Search results for "Variable"
showing 10 items of 1674 documents
Descriptive Statistics
2009
A set of medical data is based on a collection of the data of individual cases or objects, also called observation units or statistical units. Every case, for example every study participant, patient, every experimental animal, every tooth or every cell shows comparable parameters (such as body weight, gender, erosion, pH). Each of these parameters, also called variables, has a specific parameter value (gender = male, age = 30 years, weight = 70 kg) for each observation unit (for example the patient). The aim of descriptive statistics is to summarize the data, so that they can be clearly illustrated (1–3). The property of a parameter is specified by its so-called scale of measure. Generally…
FO^2 with one transitive relation is decidable
2013
We show that the satisfiability problem for the two-variable first-order logic, FO^2, over transitive structures when only one relation is required to be transitive, is decidable. The result is optimal, as FO^2 over structures with two transitive relations, or with one transitive and one equivalence relation, are known to be undecidable, so in fact, our result completes the classification of FO^2-logics over transitive structures with respect to decidability. We show that the satisfiability problem is in 2-NExpTime. Decidability of the finite satisfiability problem remains open.
Polar Classification of Nominal Data
2013
Many modern systems record various types of parameter values. Numerical values are relatively convenient for data analysis tools because there are many methods to measure distances and similarities between them. The application of dimensionality reduction techniques for data sets with such values is also a well known practice. Nominal (i.e., categorical) values, on the other hand, encompass some problems for current methods. Most of all, there is no meaningful distance between possible nominal values, which are either equal or unequal to each other. Since many dimensionality reduction methods rely on preserving some form of similarity or distance measure, their application to such data sets…
Forest of Normalized Trees: Fast and Accurate Density Estimation of Streaming Data
2018
Density estimation of streaming data is a relevant task in numerous domains. In this paper, a novel non-parametric density estimator called FRONT (forest of normalized trees) is introduced. It uses a structure of multiple normalized trees, segments the feature space of the data stream through a periodically updated linear transformation and is able to adapt to ever evolving data streams. FRONT provides accurate density estimation and performs favorably compared to existing online density estimators in terms of the average log score on multiple standard data sets. Its low complexity, linear runtime as well as constant memory usage, makes FRONT by design suitable for large data streams. Final…
Optical remote sensing and the retrieval of terrestrial vegetation bio-geophysical properties – A review
2015
Abstract: Forthcoming superspectral satellite missions dedicated to land monitoring, as well as planned imaging spectrometers, will unleash an unprecedented data stream. The processing requirements for such large data streams involve processing techniques enabling the spatio-temporally explicit quantification of vegetation properties. Typically retrieval must be accurate, robust and fast. Hence, there is a strict requirement to identify next-generation bio-geophysical variable retrieval algorithms which can be molded into an operational processing chain. This paper offers a review of state-of-the-art retrieval methods for quantitative terrestrial bio-geophysical variable extraction using op…
Land surface air temperature retrieval from EOS-MODIS images
2014
The knowledge of the spatial and temporal patterns of surface air temperature (SAT) is essential to monitor a region's climate and meteorology, to quantify surface exchange processes, to improve climatic and meteorological model results, and to study health and economic impacts. This letter analyzed correlations between SAT and geophysical land surface variables, mainly land surface temperature (LST), to establish operative techniques to obtain spatially continuous land SAT maps from satellite data, unlike data provided by meteorological station networks. The correlations were analyzed by using EOS-MODIS images, meteorological station network data, and geographical variables. Linear regress…
Bounding principles for elastic-plastic-creeping solids loaded below and above the shakedown limit
1982
Solids of elastic-perfectly plastic creeping material subjected to variable loads are considered within the infinitesimal displacement framework and a bounding principle is presented which holds below and above the shakedown limit. Through the choice of some free parameters, this principle generates a number of deformation bounds with practical meanings, some of wich coincide with known results for creeping and noncreeping material, while others constitute new results or generalizations of known results. The topic will be further studied in a subsequent paper [35].
PIRACY REVISITED: EXPLORING MUSIC USERS IN THE AGE OF TECHNOLOGY DEPENDENCY
2019
This paper empirically investigates and characterizes users of recorded music, both downloaders and purchasers. To this end we analyse the role of the variables defining the different segments of music users. In doing so, we have considered two main traits influencing the use of music. First, objective variables such as demographics, music consumption habits, music genres and technology. Second, subjective variables such as motives and attitudes towards piracy. Using data from a personal survey, subsequent latent class and fuzzy analyses show that while the former characteristics are relevant in those getting music for free from the Internet, the latter don´t pay any special part, contrary …
A macroeconomic analysis of the farmland value determinants in Italy
2013
The determinants of farmland value and the factors that have caused its changes over time have been discussed extensively in the economic literature. This studies offer different classifications of the determinants of the farmland value. The aim of this paper is to investigate the influence on the farmland value of the some macro-economic variables related to the agricultural sector both directly and indirectly. A multiple regression model is adopted to answer the research questions. The results showed, on the one hand, a strong influence of agricultural productivity, a regional expenditure allocated to the sector and an increasing diffusion in the regions of protected areas on the farmland…
Introducing randomness in the analysis of chemical reactions: An analysis based on random differential equations and probability density functions
2021
[EN] In this work we consider a particular randomized kinetic model for reaction-deactivation of hydrogen peroxide decomposition. We apply the Random Variable Transformation technique to obtain the first probability density function of the solution stochastic process under general conditions. From the rst probability density function, we can obtain fundamental statistical information, such as the mean and the variance of the solution, at every instant time. The transformation considered in the application of the Random Variable Transformation technique is not unique. Then, the first probability density function can take different expressions, although essentially equivalent in terms of comp…