Integration zeitabhängiger Funktionen mittels Glimmröhren-Kippschwinger     

Theo Dahlem  D. Paffrath 《Pure and Applied Geophysics》1968,71(1):51-55

Zusammenfassung Es wird ein im wesentlichen aus einem einfachen Kippschwinger bestehender Integrator beschrieben, der es gestattet, zeitlich veränderliche Spannungen digital zu summieren. Er ist somit zur Integration von zeitlich variablen Meßgrößen, insbesondere aus Meteorologie und Geophysik, sie sich in eine der Meßgröße proportionale Spannung umsetzen lassen, geeignet. Es werden Meß- und Anwendungsbeispiele gegeben.

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Summary An integration device consisting essentially of a simple saw-tooth oscillator is described. The instrument allows to integrate arbitrary voltages variable with time. Thus it is possible to integrate measuring functions variable with time, especially in meteorology and geophysics, that are convertible into a proportional voltage. Examples of measurements and application are represented.

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Community collaboration and climate change research in the Canadian Arctic     

Tristan D. Pearce  James D. Ford  Gita J. Laidler  Barry Smit  Frank Duerden  Mishak Allarut  Mark Andrachuk  Steven Baryluk  rew Dialla  Pootoogoo Elee  Annie Goose  Theo Ikummaq  Eric Joamie  Fred Kataoyak  Eric Loring  Stephanie Meakin  Scott Nickels  Kip Shappa  Jamal Shirley  & Johanna Wandel 《Polar research》2009,28(1):10-27

Research on climate change impacts, vulnerability and adaptation, particularly projects aiming to contribute to practical adaptation initiatives, requires active involvement and collaboration with community members and local, regional and national organizations that use this research for policy-making. Arctic communities are already experiencing and adapting to environmental and socio-cultural changes, and researchers have a practical and ethical responsibility to engage with communities that are the focus of the research. This paper draws on the experiences of researchers working with communities across the Canadian Arctic, together with the expertise of Inuit organizations, Northern research institutes and community partners, to outline key considerations for effectively engaging Arctic communities in collaborative research. These considerations include: initiating early and ongoing communication with communities, and regional and national contacts; involving communities in research design and development; facilitating opportunities for local employment; and disseminating research findings. Examples of each consideration are drawn from climate change research conducted with communities in the Canadian Arctic.  相似文献   

Contrasting responses of dimictic and polymictic lakes to environmental change: a spatial and temporal study     

Zofia Ecaterina Taranu  Dörte Köster  Roland I. Hall  Theo Charette  Francine Forrest  Les C. Cwynar  Irene Gregory-Eaves 《Aquatic Sciences - Research Across Boundaries》2010,72(1):97-115

Although comparative analyses between dimictic and polymictic lakes have noted the key role of mixing regime in governing water quality, limnologists have historically focused on dimictic lakes, leaving polymictic lakes relatively understudied. In this study, we investigated whether the effects of agricultural development on water quality differed between dimictic and polymictic lakes in a naturally nutrient-rich region of Alberta, Canada. Through a spatial limnological analysis of 36 sites, we found that the relationship between surface water total phosphorus concentration and the percent of agriculture (% Agr) in the catchments differed between dimictic and polymictic lakes, where the proportion of variance explained was much more pronounced in the dimictic (79% explained) than in the polymictic systems (7% explained). Paleolimnological analyses of subfossil chironomids in surface sediment samples (0–1 cm) from 18 of the 36 study lakes, and in sediment core profiles from the dimictic and polymictic basins of a eutrophic lake, showed that water quality differed between mixis groups. We found that the surface sediment chironomid assemblages differed significantly between polymictic and dimictic lakes. Detailed analyses of the sediment cores demonstrated that the two basin types differed in their responses to land-use change through time, as only the dimictic basin showed a parallel increase in anoxia with increasing agricultural development. We suggest that in naturally-fertile landscapes, external nutrient loading exerts a more notable effect on dimictic lakes, whereas internal nutrient loading is more important in polymictic systems.  相似文献   

Do a bit more with convolution     

Olsthoorn TN 《Ground water》2008,46(1):13-22

Convolution is a form of superposition that efficiently deals with input varying arbitrarily in time or space. It works whenever superposition is applicable, that is, for linear systems. Even though convolution is well-known since the 19th century, this valuable method is still missing in most textbooks on ground water hydrology. This limits widespread application in this field. Perhaps most papers are too complex mathematically as they tend to focus on the derivation of analytical expressions rather than solving practical problems. However, convolution is straightforward with standard mathematical software or even a spreadsheet, as is demonstrated in the paper. The necessary system responses are not limited to analytic solutions; they may also be obtained by running an already existing ground water model for a single stress period until equilibrium is reached. With these responses, high-resolution time series of head or discharge may then be computed by convolution for arbitrary points and arbitrarily varying input, without further use of the model. There are probably thousands of applications in the field of ground water hydrology that may benefit from convolution. Therefore, its inclusion in ground water textbooks and courses is strongly needed.  相似文献   

Iap general circulation models: a first step towards developing a local area model for weather prediction in nigeria     

Chineke Theo Chidiezie  Li Weiping 《大气科学进展》1999,16(1):119-132

１．ＩｎｔｒｏｄｕｃｔｉｏｎＮｕｍｅｒｉｃａｌｍｏｄｅｌｓｆｏｒｗｅａｔｈｅｒｐｒｅｄｉｃｔｉｏｎａｒｅｂｅｃｏｍｉｎｇｍｏｒｅｒｅｌｉａｂｌｅａｎｄｐｏｐｕｌａｒｉｎｍｅｔｅｏｒｏｌｏｇｙａｎｄｃｌｉｍａｔｅｒｅｓｅａｒｃｈ．Ｍｕｌｔｉ－ｌａｙｅ...  相似文献   

Investigating dune-building feedback at the plant level: Insights from a multispecies field experiment     

Elsemarie Mullins  Laura J. Moore  Evan B. Goldstein  Theo Jass  John Bruno  Orencio Durán Vinent 《地球表面变化过程与地形》2019,44(9):1734-1747

Coastal foredunes provide the first line of defense against rising sea levels and storm surge and for this reason there is increasing interest in understanding and modeling foredune formation and post-storm recovery. However, there is limited observational data available to provide empirical guidance for the development of model parameterizations. To provide guidance for improved representation of dune grass growth in models, we conducted a two-year multi-species transplant experiment on Hog Island, VA, U.S.A. and measured the dependence of plant growth on elevation and distance from the shoreline, as well as the relationship between plant growth and sand accumulation. We tracked total leaf growth (length) and aboveground leaf length and found that Ammophila breviligulata (American beachgrass) and Uniola paniculata (sea oats) grew more than Spartina patens (saltmeadow cordgrass) by a factor of 15% (though not statistically significant) and 45%, respectively. Our results also suggest a range of basal/frontal area ratios (an important model parameter) from 0.5-1 and a strong correlation between transplant growth and total sand deposition for all species at the scale of two years, but not over shorter temporal scales. Distance from the shoreline and elevation had no effect on transplant growth rate but did have an effect on survival. Based on transplant survival, the seaward limit of vegetation at the end of the experiment was approximately 30 m from the MHWL and at an elevation of 1.43 m, corresponding to inundation less than 7.5% of the time according to total water level calculations. Results from this experiment provide evidence for the dune-building capacity of all three species, suggesting S. patens is not a maintainer species, as previously thought, but rather a moderate dune builder even though its growth is less stimulated by sand deposition than A. breviligulata and U. paniculata. © 2019 John Wiley & Sons, Ltd.  相似文献   

Determinants of liner shippping network configuration: a two-region comparison     

Gordon Wilmsmeier  Theo Notteboom 《GeoJournal》2011,76(3):213-228

The worldwide network of container transport services is becoming increasingly diffuse. The different strategies of shipping lines, the balance of power between shipping lines and shippers and constraints related to inland transportation all have a potential impact on the development of maritime shipping networks. Moreover, strategic alliances between the port and the shipping industry, which have both been driven by strong concentration processes and vertical integration, have a profound influence on the maritime network structure and also on the grade of integration of a region in the global maritime transport network. This paper seeks to understand the evolution of maritime networks in and between two differently developed regions. The focus is on the trade route and networks between the West Coast of South America and Northern Europe. The paper analyses the network structures and the behaviour of shipping lines in different economic contexts and port systems. Current and historical developments in the two regions under study have led to their relative position within the global maritime network and illustrate the potential implications of being peripheral or central in this network. The empirical results are compared with known strategies of shipping lines. The authors aim to answer the question of how far the configuration of hinterlands determines calling patterns and if strategic alliances and vertical integration reduce footloose behaviour of shipping lines. Further, we discuss how far, under the current configuration, shipping lines influence port development, and also the reverse situation of how far port accessibility and performance influence maritime network developments. The two region approach provides insights on the constraining factors of maritime network development between two differently developed regions and the associated implications for trade development.  相似文献   

Multistop-based measurements of accessibility in a GTS environment     

Theo A. Arentze  Aloys W. J. Borgers  Harry J. P. Timmermans 《International journal of geographical information science》2013,27(4):343-356

Abstract

The opportunities available at a demand location are usually measured as the costs of reaching a specified critical number of facilities from that location. This method does not however, account for multistop trips nor for differences in the diversity of supply at the level of individual facilities. In this paper we introduce an alternative measurement method that overcomes these shortcomings. In this method the probability of successfully visiting a specific facility is assumed to be a function of the diversity of supply provided. Trip routes are constructed that have an acceptable probability of success. Then, the expected costs of travelling the optimum route are determined as an indicator of spatial opportunities. The proposed method has been implemented in a GIS environment, using typical GIS data and GIS tools for spatial analysis and display. The results of a case study indicate that the new method, compared to current methods, may lead to different evaluations of the level of opportunities at demand locations.  相似文献   

Active and passive ocean regimes in a low‐order climate model     

Lennaert van Veen  Theo Opsteegh  Ferdinand Verhulst 《地球，A辑:动力气象学与海洋学》2001,53(5):616-628

A low‐order climate model is studied which combines the Lorenz‐84 model for the atmosphere on a fast time scale and a box model for the ocean on a slow time scale. In this climate model, the ocean is forced strongly by the atmosphere. The feedback to the atmosphere is weak. The behaviour of the model is studied as a function of the feedback parameters. We find regions in parameter space with dominant atmospheric dynamics, i.e., a passive ocean, as well as regions with an active ocean, where the oceanic feedback is essential for the qualitative dynamics. The ocean is passive if the coupled system is fully chaotic. This is illustrated by comparing the Kaplan–Yorke dimension and the correlation dimension of the chaotic attractor to the values found in the uncoupled Lorenz‐84 model. The active ocean behaviour occurs at parameter values between fully chaotic and stable periodic motion. Here, intermittency is observed. By means of bifurcation analysis of periodic orbits, the intermittent behaviour, and the rôle played by the ocean model, is clarified. A comparison of power spectra in the active ocean regime and the passive ocean regime clearly shows an increase of energy in the low frequency modes of the atmospheric variables. The results are discussed in terms of itinerancy and quasi‐stationary states observed in realistic atmosphere and climate models.  相似文献   

Road distance and travel time for an improved house price Kriging predictor     

Henry Crosby  Theo Damoulas  Alex Caton  Paul Davis  João Porto de Albuquerque  Stephen A. Jarvis 《地球空间信息科学学报》2018,21(3):185-194

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