Search results for "probability density function"
showing 10 items of 183 documents
Modeling user preferences in content-based image retrieval: A novel attempt to bridge the semantic gap
2015
This paper is concerned with content-based image retrieval from a stochastic point of view. The semantic gap problem is addressed in two ways. First, a dimensional reduction is applied using the (pre-calculated) distances among images. The dimension of the reduced vector is the number of preferences that we allow the user to choose from, in this case, three levels. Second, the conditional probability distribution of the random user preference, given this reduced feature vector, is modeled using a proportional odds model. A new model is fitted at each iteration. The score used to rank the image database is based on the estimated probability function of the random preference. Additionally, so…
A principled approach to network-based classification and data representation
2013
Measures of similarity are fundamental in pattern recognition and data mining. Typically the Euclidean metric is used in this context, weighting all variables equally and therefore assuming equal relevance, which is very rare in real applications. In contrast, given an estimate of a conditional density function, the Fisher information calculated in primary data space implicitly measures the relevance of variables in a principled way by reference to auxiliary data such as class labels. This paper proposes a framework that uses a distance metric based on Fisher information to construct similarity networks that achieve a more informative and principled representation of data. The framework ena…
Capacity studies of spatially correlated MIMO Rice channels
2010
In this paper, we have studied the statistical properties of the capacity of spatially correlated multiple-input multiple-output (MIMO) Rice channels. We have derived an exact closed-form expression for the probability density function (PDF) and an exact expression for the cumulative distribution function (CDF) of the channel capacity for single-input multiple-output (SIMO) and multiple-input single-output (MISO) systems. Furthermore, an accurate closed-form expression has been derived for the level-crossing rate (LCR) and an accurate expression has been obtained for the average duration of fades (ADF) of the SIMO and MISO channel capacities. For the MIMO case, we have investigated the PDF,…
Statistical properties of the capacity of Rice channels with MRC and EGC
2009
In this paper, we have studied the statistical properties of the capacity of Rice channels for both maximal ratio combining (MRC) and equal gain combining (EGC) schemes. We have analyzed the effect of the number of diversity branches and the amplitude of the line-of-sight (LOS) components in the diversity branches on the statistics of the channel capacity. Specifically, we have derived analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the capacity of Rice channels when using MRC and EGC. It is observed that if the number of diversity branches or the amplitude of the LOS…
A measurement-based trajectory model for drifted motions towards a target zone
2016
Trajectory models have numerous applications in the area of wiewlwss communications. The aim of this paper is to develop an empirical trajectory model for drifted motions. Recently, a highly flexible trajectory model based on the primitives of Brownian fields (TramBrown) was proposed by A. Borhani and M. Patzold. This paper provides an empirical proof for TramBrown using global positioning system (GPS) data collected from real life user traces drifting to a particular target point or a zone. The recorded location coordinates of the mobile user are processed to compute the total travelling length and the angle-of-motion (AOM) along the drifted trajectory. It is shown that the probability den…
Optimization of the straightness measurements on rough surfaces by Monte Carlo simulation
2013
Summary The straightness error of a coordinate measuring machine (CMM) is determined by measuring a rule standard. Thanks to a reversal technique, the straightness uncertainty of the CMM is theoretically dissociated from the straightness uncertainty of the rule. However, stochastic variations of the whole measurement system involve uncertainties of the CMM straightness error. To quantify these uncertainties, different sources of stochastic variations are listed with their associated probability density functions. Then Monte Carlo methods are performed first to quantify error and secondly to optimize measurement protocol. It is shown that a 5-measurement distance from 0.1 mm to each measurem…
Modeling long-range memory with stationary Markovian processes
2009
In this paper we give explicit examples of power-law correlated stationary Markovian processes y(t) where the stationary pdf shows tails which are gaussian or exponential. These processes are obtained by simply performing a coordinate transformation of a specific power-law correlated additive process x(t), already known in the literature, whose pdf shows power-law tails 1/x^a. We give analytical and numerical evidence that although the new processes (i) are Markovian and (ii) have gaussian or exponential tails their autocorrelation function still shows a power-law decay =1/T^b where b grows with a with a law which is compatible with b=a/2-c, where c is a numerical constant. When a<2(1+c) th…
Analysis and evaluation of periodic physiological organ motion in radiotherapy treatments.
2003
Background and purpose: A system for the detection, measurement and analysis of the periodic physiological organ motion during radiotherapy treatment is proposed and clinically tested in this paper. Material and methods: The procedure is based on the acquisition of fluoroscopic sequences, followed by an automatic detection of the movement using cross-correlations with matched filters. Results: The system generates a probability density function (PDF) of finding a mobile organ in a position at a certain time. The maximum path of the mobile structures can be determined to define the planning target volume (PTV) without ambiguities. Conclusions: Physiological movements can be accurately includ…
Probabilistic Evaluation of the Adaptation Time for Structures under Seismic Loads
2016
Abstract In this paper, a probabilistic approach for the evaluation of the adaptation time for elastic perfectly plastic frames is proposed. The considered load history acting on the structure is defined as a suitable combination of quasi-statical loads and seismic actions. The proposed approach utilizes the Monte Carlo method in order to generate a suitable large number of seismic acceleration histories and for each one the related load combination is defined. Furthermore, for each load combination the related adaptation time is determined, if any, as the optimal one for which the structure is able to shakedown under the unamplified applied actions. A known generalized Ceradini's theorem i…