Nonlinear dynamics of river runoff elucidated by horizontal visibility graphs

Horizontal Visibility Graphs (HVGs) are a recently developed method to construct networks from time series. The values of the time series are considered as the nodes of the network and are linked to each other if there is no larger value between them, such as they can “see” each other. The network properties reflect the nonlinear dynamics of the time series. For some classes of stochastic processes and for periodic time series, analytical results can be obtained for network-derived quantities such as the degree distribution, the local clustering coefficient distribution, the mean path length, and others. HVGs have the potential to discern between deterministic-chaotic and correlated-stochastic time series. Here, we investigate the sensitivity of the HVG methodology to properties and pre-processing of real-world data, i.e., time series length, the presence of ties, and deseasonalization, using a set of around 150 runoff time series from managed rivers at daily resolution from Brazil with an average length of 65 years. We show that an application of HVGs on real-world time series requires a careful consideration of data pre-processing steps and analysis methodology before robust results and interpretations can be obtained. For example, one recent analysis of the degree distribution of runoff records reported pronounced sub-exponential “long-tailed” behavior of North American rivers, whereas another study of South American rivers showed hyper-exponential “short-tailed” behavior resembling correlated noise. We demonstrate, using the dataset of Brazilian rivers, that these apparently contradictory results can be reconciled by minor differences in data-preprocessing (here: small differences in subtracting the seasonal cycle). Hence, data-preprocessing that is conventional in hydrology (“deseasonalization”) changes long-term correlations and the overall runoff dynamics substantially, and we present empirical consequences and extensive simulations to investigate these issues from a HVG methodological perspective. After carefully accounting for these methodological aspects, the HVG analysis reveals that the river runoff dataset shows indeed complex behavior that appears to stem from a superposition of short-term correlated noise and “long-tailed behaviour,” i.e., highly connected nodes. Moreover, the construction of a dam along a river tends to increase short-term correlations in runoff series. In summary, the present study illustrates the (often substantial) effects of methodological and data-preprocessing choices for the interpretation of river runoff dynamics in the HVG framework and its general applicability for real-world time series.Fil: Lange, Holger. Norwegian Institute of Bioeconomy Research; NoruegaFil: Sippel, Sebastian. Norwegian Institute of Bioeconomy Research; NoruegaFil: Rosso, Osvaldo Aníbal. Instituto Universidad Escuela de Medicina del Hospital Italiano; Argentina. Universidad de Los Andes; Chile. Universidade Federal de Alagoas; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Textual data mining for industrial knowledge management and text classification: a business oriented approach

Textual databases are useful sources of information and knowledge and if these are well utilised then issues related to future project management and product or service quality improvement may be resolved. A large part of corporate information, approximately 80%, is available in textualdata formats. TextClassification techniques are well known for managing on-line sources of digital documents. The identification of key issues discussed within textualdata and their classification into two different classes could help decision makers or knowledge workers to manage their future activities better. This research is relevant for most text based documents and is demonstrated on Post Project Reviews (PPRs) which are valuable source of information and knowledge. The application of textualdatamining techniques for discovering useful knowledge and classifying textualdata into different classes is a relatively new area of research. The research work presented in this paper is focused on the use of hybrid applications of textmining or textualdatamining techniques to classify textualdata into two different classes. The research applies clustering techniques at the first stage and Apriori Association Rule Mining at the second stage. The Apriori Association Rule of Mining is applied to generate Multiple Key Term Phrasal Knowledge Sequences (MKTPKS) which are later used for classification. Additionally, studies were made to improve the classification accuracies of the classifiers i.e. C4.5, K-NN, Naïve Bayes and Support Vector Machines (SVMs). The classification accuracies were measured and the results compared with those of a single term based classification model. The methodology proposed could be used to analyse any free formatted textualdata and in the current research it has been demonstrated on an industrial dataset consisting of Post Project Reviews (PPRs) collected from the construction industry. The data or information available in these reviews is codified in multiple different formats but in the current research scenario only free formatted text documents are examined. Experiments showed that the performance of classifiers improved through adopting the proposed methodology

Learning from experience: manifestations of young children's learning from pedagogic representations

This study investigates how influences of teachers’ presentations of mathematical ideas, on children’s mental constructions for number and number operations, are manifested by the language they use to describe their mental calculation procedures, and by the mental visual imagery they report. The methodology is described as postpositivist with a phenomenographic orientation. The research method involved the observation of mathematics lessons of two classes of children aged 7- to 9-years over a two year period and structured interviews with a sample of 26 pupils from these classes at the end of each school term. The language and mental visual imagery described by children in the interviews seemed related to the way the mathematics was presented by their teachers. The use of the ‘metaphoric’ language related to a previous experience may be seen as a manifestation of the influence of that experience on the child’s ‘mental construction’. The interdependence of speech style and classroom activity gave evidence of linguistic relativism. The commonalities in the interview responses suggested that children had acquired the cultural tools of the mathematics classroom. The differences in response suggested they had constructed their own knowledge. The differences were most apparent in the calculation methods employed and the mode of generality of their expression. Linguistic indicators (use of tense, pronouns and causal connectives) also distinguished groups of children at different achievement levels. In non-calculation contexts these differences were not apparent, suggesting that the responses reveal mental constructions not just linguistic traits. The conclusion is drawn: When describing the way they perform mental calculation young children’s mental visual imagery and language use is indicative both of the experiences that have influenced their mental constructions and the qualitatively different mental constructions that have been formed. These manifestations may aid teachers in helping children develop their mental constructions to support further mathematical progression

The Six Cities Project: developing a methodology of surveying densely populated areas using social science assisted and diachronic remote sensing based classification of habitation

This paper provides a statistical evaluation of the methodology of the NSF funded Six Cities Project. The project develops a methodology for surveying densely inhabited areas by processing diachronic remote sensing imagery to create habitation strata or urban classes. These classes become part of a sampling strategy which gives every pixel associated with habitation a specified chance of selection and then draws a representative sample of pixels. These pixels become center points for household surveys which can study a variety of issues including health, environment, livelihood strategies, demographics and household labor, expenditures and income. The methodology lends itself to GIS construction and the generation of data that can be easily compared and can be of maximal use to municipalities, governments, scholars and NGOs. It also provides a long term basis for inexpensive surveys that can have a high claim to reliability and representativity. Key words: remote sensing, urbanism, survey methodology, National Science Foundation, health, environment, livelihood strategies, demographic, household labor, expenditures, income, Africa, Middle East, Morocco, Senegal, Mali, Niger, Tanzania, Botswana, Marrakech, Dakar, Bamako, Niamey, Dodoma,  Gaborone

Reusability in software engineering

This paper surveys recent work concerning reusability in software engineering. The current directions in software reusability are discussed, and the two major approaches of reusable building blocks and reusable patterns studied. An extensive bibliography, parts of which are annotated, is included

A tribute to Professor William Dearman : new small-scale engineering geological maps of the United Kingdom

Professor William Robert (“Bill”) Dearman was the first British Professor of Engineering Geology and a world leader in the development of engineering geological mapping techniques and methodologies, recognised by being awarded the IAEG’s Hans Cloos Medal. The maps described here would not have been completed without his initial ideas and interpretative work. It is a great regret that the maps were not finished in time for him to see them before his death in January 2009. This paper and the maps described in it are, therefore, dedicated to his memory

A Methodological Approach to Determine Sound Response Modalities to Coastal Erosion Processes in Mediterranean Andalusia (Spain)

Human occupation along coastal areas has been greatly increasing in recent decades and, in many places, human activities and infrastructures are threatened by erosion processes that can produce relevant economic and human losses. In order to reduce such impacts and design sound management strategies, which can range from the "no action" to the "protection" option, coastal managers need to know the intrinsic coastal sensitivity and the potential vulnerability and value of land uses. In this paper, in a first step, coastal sensitivity was determined by calculating the following: (i) the spatial distribution at the coast of the wave forcing obtained by using the ERA5 wave dataset and defined as the energy associated with the 50-year return period storm. Two storm conditions were considered, that is, one for the eastern and one for the western parts of the Andalusia Mediterranean coast, respectively, characterized by a height of 8.64-7.86 m and 4.85-4.68 m and (ii) the existence of a buffer zone, namely the dry beach width expressed as a multiple of the 20-year predicted shoreline position that was calculated using a dataset of aerial photographs covering a time span from 1956 to 2016. Coastal sensitivity values were divided into five classes with class 1 indicating the lowest sensitivity (i.e., the presence of a wide buffer zone associated with low wave energy flux values) and class 5 the highest sensitivity (i.e., a narrow buffer zone associated with very high wave energy flux values). In a second step, land uses were obtained from the official Land Use Map of the Andalusia Region, based on the results of the "Coordination of Information on the Environment" (CORINE) European Project. Such uses were divided into five classes from class 1 including natural areas (typologies "A" and "B" of the CORINE Project) to class 5 including very capital land uses (typologies "E1" and "E2"). In a third step, information concerning coastal sensitivity and land uses was crossed to determine the best mitigation strategies to cope with erosion processes. The "no action" option was observed at the westernmost area of Cadiz Province and at some areas from the west coast of Almeria Province, where both coastal sensitivity and land use classes show low values; the "adaptation" option was recorded along more than one half of the coast studied, essentially at natural areas with high sensitivity and at urbanized areas with low sensitivity; and the "protection" option was observed especially at some areas from the center and eastern part of Malaga Province and at the easternmost areas of Almeria Province, where both coastal sensitivity and land use classes presented high values