1,720,955 research outputs found
Application of mixed model and spatial analysis methods in multi-environmental and agricultural field trials.
Get PDFDoctor of Philosophy in Statistics. University of KwaZulu-Natal, Pietermaritzburg 2015.Agricultural experimentation involves selection of experimental materials,
selection of experimental units, planning of experiments, and collection of
relevant information, analysis and interpretation of the results. An overall
work of this thesis is on the importance, improvement and efficiency of variety
contrast by using linear mixed mode with spatial-variance covariance compare
to the usual ANOVA methods of analysis. A need of some considerations on the
recently widely usage of a bi-plot analysis of genotype plus genotype by
environment interaction (GEE) on the analysis of multi-environmental crop
trials. An application of some parametric bootstrap method for testing and
selecting multiplicative terms in GGE and AMMI models and to show some
statistical methods for handling missing data using multiple imputations
principal component and other deterministic approaches.
Multi-environment agricultural experiments are unbalanced because several
genotypes are not tested in some environments or missing of a
measurement from some plot during the experimental stage. A need for
imputation of the missing values sometimes is necessary. Multiple
imputation of missing data using the cross-validation by eigenvector method
and PCA methods are applied. We can see the advantage of these methods
having easy computational implementation, no need of any distributional or
structural assumptions and do not have any restrictions regarding the pattern
or mechanism of missing data in experiments.
Genotype by environment (G×E) interaction is associated with the differential
performance of genotypes tested at different locations and in different years,
and influences selection and recommendation of cultivars. Wheat genotypes
were evaluated in six environments to determine the G×E interactions and
stability of the genotypes. Additive main effects and multiplicative interactions
(AMMI) was conducted for grain yield of both year and it showed that grain
yield variation due to environments, genotypes and (G×E) were highly
significant. Stability for grain yield was determined using genotype plus
genotype by environment interaction (GGE) biplot analysis. The first two
principal components (PC1 and PC2) were used to create a 2-dimensional GGE
biplot. Which-won where pattern was based on six locations in the first and five
locations in the second year for all the twenty genotypes? The resulting pattern
is one realization among many possible outcomes, and its repeatability in the
second was different and a future year is quite unknown. A repeatability of
which won-where pattern over years is the necessary and sufficient condition
for mega-environment delineations and genotype recommendation.
The advantages of mixed models with spatial variance-covariance structures,
and direct implications of model choice on the inference of varietal
performance, ranking and testing based on two multi-environmental data sets
from realistic national trials. A model comparison with a ᵪ2-test for the trials in
the two data sets (wheat and barley data) suggested that selected spatial
variance-covariance structures fitted the data significantly better than the
ANOVA model. The forms of optimally-fitted spatial variance-covariance,
ranking and consistency ratio test were not the same from one trial (location) to
the other. Linear mixed models with single stage analysis including spatial
variance-covariance structure with a group factor of location on the random
model also improved the real genotype effect estimation and their ranking. The
model also improved varietal performance estimation because of its capacity to
handle additional sources of variation, location and genotype by location
(environment) interaction variation and accommodating of local stationary
trend. The knowledge and understanding of statistical methods for analysis of
multi-environmental data analysis is particularly important for plant breeders
and those who are working on the improvement of plant variety for proper
selection and decision making of the next level of improvement for country
agricultural development.Institute of Agricultural Research (EIAR) is acknowledged on p1039
Application of statistical multivariate techniques to wood quality data.
Get PDFThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.Sappi is one of the leading producer and supplier of Eucalyptus pulp to the world market. It is also a great contributor to South Africa economy in terms of employment opportunity to the rural people through its large plantation and export earnings. Pulp mills production of quality wood pulp is mainly affected by the supply of non uniform raw material namely Eucalyptus tree supply from various plantations. Improvement in quality of the pulp depends directly on the improvement on the quality of the raw materials. Knowing factors which affect the pulp quality is important for tree breeders. Thus, the main objective of this research is first to determine which of the anatomical, chemical and pulp properties of wood are significant factors that affect pulp properties namely viscosity, brightness and yield. Secondly the study will also investigate the effect of the difference in plantation location and site quality, trees age and species type difference on viscosity, brightness and yield of wood pulp. In order to meet the above mentioned objectives, data for this research was obtained from Sappi’s P186 trial and other two published reports from the Council for Scientific and Industrial Research (CSIR). Principal component analysis, cluster analysis, multiple regression analysis and multivariate linear regression analysis were used. These statistical analysis methods were used to carry out mean comparison of pulp quality measurements based on viscosity, brightness and yield of trees of different age, location, site quality and hybrid type and the results indicate that these four factors (age, location, site quality and hybrid type) and some anatomical and chemical measurements (fibre lumen diameter, kappa number, total hemicelluloses and total lignin) have significant effect on pulp quality measurements
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
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