1,720,982 research outputs found
Optimizing Planting Dates for Agricultural Decision-Making under Climate Change over Burkina Faso/West Africa
Get PDFRainfed agriculture is the main source of income for population and the main driver of the economy in Africa, particularly in West Africa (WA). The agricultural system is characterized by smallholder and subsistence farming in a context of farmers' low capacity. In water-limited regions of WA, most of the crop management decisions are made based on the perceived risk of climate and the socio-economic conditions of the farmers.
Therefore, technologies and approaches in the field of agricultural water management are likely to make a difference for agricultural development and thus food security. However, only those strategies which require little resources in terms of labor and money have a chance to engage a large number of farmers. As a farming strategic decision, the planting time has the potential to sustain crop production as well as to be adopted by farmers.
In the context of high rainfall variability and little irrigation options in WA, the crop planting date in WA is a crucial tactical decision for farmers and therefore their major concern. With regards to the high intra-seasonal rainfall variability in WA, early planting dates can lead to crop failure due to long dry spells which occur shortly after planting.
In contrast, late planting dates have the chance to avoid crop failure but they correspond to short growing seasons which can potentially reduce crop production. In this thesis, an approach to derive an optimal planting time has been developed. Based on the crop water requirements throughout the crop growing cycle, this planting date approach uses a process-based crop model in conjunction with a fuzzy rule-based planting date definition to derive optimized planting dates (OPDs).
First, by taking into account the inherent uncertainties of rainfall measurements and computations issues, three fuzzy logic memberships, which are fully determined by two fuzzy parameters each, have been developed to represent the three main criterions used to define planting date. Then, the General Large-Area Model for annual crops (GLAM) and the fuzzy rule-based planting date have been coupled with a genetic algorithm optimization technique. Finally, this has been applied to calibrate GLAM for maize cropping and subsequently to derive OPDs for maize cropping. To allow a time window for crop planting, an ensemble member principle has been applied to derive a 10-member ensemble of optimized fuzzy parameters. Burkina Faso (BF) has been selected as a case study area to derive OPDs. The performance of the OPDs approach have been evaluated by comparing maize yield derived from the OPDs method and two state-of-the-art methods which are currently in use in WA. The analysis comprises both present climate and future climate projections. Present climate data encompassed observed data and European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) data over BF for the period 1961-2010 and 1980-2010, respectively. Future climate encompassed eight regional climate models outputs based on the greenhouse gas emission scenarios RCP4.5 and RCP8.5 covering the period 2011-2050. Beside the climate data, soil and observed maize yield data have been involved in this study.
The results show that, on average, OPDs ranged from 1 May (South-West) to 11 July (North) across the country under present climate. In comparison to selected state-of-the art methods, the results suggest earlier planting dates across BF, ranging from 10-20 days for the northern and central BF, and less than 10 days for the southern BF. With respect to the potential yields, the OPD approach indicates that an increase of maize potential mean yield of around 20% could be achieved in water limited regions in BF. However, the potential yield surpluses strongly decrease from the North to the South. For future climate projections, the OPDs approach achieves approximately +15% higher potential maize yield regardless of the Regional Climate Model (RCM) and the time horizons. When the OPD approach is used as adaptation strategy, the change in maize mean yield varies between -23% and 34% from the baseline period (1989-2008) for the majority of locations. The regional mean yield deviations strongly depend on the location and RCM, particularly for the RCP8.5 scenario. On average, negative changes of mean yield is observed. Considering the period 2011-2050, RCMs ensemble mean of yield change is -3.4% for RCP4.5 and -8.3% for RCP8.5. Mean yield decreases are more pronounced for RCP8.5 during the period 2031-2050.
These findings highlight the potential of OPDs as a crop management strategy. The implementation of the presented approach in agricultural decision support is expected to improve agricultural water-related risk management in WA. The OPD approach can be used in combination with seasonal climate forecasts to provide planting date information to farmers. As farmers concern is how to limit the risk of crop failure and to sustain their crop production, the prediction of the OPDs might be of high relevance for farmers and a guide in the choice of crops and the planning of labor. However, the predictability of OPDs has to be investigated and further in-field validation of OPDs is required before being implemented as short-term tactical decision by farmers.
It is apparent however, that farmers need to combine OPDs with others suited farming practices to adequately respond to climate change. Moreover, in order to efficiently support agricultural long-term strategic decision-making in WA, it is worth to perform further multi-model ensemble simulations by using additional multiple RCMs driven by multiple Global Circulation Models (GCMs) and emissions scenarios. Such investigations might contribute to better capture the magnitude of climate change impacts on crop production, thereby enhancing the development of climate chance adaptation strategies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
- …
