Shallow shore zones are generally considered to provide juvenile habitats for many invertebrate and fish species and additionally serve as spawning grounds for important components of oceanic food webs and fishery resources such as herring (Clupea spp.). Herring attach their demersal eggs to benthic substrates, rendering reproduction success vulnerable to environmental changes and local habitat alterations. However, little information is available on the effects of different substrates on the survival of demersal eggs. Hypothesizing that the structural complexity of spawning substrates generally affects herring egg survival and that the effect magnitude depends on the suitability of ambient environment, field experiments were conducted on a major spawning ground of C. harengus in the Southwestern Baltic Sea. Herring eggs were artificially spawned on substrates of different structural complexities and incubated in situ under differing temperature regimes, at the beginning and the end of the natural herring spawning season, to include the full suite of stressors occurring on littoral spawning beds. Results of this study indicate a positive relation between high structural complexity of spawning substrates and herring egg survival. Mean egg mortality was three times higher on substrates of lowest complexity than on highly complex substrates. These differences became even more prominent under unfavorable conditions that appeared with rising water temperatures later in the spawning season. Although the mechanisms are still unclear, we conclude that structural complexity, particularly formed by submerged aquatic vegetation, provides a crucial prerequisite for the successful reproduction of substrate spawning marine fishes such as herring in the Baltic Sea. 相似文献
Loose programming enables analysts to program with concepts instead of procedural code. Data transformations are left underspecified, leaving out procedural details and exploiting knowledge about the applicability of functions to data types. To synthesize workflows of high quality for a geo‐analytical task, the semantic type system needs to reflect knowledge of geographic information systems (GIS) at a level that is deep enough to capture geo‐analytical concepts and intentions, yet shallow enough to generalize over GIS implementations. Recently, core concepts of spatial information and related geo‐analytical concepts were proposed as a way to add the required abstraction level to current geodata models. The core concept data types (CCD) ontology is a semantic type system that can be used to constrain GIS functions for workflow synthesis. However, to date, it is unknown what gain in precision and workflow quality can be expected. In this article we synthesize workflows by annotating GIS tools with these types, specifying a range of common analytical tasks taken from an urban livability scenario. We measure the quality of automatically synthesized workflows against a benchmark generated from common data types. Results show that CCD concepts significantly improve the precision of workflow synthesis. 相似文献
Natural Hazards - Forest fire hazard is a major problem in the Mediterranean region of Turkey and has a significant effect on both the climate system and ecosystems. During the last century, many... 相似文献
Empirical correlations provide valuable information in early design stages, and they help to validate or discard single values from site investigations. This paper presents a multivariate database from commercial projects consisting of evaluated shear strengths obtained from direct simple shear tests and fall cone tests (which are calibrated to the field vane test), including index tests. The multivariate database is used to investigate the performance of common transformation models and to test the recommended correction for fall cone tests. It is found that the measured normalised shear strength evaluated from direct simple shear tests and fall cone tests is correlated to the liquid limit and that the results conform to Swedish and Norwegian recommendations. However, the scatter is large, more for fall cone tests than for direct simple shear tests, which is thought to depend mainly on sample disturbance. It can however be concluded that the trend of normalised shear strengths increases with increasing plasticity.
PREFACE
The paper contains a brief overview of the professional activities of Professor Gottfried Konecny,Professor Emeritus at the Institute of Photogrammetry and GeoInformation,Leibniz University Hannover,Germany,and his influence on photogrammetry,remote sensing and geospatial infor-mation science during his time at the University of New Brunswick,Canada,and at the Leibniz University.His work can be divided into educational,scientific,application,organizational,and work in international societies.Additional activities comprised of giving courses in various languages,consultancy activities,and various other cooperations which took place in many South American countries,in Africa and Asia,for organizations such as the World Bank,United Nations,German Space Agency DLR,to name only a few.Activities in connection with international societies mainly took place during Prof.Konecny's engagement in the Council of the International Society for Photogrammetry(ISP),renamed the International Society for Photogrammetry and Remote Sensing(ISPRS),and the European Association of Remote Sensing Laboratories(EARSeL)Bureau.He was a key figure in bringing many countries and organizations to ISPRS as Ordinary and Sustaining Members.Professor Konecny has always been aware of the importance of international cooperation at various levels,also with sister societies such as the International Cartographic Association and the United Nations-Global Geospatial Information Management(UN-GGIM).His application activities span from the photogrammetry-oriented projects he was awarded in Canada,to remote sensing topics and geospatial sciences,combined with cartography during his Hannover period.His vision and endless effort are exemplary for a person who has always been devoted to the three geosciences mentioned above.Professor Konecny is the author of a number of books,journal papers and papers presented at international and national conferences.He has been a recognized keynote speaker at many conferences throughout the world due to his vast experience.This paper describes 75 years of a man who is an expert in fields which arose during his academic life. 相似文献
Various measurements from the Surface Heat Flux of the Arctic Ocean (SHEBA) experiment have been combined to study structures and processes producing the onset and end of summer melt over Arctic sea ice. The analysis links the surface energy budget to free-troposphere synoptic variables, clouds, precipitation, and in-ice temperatures. The key results are (1) SHEBA melt-season transitions are associated with atmospheric synoptic events (2) onset of melt clearly occurs on May 28, while the end of melt is produced by a sequence of three atmospheric storm events over a 28-day period producing step-like reductions in the net surface energy flux. The last one occurs on August 22.; (3) melt onset is primarily due to large increases in the downwelling longwave radiation and modest decreases in the surface albedo; (4) decreases in the downwelling longwave radiation occur for all end-of-melt transition steps, while increases in surface albedo occur for the first two; (5) decreases in downwelling shortwave radiation contribute only to the first end-of-melt transition step; (6) springtime free-tropospheric warming preconditions the atmosphere–ice system for the subsequent melt onset; and (7) melt-season transitions also mark transitions in system responses to radiative energy flux changes because of invariant melt-season surface temperatures. The extensive SHEBA observations enable an understanding of the complex processes not available from other field program data. The analysis provides a basis for future testing of the generality of the results, and contributes to better physical understanding of multi-year analyses of melt-season trends from less extensive data sets. 相似文献
Abstract: Sensitive, high-resolution ion microprobe zircon U–Pb ages of Paleoproterozoic, high-grade, metasedimentary rocks from the south-western part of the Siberian Craton are reported. Early Precambrian, high-grade complexes, including garnet–biotite, hypersthene–biotite, and cordierite-bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4–3.1 Ga indicate Archean-to-Paleoproterozoic source provinces. Zircons from gneisses show core-rim textures in cathodoluminescence (CL) image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are: ≥2.7, ~2.3, and 1.95–2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga; therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High-grade metaterrigenous sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the Aldan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga (Wan et al., 2006). All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high-grade metamorphism was related to the consolidation of the Siberian Craton. 相似文献
Rainfall extremes often result in the occurrence of flood events with associated loss of life and infrastructure in Malawi.
However, an understanding of the frequency of occurrence of such extreme events either for design or disaster planning purposes
is often limited by data availability at the desired temporal and spatial scales. Regionalisation, which involves “trading
time for space” by pooling together observations for stations with similar behavior, is an alternative approach for more accurate
determination of extreme events even at ungauged areas or sites with short records. In this study, regional frequency analysis
of rainfall extremes in Southern Malawi, large parts of which are flood prone, was undertaken. Observed 1-, 3-, 5- and 7-day
annual maximum rainfall series for the period 1978–2007 at 23 selected rainfall stations in Southern Malawi were analysed.
Cluster analysis using scaled at-site characteristics was used to determine homogeneous rainfall regions. L-moments were applied
to derive regional index rainfall quantiles. The procedure also validated the three rainfall regions identified through homogeneity
and heterogeneity tests based on Monte Carlo simulations with regional average L-moment ratios fitted to the Kappa distribution.
Based on assessments of the accuracy of the derived index rainfall quantiles, it was concluded that the performance of this
regional approach was satisfactory when validated for sites not included in the sample data. The study provides an estimate
of the regional characteristics of rainfall extremes that can be useful in among others flood mitigation and engineering design. 相似文献