Global navigation satellite system has been widely used,but it is vulnerable to jamming.In military satellite communications,frequency hopping(FH)signal is usually used for anti-jamming communications.If the FH signal...Global navigation satellite system has been widely used,but it is vulnerable to jamming.In military satellite communications,frequency hopping(FH)signal is usually used for anti-jamming communications.If the FH signal can be used in satellite navigation,the anti-jamming ability of satellite navigation can be improved.Although a recently proposed timefrequency matrix ranging method(TFMR)can use FH signals to realize pseudorange measurement,it cannot transmit navigation messages using the ranging signal which is crucial for satellite navigation.In this article,we propose dual-tone binary frequency shift keyingbased TFMR(DBFSK-TFMR).DBFSK-TFMR designs an extended time-frequency matrix(ETFM)and its generation algorithm,which can use the frequency differences in different dual-tone signals in ETFM to modulate data and eliminate the negative impact of data modulation on pseudorange measurement.Using ETFM,DBFSK-TFMR not only realizes the navigation message transmission but also ensures the precision and unambiguous measurement range of pseudorange measurement.DBFSK-TFMR can be used as an integrated solution for anti-jamming communication and navigation based on FH signals.Simulation results show that DBFSK-TFMR has almost the same ranging performance as TFMR.展开更多
Rechargeable aqueous zinc-ion batteries(AZIBs)have their unique advantages of cost efficiency,high safety,and environmental friendliness.However,challenges facing the cathode materials include whether they can remain ...Rechargeable aqueous zinc-ion batteries(AZIBs)have their unique advantages of cost efficiency,high safety,and environmental friendliness.However,challenges facing the cathode materials include whether they can remain chemically stable in aqueous electrolyte and provide a robust structure for the storage of Zn2+.Here,we report on H11Al2V6O23.2@graphene(HAVO@G)with exceptionally large layer spacing of(001)plane(13.36?).The graphene-wrapped structure can keep the structure stable during discharge/charge process,thereby promoting the inhibition of the dissolution of elements in the aqueous electrolyte.While used as cathode for AZIBs,HAVO@G electrode delivers ideal rate performance(reversible capacity of 305.4,276.6,230.0,201.7,180.6 mAh g?1 at current densities between 1 and 10 A g?1).Remarkably,the electrode exhibits excellent and stable cycling stability even at a high loading mass of^15.7 mg cm?2,with an ideal reversible capacity of 131.7 mAh g?1 after 400 cycles at 2 A g?1.展开更多
Recently,the China Meteorological Administration(CMA)released a new Global Atmospheric Reanalysis(CRA-40)dataset for the period 1979−2018.In this study,surface relative humidity(RH)from CRA-40 and other current reanal...Recently,the China Meteorological Administration(CMA)released a new Global Atmospheric Reanalysis(CRA-40)dataset for the period 1979−2018.In this study,surface relative humidity(RH)from CRA-40 and other current reanalyses(e.g.,CFSR,ERA5,ERA-Interim,JRA-55,and MERRA-2)is comprehensively evaluated against homogenized observations over China.The results suggest that most reanalyses overestimate the observations by 15%−30%(absolute difference)over the Tibetan Plateau but underestimate the observations by 5%−10%over most of northern China.The CRA-40 performs relatively well in describing the long-term change and variance seen in the observed surface RH over China.Most of the reanalyses reproduce the observed surface RH climatology and interannual variations well,while few reanalyses can capture the observed long-term RH trends over China.Among these reanalyses,the CFSR does poorly in describing the interannual changes in the observed RH,especially in Southwest China.An empirical orthogonal function(EOF)analysis also suggests that the CRA-40 performs better than other reanalyses to capture the first two leading EOF modes revealed by the observations.The results of this study are expected to improve understanding of the strengths and weaknesses of the current reanalysis products and thus facilitate their application.展开更多
Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China(Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties o...Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China(Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth(AOD) at 500 nm was 0.32 ± 0.06, and the ?ngstr?m exponent(α) was 0.73 ± 0.27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM(March–April–May) resulted in the seasonal maximum AOD, 0.41 ± 0.04, and a relatively smaller αvalue, 0.44 ± 0.04. The tourism seasons, JJA(June–July–August) and SON(September–October–November) coincide with serious emissions of small anthropogenic aerosols. While in DJF(December–January–February), the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and αwere 0.29 ± 0.02 and 0.66 ± 0.17, respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM, ranges of AOD(0.11–1.18) and α(0.06–0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF, the similar ranges of AOD and α under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.展开更多
Industrial pollution has a significant effect on aerosol properties in Changsha City,a typical city of central China.Therefore,year-round measurements of aerosol optical,radiative and chemical properties from 2012 to ...Industrial pollution has a significant effect on aerosol properties in Changsha City,a typical city of central China.Therefore,year-round measurements of aerosol optical,radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed.During the observation period,the energy structure was continuously optimized,which was characterized by the reduction of coal combustion.The aerosol properties have obvious seasonal variations.The seasonal average aerosol optical depth(AOD)at 500 nm ranged from 0.49 to 1.00,single scattering albedo(SSA)ranged from 0.93 to 0.97,and aerosol radiative forcing at the top of the atmosphere(TOA)ranged from−24.0 to 3.8 W m^−2.The chemical components also showed seasonal variations.Meanwhile,the scattering aerosol,such as organic carbon,SO42−,NO3−,and NH4+showed a decrease,and elemental carbon increased.Compared with observation in winter 2012,AOD and TOA decreased by 0.14 and−1.49 W m^−2 in winter 2014.The scattering components,SO42−,NO3−and NH4+,decreased by 12.8μg m^−3(56.8%),9.2μg m^−3(48.8%)and 6.4μg m^−3(45.2%),respectively.The atmospheric visibility and pollution diffusion conditions improved.The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol.The results indicate that Changsha is an industrial city with strong scattering aerosol.The energy structure optimization had a marked effect on controlling pollution,especially in winter(strong scattering aerosol).展开更多
The quality of the MODIS C6 3-km and 10-km aerosol optical depth(AOD) products retrieved by the Dark Target(DT)method is discussed using ground-based observations in the Beijing–Tianjin–Hebei region from 1 Augus...The quality of the MODIS C6 3-km and 10-km aerosol optical depth(AOD) products retrieved by the Dark Target(DT)method is discussed using ground-based observations in the Beijing–Tianjin–Hebei region from 1 August 2007 to 31 July2008. Good consistency exists between the 3-km and 10-km products and ground-based observations. The retrieval accuracy of the two products both show distinctive seasonality. The percentage falling within the expected error(EE) is largest in the winter, moderate in the spring and autumn, and smallest in the summer. A worse overestimation appears in the spring and summer(27%–66%). However, the 3-km and 10-km products over different surfaces still exhibit obvious deviations. The 10-km product performs better in the large cities, while the 3-km product has advantages in the suburbs. In urban areas, the percentage falling within EE of the 3-km AOD product(18%–59%) is lower than that for the 10-km AOD product(31%–69%). However, in suburban areas, the percentage falling within EE of the 3-km AOD product(61%–84%) is higher than for the 10 km AOD product(54%–83%).The percentages falling within EE differ considerably when the AOD is greater than1.5(73% and 63% for the 3-km and 10-km products, respectively). On the whole, the 3-km(10-km) AOD product performs better in suburban(urban) areas.展开更多
In this paper,we discuss the interfacial internal waves with a rigid boundary in a three-layer fluid system,where the density of the upper layer fluid is smaller than that of the lower layer.With the Lagrangian matchi...In this paper,we discuss the interfacial internal waves with a rigid boundary in a three-layer fluid system,where the density of the upper layer fluid is smaller than that of the lower layer.With the Lagrangian matching conditions at the interfaces,the first-order solutions,the second-order solutions and the third-order asymptotic solutions for the interfacial internal waves are obtained in the Lagrangian description using the perturbation method,and the mass transport velocity,the wave frequency,the mean level and the particle trajectory are also given.The results show that the discontinuities across the interfaces appear for the mass transport velocity,wave frequency and mean level,but we find that these discontinuities may disappear if the water depth ratio and the density ratio of the three layer fluids satisfy certain conditions.展开更多
With the rapid development of submarine oil and gas,the security issues of submarine oil and gas pipeline become increasingly prominent,and regular inspection of submarine pipeline is particularly important.Therefore,...With the rapid development of submarine oil and gas,the security issues of submarine oil and gas pipeline become increasingly prominent,and regular inspection of submarine pipeline is particularly important.Therefore,a submarine pipeline inspection robot system based on CT technology to solve the problems such as low traditional manual inspection efficiency,high labor cost,low security and backward inspection methods.Based on the platform of ROV robot,carrying CT scanner as an external detection device,the system is used for non-invasive inspection of submarine pipeline,which is safe and harmless,with good economy,high mobility,and strong environmental adaptability.Compared with traditional technology,CT scanner’s external inspection technology used in the system avoids the damage to the external protective layer of the pipeline in the measurement of pipeline wall thickness.Meantime,it can provide the tomography of the pipe wall and the composition of the sediment material on the inside wall,which fills the gap in this technical field in China.According to the test,the robot has the characteristics of stable adsorption,flexible movement,and clear pipeline CT scanning image,and can realize the intelligent inspection of submarine pipeline.展开更多
In recent years,the issue of aircraft icing has gained widespread recognition.The breaking and detachment of dynamic ice can pose a threat to flight safety.However,the shedding and fracture mechanisms of dynamic ice a...In recent years,the issue of aircraft icing has gained widespread recognition.The breaking and detachment of dynamic ice can pose a threat to flight safety.However,the shedding and fracture mechanisms of dynamic ice are unclear and cannot meet the engineering needs of ice-shedding hazard assessment.Therefore,studying the fracture toughness of ice bodies has extremely important practical significance.To address this issue,this article uses a centrally cracked Brazilian disk(CCBD)specimen to measure the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice at different loading rates.The mixed-mode(Ⅰ–Ⅱ)fracture characteristics of ice are discussed,and the experimental results are compared and analyzed with the theoretical values of the generalized maximum tangential stress(GMTS)criterion considering the influence of T-stress.The results indicated that as the loading rate increases,the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice decrease,and the fracture toughness of freshwater ice is more sensitive to the loading rate.Ⅰn terms of fracture criteria,the theoretical value of the ratio of pure modeⅡfracture toughness to pure modeⅠfracture toughness based on the GMTS criterion is in good agreement with the experimental value,while the theoretical value based on the maximum tangential stress(MTS)criterion deviates significantly from the experimental value,indicating that the GMTS criterion considering the influence of T-stress can better predict the experimental results.展开更多
The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which ...The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.展开更多
Polyhedral distortion,associated closely with the atomic arrangement and interatomic interactions,drives many unique behaviors in solids,such as phase transition and negative thermal expansion.In thermoelectric hetero...Polyhedral distortion,associated closely with the atomic arrangement and interatomic interactions,drives many unique behaviors in solids,such as phase transition and negative thermal expansion.In thermoelectric heteroanionic oxides,the anionic polyhedra are widely present,but their effect on thermal transport is rarely investigated.Here,we report an anomalous thermal conduction induced by local symmetry distortion in layered oxyselenides via solving the Boltzmann transport equation based on first-principles calculations.We found interestingly that lighter BiCuSeO exhibits lower thermal conductivity than heavier BiAgSeO.Due to the different distorted degrees of CuSe4 and AgSe4 tetrahedrons,Cu prefers the in-plane vibration,while Ag has more tendency of out-of-plane vibration.Thus,the heat-carrying phonons dominated by the rattling-like vibration of Cu are significantly suppressed,resulting in lower thermal conductivity of BiCuSeO.This study highlights the importance of polyhedral distortion in regulating thermal conduction in layered heteroanionic materials.展开更多
Solder joint quality inspection is a crucial step in the qualification inspection of printed circuit board(PCB)components,and efficient and accurate inspection methods will greatly improve its production efficiency.In...Solder joint quality inspection is a crucial step in the qualification inspection of printed circuit board(PCB)components,and efficient and accurate inspection methods will greatly improve its production efficiency.In this paper,we propose a PCB solder joint quality detection algorithm based on a lightweight classification network.First,the Select Joint segmentation method was used to obtain the solder joint information,and colour space conversion was used to locate the solder joint.The mask method,contour detection,and box line method were combined to complete the extraction of solder joint information.Then,by combining the respective characteristics of convolutional neural network and Transformer and introducing Cross-covariance attention to reduce the computational complexity and resource consumption of the model and evenly distribute the global view mutual information in the whole training process,a new lightweight network model MobileXT is proposed to complete defect classification.Only 16.4%of the Vision Transformer computing resources used in this model can achieve an average accuracy improvement of 31%.Additionally,the network is trained and validated using a dataset of 1804 solder joint images constructed from 93 PCB images and two external datasets to evaluate MobileXT performance.The proposed method achieves more effi-cient localization of the solder joint information and more accurate classification of weld joint defects,and the lightweight model design is more appropriate for industrial edge device deployments.展开更多
Background:The search for biomarkers suitable for early diagnosis of Crohn's disease(CD)is challenging.This study investigated the efficacy of serological markers for the early diagnosis of CD.Methods:This was a r...Background:The search for biomarkers suitable for early diagnosis of Crohn's disease(CD)is challenging.This study investigated the efficacy of serological markers for the early diagnosis of CD.Methods:This was a retrospective nested cohort study.Indirect immuno-fluorescence and enzyme‐linked immunosorbent assay were used to detect ASCA IgG,ASCA IgA,AYMA IgG,AYCA IgG,FI2Y IgG,p‐ANCA IgG,GAB IgG and PAB IgG in patient serum samples.Results:The positive rates of ASCA IgG,ASCA IgA,AYMA IgG,AYCA IgG,FI2Y IgG,p‐ANCA IgG,GAB IgG and PAB IgG in patients with early CD,advanced CD and other intestinal diseases were 37.0%versus 56.8%versus 27.8%;3.7%versus 20.5%versus 19.4%;14.8%versus 2.3%versus 2.8%;25.9%versus 9.1%versus 8.3%;18.5%versus 15.9%versus 8.3%;0.0%versus 2.8%,18.5%;13.6%versus 18.2%versus 16.7%;and 7.4%versus 20.5%versus 0.0%,respectively.The positive rates of ASCA IgG,AYCA IgG and PAB IgG were significantly different among the three groups(p<0.05).In 85.2%of early CD patients,at least one antibody was detected 1 year before diagnosis.The sensitivity of the ASCA/AYMA/AYCA/FI2Y/GAB combination for early diagnosis was 85.2%.The sensitivity of the ASCA/AYMA/AYCA/FI2Y/GAB/PAB/PANCA combination for differentiating CD from other diseases was 87.3%.Conclusions:ASCA IgG and AYCA IgG have potential value in identifying the course of CD.AYCA IgG may be a potential marker for the early diagnosis of CD,and ASCA IgG indicates an advanced stage.The combination of ASCA,AYMA,AYCA,FI2Y,and GAB improves early diagnostic accuracy of CD.展开更多
Oxide-based ceramics could be promising thermoelectric materials because of their thermal and chemical stability at high temperature.However,their mediocre electrical conductivity or high thermal conductivity is still...Oxide-based ceramics could be promising thermoelectric materials because of their thermal and chemical stability at high temperature.However,their mediocre electrical conductivity or high thermal conductivity is still a challenge for the use in commercial devices.Here,we report significantly suppressed thermal conductivity in SrTiO_(3)-based thermoelectric ceramics via high-entropy strategy for the first time,and optimized electrical conductivity by defect engineering.In high-entropy(Ca_(0.2)Sr_(0.2)Ba_(0.2)Pb_(0.2)La_(0.2))TiO_(3)bulks,the minimum thermal conductivity can be 1.17 W/(m·K)at 923 K,which should be ascribed to the large lattice distortion and the huge mass fluctuation effect.The power factor can reach about 295μW/(m·K^(2))by inducing oxygen vacancies.Finally,the ZT value of 0.2 can be realized at 873 K in this bulk sample.This approach proposed a new concept of high entropy into thermoelectric oxides,which could be generalized for designing high-performance thermoelectric oxides with low thermal conductivity.展开更多
A distinctive kind of organic carbon aerosol that could absorb ultraviolet-visible radiation is called brown carbon(Br C),which has an important positive influence on radiative budget and climate change.In this work,w...A distinctive kind of organic carbon aerosol that could absorb ultraviolet-visible radiation is called brown carbon(Br C),which has an important positive influence on radiative budget and climate change.In this work,we reported the absorption properties and potential source of Br C based on a seven-wavelength aethalometer in the winter of 2018–2019 at an urban site of Sanmenxia in Fenwei Plain in central China.Specifically,the mean value of Br C absorption coefficient was 59.6±36.0 Mm^(-1) at 370 nm and contributed 37.7%to total absorption,which made a significant impact on visibility and regional environment.Absorption coefficients of Br C showed double-peak pattern,and Br C had shown small fluctuations under haze days compared with clean days.As for the sources of Br C,Br C absorption coefficients expressed strong correlations with element carbon aerosols and primary organic carbon aerosols,indicating that most of Br C originated from primary emissions.The linear correlations between trace metal elements(K,As,Fe,Mn,Zn,and Pb)and Br C absorption coefficients further referred that the major sources of Br C were primary emissions,like coal burning,biomass burning,and vehicle emissions.The moderate relationship between Br C absorption coefficients and secondary organic aerosols suggested that secondary production of Br C also played an important role.The 120 hr backward air mass trajectories analysis and concentration-weighted trajectories analysis were also used to investigate potential sources of Br C in and around this area,which inferred most parts of Br C were derived from local emissions.展开更多
Orphan genes that lack detectable homologues in other lineages could contribute to a variety of biological functions. However,their origination and function mechanisms remain largely unknown. Herein, through a compreh...Orphan genes that lack detectable homologues in other lineages could contribute to a variety of biological functions. However,their origination and function mechanisms remain largely unknown. Herein, through a comprehensive and systematic computational pipeline, we identified 893 orphan genes in the lineage of C. elegans, of which only a low fraction(0.9%) were derived from transposon elements. Six new protein-coding genes that de novo originated from non-coding DNA sequences in the genome of C. elegans were also identified. The authenticity and functionality of these orphan genes and de novo genes are supported by three lines of evidences, consisting of transcriptional data, and in silico proteomic data, and the fixation status data in wild populations. Orphan genes and de novo genes exhibited simple gene structures, such as, short in protein length, of fewer exons,and are frequently X-linked. RNA-seq data analysis showed these orphan genes are enriched with expression in embryo development and gonad, and their potential function in early development was further supported by gene ontology enrichment analysis results. Meanwhile, de novo genes were found to be with significant expression in gonad, and functional enrichment analysis of the co-expression genes of these de novo genes suggested they may be functionally involved in signaling transduction pathway and metabolism process. Our results presented the first systematic evidence on the evolution of orphan genes and de novo origin of genes in nematodes and their impacts on the functional and phenotypic evolution, and thus could shed new light on our appreciation of the importance of these new genes.展开更多
To better characterize the optical properties of atmospheric aerosols, the multi-wavelength cavity ring-down aerosol extinction spectrometer(MCRD-AES) is developed and applied in this study. By using tunable light sou...To better characterize the optical properties of atmospheric aerosols, the multi-wavelength cavity ring-down aerosol extinction spectrometer(MCRD-AES) is developed and applied in this study. By using tunable light source and four parallel cavities, the MCRD-AES covers a wide and atmospherically relevant wavelength range from 360 to 663 nm. Four wavelengths(375 nm, 440 nm, 532 nm, and 620 nm) are particularly tested with ammonium sulfate and nigrosine. The refractive index values obtained from this study agree well with literature data. The stability and accuracy of the MCRD-AES are tested, and the minimum detectable extinction coefficient is 0.5 1/Mm. The high sensitivity, high precision, and wavelength changeable of MCRD-AES indicate its great application prospect in comprehensively quantifying the optical properties of atmospheric aerosols.展开更多
We analyze the global structure and evolution of human gene coexpression networks driven by new gene integration. When the Pearson correlation coefficient is greater than or equal to 0.5, we find that the coexpression...We analyze the global structure and evolution of human gene coexpression networks driven by new gene integration. When the Pearson correlation coefficient is greater than or equal to 0.5, we find that the coexpression network consists of 334 small components and one "giant" connected subnet comprising of 6317 interacting genes. This network shows the properties of power-law degree distribution and small-world. The average clustering coefficient of younger genes is larger than that of the elderly genes(0.6685 vs. 0.5762). Particularly, we find that the younger genes with a larger degree also show a property of hierarchical architecture. The younger genes play an important role in the overall pivotability of the network and this network contains few redundant duplicate genes. Moreover, we find that gene duplication and orphan genes are two dominant evolutionary forces in shaping this network. Both the duplicate genes and orphan genes develop new links through a "rich-gets-richer"mechanism. With the gradual integration of new genes into the ancestral network, most of the topological structure features of the network would gradually increase. However, the exponent of degree distribution and modularity coefficient of the whole network do not change significantly, which implies that the evolution of coexpression networks maintains the hierarchical and modular structures in human ancestors.展开更多
文摘Global navigation satellite system has been widely used,but it is vulnerable to jamming.In military satellite communications,frequency hopping(FH)signal is usually used for anti-jamming communications.If the FH signal can be used in satellite navigation,the anti-jamming ability of satellite navigation can be improved.Although a recently proposed timefrequency matrix ranging method(TFMR)can use FH signals to realize pseudorange measurement,it cannot transmit navigation messages using the ranging signal which is crucial for satellite navigation.In this article,we propose dual-tone binary frequency shift keyingbased TFMR(DBFSK-TFMR).DBFSK-TFMR designs an extended time-frequency matrix(ETFM)and its generation algorithm,which can use the frequency differences in different dual-tone signals in ETFM to modulate data and eliminate the negative impact of data modulation on pseudorange measurement.Using ETFM,DBFSK-TFMR not only realizes the navigation message transmission but also ensures the precision and unambiguous measurement range of pseudorange measurement.DBFSK-TFMR can be used as an integrated solution for anti-jamming communication and navigation based on FH signals.Simulation results show that DBFSK-TFMR has almost the same ranging performance as TFMR.
基金supported by National Natural Science Foundation of China(Nos.51972346,51932011,51802356,and 51872334)Innovation-Driven Project of Central South University(No.2018CX004).
文摘Rechargeable aqueous zinc-ion batteries(AZIBs)have their unique advantages of cost efficiency,high safety,and environmental friendliness.However,challenges facing the cathode materials include whether they can remain chemically stable in aqueous electrolyte and provide a robust structure for the storage of Zn2+.Here,we report on H11Al2V6O23.2@graphene(HAVO@G)with exceptionally large layer spacing of(001)plane(13.36?).The graphene-wrapped structure can keep the structure stable during discharge/charge process,thereby promoting the inhibition of the dissolution of elements in the aqueous electrolyte.While used as cathode for AZIBs,HAVO@G electrode delivers ideal rate performance(reversible capacity of 305.4,276.6,230.0,201.7,180.6 mAh g?1 at current densities between 1 and 10 A g?1).Remarkably,the electrode exhibits excellent and stable cycling stability even at a high loading mass of^15.7 mg cm?2,with an ideal reversible capacity of 131.7 mAh g?1 after 400 cycles at 2 A g?1.
基金This work was supported by grants from the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA19030402 and XDA19030401)the China Meteorological Administration Special Public Welfare Research Fund(Grant No.GYHY201506002),the National Natural Science Foundation of China(Grant Nos.41675094,41975115)+1 种基金the Natural Science Foundation of Shaanxi Province(Grant No.2021JQ-166),Chinese Universities Scientific Fund(Grant No.2452019224)Open Research Fund of Key Laboratory of the Loess Plateau Soil Erosion and Water Process and Control,Ministry of Water Resources of China(Grant No.HTGY202002).
文摘Recently,the China Meteorological Administration(CMA)released a new Global Atmospheric Reanalysis(CRA-40)dataset for the period 1979−2018.In this study,surface relative humidity(RH)from CRA-40 and other current reanalyses(e.g.,CFSR,ERA5,ERA-Interim,JRA-55,and MERRA-2)is comprehensively evaluated against homogenized observations over China.The results suggest that most reanalyses overestimate the observations by 15%−30%(absolute difference)over the Tibetan Plateau but underestimate the observations by 5%−10%over most of northern China.The CRA-40 performs relatively well in describing the long-term change and variance seen in the observed surface RH over China.Most of the reanalyses reproduce the observed surface RH climatology and interannual variations well,while few reanalyses can capture the observed long-term RH trends over China.Among these reanalyses,the CFSR does poorly in describing the interannual changes in the observed RH,especially in Southwest China.An empirical orthogonal function(EOF)analysis also suggests that the CRA-40 performs better than other reanalyses to capture the first two leading EOF modes revealed by the observations.The results of this study are expected to improve understanding of the strengths and weaknesses of the current reanalysis products and thus facilitate their application.
基金supported by the National Natural Science Foundation of China(Grant Nos.41375036 and 41222033)the National Basic Research Program of China(Grant No.2016YFC0202001,973 Program 2014CB441200)the CAS Strategic Priority Research Program(Grant No.XDB05020103).
文摘Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China(Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth(AOD) at 500 nm was 0.32 ± 0.06, and the ?ngstr?m exponent(α) was 0.73 ± 0.27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM(March–April–May) resulted in the seasonal maximum AOD, 0.41 ± 0.04, and a relatively smaller αvalue, 0.44 ± 0.04. The tourism seasons, JJA(June–July–August) and SON(September–October–November) coincide with serious emissions of small anthropogenic aerosols. While in DJF(December–January–February), the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and αwere 0.29 ± 0.02 and 0.66 ± 0.17, respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM, ranges of AOD(0.11–1.18) and α(0.06–0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF, the similar ranges of AOD and α under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.
基金This study was supported by the National Key Research and Development Program of China(Grant No.2016YFC0202001)the Chinese Academy of Sciences Strategic Priority Research Program(Grant No.XDA23020301)the National Natural Science Foundation of China(Grant Nos.42061130215 and 41605119).
文摘Industrial pollution has a significant effect on aerosol properties in Changsha City,a typical city of central China.Therefore,year-round measurements of aerosol optical,radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed.During the observation period,the energy structure was continuously optimized,which was characterized by the reduction of coal combustion.The aerosol properties have obvious seasonal variations.The seasonal average aerosol optical depth(AOD)at 500 nm ranged from 0.49 to 1.00,single scattering albedo(SSA)ranged from 0.93 to 0.97,and aerosol radiative forcing at the top of the atmosphere(TOA)ranged from−24.0 to 3.8 W m^−2.The chemical components also showed seasonal variations.Meanwhile,the scattering aerosol,such as organic carbon,SO42−,NO3−,and NH4+showed a decrease,and elemental carbon increased.Compared with observation in winter 2012,AOD and TOA decreased by 0.14 and−1.49 W m^−2 in winter 2014.The scattering components,SO42−,NO3−and NH4+,decreased by 12.8μg m^−3(56.8%),9.2μg m^−3(48.8%)and 6.4μg m^−3(45.2%),respectively.The atmospheric visibility and pollution diffusion conditions improved.The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol.The results indicate that Changsha is an industrial city with strong scattering aerosol.The energy structure optimization had a marked effect on controlling pollution,especially in winter(strong scattering aerosol).
基金supported by the National Natural Science Foundation of China(Grant Nos.41375036,41222033,41305076)the Key Project of National Natural Science Foundation of China(Grant Nos.91644226)+1 种基金the CAS(Chinese Academy of Sciences)Strategic Priority Research Program(Grant No.XDA05100102,XDB05020103)the National Basic Research Program of China(Grant Nos.2016YFC0202001 and 2014CB441200)
文摘The quality of the MODIS C6 3-km and 10-km aerosol optical depth(AOD) products retrieved by the Dark Target(DT)method is discussed using ground-based observations in the Beijing–Tianjin–Hebei region from 1 August 2007 to 31 July2008. Good consistency exists between the 3-km and 10-km products and ground-based observations. The retrieval accuracy of the two products both show distinctive seasonality. The percentage falling within the expected error(EE) is largest in the winter, moderate in the spring and autumn, and smallest in the summer. A worse overestimation appears in the spring and summer(27%–66%). However, the 3-km and 10-km products over different surfaces still exhibit obvious deviations. The 10-km product performs better in the large cities, while the 3-km product has advantages in the suburbs. In urban areas, the percentage falling within EE of the 3-km AOD product(18%–59%) is lower than that for the 10-km AOD product(31%–69%). However, in suburban areas, the percentage falling within EE of the 3-km AOD product(61%–84%) is higher than for the 10 km AOD product(54%–83%).The percentages falling within EE differ considerably when the AOD is greater than1.5(73% and 63% for the 3-km and 10-km products, respectively). On the whole, the 3-km(10-km) AOD product performs better in suburban(urban) areas.
基金The Science Research Project of Inner Mongolia University of Technology under contract No.ZD201613
文摘In this paper,we discuss the interfacial internal waves with a rigid boundary in a three-layer fluid system,where the density of the upper layer fluid is smaller than that of the lower layer.With the Lagrangian matching conditions at the interfaces,the first-order solutions,the second-order solutions and the third-order asymptotic solutions for the interfacial internal waves are obtained in the Lagrangian description using the perturbation method,and the mass transport velocity,the wave frequency,the mean level and the particle trajectory are also given.The results show that the discontinuities across the interfaces appear for the mass transport velocity,wave frequency and mean level,but we find that these discontinuities may disappear if the water depth ratio and the density ratio of the three layer fluids satisfy certain conditions.
文摘With the rapid development of submarine oil and gas,the security issues of submarine oil and gas pipeline become increasingly prominent,and regular inspection of submarine pipeline is particularly important.Therefore,a submarine pipeline inspection robot system based on CT technology to solve the problems such as low traditional manual inspection efficiency,high labor cost,low security and backward inspection methods.Based on the platform of ROV robot,carrying CT scanner as an external detection device,the system is used for non-invasive inspection of submarine pipeline,which is safe and harmless,with good economy,high mobility,and strong environmental adaptability.Compared with traditional technology,CT scanner’s external inspection technology used in the system avoids the damage to the external protective layer of the pipeline in the measurement of pipeline wall thickness.Meantime,it can provide the tomography of the pipe wall and the composition of the sediment material on the inside wall,which fills the gap in this technical field in China.According to the test,the robot has the characteristics of stable adsorption,flexible movement,and clear pipeline CT scanning image,and can realize the intelligent inspection of submarine pipeline.
基金supported by the National Natural Science Foundation of China(Nos.12132019 and 11872042)the Open Fund for Key Laboratory of Deep Underground Science and Engineering of Ministry of Education(No.DESEYU202301)+1 种基金the 2023 Open Project of Failure Mechanics and Engineering Disaster Prevention,Key Lab of Sichuan Province(No.FMEDP202306)the Natural Science Foundation of Sichuan Province(No.2023NSFSC0043).
文摘In recent years,the issue of aircraft icing has gained widespread recognition.The breaking and detachment of dynamic ice can pose a threat to flight safety.However,the shedding and fracture mechanisms of dynamic ice are unclear and cannot meet the engineering needs of ice-shedding hazard assessment.Therefore,studying the fracture toughness of ice bodies has extremely important practical significance.To address this issue,this article uses a centrally cracked Brazilian disk(CCBD)specimen to measure the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice at different loading rates.The mixed-mode(Ⅰ–Ⅱ)fracture characteristics of ice are discussed,and the experimental results are compared and analyzed with the theoretical values of the generalized maximum tangential stress(GMTS)criterion considering the influence of T-stress.The results indicated that as the loading rate increases,the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice decrease,and the fracture toughness of freshwater ice is more sensitive to the loading rate.Ⅰn terms of fracture criteria,the theoretical value of the ratio of pure modeⅡfracture toughness to pure modeⅠfracture toughness based on the GMTS criterion is in good agreement with the experimental value,while the theoretical value based on the maximum tangential stress(MTS)criterion deviates significantly from the experimental value,indicating that the GMTS criterion considering the influence of T-stress can better predict the experimental results.
基金the National Natural Science Foundation of China(Nos.32070070,32211530074 and 31929001)the innovative research team of high-level local universities in Shanghai.H.D.thanks Royal Society-NSFC international exchange grant(IEC\NSFC\211349).
文摘The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.
基金This work was financially supported by Basic Science Center Project of National Natural Science Foundation of China under grant No.51788104National Science Foundation of China under grant No.52172211+2 种基金The work at Henan Polytechnic University is supported by the Doctoral Foundation of Henan Polytechnic University(in Natural and Science)(NO.B202112)the Fundamental Research Funds for the Universities of Henan Province(NO.NSFRF220421)B.W.was partially supported by the postgraduate research opportunities program of HZWTECH(HZWTECH-PROP).
文摘Polyhedral distortion,associated closely with the atomic arrangement and interatomic interactions,drives many unique behaviors in solids,such as phase transition and negative thermal expansion.In thermoelectric heteroanionic oxides,the anionic polyhedra are widely present,but their effect on thermal transport is rarely investigated.Here,we report an anomalous thermal conduction induced by local symmetry distortion in layered oxyselenides via solving the Boltzmann transport equation based on first-principles calculations.We found interestingly that lighter BiCuSeO exhibits lower thermal conductivity than heavier BiAgSeO.Due to the different distorted degrees of CuSe4 and AgSe4 tetrahedrons,Cu prefers the in-plane vibration,while Ag has more tendency of out-of-plane vibration.Thus,the heat-carrying phonons dominated by the rattling-like vibration of Cu are significantly suppressed,resulting in lower thermal conductivity of BiCuSeO.This study highlights the importance of polyhedral distortion in regulating thermal conduction in layered heteroanionic materials.
基金National Natural Science Foundation of China,Grant/Award Numbers:62272418,62102058Basic Public Welfare Research Program of Zhejiang Province,Grant/Award Number:LGG18E050011。
文摘Solder joint quality inspection is a crucial step in the qualification inspection of printed circuit board(PCB)components,and efficient and accurate inspection methods will greatly improve its production efficiency.In this paper,we propose a PCB solder joint quality detection algorithm based on a lightweight classification network.First,the Select Joint segmentation method was used to obtain the solder joint information,and colour space conversion was used to locate the solder joint.The mask method,contour detection,and box line method were combined to complete the extraction of solder joint information.Then,by combining the respective characteristics of convolutional neural network and Transformer and introducing Cross-covariance attention to reduce the computational complexity and resource consumption of the model and evenly distribute the global view mutual information in the whole training process,a new lightweight network model MobileXT is proposed to complete defect classification.Only 16.4%of the Vision Transformer computing resources used in this model can achieve an average accuracy improvement of 31%.Additionally,the network is trained and validated using a dataset of 1804 solder joint images constructed from 93 PCB images and two external datasets to evaluate MobileXT performance.The proposed method achieves more effi-cient localization of the solder joint information and more accurate classification of weld joint defects,and the lightweight model design is more appropriate for industrial edge device deployments.
文摘Background:The search for biomarkers suitable for early diagnosis of Crohn's disease(CD)is challenging.This study investigated the efficacy of serological markers for the early diagnosis of CD.Methods:This was a retrospective nested cohort study.Indirect immuno-fluorescence and enzyme‐linked immunosorbent assay were used to detect ASCA IgG,ASCA IgA,AYMA IgG,AYCA IgG,FI2Y IgG,p‐ANCA IgG,GAB IgG and PAB IgG in patient serum samples.Results:The positive rates of ASCA IgG,ASCA IgA,AYMA IgG,AYCA IgG,FI2Y IgG,p‐ANCA IgG,GAB IgG and PAB IgG in patients with early CD,advanced CD and other intestinal diseases were 37.0%versus 56.8%versus 27.8%;3.7%versus 20.5%versus 19.4%;14.8%versus 2.3%versus 2.8%;25.9%versus 9.1%versus 8.3%;18.5%versus 15.9%versus 8.3%;0.0%versus 2.8%,18.5%;13.6%versus 18.2%versus 16.7%;and 7.4%versus 20.5%versus 0.0%,respectively.The positive rates of ASCA IgG,AYCA IgG and PAB IgG were significantly different among the three groups(p<0.05).In 85.2%of early CD patients,at least one antibody was detected 1 year before diagnosis.The sensitivity of the ASCA/AYMA/AYCA/FI2Y/GAB combination for early diagnosis was 85.2%.The sensitivity of the ASCA/AYMA/AYCA/FI2Y/GAB/PAB/PANCA combination for differentiating CD from other diseases was 87.3%.Conclusions:ASCA IgG and AYCA IgG have potential value in identifying the course of CD.AYCA IgG may be a potential marker for the early diagnosis of CD,and ASCA IgG indicates an advanced stage.The combination of ASCA,AYMA,AYCA,FI2Y,and GAB improves early diagnostic accuracy of CD.
基金financially supported by Basic Science Center Project of the National Natural Science Foundation of China under Grant No.51788104National Key Research Program of China under Grant No.2016YFA0201003the National Natural Science Foundation of China under Grant No.51729201。
文摘Oxide-based ceramics could be promising thermoelectric materials because of their thermal and chemical stability at high temperature.However,their mediocre electrical conductivity or high thermal conductivity is still a challenge for the use in commercial devices.Here,we report significantly suppressed thermal conductivity in SrTiO_(3)-based thermoelectric ceramics via high-entropy strategy for the first time,and optimized electrical conductivity by defect engineering.In high-entropy(Ca_(0.2)Sr_(0.2)Ba_(0.2)Pb_(0.2)La_(0.2))TiO_(3)bulks,the minimum thermal conductivity can be 1.17 W/(m·K)at 923 K,which should be ascribed to the large lattice distortion and the huge mass fluctuation effect.The power factor can reach about 295μW/(m·K^(2))by inducing oxygen vacancies.Finally,the ZT value of 0.2 can be realized at 873 K in this bulk sample.This approach proposed a new concept of high entropy into thermoelectric oxides,which could be generalized for designing high-performance thermoelectric oxides with low thermal conductivity.
基金supported by The National Key Research and Development Program of China(No.2017YFC0209500)the National Natural Science Foundation of China(Nos.91744204,41822703,and 91844301)National research program for key issues in air pollution control(No.DQGG-0103)。
文摘A distinctive kind of organic carbon aerosol that could absorb ultraviolet-visible radiation is called brown carbon(Br C),which has an important positive influence on radiative budget and climate change.In this work,we reported the absorption properties and potential source of Br C based on a seven-wavelength aethalometer in the winter of 2018–2019 at an urban site of Sanmenxia in Fenwei Plain in central China.Specifically,the mean value of Br C absorption coefficient was 59.6±36.0 Mm^(-1) at 370 nm and contributed 37.7%to total absorption,which made a significant impact on visibility and regional environment.Absorption coefficients of Br C showed double-peak pattern,and Br C had shown small fluctuations under haze days compared with clean days.As for the sources of Br C,Br C absorption coefficients expressed strong correlations with element carbon aerosols and primary organic carbon aerosols,indicating that most of Br C originated from primary emissions.The linear correlations between trace metal elements(K,As,Fe,Mn,Zn,and Pb)and Br C absorption coefficients further referred that the major sources of Br C were primary emissions,like coal burning,biomass burning,and vehicle emissions.The moderate relationship between Br C absorption coefficients and secondary organic aerosols suggested that secondary production of Br C also played an important role.The 120 hr backward air mass trajectories analysis and concentration-weighted trajectories analysis were also used to investigate potential sources of Br C in and around this area,which inferred most parts of Br C were derived from local emissions.
基金supported by EEgrid cluster of the University of Chicagosupported by National Natural Science Foundation of China(31600670 to W.Zhang,31670851 to B.Shen)
文摘Orphan genes that lack detectable homologues in other lineages could contribute to a variety of biological functions. However,their origination and function mechanisms remain largely unknown. Herein, through a comprehensive and systematic computational pipeline, we identified 893 orphan genes in the lineage of C. elegans, of which only a low fraction(0.9%) were derived from transposon elements. Six new protein-coding genes that de novo originated from non-coding DNA sequences in the genome of C. elegans were also identified. The authenticity and functionality of these orphan genes and de novo genes are supported by three lines of evidences, consisting of transcriptional data, and in silico proteomic data, and the fixation status data in wild populations. Orphan genes and de novo genes exhibited simple gene structures, such as, short in protein length, of fewer exons,and are frequently X-linked. RNA-seq data analysis showed these orphan genes are enriched with expression in embryo development and gonad, and their potential function in early development was further supported by gene ontology enrichment analysis results. Meanwhile, de novo genes were found to be with significant expression in gonad, and functional enrichment analysis of the co-expression genes of these de novo genes suggested they may be functionally involved in signaling transduction pathway and metabolism process. Our results presented the first systematic evidence on the evolution of orphan genes and de novo origin of genes in nematodes and their impacts on the functional and phenotypic evolution, and thus could shed new light on our appreciation of the importance of these new genes.
基金supported by the National Natural Science Foundation of China (No.41227805)the National Key Research and Development Program of China (No.2016YFC0202704)
文摘To better characterize the optical properties of atmospheric aerosols, the multi-wavelength cavity ring-down aerosol extinction spectrometer(MCRD-AES) is developed and applied in this study. By using tunable light source and four parallel cavities, the MCRD-AES covers a wide and atmospherically relevant wavelength range from 360 to 663 nm. Four wavelengths(375 nm, 440 nm, 532 nm, and 620 nm) are particularly tested with ammonium sulfate and nigrosine. The refractive index values obtained from this study agree well with literature data. The stability and accuracy of the MCRD-AES are tested, and the minimum detectable extinction coefficient is 0.5 1/Mm. The high sensitivity, high precision, and wavelength changeable of MCRD-AES indicate its great application prospect in comprehensively quantifying the optical properties of atmospheric aerosols.
基金supported by grants from the National Natural Science Foundation of China(11571272,11201368 and 11631012)the National Science and Technology Major Project of China(2012ZX10002001)+1 种基金the Natural Science Foundation of Shaanxi Province(2015JQ1011)the China Postdoctoral Science Foundation(2014M560755)
文摘We analyze the global structure and evolution of human gene coexpression networks driven by new gene integration. When the Pearson correlation coefficient is greater than or equal to 0.5, we find that the coexpression network consists of 334 small components and one "giant" connected subnet comprising of 6317 interacting genes. This network shows the properties of power-law degree distribution and small-world. The average clustering coefficient of younger genes is larger than that of the elderly genes(0.6685 vs. 0.5762). Particularly, we find that the younger genes with a larger degree also show a property of hierarchical architecture. The younger genes play an important role in the overall pivotability of the network and this network contains few redundant duplicate genes. Moreover, we find that gene duplication and orphan genes are two dominant evolutionary forces in shaping this network. Both the duplicate genes and orphan genes develop new links through a "rich-gets-richer"mechanism. With the gradual integration of new genes into the ancestral network, most of the topological structure features of the network would gradually increase. However, the exponent of degree distribution and modularity coefficient of the whole network do not change significantly, which implies that the evolution of coexpression networks maintains the hierarchical and modular structures in human ancestors.