Search results for " statistics."
showing 10 items of 1749 documents
Operational and financial performance of Italian airport companies: A dynamic graphical model
2016
Abstract This paper provides evidence on the relationship within a set of financial and operational indicators for Italian airports over 2008–2014. The limited sample size of national and regional airports suggests to apply the penalised RCON ( V , E ) model, which falls within the class of Gaussian graphical models. It provides both estimate and easy way to visualise conditional independence structures of the variables. Moreover, it is particularly suitable for handling longitudinal data where small number of units and huge number of variables have been collected. Findings highlight that a qualified concept of size matters in determining good financial performance. Specifically, increasing…
Connotative meaning of travel modes and activity-travel behavior
2018
Abstract This paper aims to present results of a study regarding how the meaning of travel modes influences on the performance of activities and trips. Connotative meaning of travel modes was measured using semantic differential scales, which collect the suggestive significance of the terms used to name current travel modes. More than 400 people provided that information together with values and other types of attitudes, characteristics of their usual companions, socio-demographics, and 2-days activity-travel diary that includes a weekend day and a weekday. Descriptive analysis, which include frequency distributions, Factor Analysis, and correlations, have been developed to find potential r…
Measuring situations that stress Mexicans while driving
2016
The purpose of this paper is to construct a scale that will help determine the aspects involved in driving a motor vehicle that influence the levels of stress in a human being. Two complementary studies were conducted: the first one determined, by qualitative methods, the aspects of driving that 103 participants found most stressful whilst driving; the second was a validation of the scale constructed with said information on 295 participants (142 males, 153 females, age mean 37.41, std. dev. 14.008). The scale included 22 situations that were then evaluated on a Likert scale to assess the level of stress they evoke. These items were arranged on 3 factors, and descriptive statistics were com…
Multivariate modeling and analysis of regional ocean freight rates
2018
Abstract In this paper, we propose a new multivariate model for the dynamics of regional ocean freight rates. We show that a cointegrated system of regional spot freight rates can be decomposed into a common non-stationary market factor and stationary regional deviations. The resulting integrated CAR process is new to the literature. By interpreting the common market factor as the global arithmetic average of the regional rates, both the market factor and the regional deviations are observable which simplifies the calibration of the model. Moreover, forward contracts on the market factor can be traded in the Forward Freight Agreement (FFA) market. We calibrate the model to historical spot r…
Probabilistic cross-validation estimators for Gaussian process regression
2018
Gaussian Processes (GPs) are state-of-the-art tools for regression. Inference of GP hyperparameters is typically done by maximizing the marginal log-likelihood (ML). If the data truly follows the GP model, using the ML approach is optimal and computationally efficient. Unfortunately very often this is not case and suboptimal results are obtained in terms of prediction error. Alternative procedures such as cross-validation (CV) schemes are often employed instead, but they usually incur in high computational costs. We propose a probabilistic version of CV (PCV) based on two different model pieces in order to reduce the dependence on a specific model choice. PCV presents the benefits from both…
Readability and the Web
2012
Readability indices measure how easy or difficult it is to read and comprehend a text. In this paper we look at the relation between readability indices and web documents from two different perspectives. On the one hand we analyse how to reliably measure the readability of web documents by applying content extraction techniques and incorporating a bias correction. On the other hand we investigate how web based corpus statistics can be used to measure readability in a novel and language independent way.
La délimitation de la citoyenneté en Côte-d'Or, d'après le droit électoral de la IIe République
1997
One of the essential elements of citizenship lies in participating in politics. Il is particulary through the right to vote that man will be fully integrated into society and take part in the decisions concerning the running of the government. Adopting universal suffrage is giving an important power to men. Thus, certain rulers have tried to channel the vote by excluding citizens liable to be detrimental to them. The law of May 31, 1850 meant to eliminate the « vile multitude », according to the expression used by Thiers. And it is in particular through the study of the concrete consequences of this law that the influence of the electoral system in the definition of citizenship can be measu…
Screening individual ability to perform descriptive analysis of food products : basic statements and application to a camembert cheese descriptive pa…
1995
A battery of sensory tests is proposed to select potential descriptive panelists. This set of tests is flavor specific. Several abilities are examined: odor and taste recognition, odor memory, discrimination and descriptive capacities. A detailed example of such a battery to select a Camembert cheese descriptive panel is given. The objectives of each test are discussed. Stimuli are chosen to be consistent with the sensory properties which can be perceived in cheese. Score distributions demonstrate the discrimination among candidates for each test. Globally, results show the difficulty to find 20 panelists amongst about a hundred with good scores on each test. The panel leader has to choose …
Interpretability of Recurrent Neural Networks in Remote Sensing
2020
In this work we propose the use of Long Short-Term Memory (LSTM) Recurrent Neural Networks for multivariate time series of satellite data for crop yield estimation. Recurrent nets allow exploiting the temporal dimension efficiently, but interpretability is hampered by the typically overparameterized models. The focus of the study is to understand LSTM models by looking at the hidden units distribution, the impact of increasing network complexity, and the relative importance of the input covariates. We extracted time series of three variables describing the soil-vegetation status in agroe-cosystems -soil moisture, VOD and EVI- from optical and microwave satellites, as well as available in si…
Crop nitrogen monitoring: Recent progress and principal developments in the context of imaging spectroscopy missions
2020
Abstract Nitrogen (N) is considered as one of the most important plant macronutrients and proper management of N therefore is a pre-requisite for modern agriculture. Continuous satellite-based monitoring of this key plant trait would help to understand individual crop N use efficiency and thus would enable site-specific N management. Since hyperspectral imaging sensors could provide detailed measurements of spectral signatures corresponding to the optical activity of chemical constituents, they have a theoretical advantage over multi-spectral sensing for the detection of crop N. The current study aims to provide a state-of-the-art overview of crop N retrieval methods from hyperspectral data…