Search results for "Data type"
showing 10 items of 1183 documents
A privacy-aware framework for decentralized online social networks
2015
Online social networks based on a single service provider suffer several drawbacks, first of all the privacy issues arising from the delegation of user data to a single entity. Distributed online social networks (DOSN) have been recently proposed as an alternative solution allowing users to keep control of their private data. However, the lack of a centralized entity introduces new problems, like the need of defining proper privacy policies for data access and of guaranteeing the availability of user's data when the user disconnects from the social network. This paper introduces a privacy-aware support for DOSN enabling users to define a set of privacy policies which describe who is entitle…
RANKING DECISION MAKING UNITS BY MEANS OF SOFT COMPUTING DEA MODELS
2011
This paper presents a method for ranking a set of decision making units according to their level of efficiency and which takes into account uncertainty in the data. Efficiency is analysed using fuzzy DEA techniques and the ranking is based on the statistical analysis of cases that include representative situations. The method enables the removal of the sometimes unrealistic hypothesis of a perfect trade-off between increased inputs and outputs. This model is compared with other DEA models that work with imprecise or fuzzy data. As an illustration, we apply our ranking method to the evaluation of a group of Spanish seaports, as well as teams playing in the Spanish football league. We compar…
Nomograph for rapid technical and economic assessment of solar thermal systems for DHW production
2012
Abstract Different types of tools, software and empirical methods to size and assess the performance of solar thermal systems are available today. A quick and easy-to-use graphical tool is proposed here. It is based on a single diagram, called a nomograph, which embeds technical and economic information, allowing the optimisation of the size and performance of a solar thermal system starting from the main input parameters, such as the specific costs of the system and the auxiliary fuel. The optimal surfaces are calculated as a function of the fuel cost through several regressions made on data from the application of the F-Chart method for a set of system configurations. The authors have fou…
An Exploratory Empirical Study of Internal Quality Attributes of Open Source Software Systems
2012
This exploratory empirical study has focused on open source software (OSS). Seven medium-sized OSS systems from the SourceForge repository were analysed. Over 100 internal quality attributes and programming practices were scrutinized by using two semi-automated source code analysis tools (FindBugs and SoftCalc). Many statistically significant relations were revealed by the conducted regression analyses. Seven so-called bad programming practices; as manifested by the measured source code inconsistencies were identified as having significant relations to internal software quality. Additionally we set and tested two hypotheses. That investigation provided mixed results partly supporting some o…
Space‐time dynamical models
2008
Purpose – The purpose is to present a new formal approach based on a partial integro‐differential equation, the space‐time state transition equation (STSTE), and on a set of general equations with which space‐time dynamical models of complex systems, such as social systems and ecosystems, can be built.Design/methodology/approach – The STSTE provides the partial derivative of the density of a state‐variable with regard to time as a sum of time rates and space‐time rates. Time rates describe the dynamics of the system for each space‐point irrespectively of the other points, whilst space‐time rates describe this evolution as a consequence of the relation of each space‐point with a given set of…
Effects of distance and scale dependence in geographical models of cities and territories
2019
International audience; This third chapter questions the essential role of distance and scale dependence in models to analyzing the spatial configuration of human settlements and activities, as well as the processes that lead to their evolution, with reference to urban or regional study areas. The subject of study therefore concerns both the form of human settlements and the actions of people (individuals, groups) in their territory (or territories). A human settlement consists of the materialization in space-the physical inscription-of one or more human activities. It is characterized by a certain degree of sustainability. It can be a group of a few buildings or a larger group of thousands…
Description of x-ray beams using the fluorescence yields of a set of thick targets
1995
Quantitative methods in x-ray fluorescence analysis require a knowledge of the spectral distribution of the fluorescence-exciting beam. The use of XRF yield measurements of a set of thick pure element targets is proposed for the description of a fluorescence-exciting x-ray beam, without the need to obtain its spectral distribution. This new approach is derived theoretically and verified by comparing thin-target yields calculated from XRF yield measurements of thick pure element specimens with those obtained from a calculated spectral distribution. The difference between the two methods of obtaining the thin-target yields is within 9% relative error.
Quasi-interpolating and Smoothing Local Splines
2015
In this chapter, local quasi-interpolating and smoothing splines are described. Although approximation properties of local spline are similar to properties of the global interpolating and smoothing splines, their design does not require the IIR filtering of the whole data array. The computation of a local spline value at some point utilizes only a few adjacent grid samples. Therefore, local splines can be used for real-time processing of signals and for the design of FIR filter banks generating wavelets and wavelet frames (Chaps. 12 and 14). In the chapter, local splines of different orders are designed and their approximation properties are established which are compared with the propertie…
Joint Graph Learning and Signal Recovery via Kalman Filter for Multivariate Auto-Regressive Processes
2018
In this paper, an adaptive Kalman filter algorithm is proposed for simultaneous graph topology learning and graph signal recovery from noisy time series. Each time series corresponds to one node of the graph and underlying graph edges express the causality among nodes. We assume that graph signals are generated via a multivariate auto-regressive processes (MAR), generated by an innovation noise and graph weight matrices. Then we relate the state transition matrix of Kalman filter to the graph weight matrices since both of them can play the role of signal propagation and transition. Our proposed Kalman filter for MAR processes, called KF-MAR, runs three main steps; prediction, update, and le…
Hierarchical Structure in Financial Markets
1998
I find a topological arrangement of stocks traded in a financial market which has associated a meaningful economic taxonomy. The topological space is a graph connecting the stocks of the portfolio analyzed. The graph is obtained starting from the matrix of correlation coefficient computed between all pairs of stocks of the portfolio by considering the synchronous time evolution of the difference of the logarithm of daily stock price. The hierarchical tree of the subdominant ultrametric space associated with the graph provides information useful to investigate the number and nature of the common economic factors affecting the time evolution of logarithm of price of well defined groups of sto…