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Microlens-Based Continuous Depth Map Estimation with the Plenoptic Camera
YANG Peng, YAN Lei, ZHAO Shoujiang, YAN Yizhen, ZHAO Hongying
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 951-960.   DOI: 10.13209/j.0479-8023.2018.053
Abstract776)   HTML    PDF(pc) (39821KB)(90)       Save

Because the micro lenses segment the plenoptic image physically, the global optimization method is hard to be applied on the depth estimation progress and the WTA (winner-take-all) method based on the multibaseline system will generate very coarse but continuous depth map. The global optimizations method always generate robust but concrete depth map when using multi-label technique. So cost projection strategy by directly processing the lenslet plenoptic image is proposed to build the cost volume based on the projection image for global optimization. A method based on Markov Random Fields Propagation (MRFsP) is adopted by merging the modified WTA depth result to refine the concrete depth map. For validation, the depth map built with the proposed method is compared with the microlens-based optimization result, and the result shows obvious improvement.

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Disparity Estimation Method for Free-Texture Scenes Based on Light Field
ZHENG Miao, ZHAO Hongying, YANG Peng, YAN Lei, ZHENG Hongyun, CUI Jialiang
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (2): 336-340.   DOI: 10.13209/j.0479-8023.2017.116
Abstract979)   HTML1)    PDF(pc) (7513KB)(157)       Save

In order to improve the pixel distinguishability, this paper introduces an algorithm that the quantized geometric relationship among sub images of light field replaced the pixel value. Based on this relationship, the epipolar line division ratio is calculated to take place of pixel value. Experimental results showed that the disparity map with the division ratio images are obviously superior to those obtained by using the subaperture images.

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A New Species of Qianichthyosaurus (Reptilia: Ichthyosauria) from Xingyi Fauna (Ladinian, Middle Triassic) of Guizhou
YANG Pengfei,JI Cheng,JIANG Dayong,Ryosuke Motani,Andrea Tintori,SUN Yuanlin,SUN Zuoyu
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1202)      PDF(pc) (12466KB)(100)       Save
A new species of Qianichthyosaurus Li, 1999 from the Zhuganpo Member of the Falang Formation (Ladinian, Middle Triassic), Wusha Town, Xingyi City of Guizhou is described here, namely Qianichthyosaurus xingyiensis sp. nov. The recognition of the new species revises the diagnosis of the genus: tooth size relative to the skull width slightly below 0.1; ulna peripheral “shaft” notched or largely reduced; hindlimb nearly equal or longer than forelimb; tibia peripheral “shaft” notched or largely reduced. Qianichthyosaurus xingyiensis sp. nov. differs from the type species in having relatively longer snout (snout length/skull length over 60%); humerus radial facet being prominently larger than ulnar facet; unenclosed obturator foramen on pubis; fibula posterior process on the posterior margin and the ischium sub-triangular lacking shaft. The new species is stratigraphically older than Q. zhoui, the specimens of which were exclusively known from the Wayao Member of the Falang Formation (Carnian, Late Triassic). Along with askeptosaurid thalattosaur Anshunsaurus and shastasaurid ichthyosaur Guizhouich- thyosaurus, the occurrence of Q. xingyiensis sp. nov. in Xingyi Fauna suggests a closer relationship between Xingyi Fauna (late Ladinian, Middle Triassic) and Guanling Biota (Carnian, Late Triassic).
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Identification and Application of Seasonality Parameters of Crop Growing Season in Northeast China Based on NDVI Time Series Data
LI Zhengguo,TANG Huajun,YANG Peng,ZHOU Qingbo,WANG Yanglin,WU Wengbin,YIN He,ZHANG Li
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract698)      PDF(pc) (3348KB)(555)       Save
The authors investigated spatio-temporal patterns of seasonality parameters of crop growing season in Northeast China, by using the SPOT/VGT NDVI ten day composed time-series data collected from 1998 to 2009. First, to minimize the effects of anomalous values caused by atmospheric haze and cloud contamination, the software TIMESAT was used to generate smooth time series of NDVI based on an asymmetric Gaussian function; second, the seasonality parameters, such as the start date, the end date, the peak date, and length of the growing season, were defined and extracted from the smoothed NVDI time-series dataset; third, each of the extracted parameters and the observed agricultural phenophases (including the stages of seedling, heading and maturity for harvest, length of growth period) were compared and validated by using a scatter plot, respectively; finally, the temporal trends and spatial patterns of the major crop seasonality parameters in Northeast China were illustrated and analyzed over the past 10 years. The results show that the growth process of major crops can be discriminated to a certain extent from the temporal trend of observed crop phenological characteristics. Obvious linear correlations can be found between the extracted seasonality parameters and the observed crop phenophases, which indicates that spatio-temporal variations of crop phenophase can be expressed in details by utilizing the extracted parameters from the smoothed NDVI time series. Meanwhile, all these grid-based crop phenophases can be used as data alternative for studying the spatio-temporal responses of crop growth process caused from fluctuation in external environmental conditions, such as air temperature, precipitation and daylight hours, etc.
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Emplaced and Metallogenetic Times of Tongchang Diorities, Southern Shaanxi Province and Its Geological Implications
WANG Wei,LIU Shuwen,WU Fenghui,LI Qiugen,WANG Zongqi,YANG Kai,YAN Quanren,WANG Ruiting,YANG Pengtao
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract653)            Save
Tongchang dioritic pluton in Southern Shaanxi Province is located in the tectonic domain of the Mianxian-Lueyang-Yangpingguan triangle block, northern margin of Yangzi Craton, and consists mainly of diorite, quartzdiorite and granodiorite. Zircon grains separated from these rocks are dated using LA-ICPMS and SHRIMP U-Pb isotopic methods. The dating results indicate three intrusive stages of the Tongchang dioritic pluton, and early diorite emplaced at 879±7 Ma; middle quartz diorite at 848±5 Ma to 840 ±7 Ma, with copper ore-bearing albitite emplced at 834±7 Ma, which is consistent with the crystallization age of quartz diorite within error range, and the last granodiorite at 824±5 Ma. These zircon U-Pb isotopic dating results reveal that the emplacements of the Tongchang diorites and related copper deposit did not occur in Paleozoic but in Jinning stage of Neoproterozoic era. The magmatic activity and related copper deposit mineralization are important responses to the breakup event of global Rodinia supercontinent( 860-750 Ma).
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Geology, Geochemistry of Langao Mafic Volcanic Rocks in South Qinling Orogenic Belt and Its Tectonic Implications
CHEN Youzhang,LIU Shuwen,LI Qiugen,DAI Junzhi,ZHANG Fan,YANG Pengtao,GUO Lishuang
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract705)            Save
To study the petrogenesis and tectonic setting of Langao mafic volcanic rocks in South Qinling orogenic belt, basalts and volcanic breccias are sampled from Langao County for petrography, major elements, trace elements and REE analysis. The results show that they are classified to alkaline basalts, and characterized by strong differentiation between LREE and HREE, Rb,K depletion relative to Th, Hf and no Nb, Ta, Zr, Ti negative anomalies. All of the samples display highly consistent REE patterns and trace elements spider diagrams with OIB. Petrogenenis studies reveal that they were derived from a congenetic primitive magma which was the product of low-degree partial melting of the spinel-garnet lherzolites and garnet lherzolites. These rocks mainly underwent fractional crystallization of clinopyroxene with minor plagioclases and were not accompanied by contamination of continent crustal materials during their magmatic evolution processes. Tectonic discrimination for mafic volcanics, using trace elements, and regional geological analysis demonstrate that Langao mafic volcanic rocks were most likely formed in the ocean basin plateau or ocean island setting.
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Stability of A Class of Hybrid Dynamic Systems
YANG Peng,XIE Guangming,WANG Long
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract575)            Save
The stability condition of a class of hybrid dynamic systems is discussed. The characteristic of this class of hybrid dynamic systems is that a center controller controls N continuous plants in sharing time manner. The plants are described by differential equations. Event feedback strategy is used as the real-time scheduling policy such that only one plant is chosen to be controlled by the controller at any time. The main result of this paper is as follows: First, a discrete time system derived from the hybrid dynamic system with event feedback scheduling strategy is introduced, and it is shown that the stability of hybrid dynamic system is equivalent to that the state of the derived discrete time system tends to negative infinite. Based on this fact, a new proof of an existing stability condition is presented. Then, a conjecture as a new stability condition is proposed. It is showed that the conjecture holds in certain special cases. Finally, two numeric examples are presented to support the conjecture in general case.
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