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3D robust anisotropic diffusion filtering algorithm for sparse view neutron computed tomography 3D image reconstruction

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Nuclear Science and Techniques 2024年第3期35卷 13-29页

作者： Yang Liu Teng-Fei Zhu Zhi Luo Xiao-Ping Ouyang School of Nuclear Science and Engineering North China Electric Power UniversityBeijing 102206China State key laboratory of Nuclear Resources and Environment East China University of TechnologyNanchang 330013China State key laboratory of Intense Pulsed Radiation Simulation and Effect Xi’an 710024China

The most critical part of a neutron computed tomography(NCT) system is the image processing algorithm,which directly affects the quality and speed of the reconstructed images.Various types of noise in the system can degrade the quality of the reconstructed images.Therefore,to improve the quality of the reconstructed images of NCT systems,efficient image processing algorithms must be used.The anisotropic diffusion filtering(ADF) algorithm can not only effectively suppress the noise in the projection data,but also preserve the image edge structure information by reducing the diffusion at the image edges.Therefore,we propose the application of the ADF algorithm for NCT image reconstruction.To compare the performance of different algorithms in NCT systems,we reconstructed images using the ordered subset simultaneous algebraic reconstruction technique(OS-SART) algorithm with different regular terms as image processing algorithms.In the iterative reconstruction,we selected two image processing algorithms,the Total Variation and split Bregman solved total variation algorithms,for comparison with the performance of the ADF algorithm.Additionally,the filtered back-projection algorithm was used for comparison with an iterative algorithm.By reconstructing the projection data of the numerical and clock models,we compared and analyzed the effects of each algorithm applied in the NCT system.Based on the reconstruction results,OS-SART-ADF outperformed the other algorithms in terms of denoising,preserving the edge structure,and suppressing artifacts.For example,when the 3D Shepp–Logan was reconstructed at 25 views,the root mean square error of OS-SART-ADF was the smallest among the four iterative algorithms,at only 0.0292.The universal quality index,mean structural similarity,and correlation coefficient of the reconstructed image were the largest among all algorithms,with values of 0.9877,0.9878,and 0.9887,respectively.

关键词： NCT OS-SART Sparse-view Anisotropic diffusion filtering

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Evolutionary mechanisms and practical significance of reproductive success and clonal diversity in unisexual vertebrate polyploids

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Science China(Life Sciences) 2024年第3期67卷 449-459页

作者： Meng Lu Li Zhou Jian-Fang Gui State key laboratory of Freshwater Ecology and Biotechnology Hubei Hongshan Laboratorythe Innovation Academy of Seed DesignInstitute of HydrobiologyChinese Academy of SciencesWuhan 430072China University of Chinese Academy of Sciences Beijing 100049China

Unisexual reproduction is generally relevant to polyploidy, and unisexual vertebrates are often considered an evolutionary “dead end” due to the accumulation of deleterious mutations and absence of genetic diversity. However, some unisexual polyploids have developed strategies to avoid genomic decay, and thus provide ideal models to unveil unexplored evolutionary mechanisms, from the reproductive success to clonal diversity creation. This article reviews the evolutionary mechanisms for overcoming meiotic barrier and generating genetic diversity in unisexual vertebrates, and summarizes recent research advancements in the polyploid Carassius complex. Gynogenetic gibel carp(Carassius gibelio) is a unique amphitriploid that has undergone a recurrent autotriploidy and has overcome the bottleneck of triploid sterility via gynogenesis. Recently, an efficient strategy in which ploidy changes, including from amphitriploid to amphitetraploid, then from amphitetraploid to novel amphitriploid, drive unisexual-sexual-unisexual reproduction transition and clonal diversity has been revealed.Based on this new discovery, multigenomic reconstruction biotechnology has been used to breed a novel strain with superior growth and stronger disease resistance. Moreover, a unique reproduction mode that combines both abilities of ameiotic oogenesis and sperm-egg fusion,termed as ameio-fusiongensis, has been discovered, and it provides an efficient approach to synthesize sterile allopolyploids. In order to avoid ecological risks upon escape and protect the sustainable property rights of the aquaculture seed industry, a controllable fertility biotechnology approach for precise breeding is being developed by integrating sterile allopolyploid synthesis and gene-editing techniques.This review provides novel insights into the origin and evolution of unisexual vertebrates and into the attempts being made to exploit new breeding biotechnologies in aquaculture.

关键词： unisexual vertebrates polyploidy reproduction transition clonal diversity precise breeding genomic reconstruction controllable fertility

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Dynamic mechanical characteristics of deep Jinping marble in complex stress environments

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 630-644页

作者： Chendi Lou Heping Xie Ru Zhang Hai Ren Hao Luo Kun Xiao Yuan Peng Qiang Tan Li Ren Institute for Disaster Management and reconstruction Sichuan UniversityChengdu610207China College of Water Resource&Hydropower Sichuan UniversityChengdu610065China MOE key laboratory of Deep Earth Science&Engineering Sichuan UniversityChengdu610065China Yalong River Hydropower Development Company Ltd.Chengdu610051China (Chongqing)International Engineering Technology Company Ltd.Chongqing401121China

To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.

关键词： Rock mechanics Split-Hopkinson pressure bar Coupled static‒dynamic loading Different depths Holmquist-Johnson-Cook(HJC)model

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Assessment of tree-ring mercury radial translocation and age effect in Masson pine:Implications for historical atmospheric mercury reconstruction

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Journal of Environmental Sciences 2024年第4期138卷 266-276页

作者： Xu Liu Xun Wang Dingyong Wang College of Resources and Environment Southwest UniversityChongqing 400715China State key laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China

The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the reliability.In this study,we comprehensively evaluated the Hg source,radial translocation and age effect of Masson pine(Pinus massoniana)tree ring at Mt.Jinyun in Chongqing,to assess the suitability of such tree ring as the archive of atmospheric Hg.Results showed that distinct variabilities among Masson pine tree-ring Hg concentration profiles.The Hg concentration significantly increased along with stem height(P<0.05),indicating the Hg in tree rings mainly derived from foliage uptake atmospheric Hg.We found a distinct age effect that the tree ring of young trees had the higher Hg concentration.Besides,we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree rings.The modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in Chongqing.We finally suggest that in further Hg dendrochemistry,better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.

关键词： Masson pine Tree-ring mercury Radial translocation Tree age effect

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Sparse Modal Decomposition Method Addressing Underdetermined Vortex-Induced Vibration reconstruction Problem for Marine Risers

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China Ocean Engineering 2024年第2期38卷 285-296页

作者： DU Zun-feng ZHU Hai-ming YU Jian-xing State key laboratory of Hydraulic Engineering Intelligent Construction and Operation School of Civil EngineeringTianjin UniversityTianjin 300350China

When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.

关键词： motion reconstruction vortex-induced vibration(VIV) marine riser modal decomposition method compressed sensing

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Pan-African metamorphism and magmatism in the Prydz Belt,East Antarctica:a geochronological perspective

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Advances in Polar Science 2024年第2期35卷 143-156页

作者： BAO Hong WANG Wei-(RZ) LIU Xinshu ZHAO Yue GONG Tingnan LIU Xiaochun CUI Ying TIAN Zuolin Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China key laboratory of Paleomagnetism and Tectonic reconstruction Ministry of Natural ResourcesBeijing 100081China China University of Geosciences(Beijing) Beijing 100081China MOE key laboratory of Orogenic Belt and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China

The Prydz Belt in East Antarctica underwent extensive reworking during the late Neoprotertozoic–early Paleozoic Pan-African orogeny,which is characterized by granulite facies,clockwise P–T paths,and high dT/dP values.This study compiles the existing age and composition data of zircon and monazite from metamorphic rocks and links their key characteristics to the metamorphic evolution of the Prydz Belt.The frequency of zircon U–Pb ages starts to increase noticeably from~555 Ma,peaking between 530 Ma and 520 Ma,followed by a dramatic decline after 520 Ma.High Th/U values(>0.1)of zircon are observed from~545 Ma,displaying a noticeable increasing trend in Th/U values before a rapid decline from~520 Ma.The frequency of monazite ages progressively increases from~540 Ma,reaching its peak at 515 Ma,and then rapidly decreases after 490 Ma.Combined with the crystallization behaviors of zircon and monazite,this study suggests that the systematic changes in Th/U values of zircon after 545 Ma indicate a transition in the thermal regime of the Prydz Belt towards the cooling stage.Abundant growth of zircon and monazite corresponds to the post-peak cooling process,while the crystallization peak of monazite lags behind that of zircon by~5–15 Ma,which indicates a relatively low cooling rate.Though the granitic intrusions accompanied the entire metamorphic evolution,the majority of them are younger than 520 Ma.The results suggest that the Pan-African event likely peaked at~555–545 Ma and gradually cooled to near-solidus conditions at~520–510 Ma,with a relatively slow average cooling process.

关键词： East Antarctica Prydz Belt Pan-African orogeny zircon monazite U–Pb dating

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Across two phylogeographic breaks: Quaternary evolutionary history of a mountain aspen (Populus rotundifolia) in the Hengduan Mountains

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Plant Diversity 2024年第3期46卷 321-332页

作者： Jieshi Tang Xiaoyan Fan Richard I.Milne Heng Yang Wenjing Tao Xinran Zhang Mengyun Guo Jialiang Li Kangshan Mao key laboratory of Bio-Resource and Eco-Environment of Ministry of Education College of Life SciencesState Key Laboratory of Hydraulics and Mountain River EngineeringSichuan UniversityChengdu 610065PR China Institute of Molecular Plant Sciences University of EdinburghEdinburgh EH93JHUK School of Ecology and Environment Tibet UniversityLhasa 850000PR China

Biogeographical barriers to gene flow are central to plant phylogeography.In East Asia,plant distribution is greatly influenced by two phylogeographic breaks,the Mekong-Salween Divide and Tanaka-Kaiyong Line,however,few studies have investigated how these barriers affect the genetic diversity of species that are distributed across both.Here we used 14 microsatellite loci and four chloroplast DNA fragments to examine genetic diversity and distribution patterns of 49 populations of Populus rotundifolia,a species that spans both the Mekong-Salween Divide and the Tanaka-Kaiyong Line in southwestern China.Demographic and migration hypotheses were tested using coalescent-based approaches.Limited historical gene flow was observed between the western and eastern groups of P.rotundifolia,but substantial flow occurred across both the Mekong-Salween Divide and Tanaka-Kaiyong Line,manifesting in clear admixture and high genetic diversity in the central group.Wind-borne pollen and seeds may have facilitated the dispersal of P.rotundifolia following prevalent northwest winds in the spring.We also found that the Hengduan Mountains,where multiple genetic barriers were detected,acted on the whole as a barrier between the western and eastern groups of P.rotundifolia.Ecological niche modeling suggested that P.rotundifolia has undergone range expansion since the last glacial maximum,and demographic reconstruction indicated an earlier population expansion around 600 Ka.The phylogeographic pattern of P.rotundifolia reflects the interplay of biological traits,wind patterns,barriers,niche differentiation,and Quaternary climate history.This study emphasizes the need for multiple lines of evidence in understanding the Quaternary evolution of plants in topographically complex areas.

关键词： Chloroplast DNA Microsatellite Phylogeographic break Populus rotundifolia Quaternary history Wind direction

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Unraveling the Cenozoic carbon cycle by reconstructing carbonate compensation depth(CCD)

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Science China Earth Sciences 2024年第6期67卷 1743-1758页

作者： Kaixun XIAO Xiumian HU Jingxin JIANG Jiahao WANG State key laboratory of Mineral Deposit Research School of Earth Sciences and EngineeringNanjing UniversityNanjing 210023China

The Carbonate Compensation Depth(CCD)refers to the depth within the ocean where the production and dissolution rates of carbonates reach equilibrium,widely likened to the oceanic calcareous‘snowline’.The reconstruction of deep-time CCD has significant implications for understanding ocean circulation,seawater chemical conditions,sediment distribution,and the surface carbon cycle.This paper critically reviews the methods for CCD reconstruction,summarizes the driving mechanisms of the Cenozoic CCD evolution and its association with the carbon cycle,and offers insights into future directions for CCD research.CCD reconstruction has evolved over the past half century from early qualitative to quantitative methods.These methodological improvements have markedly improved the accuracy and resolution of CCD.Existing studies have indicated a general trend of the CCD deepening across major ocean basins since the Cenozoic,interspersed with a minor shallowing phase during the mid-Miocene.The variations in the CCD are primarily influenced by factors such as ocean productivity,weathering,and shelf-basin partitioning.During climate events such as the Paleocene-Eocene Thermal Maximum,the CCD exhibits pulselike fluctuations.Future research should focus on precision and quantification while integrating model simulations to further explore the correlations and response mechanisms between the CCD and the paleoclimate as well as the carbon cycle.

关键词： Carbonate Compensation Depth Cenozoic Carbon cycle Paleoclimate Paleoceanography

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Challenges and opportunities in Quaternary palynology

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Science China Earth Sciences 2024年第7期67卷 2148-2161页

作者： Qinghai XU Houyuan LU Zhuo ZHENG College of Geographical Sciences Hebei Key Laboratory of Environmental Change and Ecological ConstructionHebei Normal UniversityShijiazhuang 050024China key laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China School of Earth Sciences and Engineering Sun Yat-sen UniversityZhuhai 519082China

Quaternary palynology plays a pivotal role in investigating global climate change and various other research fields,serving as an essential tool for the quantitative analysis of paleoenvironment changes.However,due to the vast diversity of terrestrial ecosystems and intricate interactions between vegetation,climate,and human activities,further advancements are required in the following aspects within this discipline.(1)The accuracy of classification in pollen morphology and fossil pollen identification needs improvement,particularly at the species level.This represents a significant challenge in present Quaternary palynology.Computer-aided intelligent recognition holds promise as a solution for species identification based on more detail pollen morphology.(2)Most pollen-based vegetation and climate reconstructions overlook the significance of bare ground.Neglecting bare ground can lead to substantial inaccuracies when quantitatively reconstructing past vegetation and climate.(3)While pollen records provide reliable information on paleoclimate changes,current quantitative climate reconstruction models heavily rely on modern pollen datasets derived from present-day vegetation disturbed more or less by human activities.This introduces bias and uncertainties into paleoclimate reconstruction.(4)Although pollen can serve as an indicator of human activities,accurately quantifying the intensity of human influence remains challenging.Improving accurate identification of crop pollen,reconstructing reliable land cover/use data,and integrating multidisciplinary data may enhance the identification and quantification of signals related to human activity in pollen records.

关键词： Quaternary palynology Paleoclimate Paleovegetation Human activity

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3D hand pose and shape estimation from monocular RGB via efficient 2D cues

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Computational Visual Media 2024年第1期10卷 79-96页

作者： Fenghao Zhang Lin Zhao Shengling Li Wanjuan Su Liman Liu Wenbing Tao Hubei key laboratory of Medical Information Analysis and Tumor Diagnosis&Treatment School of Biomedical EngineeringSouth Central Minzu UniversityWuhan430074China National key laboratory of Science and Technology of Multi-spectral Information Processing School of Artificial Intelligence and AutomationHuazhong University of Science and TechnologyWuhan430074China

Estimating 3D hand shape from a single-view RGB image is important for many applications.However,the diversity of hand shapes and postures,depth ambiguity,and occlusion may result in pose errors and noisy hand meshes.Making full use of 2D cues such as 2D pose can effectively improve the quality of 3D human hand shape estimation.In this paper,we use 2D joint heatmaps to obtain spatial details for robust pose estimation.We also introduce a depth-independent 2D mesh to avoid depth ambiguity in mesh regression for efficient hand-image alignment.Our method has four cascaded stages:2D cue extraction,pose feature encoding,initial reconstruction,and reconstruction refinement.Specifically,we first encode the image to determine semantic features during 2D cue extraction;this is also used to predict hand joints and for segmentation.Then,during the pose feature encoding stage,we use a hand joints encoder to learn spatial information from the joint heatmaps.Next,a coarse 3D hand mesh and 2D mesh are obtained in the initial reconstruction step;a mesh squeeze-and-excitation block is used to fuse different hand features to enhance perception of 3D hand structures.Finally,a global mesh refinement stage learns non-local relations between vertices of the hand mesh from the predicted 2D mesh,to predict an offset hand mesh to fine-tune the reconstruction results.Quantitative and qualitative results on the Freihand benchmark dataset demonstrate that our approach achieves state-of-the-art performance.

关键词： hand 3D reconstruction deep learning image features 3D mesh

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