检索结果-南通市图书馆

Taxonomic and phylogenetic composition show biotic resistance to exotic invasion in acid seep springs

在线全文

学校读者我要写书评

暂无评论

Ecological Processes 2021年第1期10卷 77-88页

作者： david F.Barfknecht david J.Gibson School of Biological Sciences Southern Illinois University–CarbondaleCarbondaleIL 62901-6509USA

Background:Few studies have incorporated the evolutionary insights provided by analysis of phylogenetic structure along with community composition to assess the effects of exotic invasion on freshwater ***,we assess the taxonomic and phylogenetic relationships among acid seep springs to investigate the potential homogenization or resistance of communities due to invasion of an exotic ***:Multivariate community analyses indicated differences in community and phylogenetic composition and dispersion among acid seep springs,associated with gradients in soil moisture,canopy cover,and phylogenetic *** contrast,univariate analyses showed differences in taxonomic diversity but not phylogenetic diversity among acid seep ***:Despite exotic invasion,individual acid seep springs remained taxonomically and phylogenetically distinct from each *** and phylogenetic diversity metrics revealed different aspects of composition,reinforcing the importance of including both in analyses of plant communities for understanding community assembly following exotic invasion and for management *** acid seep springs,taxonomic and phylogenetic composition appear to be driven more through environmental filtering by light and moisture than by the competitive effects following invasion of an exotic grass in support of Elton’s biotic resistance hypothesis.

关键词： Acid seep springs Diversity Community Phylogenetics Exotic invasion Environmental filtering NMDS UniFrac Vector analysis

Functional origins of the vertebrate cerebellum from a sensory processing antecedent

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Current Zoology 2010年第3期56卷 277-284页

作者： John MONTGOMERY david BODZNICK Leigh Marine Laboratory and School of Biological Sciences University of Auckland Department of Biology Wesleyan University

The structure of the cerebellar cortex is remarkably similar across vertebrate phylogeny. It is well developed in basaljawed fishes, such as sharks and rays with many of the same cell types and organizational features found in other vertebrategroups, including mammals. In particular, the lattice-like organization of cerebellar cortex (with a molecular layer of parallel fibres,interneurons, spiny Purkinje cell dendrites, and climbing fires) is a common defining characteristic. In addition to the cerebellarcortex, fishes and aquatic amphibians have a variety of cerebellum-like structures in the dorso-lateral wall of the *** structures are adjacent to, and in part, contiguous with, the cerebellum. They derive their cerebellum-like name from thepresence of a molecular layer of parallel fibers and inhibitory interneurons, which has striking organizational similarities to themolecular layer of the cerebellar cortex. However, these structures also have characteristics which differ from the cerebellum. Forexample, cerebellum-like structures do not have climbing fibres, and they are clearly sensory. They receive direct afferent inputfrom peripheral sensory receptors and relay their outputs to midbrain sensory areas. As a consequence of this close sensory association,and the ability to characterise their signal processing in a behaviourally relevant context, good progress has been made indetermining the fundamental processing algorithm in cerebellar-like structures. In particular, we have come to understand thecontribution to signal processing made by the molecular layer, which provides an adaptive filter to cancel self-generated noise inelectrosensory and lateral line systems. Given the fundamental similarities of the molecular layer across these structures, coupledwith evidence that cerebellum-like structures may have been the evolutionary antecedent of the cerebellum, we address the question:do both share the same functional algorithm? [Current Zoology 56 (3):

关键词： Origin Vertebrate Cerebellum

Fluid dynamic modeling of junctions in internal combustion engine inlet and exhaust systems

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2010年第5期19卷 410-418页

作者： david Chalet Pascal Chesse Internal Combustion Engine Team Laboratory of Fluid Mechanics-UMR CNRS 6598 Ecole Centrale de NantesBP 92101 44321 NantesFrance

The modeling of inlet and exhaust systems of internal combustion engine is very important in order to evaluate the engine *** paper presents new pressure losses models which can be included in a one dimensional engine simulation *** a first part,a CFD analysis is made in order to show the importance of the density in the modeling ***,the CFD code is used,as a numerical test bench,for the pressure losses models *** coefficients depend on the geometrical characteristics of the junction and an experimental validation is made with the use of a shock tube test *** the models are then included in the engine simulation code of the *** numerical calculation of unsteady compressible flow,in each pipe of the inlet and exhaust systems,is made and the calculated engine torque is compared with experimental measurements.

关键词： compressible flow gas dynamics pressure wave propagation discharge coefficient internal combustion engine CFD simulation

On the unsteady motion and stability of a heaving airfoil in ground effect

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2011年第2期27卷 164-178页

作者： Juan Molina david Angland School of Engineering Sciences University of Southampton Southampton SO17 1BJ UK

This study explores the fluid mechanics and force generation capabilities of an inverted heaving airfoil placed close to a moving ground using a URANS solver with the Spalart-Allmaras turbulence model. By varying the mean ground clearance and motion frequency of the airfoil, it was possible to construct a frequency-height diagram of the various forces acting on the airfoil. The ground was found to enhance the downforce and reduce the drag with respect to freestream. The unsteady motion induces hysteresis in the forces’ behaviour. At moderate ground clearance, the hysteresis increases with frequency and the airfoil loses energy to the flow, resulting in a stabilizing motion. By analogy with a pitching motion, the airfoil stalls in close proximity to the ground. At low frequencies, the motion is unstable and could lead to stall flutter. A stall flutter analysis was undertaken. At higher frequencies, inviscid effects overcome the large separation and the motion becomes stable. Forced trailing edge vortex shedding appears at high frequencies. The shedding mechanism seems to be independent of ground proximity. However, the wake is altered at low heights as a result of an interaction between the vortices and the ground.

关键词： Oscillating airfoil · Flutter · Wing in ground effect · Vortex shedding

Positron emission particle tracking——Application and labelling techniques

在线全文

学校读者我要写书评

暂无评论

Particuology 2008年第1期6卷 16-23页

作者： david J. Parker School of Physics and Astronomy the University of Birmingham Edgbaston Birmingham B15 2TT UK

The positron emission particle tracking （PEPT） technique has been widely used in science and engineering to obtain detailed information on the motion and flow fields of fluids or granular materials in multiphase systems, for example, fluids in rock cracks, chemical reactors and food processors; dynamic behaviour of granular materials in chemical reactors, granulators, mixers, dryers, rotating kilns and ball mills. The information obtained by the PEPT technique can be used to optimise the design, operational conditions for a wide range of industrial process systems, and to evaluate modelling work. The technique is based on tracking radioactively labelled particles （up to three particles） by detecting the pairs of backto-back 511 keV γ-rays arising from annihilation of emitted positrons. It therefore involves a positron camera, location algorithms for calculating the tracer location and speed, and tracer labelling techniques. This paper will review the particle tracking technique from tracking algorithm, tracer labelling to their application.

关键词： PEPT Tracer Algorithm Tracking

FloodNet： Coupling Adaptive Sampling with Energy Aware Routing in a Flood Warning System

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2007年第1期22卷 121-130页

作者：周菁 david De Roure School of Computer and Software Communication University of China Beijing 100024 China School of Electronics and Computer Science University of Southampton U.K.

We describe the design of FloodNet, a flood warning system, which uses a grid-based flood predictor model developed by environmental experts to make flood predictions based on readings of water level collected by a set of sensor nodes. To optimize battery consumption, the reporting frequency of sensor nodes is required to be adaptive to local conditions as well as the flood predictor model. We therefore propose an energy aware routing protocol which allows sensor nodes to consume energy according to this need. This system is notable both for the adaptive sampling regime and the methodology adopted in the design of the adaptive behavior, which involved development of simulation tools and very close collaboration with environmental experts.

关键词： adaptive sampling communication system routing energy awareness environmental sensor networks

Plant conservation in Australia:Current directions and future challenges

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plant Diversity 2017年第6期39卷 348-356页

作者： Linda Broadhurst david Coates CANBR CSIRO National Research Collections Australia Department of Biodiversity Conservation and Attractions

Australia is a large, old and flat island continent that became isolated following the breakup of the Gondwanan super continent. After more than 40-50 M years of independent evolution, approx. 600,000-700,000 species now call Australia home. More than 21,000 of these species are plants, with at least84% of these being endemic. Plant taxa are protected, conserved and managed under a range of legislation at the State-and Territory-level as well as Federally for matters of national significance. This can create issues of misalignment among threatened species lists but generally there is co-operation among conservation agencies to reduce misalignments and to manage species irrespective of jurisdictional borders. Despite significant investment in programs designed to assist the recovery of Australian biodiversity, threatened plants in particular appear to be continuing to decline. This can be attributed to a range of factors including major threatening processes associated with habitat loss and invasive species,lack of public awareness of the cultural and socio-economic value of plant conservation, and our relatively poor understanding of basic species taxonomy and biology, especially for those species that have specific interactions with pollinators, symbionts and herbivores. A recent shift in Federally-based conservation programs has been to identify 30 key plant species for recovery through the setting of measurable targets, improving the support provided to recovery teams and encouraging industry,business and philanthropy to support conservation actions.

关键词： Conservation Plant Australia Threatened species Recovery

A collaboration into research on nanoparticles (ACORN)

在线全文

学校读者我要写书评

暂无评论

Particuology 2009年第2期7卷 93-105页

作者： david G. Parker Chemistry Innovation The HeathRuncorn WA7 4QXUnited Kingdom

This paper describes the operation and outcome of one of the United Kingdom＇s largest multi-partner research activities in nanoparticles. The research covers the discovery and development of organic and inorganic crystals/nanoparticles, nanoparticle properties towards specific product applications. The research also encompassed bespoke measurement technology for nanoparticles and structure interactions. Significant research outcomes are summarised. The paper illustrates the advantages from industrially motivated research and value of collective action between a broad group of researchers in a nation.

关键词： Nanoparticles Nanoparticle manufacture Nanocrystals Nanoassembly structure Modelling

Cellular automata modelling of phase-change memories

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2008年第4期15卷 444-450页

作者： Wanhua Yu david Wright School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China School of Engineering Computer Science and Mathematics The University of Exeter Exeter EX4 4QF UK

A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton （CA） approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.

关键词： crystallization bchaviour cellular automation computer simulation memory data storage modelling phase change