Search results for "Methodology"

Dynamic copula models for the spark spread

2011

We propose a non-symmetric copula to model the evolution of electricity and gas prices by a bivariate non-Gaussian autoregressive process. We identify the marginal dynamics as driven by normal inverse Gaussian processes, estimating them from a series of observed UK electricity and gas spot data. We estimate the copula by modeling the difference between the empirical copula and the independent copula. We then simulate the joint process and price options written on the spark spread. We find that option prices are significantly influenced by the copula and the marginal distributions, along with the seasonality of the underlying prices.

On the ambiguous consequences of omitting variables

2015

This paper studies what happens when we move from a short regression to a long regression (or vice versa), when the long regression is shorter than the data-generation process. In the special case where the long regression equals the data-generation process, the least-squares estimators have smaller bias (in fact zero bias) but larger variances in the long regression than in the short regression. But if the long regression is also misspecified, the bias may not be smaller. We provide bias and mean squared error comparisons and study the dependence of the differences on the misspecification parameter.

On the sign recovery by LASSO, thresholded LASSO and thresholded Basis Pursuit Denoising

2020

Basis Pursuit (BP), Basis Pursuit DeNoising (BPDN), and LASSO are popular methods for identifyingimportant predictors in the high-dimensional linear regression model Y = Xβ + ε. By definition, whenε = 0, BP uniquely recovers β when Xβ = Xb and β different than b implies L1 norm of β is smaller than the L1 norm of b (identifiability condition). Furthermore, LASSO can recover the sign of β only under a much stronger irrepresentability condition. Meanwhile, it is known that the model selection properties of LASSO can be improved by hard-thresholdingits estimates. This article supports these findings by proving that thresholded LASSO, thresholded BPDNand thresholded BP recover the sign of β in …

Purification of recovered phosphoric acid by extracting aluminium with di-2-ethylhexyl phosphoric acid

2021

AbstractThe extraction of aluminium from dilute phosphoric acid with di-2-ethylhexyl phosphoric acid (DEHPA) was optimized using response surface methodology. The optimization was based on the experimental three-level central composite face-centred design (CCF) and was conducted on real-life samples. The three variables included were pH, extractant concentration and aqueous to organic phase ratio (AO). Under the optimized conditions (pH 2.5, 0.6 M DEHPA and AO ratio 1:2), extraction efficiency of 99% for aluminium in four extraction stages is achieved. The purified phosphoric acid solution can then be utilized by the fertilizing industry. Stripping tests for organic phase loaded with alumin…

First morphogenetic analysis of parasite eggs from Schistosomiasis haematobium infected sub-Saharan migrants in Spain and proposal for a new standard…

2021

International audience; Schistosomiasis is a Neglected Tropical Disease caused by trematode species of the genus Schistosoma. Both, autochthonous and imported cases of urogenital schistosomiasis have been described in Europe. The present study focuses on eggs, considered pure S. haematobium by genetic characterisation (intergenic ITS region of the rDNA and cox1 mtDNA). A phenotypic characterisation of S. haematobium eggs was made by morphometric comparison with experimental populations of S. bovis and S. mansoni, to help in the diagnosis of S. haematobium populations infecting sub-Saharan migrants in Spain. Analyses were made by Computer Image Analysis System (CIAS) applied on the basis of …

Subjectivation, togetherness, environment. Potentials of participatory art for Art Education for Sustainable Development (AESD)

2017

Through a process-oriented analysis of the participatory art project The Hill this article explores the relevance of participatory art projects for the development of AESD – Art Education for Sustainable Development. Inspired by Felix Guattari’s Three Ecologies (2008) the analysis moves through three sub-studies delving into three different aspects of the project. Each sub-study adopts two overlapping analytical ‘lenses’: The lens of a contemporary art form (performance art, community art, and site-specific art) and the lens of a related theoretical concept (subjectivation, togetherness, environment). The aim is to propose art educational ideas and strategies that stimulate students to chal…

Improving predictive accuracy of exit polls

2010

Abstract Exit polls are best known for their use in election forecasting. In recent years, however, some prominent mistaken predictions have been made, undermining public confidence in the accuracy of both exit polls and survey methods. Nonresponse bias has been claimed as being one of the main reasons for inaccurate projections. Traditionally, the issue has been handled through an age–race–sex adjustment at the national and state levels. An alternative solution is suggested and detailed in this paper. A two-step strategy is proposed to reduce nonresponse bias and improve predictions. First, “vote-remembering” (vote recall) is used to correct party proportion estimates at polling locations;…

Media Effects: Levels of Analysis

2017

AN EMPIRICAL STUDY OF LATVIAN CONSUMER’S ATTITUDES AND PERCEPTIONS TOWARDS GENETICALLY MODIFIED ORGANISMS

2016

Genetic modification and genetically modified organisms (GMO) remains a controversial issue. Latvian consumers’ attitude towards genetic modification and GMO have been characterized as negative using Eurobarometer data, but so far no specific investigation of Latvian consumers has been done in this field. The aim of this study was to analyse Latvian consumers’ attitude towards genetic modification and GMO, the subjective and objective knowledge about this questions and acceptability of use of GMO in different application areas. Main task in frame of this research is to summarize different literature and data available to outline some of factors that influence attitudes towards GMO: mainly p…

Insights on integrated marketing communications: implementation and impact in hotel companies

2015

Purpose – The purpose of this paper is to provide insights on integrated marketing communications (IMC) by empirically examining the concept in a new context, that is hotel companies, and comparing its implementation and impact in Italian and Croatian hotels. Design/methodology/approach – The study uses survey methodology to assess IMC, approaching managers and guests in high-quality hotels. Findings – From the manager’s point of view, both Italian and Croatian hotels show a high level of IMC implementation and significant differences regarding some items. From the guest’s point of view, significant differences are obtained between the two hotel groups. In addition, IMC is found to influen…