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Sökning: WFRF:(Liu Pengju)

  • Resultat 1-7 av 7
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1.
  • Shang, Xiaodong, et al. (författare)
  • Organic composition and diagenetic mineralization of microfossils in the Ediacaran Doushantuo chert nodule by Raman and petrographic analyses
  • 2018
  • Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268 .- 1872-7433. ; 314, s. 145-159
  • Tidskriftsartikel (refereegranskat)abstract
    • We studied microfossils and their embedding matrix minerals from chert nodules in the Ediacaran Doushantuo Formation of the Yangtze Gorges area in South China using Raman spectroscopy as well as transmitted- and polarized light microscopy. The microfossils are composed of organic carbonaceous material with weak structural organization/ordering, which indicates a low degree of thermal maturation and alteration. Raman spectral disparity of carbonaceous material among different portions (vesicle/inclusion) of microfossils reveals some differences in organic composition and structure of their precursor biological matters. The mineral phases of silica matrix that entombs the microfossils are recognized as opal-CT, cryptocrystalline quartz, and their transitional phases. Overall, Raman spectral analyses and petrographic observations document a complete and continuous sequence of silica phase transformation from opal-CT to quartz. When reconstructing the diagenetic history of sediments and mineralization process of microfossils in a localized microenvironment, the silica in pore waters precipitated preferentially at the periphery of microorganisms in the form of opal, gradually decreasing in abundance as it transformed into more stable cryptocrystalline quartz. The recrystallization took place in cryptocrystalline quartz to form grains. Authigenic fluorapatite readily precipitated in the vicinity of some microfossils and within their degraded organic fragments. While apatite was crystallizing around organisms and their biostructures, silica precipitated in the surrounding voids, inhibiting the space of potential apatite crystallization. The silicification and phosphatization of microfossils occurred in the microbial sulfate reduction (MSR) zone of the sediment column, and both were driven by the localized pH change resulting from MSR and pyrite precipitation in the microenvironment, thus facilitating the exceptional fossil preservation in the Doushantuo chert nodules.
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2.
  • Yang, Bin, et al. (författare)
  • A novel occupant-centric stratum ventilation system using computer vision : Occupant detection, thermal comfort, air quality, and energy savings
  • 2023
  • Ingår i: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 237
  • Tidskriftsartikel (refereegranskat)abstract
    • Traditional ventilation and air conditioning systems typically operate on a predetermined schedule with fixed operating parameters. Occupant-centric control (OCC) strategies have been proposed to reduce system operation energy consumption without sacrificing thermal comfort. Indoor occupancy detection in real time is a critical step in successfully implementing the OCC strategy. Thus, the deep learning-based computer vision method was adopted in the first step of the study, and the detection performance and camera position were analyzed in an office scenario. Next, the proposed OCC strategy was used to regulate the supply air parameters and outdoor air volume in stratum ventilation based on the monitored occupant number. The traditional static control strategy was then compared to two control strategies: constant air volume and variable air volume. Occupant detection performance results showed the mean NRMSD for the five most common relative positions of the occupants and camera was 0.1109, with sitting back to camera having the lowest accuracy. Subjective response results demonstrated that, when compared to the traditional control strategy, thermal comfort was improved by 43%-73%, perceived air quality was maintained at an acceptable level, CO2 concentration was less than 700 ppm, and energy could be saved by 2.3%-8.1%. Furthermore, the lower the occupancy, the greater the improvement in comfort and the greater the energy savings. This research focused on how the stratum ventilation system responds to dynamic changes in occupancy and provided insights into reducing unnecessary energy waste while maintaining comfort.
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3.
  • Cunningham, John, et al. (författare)
  • Critical appraisal of tubular putative eumetazoans from the Ediacaran Weng’an Doushantuo biota
  • 2015
  • Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 282, s. 1-9
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular clock analyses estimate that crown-group animals began diversifying hundreds of millions of years before the start of the Cambrian period. However, the fossil record has not yielded unequivocal evidence for animals during this interval. Some of the most promising candidates for Precambrian animals occur in theWeng’an biota of South China, including a suite of tubular fossils assigned to Sinocyclocyclicus, Ramitubus, Crassitubus and Quadratitubus, that have been interpreted as soft-bodied eumetazoans comparable to tabulate corals. Here, we present new insights into the anatomy, original composition and phylogenetic affinities of these taxa based on data from synchrotron radiation X-ray tomographic microscopy, ptychographic nanotomography, scanning electron microscopy and electron probe microanalysis. The patterns of deformation observed suggest that the cross walls of Sinocyclocyclicus and Quadratitubus were more rigid than those of Ramitubus and Crassitubus. Ramitubus and Crassitubus specimens preserve enigmatic cellular clusters at terminal positions in the tubes. Specimens of Sinocyclocyclicus and Ramitubus have biological features that might be cellular tissue or subcellular structures filling the spaces between the crosswalls. These observations are incompatible with a cnidarian interpretation, in which the spaces between cross walls are abandoned parts of the former living positions of the polyp. The affinity of the Weng’an tubular fossils may lie within the algae.
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4.
  • Moczydlowska-Vidal, Malgorzata, 1951-, et al. (författare)
  • Ediacaran algal cysts from the Doushantuo Formation, South China
  • 2022
  • Ingår i: Geological Magazine. - : Cambridge University Press. - 0016-7568 .- 1469-5081. ; 159:7, s. 1050-1070
  • Tidskriftsartikel (refereegranskat)abstract
    • Early-middle Ediacaran organic-walled microfossils from the Doushantuo Formation studied in several sections in the Yangtze Gorges area, South China, show ornamented cyst-like vesicles of very high diversity. These microfossils are diagenetically permineralized and observed in petrographic thin-sections of chert nodules. Exquisitely preserved specimens belonging to seven species of Appendisphaera, Mengeosphaera, Tanarium, Urasphaera and Tianzhushania contain either single or multiple spheroidal internal bodies inside the vesicles. These structures indicate reproductive stages, endocyst and dividing cells, respectively, and are preserved at early to late ontogenetic stages in the same taxa. This new evidence supports the algal affiliations for the studied taxa and refutes previous suggestions of Tianzhushania being animal embryo or holozoan. The first record of a late developmental stage of a completely preserved specimen of T. spinosa observed in thin-section demonstrates the interior of vesicles with clusters of identical cells but without any cavity that is diagnostic for recognizing algal cysts vs animal diapause cysts. Various lines of evidence to infer biological affinities of these microfossils - morphology, reproductive characters, spatial arrangement of cells, and biochemical properties of the vesicle wall - are collectively characteristic of algal clades. Recognizing the biological affinities of these microfossils is key to understanding whether animals capable of producing such morphologically complex diapause cysts had an early Ediacaran fossil record (633-610 Ma), or the microfossils were non-animal holozoans or algae as argued herein for Tianzhushania spinosa and other studied microfossils.
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5.
  • Shang, Xiaodong, et al. (författare)
  • Acritarchs from the Doushantuo Formation at Liujing section in Songlin area of Guizhou Province, South China : Implications for early-middle Ediacaran biostratigraphy
  • 2019
  • Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 334
  • Tidskriftsartikel (refereegranskat)abstract
    • A taxonomically diverse and morphologically disparate microfossil assemblage is recovered from the upper Doushantuo Formation in the Liujing section of Songlin area, Guizhou Province, including acanthomorphic and sphaeromorphic acritarchs, multicellular algae, and filamentous cyanobacteria. Acritarch Mengeosphaera membranifera sp. nov. is newly erected and genus Cymatiosphaeroides and several species (C. forabilatus, C. kullingii, Bacatisphaera baokangensis) are emended in the systematics. The acanthomorphic species are dominated by Cymatiosphaeroides forabilatus and Mengeosphaera membranifera sp. nov. The Liujing assemblage shares many species with other Ediacaran coeval assemblages from South China, Australia, Siberia, the East European Platform, India, Mongolia and Svalbard, and indicates a significant taxonomic similarity to the global, agediagnostic assemblages. New occurrence of those known taxa in the Liujing succession documents the biodiversity of the Ediacaran acritarchs in South China. The Liujing assemblage extends the palaeogeographic distribution of the Ediacaran acritarchs and may be assigned to the Tanarium conoideum-Cavospina basiconica Assemblage Zone that was recognized in the Yangtze Gorges area of South China. Alternatively, it could be partially correlated with the barren interval between T. conoideum-C. basiconica Assemblage Zone and the overlying Tanarium pycnacanthum-Ceratosphaeridium glaberosum Assemblage Zone.
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6.
  • Shang, Xiaodong, et al. (författare)
  • Algal affinity and possible life cycle of the early Cambrian acritarch Yurtusia uniformis from South China
  • 2020
  • Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 63:6, s. 903-917
  • Tidskriftsartikel (refereegranskat)abstract
    • Abundant, well‐preserved specimens of spheroidal organic‐walled microfossil Yurtusia uniformis are reported from the basal Cambrian Yanjiahe Formation in the Changyang area of Hubei Province, South China. Thin and hollow processes extend between the double walls of the vesicle. The single to multiple internal bodies within the vesicle cavity are observed in the genus for the first time, representing reproductive structures (dividing daughter cells). A small circular perforation may occur on the vesicle wall to release the internal bodies. Morphological analyses of specimens preserved at various life stages reveal that processes gradually became longer as the vesicle grew in size. The internal bodies (daughter cells) underwent several successive divisions within the vesicle, which was accompanied by the simultaneous growth of both vesicle and processes. The regular growth of cells, formation and release of daughter cells, and the remarkable morphological similarity between extant algae and the studied microfossils suggest that Yurtusia uniformis is probably a green microalga that may be closely related to the Trebouxiophyceae or even Chlorellales (Chlorophyta). The growth and reproductive mode of individuals indicates that Y. uniformis is an actively growing vegetative cell of microalgae, rather than a metabolically inert cyst or resting spore. A life cycle involving vegetative growth and asexual reproduction is proposed for Y. uniformis on the basis of the life histories of modern chlorophytes. The multiple internal cells may represent autospores produced by a mature autosporangium during asexual reproduction, which subsequently developed into separate young vegetative cells after their release from the opened autosporangium.
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7.
  • Wei, Bo’an, et al. (författare)
  • Construction site hazard identification and worker adverse reaction monitoring using electroencephalograms : a review
  • 2024
  • Ingår i: Buildings. - : MDPI. - 2075-5309. ; 14:1
  • Forskningsöversikt (refereegranskat)abstract
    • The construction process is a dynamic one, and the complexity of the working conditions and the high level of uncertainty make the construction industry the third most dangerous industry after mining and agriculture. And since the construction industry is vital to the development of a country, safety during construction is of particular importance. A great deal of research, studies and practices have been conducted to reduce potential risks and improve worker efficiency during the construction process. In recent years, with the rapid development of cognitive neuroscience and the integration of medical technology, various wearable monitoring devices have been widely used in the field of building construction for real-time monitoring of workers’ physical and mental conditions. Among them, the application of EEG (electroencephalogram) in the building construction process enables researchers to gain insight into the physical and mental state of construction workers while performing construction tasks. This paper introduces EEG technology and portable EEG monitoring equipment and summarizes its application in monitoring workers’ adverse reactions (emotion, fatigue, psychological burden, and vigilance) and construction hazard identification during the process of construction in recent years, which provides future EEG research in the field of building construction and construction site safety management.
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  • Resultat 1-7 av 7

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