1,720,960 research outputs found
Analysis of system drought for Manitoba Hydro using stochastic methods
No full textStochastic time series models are commonly used in the analysis of large-scale water resources systems. In the stochastic approach, synthetic flow scenarios are generated and used for the analysis of complex events such as multi-year droughts. Conclusions drawn from such analyses are only plausible to the extent that the underlying time series model realistically represents the natural variability of flows. Traditionally hydrologists have favoured autoregressive moving average (ARMA) models to describe annual flows. In this research project, a class of model called Markov-Switching (MS) model (also referred to as a Hidden Markov model) is presented as an alternative to conventional ARMA models. The basic assumption underlying this model is that a limited number of flow regimes exists and that each flow year can be classified as belonging to one of these regimes. The persistence of and switching between regimes is described by a Markov chain. Within each regime, it is assumed that annual flows follow a normal distribution with mean and variance that depend on the regime. The simplicity of this model makes it possible to derive a number of model characteristics analytically such as moments, autocorrelation, and crosscorrelation. Model estimation is possible with the maximum likelihood method implemented using the Expectation Maximization (EM) algorithm. The uncertainty in the model parameters can be assessed through Bayesian inference using Markov Chain Monte Carlo (MCMC) methods. A Markov-Switching disaggregation (MSD) model is also proposed in this research project to disaggregate higher-level flows generated using the MS model into lower-level flows. The MSD model preserves the additivity property because for a given year both the higher-level and lower-level variables are generated from normal distributions. The 2-state MS and MSD models are applied to Manitoba Hydro's system along with more conventional first order autoregressive and disaggregation models and parameter and missing data uncertainty are identified in the analysis of system drought
Optimal sizing of storage tanks in domestic rainwater harvesting systems: A linear programming approach
No full textThis paper proposes an optimization model to determine the optimal tank size of a single residential housing unit for rainwater harvesting and storage. Taking into account the site specific data such as the rainfall profile, the roof area of the building, the water consumption per capita and the number of residents, an integrated optimization model based on linear programming is proposed to decide on the size of rainwater storage tank to build such that the net present value of the total tank construction costs and freshwater purchase costs is minimized. The proposed model was tested on a case study from Northern Cyprus, the results of which emphasized the feasibility of rainwater harvesting as a sustainable supplement to the depleting aquifers in the region. The study also offers managerial insights on the impact of various parameters such as the number of residents, roof area, discount rate, water consumption per capita, unit cost of building the rainwater tank, and rainfall characteristics on the optimal tank size and on the net financial benefit gained from rainwater harvesting through detailed sensitivity analysis
A Case Study of Rainfall Water Harvesting Effects on Runoff for Guzelyurt, Northern Cyprus
Get PDFDevelopment of the cities and growing population significantly change the natural water cycle in urban districts and consequently increase the amount of runoff water which results in higher flood risks. For mitigating the negative impacts of urbanization on runoff, rainfall water harvesting (RWH) is proposed and applied in several regions for reducing the amount of runoff. In this study, the RWH by installing storage tanks and the methodology for studying its effects on runoff are introduced. The main objective for this study is to quantify the effect of applying RWH on reducing the pressure on the existing drainage system in order to avoid the necessity of renewing the existing drainage infrastructures. The methodology is applied on a small catchment in East Guzelyurt, Northern Cyprus as a case study, in order to investigate the effectiveness of RWH for this region. The results show that considering a 6 hour rainfall with a critical intensity of 30 mm/hr, for the selected catchment the runoff can be reduced up to ~15% in first 2 hours; however before the peak rainfall, the storage tanks get full and the runoff is not significantly reduced for the next 4 hours. The results
show that RWH by installing storage tank in residential buildings for this catchment is not sufficient for reducing the amount of runoff and other harvesting methods should also be considered
Spatial and Temporal Analysis of Daily, Monthly, and Seasonal Rainfall Characteristics across Northern Cyprus
No full textIn this study, rainfall time series data of 36 years collected at 33 meteorological stations were analyzed to introduce spatial and temporal characteristics of daily, monthly, and seasonal rainfall patterns for Northern Cyprus. For this purpose, concentration index (CI), precipitation concentration index (PCI), and seasonality index (SI) were employed. Additionally, the temporal trend of these indexes was evaluated using the Mann-Kendall (MK) trend test and innovative-Sen test (IST). Analyzing the temporal changes of rainfall patterns in the Eastern Mediterranean region is valuable to the whole area, where many countries are suffering from both water scarcity and increasing flash flood frequency. Therefore, the findings of this study were compared with the results of regional studies. The results of CI analysis show that Northern Cyprus has a moderately concentrated distribution of rainfall. On the other hand, the North Coast and Kyrenia Mountains regions are characterized by high annual rainfall as well as high risk of flood events. PCI and SI results show a greatly seasonal rainfall distribution pattern across the study area. Additionally, significant upward trends are observed in the majority of the stations in daily rainfall concentration
Optimum tank size for a rainwater harvesting system: Case study for Northern Cyprus
Get PDFThe available freshwater is limited on earth. On the other hand, available water resources on earth have been depleting and being polluted due to climate change and population growth. In order to reduce the risk of water scarcity and water resources contamination, Integrated water resources management (IWRM) is required. IWRM is a concept to manage water resources that aims to balance economic efficiency, social equity, and environmental sustainability. When rainwater harvesting systems (RWHS), one of the techniques of IWRM, are implemented, the stress on water resources is reduced. Since the installation cost of rainwater harvesting systems significantly depends on the size of the rainwater storage tanks, in the implementation of rainwater harvesting, the selection of tank size is one of the main concerns for the feasibility of the system. This study aims to investigate the feasibility of domestic rainwater harvesting systems for a single house. In order to find the optimum storage tank size of the rainwater harvesting system, a linear programming (LP) optimization model is employed. As a case study, the LP model is applied to six regions from semi-arid Eastern Mediterranean island Northern Cyprus, where water resources are limited. The model considers thirty-seven years monthly rainfall data, the roof area of the building, the water consumption per capita, the discount rate, the cost of the rainwater storage tank, and the number of residents. The results of the selected study areas show that the implementation of the RWHS for a single house is infeasible due to the substantial installation costs and maintenance expenses. The financial losses caused by the implementation of the RWHS are found higher than the installation costs and maintenance expenses for all regions. In addition to economic analyses, environmental benefits of the RWHS should be included into the feasibility analysis
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
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