The 21st Himalayan-Karakoram-Tibet workshop     

Masaru Yoshida  Shuichi Hasegawa  Ranjan Kumar Dahal   《Gondwana Research》2006,10(3-4):396-397

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A general Lagrangian tracking methodology for riverine flow and transport     

Jonathan Nelson  Yasuyuki Shimizu  Tomoko Kyuka  Scott Charlton 《地球表面变化过程与地形》2023,48(1):87-103

This article presents a new public domain tool for generalized Lagrangian particle tracking in rivers. The approach can be applied with a variety of two- and three-dimensional flow solvers. Particle advection by the flow is incorporated using flow fields from the chosen solver assuming particles follow the Reynolds-averaged flow, although some other simple passive and active particle behaviors are also treated. Turbulence effects are treated using a random walk algorithm with spatial step lengths randomly chosen from Gaussian distributions characterized by the diffusivity from the flow solver. Our work extends this concept to a general framework that is solver and coordinate system independent to allow easy comparisons between differing flow treatments. To better treat problems where detailed information is required in specific regions, the approach includes novel cloning and colligation algorithms which enhance local resolution at modest computational expense. We also provide tools for computing local concentrations and total exposure over a user-specified time interval. Several examples of predictions are provided to illustrate applications of the technique, including examination of the role of curvature-driven secondary flows, storage in lateral separation eddies, treatment of larval drift, treatment of fuel spill dispersion, river-floodplain connections, and sedimentation in floodplain ponds by tie channel connections. We also demonstrate that the model can reproduce analytically derived concentration profiles for simple diffusivities. These examples show that the Lagrangian particle tracking approach and the extensions proposed here are broadly applicable and viable for treating difficult river problems with multiple temporal and spatial scales. The examples also illustrate the utility of the cloning/colligation extensions and show how these can decrease the computational effort required on problems where high local resolution is required. Enhancement of the tools and even broader applicability can be achieved through the inclusion of multiple particle populations and particle–particle interactions.  相似文献   

Food sources of benthic animals on intertidal and subtidal bottoms in inner Ariake Sound,southern Japan,determined by stable isotopes     

Hisashi Yokoyama  Tomoko SakamiYuka Ishihi 《Estuarine, Coastal and Shelf Science》2009

To evaluate the relative importance of possible food sources, including riverine particulate organic matter, reeds, benthic microalgae, seaweeds, cultured laver (Porphyra) and coastal phytoplankton, for commercial bivalves and co-occurring benthic animals, 73 macrofaunal species were collected from intertidal and subtidal soft bottoms in the inner part of Ariake Sound, Kyushu, southern Japan, and their isotopic compositions were analyzed. The results revealed that (1) both intertidal and subtidal food webs were constituted of 3 trophic levels, (2) suspension-feeding bivalves utilize a mixture of benthic microalgae and coastal phytoplankton, and omnivores and carnivores incorporate benthic microalgae and phytoplankton through their intermediate prey, and (3) 3 bivalves (Scapharca kagoshimensis, Modiolus metcalfei and Atrina lischkeana) inhabiting both intertidal and subtidal bottoms showed similar seasonal fluctuations, suggesting no difference in the diet composition among the species and between the 2 habitats. We conclude that a large biomass of benthic microalgae which was approximately equal to that of phytoplankton and the strong tidal currents that would resuspend benthic microalgae and transport them to subtidal bottom areas account for the benthic microalgal and phytoplankton based trophic structure in the inner part of Ariake Sound.  相似文献   

Radioastronomical observations of comets IRAS-Araki-Alcock (1983d) and Sugano-Saigusa-Fujikawa (1983e)     

W.M. Irvine  Z. Abraham  M. A&#x;Hearn  W. Altenhoff  Ch. Andersson  J. Bally  W. Batrla  A. Baudry  D. Bockelée-Morvan  G. Chin  J. Crovisier  I. de Pater  D. Despois  L. Ekelund  E. Gerard  T. Hasegawa  C. Heiles  J.M. Hollis  A. Wootten 《Icarus》1984,60(1):215-220

Detections and upper limits to the continuum emission (1 ≤ λ ≤6 cm) and spectral line emission (OH, CO, CS, HCN, HCO⁺, CN, CH₃CN, CH₃C₂H, NH₃, H₂O, HC₃N, CH₃CH₂CN) are reported from radio observations of Comets 1983d and 1983e. Comparison is made with observations of CN at optical wavelengths. These results may be useful in planning future cometary observations.  相似文献