Pyrus pyrifolia Nakai‘Whangkeumbae'is a sand pear fruit with excellent nutritional quality and taste.However,the industrial development of pear fruit is significantly limited by its short shelf life.Salicylic aci...Pyrus pyrifolia Nakai‘Whangkeumbae'is a sand pear fruit with excellent nutritional quality and taste.However,the industrial development of pear fruit is significantly limited by its short shelf life.Salicylic acid(SA),a well-known phytohormone,can delay fruit senescence and improve shelf life.However,the mechanism by which SA regulates CONSTANS-LIKE genes(COLs)during fruit senescence and the role of COL genes in mediating fruit senescence in sand pear are poorly understood.In this study,22 COL genes were identified in sand pear,including four COLs(Pp COL8,Pp COL9a,Pp COL9b,and Pp COL14)identified via transcriptome analysis and 18 COLs through genome-wide analysis.These COL genes were divided into three subgroups according to the structural domains of the COL protein.Pp COL8,with two B-box motifs and one CCT domain,belonged to the first subgroup.In contrast,the other three Pp COLs,Pp COL9a,Pp COL9b,and Pp COL14,with similar conserved protein domains and gene structures,were assigned to the third subgroup.The four COLs showed different expression patterns in pear tissues and were preferentially expressed at the early stage of fruit development.Moreover,the expression of Pp COL8 was inhibited by exogenous SA treatment,while SA up-regulated the expression of Pp COL9a and Pp COL9b.Interestingly,Pp COL8 interacts with Pp MADS,a MADS-box protein preferentially expressed in fruit,and SA up-regulated its expression.While the production of ethylene and the content of malondialdehyde(MDA)were increased in Pp COL8-overexpression sand pear fruit,the antioxidant enzyme(POD and SOD)activity and the expression of Pp POD1 and Pp SOD1 in the sand pear fruits were down-regulated,which showed that Pp COL8 promoted sand pear fruit senescence.In contrast,the corresponding changes were the opposite in Pp MADS-overexpression sand pear fruits,suggesting that Pp MADS delayed sand pear fruit senescence.The co-transformation of Pp COL8 and Pp MADS also delayed sand pear fruit senescence.The results of this study revealed that Pp COL8 can play a key role in pear fruit senescence by interacting with Pp MADS through the SA signaling pathway.展开更多
This paper discusses the implicit function of refusal expressions that has been used by Chinese native speakers when responding to people’s offerings.By analyzing three conversations regarding how Chinese people have...This paper discusses the implicit function of refusal expressions that has been used by Chinese native speakers when responding to people’s offerings.By analyzing three conversations regarding how Chinese people have accepted people’s offerings during different time periods(1960’s,1980’s,and 2000’s),the author argues that the verbal refusal in reacting to people’s offerings(especially gifts)does not literally mean“No,I don’t want it.”Instead,it is a way to show humility,politeness,and respect to the gift giver,and it functions as an implicit form of acceptance.By referring to three excerpts chosen from The Book of Rites(Liji禮記),the author demonstrates the Chinese cultural values and cultural themes,focusing on what Chinese people say and do to show respect and politeness when dealing with gifts or other friendliness related offerings.The paper finds two pedagogical implications:1)it is the instructor’s responsibility to highlight the verbal and non-verbal behaviors that both native speakers and language learners do not ordinarily notice in language class,and 2)the repetitive contextualized performances in different levels of learning are necessary and play crucial roles in teaching and learning.展开更多
Microscopic vision has been widely applied in precision assembly.To achieve sufficiently high resolution in measurements for precision assembly when the sizes of the parts involved exceed the field of view of the visi...Microscopic vision has been widely applied in precision assembly.To achieve sufficiently high resolution in measurements for precision assembly when the sizes of the parts involved exceed the field of view of the vision system,an image mosaic technique must be used.In this paper,a method for constructing an image mosaic with non-overlapping areas with enhanced efficiency is proposed.First,an image mosaic model for the part is created using a geometric model of the measurement system installed on a X-Y-Z precision stages with high repeatability,and a path for image acquisition is established.Second,images are captured along the same path for a specified calibration plate,and an entire image is formed based on the given model.The measurement results obtained from the specified calibration plate are utilized to identify mosaic errors and apply compensation for the part requiring measurement.Experimental results show that the maximum error is less than 4μm for a camera with pixel equivalent 2.46μm,thereby demonstrating the accuracy of the proposed method.This image mosaic technique with non-overlapping regions can simplify image acquisition and reduce the workload involved in constructing an image mosaic.展开更多
Pollution flashover is one of themajor insulation accidents that can occur inmodern power systems.If the local arc is not sufficiently elongated by the creepage distance,the flashover performance of the insulator will...Pollution flashover is one of themajor insulation accidents that can occur inmodern power systems.If the local arc is not sufficiently elongated by the creepage distance,the flashover performance of the insulator will decrease.The insulator structure and equivalent salt deposition density(ESDD)are the main factors affecting the arc path and length.To investigate the forms of arc paths under different insulator structures and their influence on flashover characteristics,a platformfor recording arc paths is established.This study presents amethod to identify the pattern and distribution of insulator arc paths based on the effect of initial arc on electric field distribution.The results show that there are two main types of local arc paths between umbrellas—the cling-surface arc and the air-jump arc.Moreover,the air-jump arc includes two types—the bridging arc and the gap arc.With the increase in umbrella spacing and ESDD,the probability of arc propagation along the surface increases.The use of the creepage distance can be improved by changing the creepage coefficient to increase the distance between umbrellas.This method has over 90%accuracy.This study is of great significance for improving insulator structure and reducing pollution flashover accidents.展开更多
Straw strip mulching(SM)is a new mulching technology.From 2012 to 2018,SM’s effects on soil moisture and temperature and production performances were compared with other mulching practices,using three treatments:full...Straw strip mulching(SM)is a new mulching technology.From 2012 to 2018,SM’s effects on soil moisture and temperature and production performances were compared with other mulching practices,using three treatments:full-cover plastic mulch(PM),no mulch with wheat sown in rows as the control(CK),and SM with 50%to 59%of the field area mulched.Compared with CK,on average over six growing seasons,SM and PM increased grain yield by 27.0%and 21.7%,straw yield by 21.6%and 22.6%,kernels ha;by 26.6%and 19.0%,net income by 29.8%and-25.0%,soil temperature at 5 cm by-1.5°C and 0.2°C from overwintering to maturity,and soil water storage at 0–200 cm by 25 and 22 mm,respectively.The increase in soil moisture in SM and PM was greater in the early period(overwintering to jointing)than in the later period(booting to maturity)and at 0 to 120 cm than at 120–200 cm in the early period.Although the mean evapotranspiration of whole growth period across six seasons was similar among treatments,SM and PM increased water consumption during the key formation period of yield components after overwintering by 16 and 32 mm,respectively,while reducing it before overwintering.Compared with CK,SM and PM had the effects of warming during overwintering and cooling after jointing.By increasing water consumption after overwintering and ratio of transpiration to evapotranspiration and providing favorable soil temperature for multiple growth stages and more sufficient soil moisture,SM and PM promoted vegetative growth and increased kernels ha^(-1),the main mechanisms by which SM and PM increased grain yield relative to CK.Relative to PM,SM is a more economically beneficial and environment-friendly technology for dryland wheat production.展开更多
Super-resolution(SR) techniques, which are based on single or multi-frame low-resolution(LR) images, have been extensively investigated in the last two decades. Mixed-resolution multiview video format plays an importa...Super-resolution(SR) techniques, which are based on single or multi-frame low-resolution(LR) images, have been extensively investigated in the last two decades. Mixed-resolution multiview video format plays an important role in three-dimensional television(3DTV) coding scheme. Previous work considers multiview or multi-camera images and videos at the same resolution,which performs well under the planar model without or with little projection error among the videos captured by different cameras.In recent years, several researchers have discussed the SR problem in mixed-resolution multi-view video format, where the superresolved image is created using the up-sampled version of the LR image and the high frequency components extracted from the warped image in the adjacent high-resolution(HR) views. Unfortunately, the output HR images suffer from artifacts caused by depth error. To obtain the detailed texture and edge information from the HR image as much as possible, while preserving the structure of the LR image, a novel SR reconstruction algorithm is proposed.The algorithm is composed of three components: the structure term, the detail information term, and the regularization term. The first term preserves the structure similarity of the LR image; the second term extracts detailed information from the adjacent HR image; and the last term ensures the uniqueness of the solution.Experimental results show the effectiveness and robustness of the proposed algorithm, which achieves high performance both subjectively and objectively.展开更多
To widen the understanding of tensile failure of reticulated ceramic foams and expand the available mechanical method,a cylindrical splitting test is developed in the present study based on alumina open-cell foams of ...To widen the understanding of tensile failure of reticulated ceramic foams and expand the available mechanical method,a cylindrical splitting test is developed in the present study based on alumina open-cell foams of three different pore densities.The biaxial method is validated by characterization of mechanical parameters,and the in-situ fracture process is validated by a digital image correlation,followed by a formula correction for effective tensile strength with consideration of discrete crack paths.For experimental setup curved loading platens,compliant pad and intermediate quasi-static loading rate are proposed for guaranteeing tensile failure under a radial compressive load.Tensile strength,fracture energy,and brittleness increase with the foam pore density,and the fracture behavior is a balanced result of materials and foam structural support strength.An analytical model of splitting tensile strength with structural parameters is derived,which implies its dependence on cell size and critical stress intensity factor of strut materials.展开更多
High-temperature(HT)stress causes male sterility in crops,thus decreasing yields.To explore the possible contribution of histone modifications to male fertility under HT conditions,we defined the histone methylation l...High-temperature(HT)stress causes male sterility in crops,thus decreasing yields.To explore the possible contribution of histone modifications to male fertility under HT conditions,we defined the histone methylation landscape for the marks histone H3 lysine 27 trimethylation(H3K27me3)and histone H3 lysine 4 trimethylation(H3K4me3)by chromatin immunoprecipitation sequencing(ChIP-seq)in two differing upland cotton(Gossypium hirsutum)varieties.We observed a global disruption in H3K4me3 and H3K27me3 modifications,especially H3K27me3,in cotton anthers subjected to HT.HT affected the bivalent H3K4me3–H3K27me3 modification more than either monovalent modification.We determined that removal of H3K27me3 at the promoters of jasmonate-related genes increased their expression,maintaining male fertility under HT in the HT-tolerant variety at the anther dehiscence stage.Modulating jasmonate homeostasis or signaling resulted in an anther indehiscence phenotype under HT.Chemical suppression of H3K27me3 deposition increased jasmonic acid contents and maintained male fertility under HT.In summary,our study provides new insights into the regulation of male fertility by histone modifications under HT and suggests a potential strategy for improving cotton HT tolerance.展开更多
While recent years have witnessed a dramatic upsurge of exploiting deep neural networks toward solving image denoising,existing methods mostly rely on simple noise assumptions,such as additive white Gaussian noise(AWG...While recent years have witnessed a dramatic upsurge of exploiting deep neural networks toward solving image denoising,existing methods mostly rely on simple noise assumptions,such as additive white Gaussian noise(AWGN),JPEG compression noise and camera sensor noise,and a general-purpose blind denoising method for real images remains unsolved.In this paper,we attempt to solve this problem from the perspective of network architecture design and training data synthesis.Specifically,for the network architecture design,we propose a swin-conv block to incorporate the local modeling ability of residual convolutional layer and non-local modeling ability of swin transformer block,and then plug it as the main building block into the widely-used image-to-image translation UNet architecture.For the training data synthesis,we design a practical noise degradation model which takes into consideration different kinds of noise(including Gaussian,Poisson,speckle,JPEG compression,and processed camera sensor noises)and resizing,and also involves a random shuffle strategy and a double degradation strategy.Extensive experiments on AGWN removal and real image denoising demonstrate that the new network architecture design achieves state-of-the-art performance and the new degradation model can help to significantly improve the practicability.We believe our work can provide useful insights into current denoising research.The source code is available at https://github.com/cszn/SCUNet.展开更多
Two novel seco-polycyclic polyprenylated acylphloroglucinols(PPAPs),hyperbenzones A(1)and B(2),were isolated from the roots of Hypericum beanii,together with one known biosynthetic congener 3.Compound 1 incorporates a...Two novel seco-polycyclic polyprenylated acylphloroglucinols(PPAPs),hyperbenzones A(1)and B(2),were isolated from the roots of Hypericum beanii,together with one known biosynthetic congener 3.Compound 1 incorporates a 6/5/5 ring system with an unprecedented spiro[bicyclo[3.3.0]octane-3,1'-cyclohexane]-2,2'-dione motif.The structures of 1 and 2 were determined by a combination of high resolution electrospray ionization mass spectroscopy(HRESIMS),nuclear magnetic resonance(NMR)spectroscopic analyses,gage-independent atomic orbital(GIAO)NMR chemical shift calculation with DP4+analyses,electronic circular dichroism(ECD)calculation,and X-ray diffraction analysis.A 1,2-seco retroClaisen rearrangement from a bicyclo[3.3.1]nonane PPAP precursor and following chemodivergent radical cascade cyclizations are proposed as the key steps in the biosynthetic pathway to yield compounds 1 and2.Biological investigations indicated that compounds 1 and 3 could decrease intracellular lipid accumulation in a palmitic acid-induced nonalcoholic steatohepatitis(NASH)cell model.展开更多
What is already known about this topic?Environmental and occupational lead exposure has generally declined in the past two decades.However,there is no large-scale monitoring of blood lead levels(BLLs)in the Chinese ge...What is already known about this topic?Environmental and occupational lead exposure has generally declined in the past two decades.However,there is no large-scale monitoring of blood lead levels(BLLs)in the Chinese general population.What is added by this report?This nationally representative study showed declines of BLLs in all ages of participants;for children aged 3–5 years,down from 78.1μg/L to 16.9μg/L,corresponding to 78.4%decrease in the past two decades(2000–2018).What are the implications for public health practice?Recommendations for elevated BLLs on screening children at high risk now need to be revisited and updated from 100μg/L to 50μg/L in guidelines to conform with the substantial declines in China.展开更多
The recent development of imaging and sequencing technologies enables systematic advances in the clinical study of lung cancer.Meanwhile,the human mind is limited in effectively handling and fully utilizing the accumu...The recent development of imaging and sequencing technologies enables systematic advances in the clinical study of lung cancer.Meanwhile,the human mind is limited in effectively handling and fully utilizing the accumulation of such enormous amounts of data.Machine learningbased approaches play a critical role in integrating and analyzing these large and complex datasets,which have extensively characterized lung cancer through the use of different perspectives from these accrued data.In this review,we provide an overview of machine learning-based approaches that strengthen the varying aspects of lung cancer diagnosis and therapy,including early detection,auxiliary diagnosis,prognosis prediction,and immunotherapy practice.Moreover,we highlight the challenges and opportunities for future applications of machine learning in lung cancer.展开更多
Multi-walled carbon nanotubes(MWCNTs)reinforced Si_2BC_3N ceramics were prepared through mechanical alloying(MA)and following spark plasma sintering(SPS).The thermal shock resistance of Si_2BC_3N ceramics was evaluate...Multi-walled carbon nanotubes(MWCNTs)reinforced Si_2BC_3N ceramics were prepared through mechanical alloying(MA)and following spark plasma sintering(SPS).The thermal shock resistance of Si_2BC_3N ceramics was evaluated comparatively through ice water quenching test and theoretical prediction.Furthermore,the oxidation resistance of MWCNTs incorporated Si_2BC_3N ceramics was evaluated under high temperature.The results show that the calculated parameters such as the critical thermal shock temperature(R)and the thermal stresses resistance(R_(st)),as well as the toughness(R"")are improved with addition of 1 vol%MWCNTs.In addition,the crack propagation resistance of 1 vol%MWCNTs incorporated Si_2BC_3N ceramics is obviously improved through generating more tortuous crack propagation paths attributing to the"crack bridging","pull-out",and"crack deflection"mechanisms of MWCNTs.Therefore,the residual strengths of 1 vol%MWCNTs containing specimens remained the highest after the thermal shock tests.Besides,the present work also reveals that the oxidation resistance is more sensitive to relative density than MWCNTs addition.展开更多
C2 is a well-known pseudo-oxygen unit with an electron affinity of 3.4 eV. We show that it can exhibit metal-ion like behavior when embedded in a porphyrin sheet and form a metal-free two-dimensional material with sup...C2 is a well-known pseudo-oxygen unit with an electron affinity of 3.4 eV. We show that it can exhibit metal-ion like behavior when embedded in a porphyrin sheet and form a metal-free two-dimensional material with superior oxygen reduction performance. Here, the positively charged C=C units are highly active for oxygen reduction reaction （ORR） via dissociation pathways with a small energy barrier of 0.09 eV, much smaller than that of other non-platinum group metal （non-PGM） ORR catalysts. Using a microkinetics-based model we calculated the partial current density to be 3.0 mA/cm2 at 0.65 V vs. a standard hydrogen electrode （SHE）, which is comparable to that of the state-of-the-art Pt/C catalyst. We further confirm that the C=C embedded porphyrin sheet is dynamically and thermally stable with a quasi-direct band gap of 1.14 eV. The superior catalytic performance and geometric stability make the metal-free C=C porphyrin sheet ideal for fuel cell applications.展开更多
The porous p-type Bi_(0.4)Sb_(1.6)Te_3 bulks containing irregularly and randomly oriented pores were obtained by artificially controlling the relative density of sintered samples during resistance pressing sintering p...The porous p-type Bi_(0.4)Sb_(1.6)Te_3 bulks containing irregularly and randomly oriented pores were obtained by artificially controlling the relative density of sintered samples during resistance pressing sintering process. It is demonstrated that the thermoelectric performances are significantly affected by the porous structure, especially for the electrical and thermal conductivity due to the enhanced carrier scattering and phonon scattering. The increasing porosity resulted in the obvious decrease in electrical and thermal conductivity, and little change in Seebeck coefficients. It is encouraging that the reduction of thermal conductivity can compensate for the deterioration of electrical performance, leading to the enhancement in thermoelectric figure of merit(ZT). The maximum ZT value of 1.0 was obtained for the sample with a relative density of 90% at 333 K. Unfortunately, the increase in porosity also brought in obvious degradations in Vickers hardness from 51.71 to 27.74 HV. It is worth mentioning that although the Vickers hardness of the sample with a relative density of 90% decreased to 40.12 HV, it was still about twice as high as that of the zone melting sample(21.25 HV). To summarize, introducing pores structure into bulks properly not only enhances the ZT value of Bi_2Te_3 based alloys, but also reduces the use of raw materials and saves production cost.展开更多
Background:With improvements in next-generation DNA sequencing technology,lower cost is needed to collect genetic data.More machine learning techniques can be used to help with cancer analysis and diagnosis.Methods:We...Background:With improvements in next-generation DNA sequencing technology,lower cost is needed to collect genetic data.More machine learning techniques can be used to help with cancer analysis and diagnosis.Methods:We developed an ensemble machine learning system named performance-weighted-voting model for cancer type classification in 6,249 samples across 14 cancer types.Our ensemble system consists of five weak classifiers(logistic regression,SVM,random forest,XGBoost and neural networks).We first used cross-validation to get the predicted results for the five classifiers.The weights of the five weak classifiers can be obtained based on their predictive performance by solving linear regression functions.The final predicted probability of the performance-weighted-voting model for a cancer type can be determined by the summation of each classifier's weight multiplied by its predicted probability.Results:Using the somatic mutation count of each gene as the input feature,the overall accuracy of the performance-weighted-voting model reached 71.46%,which was significantly higher than the five weak classifiers and two other ensemble models:the hard-voting model and the soft-voting model.In addition,by analyzing the predictive pattern of the performance-weighted-voting model,we found that in most cancer types,higher tumor mutational burden can improve overall accuracy.Conclusion:This study has important clinical significance for identifying the origin of cancer,especially for those where the primary cannot be determined.In addition,our model presents a good strategy for using ensemble systems for cancer type classification.展开更多
High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process,including the synthesis of boron/nickel containing precursors by precipitation reactions and subseq...High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process,including the synthesis of boron/nickel containing precursors by precipitation reactions and subsequent thermally catalytic chemical vapor deposition reactions.The influence of catalyst content and annealing temperature on the phase composition and microstructure of the products were investigated.The results show that it is difficult to exert the catalytic effect of nickel-based catalyst at low temperatures(<1400℃).At appropriate temperatures(1400-1500℃),highly crystalline boron nitride nanotubes with a length of more than 50 mm and a diameter of 50 nm are formed.The content of catalyst in the precursor mainly affects the morphology of the boron nitride product.If the content is too low,it is easy to form boron nitride particles;while high catalyst content can easily lead to catalyst aggregation and form a submicron one-dimensional boron nitride with unregular structure.Based on microstructural evolutions,phase changes,and thermodynamic analysis,the vapor-liquid-solid(V-L-S)growth mechanism of the tip growth mode dominates the formation of boron nitride nanotubes has also been verified.展开更多
基金supported by the National Natural Science Foundation of China(32272654)the Natural Science Foundation of Hebei Province China(C2023204016)+2 种基金the Hebei Province Introduced Overseas-Scholar Fund China(C20220361)the S&T Program of Hebei China(20326330D)the Hebei Province Outstanding Youth Fund China(2016,2019)。
文摘Pyrus pyrifolia Nakai‘Whangkeumbae'is a sand pear fruit with excellent nutritional quality and taste.However,the industrial development of pear fruit is significantly limited by its short shelf life.Salicylic acid(SA),a well-known phytohormone,can delay fruit senescence and improve shelf life.However,the mechanism by which SA regulates CONSTANS-LIKE genes(COLs)during fruit senescence and the role of COL genes in mediating fruit senescence in sand pear are poorly understood.In this study,22 COL genes were identified in sand pear,including four COLs(Pp COL8,Pp COL9a,Pp COL9b,and Pp COL14)identified via transcriptome analysis and 18 COLs through genome-wide analysis.These COL genes were divided into three subgroups according to the structural domains of the COL protein.Pp COL8,with two B-box motifs and one CCT domain,belonged to the first subgroup.In contrast,the other three Pp COLs,Pp COL9a,Pp COL9b,and Pp COL14,with similar conserved protein domains and gene structures,were assigned to the third subgroup.The four COLs showed different expression patterns in pear tissues and were preferentially expressed at the early stage of fruit development.Moreover,the expression of Pp COL8 was inhibited by exogenous SA treatment,while SA up-regulated the expression of Pp COL9a and Pp COL9b.Interestingly,Pp COL8 interacts with Pp MADS,a MADS-box protein preferentially expressed in fruit,and SA up-regulated its expression.While the production of ethylene and the content of malondialdehyde(MDA)were increased in Pp COL8-overexpression sand pear fruit,the antioxidant enzyme(POD and SOD)activity and the expression of Pp POD1 and Pp SOD1 in the sand pear fruits were down-regulated,which showed that Pp COL8 promoted sand pear fruit senescence.In contrast,the corresponding changes were the opposite in Pp MADS-overexpression sand pear fruits,suggesting that Pp MADS delayed sand pear fruit senescence.The co-transformation of Pp COL8 and Pp MADS also delayed sand pear fruit senescence.The results of this study revealed that Pp COL8 can play a key role in pear fruit senescence by interacting with Pp MADS through the SA signaling pathway.
文摘This paper discusses the implicit function of refusal expressions that has been used by Chinese native speakers when responding to people’s offerings.By analyzing three conversations regarding how Chinese people have accepted people’s offerings during different time periods(1960’s,1980’s,and 2000’s),the author argues that the verbal refusal in reacting to people’s offerings(especially gifts)does not literally mean“No,I don’t want it.”Instead,it is a way to show humility,politeness,and respect to the gift giver,and it functions as an implicit form of acceptance.By referring to three excerpts chosen from The Book of Rites(Liji禮記),the author demonstrates the Chinese cultural values and cultural themes,focusing on what Chinese people say and do to show respect and politeness when dealing with gifts or other friendliness related offerings.The paper finds two pedagogical implications:1)it is the instructor’s responsibility to highlight the verbal and non-verbal behaviors that both native speakers and language learners do not ordinarily notice in language class,and 2)the repetitive contextualized performances in different levels of learning are necessary and play crucial roles in teaching and learning.
基金supported by the Liaoning Revitalization Talents Program(Grant No.XLYC2002020)the Major Project of Basic Scientific Research of Chinese Ministry(Grant No.JCYK2016205A003).
文摘Microscopic vision has been widely applied in precision assembly.To achieve sufficiently high resolution in measurements for precision assembly when the sizes of the parts involved exceed the field of view of the vision system,an image mosaic technique must be used.In this paper,a method for constructing an image mosaic with non-overlapping areas with enhanced efficiency is proposed.First,an image mosaic model for the part is created using a geometric model of the measurement system installed on a X-Y-Z precision stages with high repeatability,and a path for image acquisition is established.Second,images are captured along the same path for a specified calibration plate,and an entire image is formed based on the given model.The measurement results obtained from the specified calibration plate are utilized to identify mosaic errors and apply compensation for the part requiring measurement.Experimental results show that the maximum error is less than 4μm for a camera with pixel equivalent 2.46μm,thereby demonstrating the accuracy of the proposed method.This image mosaic technique with non-overlapping regions can simplify image acquisition and reduce the workload involved in constructing an image mosaic.
基金This work was supported by the National Natural Science Foundation of China(52007138)Chengdu Technology Innovation R&D Project(2022-YF05-00971-SN).
文摘Pollution flashover is one of themajor insulation accidents that can occur inmodern power systems.If the local arc is not sufficiently elongated by the creepage distance,the flashover performance of the insulator will decrease.The insulator structure and equivalent salt deposition density(ESDD)are the main factors affecting the arc path and length.To investigate the forms of arc paths under different insulator structures and their influence on flashover characteristics,a platformfor recording arc paths is established.This study presents amethod to identify the pattern and distribution of insulator arc paths based on the effect of initial arc on electric field distribution.The results show that there are two main types of local arc paths between umbrellas—the cling-surface arc and the air-jump arc.Moreover,the air-jump arc includes two types—the bridging arc and the gap arc.With the increase in umbrella spacing and ESDD,the probability of arc propagation along the surface increases.The use of the creepage distance can be improved by changing the creepage coefficient to increase the distance between umbrellas.This method has over 90%accuracy.This study is of great significance for improving insulator structure and reducing pollution flashover accidents.
基金State Key Laboratory of Aridland Crop Science,Gansu Agricultural University(GSCS-2019-Z05)China Agricultural Research System of the Ministry of Finance(MOF)and Ministry of Agriculture and Rural Affairs(MARA)(CARS-3-2-47)。
文摘Straw strip mulching(SM)is a new mulching technology.From 2012 to 2018,SM’s effects on soil moisture and temperature and production performances were compared with other mulching practices,using three treatments:full-cover plastic mulch(PM),no mulch with wheat sown in rows as the control(CK),and SM with 50%to 59%of the field area mulched.Compared with CK,on average over six growing seasons,SM and PM increased grain yield by 27.0%and 21.7%,straw yield by 21.6%and 22.6%,kernels ha;by 26.6%and 19.0%,net income by 29.8%and-25.0%,soil temperature at 5 cm by-1.5°C and 0.2°C from overwintering to maturity,and soil water storage at 0–200 cm by 25 and 22 mm,respectively.The increase in soil moisture in SM and PM was greater in the early period(overwintering to jointing)than in the later period(booting to maturity)and at 0 to 120 cm than at 120–200 cm in the early period.Although the mean evapotranspiration of whole growth period across six seasons was similar among treatments,SM and PM increased water consumption during the key formation period of yield components after overwintering by 16 and 32 mm,respectively,while reducing it before overwintering.Compared with CK,SM and PM had the effects of warming during overwintering and cooling after jointing.By increasing water consumption after overwintering and ratio of transpiration to evapotranspiration and providing favorable soil temperature for multiple growth stages and more sufficient soil moisture,SM and PM promoted vegetative growth and increased kernels ha^(-1),the main mechanisms by which SM and PM increased grain yield relative to CK.Relative to PM,SM is a more economically beneficial and environment-friendly technology for dryland wheat production.
基金supported by the National Natural Science Foundation of China(6107501361671126)
文摘Super-resolution(SR) techniques, which are based on single or multi-frame low-resolution(LR) images, have been extensively investigated in the last two decades. Mixed-resolution multiview video format plays an important role in three-dimensional television(3DTV) coding scheme. Previous work considers multiview or multi-camera images and videos at the same resolution,which performs well under the planar model without or with little projection error among the videos captured by different cameras.In recent years, several researchers have discussed the SR problem in mixed-resolution multi-view video format, where the superresolved image is created using the up-sampled version of the LR image and the high frequency components extracted from the warped image in the adjacent high-resolution(HR) views. Unfortunately, the output HR images suffer from artifacts caused by depth error. To obtain the detailed texture and edge information from the HR image as much as possible, while preserving the structure of the LR image, a novel SR reconstruction algorithm is proposed.The algorithm is composed of three components: the structure term, the detail information term, and the regularization term. The first term preserves the structure similarity of the LR image; the second term extracts detailed information from the adjacent HR image; and the last term ensures the uniqueness of the solution.Experimental results show the effectiveness and robustness of the proposed algorithm, which achieves high performance both subjectively and objectively.
基金support from the National Natural Science Foundation of China(Nos.U21A2058 and U22A20127)the German Research Foundation(Collaborative Research Center 920,Multi-Functional Filters for Metal Melt Filtration-A Contribution toward Zero Defect Materials)are appreciated.The author Claudia Voigt would like to thank the Federal Ministry of Education and Research(BMBF)for supporting these investigations as part of the junior research group PurCo(No.03XP0420).
文摘To widen the understanding of tensile failure of reticulated ceramic foams and expand the available mechanical method,a cylindrical splitting test is developed in the present study based on alumina open-cell foams of three different pore densities.The biaxial method is validated by characterization of mechanical parameters,and the in-situ fracture process is validated by a digital image correlation,followed by a formula correction for effective tensile strength with consideration of discrete crack paths.For experimental setup curved loading platens,compliant pad and intermediate quasi-static loading rate are proposed for guaranteeing tensile failure under a radial compressive load.Tensile strength,fracture energy,and brittleness increase with the foam pore density,and the fracture behavior is a balanced result of materials and foam structural support strength.An analytical model of splitting tensile strength with structural parameters is derived,which implies its dependence on cell size and critical stress intensity factor of strut materials.
基金supported by the Major Project of Hubei Hongshan Laboratory(2022hszd004)the National Cotton Production System,Ministry of Agriculture and Rural Affairs of China(CARS-15-04)+1 种基金the National Key R&D Program of China(2022YFF1003502)the National Natural Science Foundation of China(32072024).
文摘High-temperature(HT)stress causes male sterility in crops,thus decreasing yields.To explore the possible contribution of histone modifications to male fertility under HT conditions,we defined the histone methylation landscape for the marks histone H3 lysine 27 trimethylation(H3K27me3)and histone H3 lysine 4 trimethylation(H3K4me3)by chromatin immunoprecipitation sequencing(ChIP-seq)in two differing upland cotton(Gossypium hirsutum)varieties.We observed a global disruption in H3K4me3 and H3K27me3 modifications,especially H3K27me3,in cotton anthers subjected to HT.HT affected the bivalent H3K4me3–H3K27me3 modification more than either monovalent modification.We determined that removal of H3K27me3 at the promoters of jasmonate-related genes increased their expression,maintaining male fertility under HT in the HT-tolerant variety at the anther dehiscence stage.Modulating jasmonate homeostasis or signaling resulted in an anther indehiscence phenotype under HT.Chemical suppression of H3K27me3 deposition increased jasmonic acid contents and maintained male fertility under HT.In summary,our study provides new insights into the regulation of male fertility by histone modifications under HT and suggests a potential strategy for improving cotton HT tolerance.
基金This work was partly supported by the ETH Zürich Fund(OK),and by Huawei grants.
文摘While recent years have witnessed a dramatic upsurge of exploiting deep neural networks toward solving image denoising,existing methods mostly rely on simple noise assumptions,such as additive white Gaussian noise(AWGN),JPEG compression noise and camera sensor noise,and a general-purpose blind denoising method for real images remains unsolved.In this paper,we attempt to solve this problem from the perspective of network architecture design and training data synthesis.Specifically,for the network architecture design,we propose a swin-conv block to incorporate the local modeling ability of residual convolutional layer and non-local modeling ability of swin transformer block,and then plug it as the main building block into the widely-used image-to-image translation UNet architecture.For the training data synthesis,we design a practical noise degradation model which takes into consideration different kinds of noise(including Gaussian,Poisson,speckle,JPEG compression,and processed camera sensor noises)and resizing,and also involves a random shuffle strategy and a double degradation strategy.Extensive experiments on AGWN removal and real image denoising demonstrate that the new network architecture design achieves state-of-the-art performance and the new degradation model can help to significantly improve the practicability.We believe our work can provide useful insights into current denoising research.The source code is available at https://github.com/cszn/SCUNet.
基金supported by the National Natural Science Foundation of China(Nos.31900287 and 81773886)the 111 Project from Ministry of Education of China and the State Administration of Foreign Export Affairs of China(No.B18056)Special fund from the Central Committee for guiding local scientific and technological development of Shenzhen(No.2021Szvup161)。
文摘Two novel seco-polycyclic polyprenylated acylphloroglucinols(PPAPs),hyperbenzones A(1)and B(2),were isolated from the roots of Hypericum beanii,together with one known biosynthetic congener 3.Compound 1 incorporates a 6/5/5 ring system with an unprecedented spiro[bicyclo[3.3.0]octane-3,1'-cyclohexane]-2,2'-dione motif.The structures of 1 and 2 were determined by a combination of high resolution electrospray ionization mass spectroscopy(HRESIMS),nuclear magnetic resonance(NMR)spectroscopic analyses,gage-independent atomic orbital(GIAO)NMR chemical shift calculation with DP4+analyses,electronic circular dichroism(ECD)calculation,and X-ray diffraction analysis.A 1,2-seco retroClaisen rearrangement from a bicyclo[3.3.1]nonane PPAP precursor and following chemodivergent radical cascade cyclizations are proposed as the key steps in the biosynthetic pathway to yield compounds 1 and2.Biological investigations indicated that compounds 1 and 3 could decrease intracellular lipid accumulation in a palmitic acid-induced nonalcoholic steatohepatitis(NASH)cell model.
基金supported by National Health Commission of the People's Republic of China,the National Institute of Environmental Health of Chinese Center for Disease Control and Prevention,and National Natural Sciences Foundation of China(81872707).
文摘What is already known about this topic?Environmental and occupational lead exposure has generally declined in the past two decades.However,there is no large-scale monitoring of blood lead levels(BLLs)in the Chinese general population.What is added by this report?This nationally representative study showed declines of BLLs in all ages of participants;for children aged 3–5 years,down from 78.1μg/L to 16.9μg/L,corresponding to 78.4%decrease in the past two decades(2000–2018).What are the implications for public health practice?Recommendations for elevated BLLs on screening children at high risk now need to be revisited and updated from 100μg/L to 50μg/L in guidelines to conform with the substantial declines in China.
基金supported in part by the National Institutes of Health,USA(Grant Nos.U01TR003528 and R01LM013337).
文摘The recent development of imaging and sequencing technologies enables systematic advances in the clinical study of lung cancer.Meanwhile,the human mind is limited in effectively handling and fully utilizing the accumulation of such enormous amounts of data.Machine learningbased approaches play a critical role in integrating and analyzing these large and complex datasets,which have extensively characterized lung cancer through the use of different perspectives from these accrued data.In this review,we provide an overview of machine learning-based approaches that strengthen the varying aspects of lung cancer diagnosis and therapy,including early detection,auxiliary diagnosis,prognosis prediction,and immunotherapy practice.Moreover,we highlight the challenges and opportunities for future applications of machine learning in lung cancer.
基金supported financially by National Natural Science Foundation of China (NSFC,Grant Nos. 51702065 and 51621091)
文摘Multi-walled carbon nanotubes(MWCNTs)reinforced Si_2BC_3N ceramics were prepared through mechanical alloying(MA)and following spark plasma sintering(SPS).The thermal shock resistance of Si_2BC_3N ceramics was evaluated comparatively through ice water quenching test and theoretical prediction.Furthermore,the oxidation resistance of MWCNTs incorporated Si_2BC_3N ceramics was evaluated under high temperature.The results show that the calculated parameters such as the critical thermal shock temperature(R)and the thermal stresses resistance(R_(st)),as well as the toughness(R"")are improved with addition of 1 vol%MWCNTs.In addition,the crack propagation resistance of 1 vol%MWCNTs incorporated Si_2BC_3N ceramics is obviously improved through generating more tortuous crack propagation paths attributing to the"crack bridging","pull-out",and"crack deflection"mechanisms of MWCNTs.Therefore,the residual strengths of 1 vol%MWCNTs containing specimens remained the highest after the thermal shock tests.Besides,the present work also reveals that the oxidation resistance is more sensitive to relative density than MWCNTs addition.
文摘C2 is a well-known pseudo-oxygen unit with an electron affinity of 3.4 eV. We show that it can exhibit metal-ion like behavior when embedded in a porphyrin sheet and form a metal-free two-dimensional material with superior oxygen reduction performance. Here, the positively charged C=C units are highly active for oxygen reduction reaction （ORR） via dissociation pathways with a small energy barrier of 0.09 eV, much smaller than that of other non-platinum group metal （non-PGM） ORR catalysts. Using a microkinetics-based model we calculated the partial current density to be 3.0 mA/cm2 at 0.65 V vs. a standard hydrogen electrode （SHE）, which is comparable to that of the state-of-the-art Pt/C catalyst. We further confirm that the C=C embedded porphyrin sheet is dynamically and thermally stable with a quasi-direct band gap of 1.14 eV. The superior catalytic performance and geometric stability make the metal-free C=C porphyrin sheet ideal for fuel cell applications.
基金supported financially by the National Natural Science Foundation of China(Nos.11074195 and 51674181)the Key Projects of Hubei Provincial Department of Education(No.D20151103)
文摘The porous p-type Bi_(0.4)Sb_(1.6)Te_3 bulks containing irregularly and randomly oriented pores were obtained by artificially controlling the relative density of sintered samples during resistance pressing sintering process. It is demonstrated that the thermoelectric performances are significantly affected by the porous structure, especially for the electrical and thermal conductivity due to the enhanced carrier scattering and phonon scattering. The increasing porosity resulted in the obvious decrease in electrical and thermal conductivity, and little change in Seebeck coefficients. It is encouraging that the reduction of thermal conductivity can compensate for the deterioration of electrical performance, leading to the enhancement in thermoelectric figure of merit(ZT). The maximum ZT value of 1.0 was obtained for the sample with a relative density of 90% at 333 K. Unfortunately, the increase in porosity also brought in obvious degradations in Vickers hardness from 51.71 to 27.74 HV. It is worth mentioning that although the Vickers hardness of the sample with a relative density of 90% decreased to 40.12 HV, it was still about twice as high as that of the zone melting sample(21.25 HV). To summarize, introducing pores structure into bulks properly not only enhances the ZT value of Bi_2Te_3 based alloys, but also reduces the use of raw materials and saves production cost.
文摘Background:With improvements in next-generation DNA sequencing technology,lower cost is needed to collect genetic data.More machine learning techniques can be used to help with cancer analysis and diagnosis.Methods:We developed an ensemble machine learning system named performance-weighted-voting model for cancer type classification in 6,249 samples across 14 cancer types.Our ensemble system consists of five weak classifiers(logistic regression,SVM,random forest,XGBoost and neural networks).We first used cross-validation to get the predicted results for the five classifiers.The weights of the five weak classifiers can be obtained based on their predictive performance by solving linear regression functions.The final predicted probability of the performance-weighted-voting model for a cancer type can be determined by the summation of each classifier's weight multiplied by its predicted probability.Results:Using the somatic mutation count of each gene as the input feature,the overall accuracy of the performance-weighted-voting model reached 71.46%,which was significantly higher than the five weak classifiers and two other ensemble models:the hard-voting model and the soft-voting model.In addition,by analyzing the predictive pattern of the performance-weighted-voting model,we found that in most cancer types,higher tumor mutational burden can improve overall accuracy.Conclusion:This study has important clinical significance for identifying the origin of cancer,especially for those where the primary cannot be determined.In addition,our model presents a good strategy for using ensemble systems for cancer type classification.
基金supported by the National Natural Science Foundation of China,China(52002293)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology,China(2021QNRC001,YESS20210230)+3 种基金the Open Project of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing of Wuhan University of Technology,China(21-KF-25)the Innovative Project of Key Laboratory of Green Chemical Engineering Process of Ministry of Education(GCX202106)Science Research Fund(K202029)College Students Innovation and Entrepreneurship Training Program(S202110490021)of Wuhan Institute of Technology,China.
文摘High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process,including the synthesis of boron/nickel containing precursors by precipitation reactions and subsequent thermally catalytic chemical vapor deposition reactions.The influence of catalyst content and annealing temperature on the phase composition and microstructure of the products were investigated.The results show that it is difficult to exert the catalytic effect of nickel-based catalyst at low temperatures(<1400℃).At appropriate temperatures(1400-1500℃),highly crystalline boron nitride nanotubes with a length of more than 50 mm and a diameter of 50 nm are formed.The content of catalyst in the precursor mainly affects the morphology of the boron nitride product.If the content is too low,it is easy to form boron nitride particles;while high catalyst content can easily lead to catalyst aggregation and form a submicron one-dimensional boron nitride with unregular structure.Based on microstructural evolutions,phase changes,and thermodynamic analysis,the vapor-liquid-solid(V-L-S)growth mechanism of the tip growth mode dominates the formation of boron nitride nanotubes has also been verified.
