerve cell microenvironment.Hypoxia-inducible factor1α(HIF1-α)can mediate mitochondrial autophagy in neurodegenerative diseases,but the mechanisms are complex and diverse,which need to be further elucidated.Electroacupuncture plays a significant role in improving the neural microenvironment after spinal cord injury,promote long-term neurological function recovery in SCI patients,but whether electroacupuncture can participate in HIF1-α mediated mitophagy remains unknown.Objective:Investigated the effects of HIF1-α on mitochondrial autophagy in rats with spinal cord contusion and the potential mechanism of electroacupuncture.Methods:Following the successful construction of an SCI model of Sprague-Dawley rat utilizing a modified Allen method,electroacupuncture intervention was performed at T9 and T11 Jiaji acupoint(EX-B2),with further molecular biology and morphology examined by perfusion.To observe the effect of HIF1-α on local damage repair,the stereotypic injection of Hif1a knockdown virus was performed,and the changes of mitophagy in damaged local area was detected employing Western blotting,real-time fluorescence quantitative PCR,immunofluorescence,transmission electron microscopy and Nissl staining.Results:HIF1-α as well as its mitophagy receptor BNIP3 and NIX are upregulated after spinal cord injury.Elec-troacupuncture treatment or local inhibition of HIF1-α expression can reverse the early autophagy state after spinal cord injury,reduce cell apoptosis and injury area,promote neuronal survival.Conclusion:Electroacupuncture may serve as a promising strategy for spinal cord injury treatment,by alleviating HIF1-α mediated early mitochondrial autophagy.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 62272062the Scientific Research Fund of Hunan Provincial Transportation Department(No.202143)the Open Fund ofKey Laboratory of Safety Control of Bridge Engineering,Ministry of Education(Changsha University of Science Technology)under Grant 21KB07.
文摘Log anomaly detection is an important paradigm for system troubleshooting.Existing log anomaly detection based on Long Short-Term Memory(LSTM)networks is time-consuming to handle long sequences.Transformer model is introduced to promote efficiency.However,most existing Transformer-based log anomaly detection methods convert unstructured log messages into structured templates by log parsing,which introduces parsing errors.They only extract simple semantic feature,which ignores other features,and are generally supervised,relying on the amount of labeled data.To overcome the limitations of existing methods,this paper proposes a novel unsupervised log anomaly detection method based on multi-feature(UMFLog).UMFLog includes two sub-models to consider two kinds of features:semantic feature and statistical feature,respectively.UMFLog applies the log original content with detailed parameters instead of templates or template IDs to avoid log parsing errors.In the first sub-model,UMFLog uses Bidirectional Encoder Representations from Transformers(BERT)instead of random initialization to extract effective semantic feature,and an unsupervised hypersphere-based Transformer model to learn compact log sequence representations and obtain anomaly candidates.In the second sub-model,UMFLog exploits a statistical feature-based Variational Autoencoder(VAE)about word occurrence times to identify the final anomaly from anomaly candidates.Extensive experiments and evaluations are conducted on three real public log datasets.The results show that UMFLog significantly improves F1-scores compared to the state-of-the-art(SOTA)methods because of the multi-feature.
基金Project supported by the National Key R&D Program of China (Grant No. 2021YFA1202802)the National Natural Science Foundation of China (Grant Nos. 21875280,21991150, 21991153, and 22022205)+1 种基金the CAS Project for Young Scientists in Basic Research (Grant No. YSBR-054)the Special Foundation for Carbon Peak Neutralization Technology Innovation Program of Jiangsu Province,China(Grant No. BE2022026)
文摘The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance.Dielectric force microscopy(DFM)has been previously developed to map charge carrier concentrations with nanometer-scale spatial resolution.However,it is challenging to quantitatively obtain the charge carrier concentration,since the dielectric force is also affected by the mobility.Here,we quantitative measured the charge carrier concentration at the saturation mobility regime via the rectification effect-dependent gating ratio of DFM.By measuring a series of n-type GaAs and GaN thin films with mobility in the saturation regime,we confirmed the decreased DFM-measured gating ratio with increasing electron concentration.Combined with numerical simulation to calibrate the tip–sample geometry-induced systematic error,the quantitative correlation between the DFM-measured gating ratio and the electron concentration has been established,where the extracted electron concentration presents high accuracy in the range of 4×10^(16)–1×10^(18)cm^(-3).We expect the quantitative DFM to find broad applications in characterizing the charge carrier transport properties of various semiconducting materials and devices.
基金supported by the Project of China Vocational Education Association(Project number:ZJS2022YB024)the Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project number:2022X305-SXZC)+1 种基金the Project of Beijing Municipal Social Science Foundation(Project number:22XCC015)the Project of Key Program of Beijing Polytechnic(Project number:2023X018-SXZ).
文摘Engineering mechanics is as a basic course,and the learning effect of this course directly affects the learning of subsequent professional courses.However,the teaching quality of engineering mechanics in vocational colleges has been subpar for a long time.In this study,we explored the teaching situation of engineering mechanics by using questionnaires,pointing out the challenges faced in the teaching of engineering mechanics and putting forward four targeted suggestions,which include stimulating students’interest and increasing the investment in laboratory equipment,to improve the teaching quality.The findings of this study may provide some reference for the teaching reform of engineering mechanics.
基金supported by the Guangxi Natural Science Foundation(2014GXNSFBA118106)
文摘Geranylgeranyl pyrophosphate synthetase(GGPPS) has gained increasing attention as a key enzyme in terpene analysis.We designed specific primers based on plant GGPPS homologs and used reverse transcription polymerase chain reaction(RT-PCR) to obtain and identify Pin GGPPS,a GGPPS gene sequence from Pinus massoniana,using bioinformatics tools.Quantitative PCR analysis of Pin GGPPS expression levels in roots,pine needles,immature stems,and semilignified stems from 6-month-old P.massoniana showed that expression levels of Pin GGPPS were highest in pine needles,followed by immature stems and semilignified stems,and lowest in roots.When we examined the correlation between Pin GGPPS gene expression levels and resin productivity in 20 adult plants for 28 successive days,Pin GGPPS expression levels presented a substantially linear distribution when plotted against their corresponding resin yields.In summary,we characterized the gene Pin GGPPS for the first time in P.massoniana,and established a correlation between Pin GGPPS gene expression levels and resin productivity,suggesting the importance of theory and production practice for P.massoniana.
基金Supported by the Scientific Research and Technological Development Project of Guangxi(1598025-42)the Guangxi Youth Fund Project(2013GXNSFBA019093)+1 种基金the National Forestry Public Welfare Industry Research Project(200904011)the Open Project for Guangxi Key Laboratory of Superior Timber Trees Resource Cultivation(15-B-03-01)
文摘We analyzed the fine-scale spatial genetic structure of the individuals of Zelkova schneideriana,which were classified by age using the spatial autocorrelation method,to quantify spatial patterns of genetic variation within the population and to explore potential mechanisms that determine genetic variation in population. The spatial autocorrelation coefficient( r) at 13 distance classes was determined on the basis of both geographical distance and genetic distance matrix which was derived from co-dominant SSR data using Gen Al Ex software. The results showed that all the individuals of Z. schneideriana exhibited significantly positive spatial genetic structure at distance less than 40 m( the X-intercept was 53. 568),indicating that the average length of the smallest genetic patch for the same genotype clustering of the Z. schneideriana Mailing population was about 50 m. Limited seed dispersal is the main factor that leads to the spatial genetic variation within populations. The individuals in age Class II showed significantly positive spatial genetic structure at distance less than 30 m( the X-intercept was 47. 882),while the individuals in age Class I and age Class III showed no significant spatial genetic structure in any of the spatial distance classes. Z. schneideriana is a long-lived perennial plant; the self-thinning resulted from the cohort competition between individuals in the growing process may lead to this certain spatial structure in age Class III of Z. schneideriana population.
基金the support of the National Natural Science Foundation of China(Nos.U22B2059,62176079)National Natural Science Foundation of Heilongjiang Province,China(No.YQ 2022F005)the Industry-University-Research Innovation Foundation of China University(No.2021ITA05009).
文摘With the emergence of pre-trained models,current neural networks are able to give task performance that is comparable to humans.However,we know little about the fundamental working mechanism of pre-trained models in which we do not know how they approach such performance and how the task is solved by the model.For example,given a task,human learns from easy to hard,whereas the model learns randomly.Undeniably,difficulty-insensitive learning leads to great success in natural language processing(NLP),but little attention has been paid to the effect of text difficulty in NLP.We propose a human learning matching index(HLM Index)to investigate the effect of text difficulty.Experiment results show:1)LSTM gives more human-like learning behavior than BERT.Additionally,UID-SuperLinear gives the best evaluation of text difficulty among four text difficulty criteria.Among nine tasks,some tasks’performance is related to text difficulty,whereas others are not.2)Model trained on easy data performs best in both easy and medium test data,whereas trained on hard data only performs well on hard test data.3)Train the model from easy to hard,leading to quicker convergence.
基金supported by the National Natural Science Foundation of China(NSFC)(No.82002312,81972069)supported in part by research grants from the National Institutes of Health,USA(No.CA226303 to TCH,No.DE030480 to RRR)+10 种基金supported by the Science and Technology Research Program of Chongqing Education Commission,China(No.KJQN202100431,KJZD-M202100401)the Top Talent Award from The First Affiliated Hospital of Chongqing Medical University,China(No.BJRC2021-04)Cultivation Program of Postdoctoral Research of The First Affiliated Hospital of Chongqing Medical University,China(No.CYYY-BSHPYXM-202202)supported by a post-doctoral fellowship from Chongqing Medical University and rewarded by China Postdoctoral Science Foundation(No.2022M720605)supported in part by research grants from the 2019 Science and Technology Project of Chongqing Education Commission,China(No.KJQN201900410)the 2019 Funding for Postdoctoral Research(Chongqing Human Resources and Social Security Bureau No.298)the Natural Science Foundation of China(No.82102696)supported by the Medical Scientist Training Program of the National Institutes of Health,USA(No.T32 GM007281)supported in part by The University of Chicago Cancer Center Support Grant,USA(No.P30CA014599)the National Center for Advancing Translational Sciences(NCATS)of the National Institutes of Health,USA(No.5UL1TR002389)supported by the Mabel Green Myers Research Endowment Fund and The University of Chicago Orthopedics Alumni Fund.
文摘Recent advances in deep sequencing technologies have revealed that,while less than 2%of the human genome is transcribed into mRNA for protein synthesis,over 80%of the genome is transcribed,leading to the production of large amounts of noncoding RNAs(ncRNAs).It has been shown that ncRNAs,especially long non-coding RNAs(lncRNAs),may play crucial regulatory roles in gene expression.As one of the first isolated and reported lncRNAs,H19 has gained much attention due to its essential roles in regulating many physiological and/or pathological processes including embryogenesis,development,tumorigenesis,osteogen-esis,and metabolism.Mechanistically,H19 mediates diverse regulatory functions by serving as competing endogenous RNAs(CeRNAs),Igf2/H19 imprinted tandem gene,modular scaffold,cooperating with H19 antisense,and acting directly with other mRNAs or lncRNAs.Here,we summarized the current understanding of H19 in embryogenesis and development,cancer development and progression,mesenchymal stem cell lineage-specific differentiation,and metabolic diseases.We discussed the potential regulatory mechanisms underlying H19’s func-tions in those processes although more in-depth studies are warranted to delineate the exact molecular,cellular,epigenetic,and genomic regulatory mechanisms underlying the physiolog-ical and pathological roles of H19.Ultimately,these lines of investigation may lead to the development of novel therapeutics for human diseases by exploiting H19 functions.
基金financially supported by the National Natural Science Foundation of China (22071069 and 22275060)technical support from the Analytical and Testing Center at Huazhong University of Science and Technology。
基金supported by the National Natural Science Foundation of China(Nos.21733012 and 22179143)the National Key R&D Program of China(No.2021YFB3800300).
文摘The development of high-performance solid-state electrolyte(SSE)films is critical to the practical application of all-solid-state Li metal batteries(ASSLMBs).However,developing high-performance free-standing electrolyte films remains a challenging task.In this work,we demonstrate a novel scalable solvent-free process for fabricating high ceramic content composite solid-state electrolyte(HCCSE)films.Specifically speaking,a mixture of ceramic and polymer is dry mixed,fibered,and calendered into a free-standing porous ceramic film,on which polymer precursor is coated and polymerized to bridge the inorganic ceramic particles,resulting in a flexible HCCSE film with a ceramic content of up to 80 wt.%.High ceramic content not only leads to high ionic conductivity but also brings good mechanical properties;while the organic phase enables electrode|electrolyte interfacial stability.When Li_(10)GeP_(2)S_(12)(LGPS)and polymeric ionic liquid-based solid polymer electrolytes(PIL-SPEs)were used as the inorganic and organic phases,respectively,the room temperature ionic conductivity of the resulted HCCSE reaches 0.91 mS·cm−1.Based on this HCCSE,Li||Li symmetric battery cycled stably for more than 2,400 h with ultra-low overpotential,and ASSLMBs with different cathodes(LiFePO4 and sulfurized polyacrylonitrile(PAN-S))present small polarization and decent cyclability at room temperature.This work provides a novel scalable solvent-free strategy for preparing high-performance freestanding composite solid-state electrolyte(CSE)film for room temperature ASSLMBs.
基金support from the National Key R&D Program of China(No.2022YFB3707700)Program of Shanghai Academic/Technology Research Leader(No.23XD1424300)the National Natural Science Foundation of China(No.52332003)are greatly acknowledged.
文摘C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(x)Hf_(1−x)C–SiC composites still faces some challenges.Furthermore,mechanical properties and thermophysical properties of Ta_(x)Hf_(1−x)C vary with the composition,but not monotonically.In-depth analysis of mechanical behaviors of the C_(f)/Ta_(x)Hf_(1−x)C–SiC composites is extremely important for their development and applications.In this study,the Ta_(x)Hf_(1−x)C powders(x=0.2,0.5,0.8)were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800℃,with a small amount of Si as an additive.Subsequently,the efficient fabrication of 2D-C_(f)/Ta_(x)Hf_(1−x)C–SiC composites was achieved by slurry impregnation and lamination(SIL)combined with precursor infiltration and pyrolysis(PIP).In addition,the mechanical behavior of the composites was investigated systematically.It is demonstrated that the composites present remarkable non-brittle fractures,including a large number of fiber pull out and interphase debonding.Also,the fracture failure involves a complex process of microcrack generation and propagation,matrix cracking,and layer fracture.Moreover,the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4.As a result,C_(f)/Ta_(0.2)Hf_(0.8)C–SiC composites exhibit exceptional flexural strength of 437±19 MPa,improved by 46%compared with C_(f)/Ta_(0.8)Hf_(0.2)C–SiC(299±19 MPa).This study provides a new perception of design and fabrication of ultra-high-temperature ceramic(UHTC)matrix composites with high performance.
基金supported by the National Natural Science Foundation of China,PRC(No.#82002312 and#81972069)This project was also supported by Science and Technology Research Program of Chongqing Education Commission,PRC(No.#KJQN202100431 and#KJZD-M202100401)+1 种基金Candidate of Tip-Top Talent of the First Affiliated Hospital of Chongqing Medical University,PRC(No.BJRC2021-04)Natural Science Foundation of Chongqing Science and Technology Commission,PRC(No.#cstc2018jcyjAX0088).
文摘BMP9 mediated osteogenic differentiation mechanisms of MSCs were widely explored, however, mechanisms of BMP9-induced angiogenesis still need to be clarified. We previously characterized that Notch1 promoted BMP9-induced osteogenesis–angiogenesis coupling process in mesenchymal stem cells (MSCs). Here, we explored the underlying mechanisms of lncRNA H19 (H19) mediated regulation of BMP9-induced angiogenesis through activating Notch1 signaling. We demonstrated that basal expression level of H19 was high in MSCs, and silencing H19 attenuates BMP9-induced osteogenesis and angiogenesis of MSCs both in vitro and in vivo. Meanwhile, we identified that BMP9-induced production of CD31+ cells was indispensable for BMP9-induced bone formation, and silencing H19 dramatically blocked BMP9-induced production of CD31^(+) cells. In addition, we found that down-regulation of H19 inhibited BMP9 mediated blood vessel formation and followed subsequent bone formation in vivo. Mechanistically, we clarified that H19 promoted p53 phosphorylation by direct interacting and phosphorylating binding, and phosphorylated p53 potentiated Notch1 expression and activation of Notch1 targeting genes by binding on the promoter area of Notch1 gene. These findings suggested that H19 regulated BMP9-induced angiogenesis of MSCs by promoting the p53-Notch1 angiogenic signaling axis.
基金support from the National Natural Science Foundation of China(52032001,52022072,52032003,51972243,92060202,51872239,51872059,51772061,52061135102,52002321,50632070,51272266,and 52102093)bilateral project of NSFC-JSPS(51111140017 and 51611140121)+4 种基金China Postdoctoral Science Foundation(2021M690817)Fundamental Research Funds for the Central Universities(G2020KY05125)Key Research Program of Frontier Sciences,CAS(QYZDY-SSW-JSC031)the projects supported by fee State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology(2021-KF-5)fee State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University(KF2116)are greatly acknowledged.
文摘Ultra-high temperature ceramics(UHTCs)are generally referred to the carbides,nitrides,and borides of the transition metals,with the Group IVB compounds(Zr&Hf)and TaC as the main focus.The UHTCs are endowed with ultra-high melting points,excellent mechanical properties,and ablation resistance at elevated temperatures.These unique combinations of properties make them promising materials for extremely environmental structural applications in rocket and hypersonic vehicles,particularly nozzles,leading edges,and engine components,etc.In addition to bulk UHTCs,UHTC coatings and fiber reinforced UHTC composites are extensively developed and applied to avoid the intrinsic brittleness and poor thermal shock resistance of bulk ceramics.Recently,high-entropy UHTCs are developed rapidly and attract a lot of attention as an emerging direction for ultra-high temperature materials.This review presents the state of the art of processing approaches,microstructure design and properties of UHTCs from bulk materials to composites and coatings,as well as the future directions.
基金the National Key Research and Development Program of China(2016YFB0700202)the Key Research Program of Frontier Sciences,CAS(QYZDY-SSW-JSC031)+1 种基金the National Natural Science Foundation of China(51702341,51872310)the project supported by State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology,2021-KF-5)are greatly acknowledged.
文摘In this work,three-dimensional(3D)Cf/SiBCN composites were fabricated by polymer infiltration and pyrolysis(PIP)with poly(methylvinyl)borosilazane as SiBCN precursor.The 3D microstructure evolution process of the composites was investigated by an advanced X-ray computed tomography(XCT).The effect of dicumyl peroxide(DCP)initiator addition on the crosslinking process,microstructure evolution,and mechanical properties of the composites were uncovered.With the addition of a DCP initiator,the liquid precursor can cross-linking to solid-state at 120℃.Moreover,DCP addition decreases the release of small molecule gas during pyrolysis,leading to an improved ceramic yield 4.67 times higher than that without DCP addition.After 7 PIP cycles,density and open porosity of the final Cf/SiBCN composite with DCP addition are 1.73 g.cm^(-3)and〜10%,respectively,which are 143.0%higher and 30.3%lower compared with the composites without DCP addition.As a result,the flexural strength and elastic modulus of Cf/SiBCN composites with DCP addition(371 MPa and 31 GPa)are 1.74 and 1.60 times higher than that without DCP addition(213 MPa and 19.4 GPa),respectively.
基金Project supported by Natural Science Foundation of Zhejiang Province,China(LY19E020005)Science and Technology Innovation Platform and Talent Plan of Zhejiang(2017R52037)。
文摘Eu^(2+)/Sm^(3+)co-doped dual-emitting Sr_(4)La(PO_(4))_(3)O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu^(2+)/Sm^(3+)co-doped Sr_(4)La(PO_(4))_(3)O phosphors were researched and analyzed in detail.The blue emission of Eu^(2+)and the red emission of Sm^(3+)can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(^(3+))phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(3+)phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu^(2+)and Sm^(3+)ions.
基金support from the Key Research Program of Frontier Sciences,CAS(No.QYZDY-SSW-JSC031)the projects supported by State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology(No.2021-KF-5)State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University(No.KF2116)are greatly acknowledged.
文摘Fiber damage and uniform interphase preparation are the main challenges in conventional short fiber reinforced ceramic matrix composites.In this work,we develop a novel processing route in fabrication of short carbon fiber reinforced ZrB_(2)-SiC composites(C_(sf)/ZrB_(2)-SiC)overcoming the above two issues.At first,C_(sf) preforms with oriented designation and uniform PyC/SiC interphase are fabricated via direct ink writing(DIW)of short carbon fiber paste followed by chemical vapor infiltration.After that,ZrB_(2) and SiC are introduced into the preforms by slurry impregnation and reactive melt infiltration,respectively.Microstructure evolution and optimization of the composites during fabrication are investigated in detail.The as-fabricated C_(sf)/ZrB_(2)-SiC composites have a bulk density of 2.47 g/cm^(3),with uniform weak interphase and without serious fiber damage.Consequently,non-brittle fracture occurs in the C_(sf)/ZrB_(2)-SiC composites with widespread toughening mechanisms such as crack deflection and bridging,interphase debonding,and fiber pull-out.This work provides a new opportunity to the material design and selection of short fiber reinforced composites.
基金Project supported by Natural Science Foundation of Zhejiang Province,China(LY19E020005)Science and Technology Innovation Platform and Talent Plan of Zhejiang(2017R52037)。
文摘A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.
基金National Natural Science Foundation of China(Nos.82174487 and 82205258)Zhejiang Medical and Health Science and Technology Plan Project(No.2021RC099)+2 种基金General scientific research project of Edu-cation Department of Zhejiang Province(No.Y202044576)Graduate Scientific Research Fund project of Zhejiang Chinese Medical Univer-sity(No.2022YKJ10)Zhejiang Provincial Program for the Cultivation of High-level Innovative Health Talents.
文摘Background:The inhibitory microenvironment around spinal cord injury(SCI)severely restricted functional repair after injury.Mitophagy was one of the important measures to maintain cellular homeostasis and ensure the harmonious nerve cell microenvironment.Hypoxia-inducible factor1α(HIF1-α)can mediate mitochondrial autophagy in neurodegenerative diseases,but the mechanisms are complex and diverse,which need to be further elucidated.Electroacupuncture plays a significant role in improving the neural microenvironment after spinal cord injury,promote long-term neurological function recovery in SCI patients,but whether electroacupuncture can participate in HIF1-α mediated mitophagy remains unknown.Objective:Investigated the effects of HIF1-α on mitochondrial autophagy in rats with spinal cord contusion and the potential mechanism of electroacupuncture.Methods:Following the successful construction of an SCI model of Sprague-Dawley rat utilizing a modified Allen method,electroacupuncture intervention was performed at T9 and T11 Jiaji acupoint(EX-B2),with further molecular biology and morphology examined by perfusion.To observe the effect of HIF1-α on local damage repair,the stereotypic injection of Hif1a knockdown virus was performed,and the changes of mitophagy in damaged local area was detected employing Western blotting,real-time fluorescence quantitative PCR,immunofluorescence,transmission electron microscopy and Nissl staining.Results:HIF1-α as well as its mitophagy receptor BNIP3 and NIX are upregulated after spinal cord injury.Elec-troacupuncture treatment or local inhibition of HIF1-α expression can reverse the early autophagy state after spinal cord injury,reduce cell apoptosis and injury area,promote neuronal survival.Conclusion:Electroacupuncture may serve as a promising strategy for spinal cord injury treatment,by alleviating HIF1-α mediated early mitochondrial autophagy.
