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Pelagic-benthic coupling of the microbial food web modifies nutrient cycles along a cascade-dammed river

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Frontiers of Environmental Science & Engineering 2022年第4期16卷 125-137页

作者： Nan Yang Linqiong Wang Li Lin Yi Li Wenlong Zhang Lihua Niu Huanjun Zhang Longfei Wang Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education College of EnvironmentHohai UniversityNanjing 210098China College of Oceanography Hohai UniversityNanjing 210098China Department of Basin Water Environment Changjiang River Scientific Research InstituteWuhan 430010China Hubei Provincial Key Laboratory of Basin Water Resources and Ecological Environment Sciences Changjiang River Scientific Research InstituteWuhan 430010China

Cascade dams disrupt the river continuum,altering hydrology,biodiversity and nutrient *** the diversity of multi-trophic microbiota and assessing microbial contributions to the ecosystem processes are prerequisites for the restoration of these aquatic *** study investigated the microbial food web structure along a cascade-dammed river,paying special attention to the multi-trophic relationships and the potential role of pelagic-benthic coupling in nutrient *** results revealed the discontinuity in bacterial and eukaryotic community composition,functional group proportion,as well as a-diversity due to fragmentation by *** high microbial dissimilarity along the river,with the total multi-trophic P-diversity was 0.84,was almost completely caused by species *** among trophic levels suggests potential interactions of the pelagic and the benthic groups,of which the p-diversities were primarily influenced by geographic and environmental factors,***-induced environmental variations,especially hydrological and nutrient variables,potentially influence the microbial food web via both top-down and bottom-up *** proposed that the cycles of carbon,nitrogen and phosphorus are influenced by multi-trophic groups through autotrophic and heterotrophic processes,predator-prey relationships,as well as the release of nutrients mainly by *** results advance the notion that pelagic-benthic trophic coupling may intensify the accumulation of organic carbon,ammonium and inorganic phosphorus,thereby changing the biogeochemical patterns along river *** a consequence,researchers should pay more attention to the multi-trophic studies when assessing the environmental impacts,and to provide the necessary guidance for the ecological conservation and restoration of the dam-regulated systems.

关键词： Reservoir Multi-trophic Beta diversity Predator-prey Nutrient accumulation

Geometrical Design and Hydraulic Feasibility of Inner-Reinforced Girders in Hydropower Bifurcations

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Transactions of Tianjin University 2017年第5期23卷 461-470页

作者： Zhimin Zhang Hegao Wu Yang Wang Qiling Zhang Teng Li State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072China changjiang institute of Survey Planning Design and research Wuhan 430010 China changjiang river scientific research institute Wuhan 430010 China

Inner-reinforced girders, also known as ribs, are widely used in hydropower bifurcations. However, while they strengthen structures, they also cause energy loss. This work aims to develop an appropriate geometry form for ribs that can diminish head loss in hydropower bifurcations. The term rib/breadth ratio (RBR) is defined to describe the geometrical form of ribs. An investigation is conducted to study the flow and performance characteristics of bifurcations with ribs using computational fluid dynamics. The dependence of the head loss coefficient on the RBR is given in six working conditions. Results show that the ribs change the local flow patterns and slightly increase the water head loss in some cases. In other cases, however, the ribs make the flow smooth. An appropriate RBR is the key to improve the flow patterns in hydropower bifurcations. The head loss varies with the RBR and reaches the minimum when the RBR is 0.3. © 2017, Tianjin University and Springer-Verlag GmbH Germany.

关键词： Computational fluid dynamics Energy dissipation Flow patterns Fluid dynamics Geometry Hydroelectric power Reinforcement

Graded and uniform bed load sediment transport in a degrading channel

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International Journal of Sediment research 2016年第4期31卷 376-385页

作者： Zhijing Li Zhixian Cao Huaihan Liu Gareth Pender State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University changjiang river scientific research institute School of the Built Environment Heriot-Watt University Yangtze river Waterway Bureau

Twenty runs of experiments are carried out to investigate non-equilibrium transport of graded and uniform bed load sediment in a degrading ***-sorted gravel and sand are employed to compose four kinds of sediment beds with different gravel/sand contents,i.e.,uniform 100%gravel bed,uniform 100%sand bed,and two graded sediment beds respectively with 53%gravel and 47%sand as well as 22%gravel and 78%*** different sediment beds,the experiments are conducted under the same discharges,thereby allowing for the role of sediment composition in dictating the bed load transport rate to be identified.A new observed dataset is generated concerning the flow,sediment transport and evolution of bed elevation and composition,which can be exploited to underpin developments of mathematical river *** data shows that in a degrading channel,the sand greatly promotes the transport of gravel,whilst the gravel considerably hinders the transport of *** promoting and hindering effects are evaluated by means of impact factors defined based on sediment transport *** impact factors are shown to vary with flow discharge by orders of magnitude,being most pronounced at the lowest *** is characterized that variations in sand or gravel inputs as a result of human activities and climate change may lead to severe morphological changes in degrading channels.

关键词： Sediment transport Bed load Gravel Sand Promoting Hindering

Effects of Carbonation and Freeze-thaw Cycles on Microstructure of Concrete

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Journal of Wuhan University of Technology(Materials Science) 2016年第5期31卷 1018-1025页

作者：饶美娟 LI Mingxia 杨华全 LI Xiang DONG Yun changjiang river scientific research institute Wuhan 430010China School of Civil Engineering Wuhan UniversityWuhan 430072China Collaborative Innovation center for Geo-hazards and Eco-environment in the Three Gorges Area Yichang 443002China

The hydraulic concrete durability under the alternation of freeze-thaw and carbonation has been systematically investigated in this work, where both the micro part and the microscopic characteristics of concrete interface were analyzed based on computed tomography（CT） test and scanning electron microscopy（SEM）. Average CT numbers of each section, declined at water-cement ratio of 0.35, increased at 0.45, and changed a little at 0.55. The specimen in the absence of fly ash exhibited less types of hydration products and the surface was observed to be a needle-like ettringite, with a relatively dense overall structure. However, with the increase of fly ash content, pores and micro-cracks of specimen structure increased. Hexagonal flake calcium hydroxide, present in the specimen after the first carbonation, was negligible in the test pieces of the first freezethaw where the main hydration products were ettringite and calcium silicate gel. Regular hexagonal plates of calcium hydroxide exhibited in the interior of the specimen in which charring first occurred but calcium hydroxide rarely existed in the interior of the specimen in which freeze-thaw first occurred.

关键词： fly ash carbonization Freeze-thaw combined effect CT numbers

Edge Detection of river in SAR Image Based on Contourlet Modulus Maxima and Improved Mathematical Morphology

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Transactions of Nanjing University of Aeronautics and Astronautics 2014年第5期31卷 478-483页

作者：吴一全朱丽郝亚冰李立卢文平 College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics Engineering Technology research center of Wuhan Intelligent Basin Changjiang River Scientific Research InstituteChangjiang Water Resources Commission of the Ministry of Water Resources Key Laboratory of the Yellow river Sediment of Ministry of Water Resource Yellow River Institute of Hydraulic Research Key Laboratory of Port Waterway and Sedimentation Engineering of the Ministry of TransportNanjing Hydraulic Research Institute State Key Laboratory of Urban Water Resource and Environment Harbin Institute of Technology

To cope with the problems that edge detection operators are liable to make the detected edges too blurry for synthetic aperture radar(SAR)images,an edge detection method for detecting river in SAR images is proposed based on contourlet modulus maxima and improved mathematical *** SAR image is firstly transformed to a contourlet *** to the directional information and gradient information of directional subband of contourlet transform,the modulus maximum and the improved mathematical morphology are used to detect high frequency and low frequency sub-image edges,***,the edges of river in SAR image are obtained after fusing the high frequency sub-image and the low frequency *** results demonstrate that the proposed edge detection method can obtain more accurate edge location and reduce false edges,compared with the Canny method,the method based on wavelet and Canny,the method based on contourlet modulus maxima,and the method based on improved(ROEWA).The obtained river edges are complete and clear.

关键词： synthetic aperture radar(SAR) image river detection edge detection contourlet transform modulus maxima

Analysis of the spanwise vortex of open channel flows based on the Omega-Liutex vortex identification method

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Journal of Hydrodynamics 2022年第1期34卷 148-155页

作者： Bin Li Wen-jun Yang Jie Li Si-yu Jing Yue Chen changjiang river scientific research institute Wuhan430010China Fujian College of Water Conservancy and Electric Power Sanming353000China Department of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China

In this paper, a particle imaging velocimetry (PIV) system of high-temporal-spatial resolution is used to investigate the spanwise vortex distribution of fully developed turbulent flows in an open channel and its relationship with the turbulence. The distributions of the time-averaged velocity, the turbulence intensity and the Reynolds stress are obtained in the longitudinal profile. The third-generation vortex identification method (based on the Omega-Liutex vector) is applied to accurately identify and analyze the vortex in the spanwise direction. The results suggest that the vortex density increases with the Reynolds number at a given aspect ratio (B / H) of the flow. The distribution trend of the spanwise vortex density in the vertical direction remains unchanged for different discharges. Specifically, the vortex density increases along the vertical direction and reaches the peak at y / H = 0.15, then decreases and reaches the bottoms at the flow surface.

关键词： Open channel turbulent flows spanwise vortex Reynolds number particle imaging velocimetry(PIV) aspect ratio

Threshold Selection Method Based on Reciprocal Gray Entropy and Artificial Bee Colony Optimization

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Transactions of Nanjing University of Aeronautics and Astronautics 2014年第4期31卷 362-369页

作者：吴一全孟天亮吴诗婳卢文平 College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics Engineering Technology research center of Wuhan Intelligent Basin Changjiang River Scientific Research InstituteChangjiang Water Resources Commission of the Ministry of Water Resources Key Laboratory of the Yellow river Sediment of Ministry of Water Resource Yellow River Institute of Hydraulic Research State Key Laboratory of Urban Water Resource and Environment Harbin Institute of Technology State Key Laboratory of Food Science and Technology Jiangnan University

Since the logarithmic form of Shannon entropy has the drawback of undefined value at zero points,and most existing threshold selection methods only depend on the probability information,ignoring the within-class uniformity of gray level,a method of reciprocal gray entropy threshold selection is proposed based on two-dimensional(2-D)histogram region oblique division and artificial bee colony(ABC)***,the definition of reciprocal gray entropy is *** on the basis of one-dimensional(1-D)method,2-D threshold selection criterion function based on reciprocal gray entropy with histogram oblique division is *** accelerate the progress of searching the optimal threshold,the recently proposed ABC optimization algorithm is *** proposed method not only avoids the undefined value points in Shannon entropy,but also achieves high accuracy and anti-noise performance due to reasonable 2-D histogram region division and the consideration of within-class uniformity of gray level.A large number of experimental results show that,compared with the maximum Shannon entropy method with 2-D histogram oblique division and the reciprocal entropy method with 2-D histogram oblique division based on niche chaotic mutation particle swarm optimization(NCPSO),the proposed method can achieve better segmentation results and can satisfy the requirement of real-time processing.

关键词： image processing threshold selection reciprocal gray entropy 2-D histogram oblique division artificial bee colony (ABC) optimization algorithm

Assessment of the predictive capability of RANS models in simulating mean-dering open channel flows

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Journal of Hydrodynamics 2017年第1期29卷 40-51页

作者：周建银邵学军王虹假冬冬 Key Laboratory of river Regulation and Flood Control of MWR Changjiang River Scientific Research InstituteWuhan 430010China State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing Hydraulic Research InstituteNanjing 210029China

The predictive capability of Reynolds-averaged numerical simulation （RANS） models is investigated by simulating the flow in meandering open channel flumes and comparing the obtained results with the measured data. The flow structures of the two experiments are much different in order to get better insights. Two eddy viscosity turbulence models and different wall treatment methods are tested. Comparisons show that no essential difference exists among the predictions. The difference of turbulence models has a limited effect, and the near wall refinement improves the predictions slightly. Results show that, while the longitudinal velo- cities are generally well predicted, the predictive capability of the secondary flow is largely determined by the complexity of the flow structure. In Case 1 of a simple flow structure, the secondary flow velocity is reasonably predicted. In Case 2, consisting of sharp curved consecutive reverse bends, the flow structure becomes complex after the first bend, and the complex flow structure leads to the poor prediction of the secondary flow. The analysis shows that the high level of turbulence anisotropy is related with the boundary layer separation, but not with the flow structure complexity in the central area which definitely causes the poor prediction of RANS models. The turbulence model modifications and the wall treatment methods barely improve the predictive capability of RANS models in simulating complex flow structures.

关键词： RANS model secondary flows boundary layer separation turbulence model meandering channel near-wall treatment

Effects of phosphorus limitation on sinking velocities of phytoplankton during summer in the changjiang river Estuary

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Acta Oceanologica Sinica 2024年第6期43卷 131-141页

作者： Xinchi You Qiang Hao Jie Zhu Wei Zhang Haiyan Jin Dewang Li Huanhong Ji Yu Ke Feng Zhou Ocean College Zhejiang UniversityZhoushan 316021China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310000China Key Laboratory of Marine Ecosystem Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Donghai Laboratory Zhoushan 316021China East China Sea Ecological center Ministry of Natural ResourcesShanghai 201206China Key Laboratory of Marine Ecological Monitoring and Restoration Technologies Ministry of Natural ResourcesShanghai 201206China Observation and research Station of Yangtze river Delta Marine Ecosystems Ministry of Natural ResourcesZhoushan 316021China

The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic *** study was based on a field investigation conducted during the summer of 2022 in the changjiang river(Yangtze river) Estuary(CJE) and its adjacent *** settling column method was employed to measure the sinking velocity(SV) of different size fractions of phytoplankton at the surface of the sea and to analyze their environmental control *** findings reveal significant spatial variation in phytoplankton SV(-0.55-2.41 m/d) within the ***-speed sinking was predominantly observed in phosphate-depleted regions beyond the CJE *** the same time,an upward trend was more commonly observed in the phosphate-rich regions near the CJE *** SV ranges for different sizefractionated phytoplankton,including micro-(>20 μm),nano-(2-20 μm),and picophytoplankton(0.7-2 μm),were-0.50-4.74 m/d,-1.04-1.59 m/d,and-1.24-1.65 m/d,*** analysis revealed a significant negative correlation between SV and dissolved inorganic phosphorus(DIP),implying that the influence of DIP contributes to *** variations in phytoplankton alkaline phosphatase activity suggested a significant increase in SV across all size fractions in the event of phosphorus *** communities with limited photo synthetic capacity(maximum photochemical efficience,Fv/Fm river of elevated SV in the *** study enhances the comprehension of the potential mechanisms underlying hypoxic zone formation in the CJE,providing no

关键词： phytoplankton sinking velocity changjiang river Estuary phosphorus limitation alkaline phosphatase