Bernardino Roig

Rank-Ordered differences statistic based switching vector filter

In this paper a new switching vector filter for impulsive noise removal in color images is proposed. The new method is based on a recently introduced impulse detector named Rank-Ordered Differences Statistic (ROD) which is adapted to be used in color images. The switching scheme between the identity operation and the Arithmetic Mean Filter is defined using the mentioned impulse detector. Extensive experiments show that the proposed technique is simple, easy to implement and significantly outperforms the classical vector filters presenting a competitive performance respect to recent impulsive noise vector filters.

Localised rank-ordered differences vector filter for suppression of high-density impulse noise in colour images

This research presents a complete study of a new alternating vector filter for the removal of impulsive noise in colour images. The method is based on an impulsive noise detector for greyscale images that has been adapted in a localised manner using geometric information for processing colour images. Based on this statistic, a filtering scheme alternating between the identity and a non-linear vector filter is proposed. A geometric and experimental study was performed to obtain the optimal filter design. Experimental studies show that the proposed technique is simple, easy to implement, robust to noise, and outperforms the classic vector filters, as well as more recent filters.

How to perform AMP? Cubic adjustments for improving the QoE

Smooth playout adjustment techniques are much more convenient than aggressive ones.We propose a Cubic Adaptive Media Playout (AMP) strategy to adjust a deviated playout point to a given reference.Cubic AMP guarantees the smoothness of the playout curve, while keeping the computational complexity low.Cubic AMP provides better Quality of Experience (QoE) than other existing Linear and Quadratic AMP strategies.Cubic AMP can be used for different goals (e.g., buffer underflow/overflow avoidance or media synchronization). Adaptive Media Playout (AMP) consists of smoothly and dynamically adjusting the media playout rate to recover from undesired (e.g., buffer overflow/underflow or out-of-sync) situations. The existing AMP solutions are mainly characterized by two main aspects. The first one is their goal (e.g., keeping the buffers occupancy into safe ranges or enabling media synchronization). The second one is the criteria that determine the need for triggering the playout adjustments (e.g., buffer fullness or asynchrony levels). This paper instead focuses on a third key aspect, which has not been sufficiently investigated yet: the specific adjustment strategy to be performed. In particular, we propose a novel AMP strategy, called Cubic AMP, which is based on employing a cubic interpolation method to adjust a deviated playout point to a given reference. On the one hand, mathematical analysis and graphical examples show that our proposal provides superior performance than other existing linear and quadratic AMP strategies in terms of the smoothness of the playout curve, while significantly outperforming the quadratic AMP strategy regarding the duration of the adjustment period and without increasing the computational complexity. It has also been proved and discussed that higher-order polynomial interpolation methods are less convenient than cubic ones. On the other hand, the results of subjective tests confirm that our proposal provides better Quality of Experience (QoE) than the other existing AMP strategies. Display Omitted

Impulsive Noise Filters for Colour Images

Noise is often introduced into digital images during the acquisition and transmission processes because of different reasons such as charge-coupled device (CCD) sensor malfunction, transmission errors, storage faults and difficult acquisition conditions. The presence of noise hampers the automatic processing of digital images and also affects their visualization quality. In this context, colour images may be contaminated by several types of noise and they have been widely studied in the literature.

Fuzzy quasi-metrics for the Sorgenfrey line

We endow the set of real numbers with a family of fuzzy quasi-metrics, in the sense of George and Veeramani, which are compatible with the Sorgenfrey topology. Although these fuzzy quasi-metrics are not deduced explicitly from a quasi-metric, they possess interesting properties related to completeness. For instance, we prove that they are balanced and complete in the sense of Doitchinov and that only one of them is right K-sequentially complete. We also observe that compatible fuzzy quasi-metrics for the Sorgenfrey line cannot be left (weakly right) K-sequentially complete.

Fuzzy averaging filter for impulse noise reduction in colour images with a correction step

Abstract In this paper we propose a fuzzy detection and reduction method for impulse noise in colour images. Detection is based on the fuzzyfication of a well-known statistic called ROD. The noise degrees obtained are used to reduce impulses by employing a fuzzy averaging between the input colour vector and a robust estimate of noise-free colour vector within the input neighbourhood. Fuzzy averaging has some advantages in terms of both noise reduction and detail preservation in front of detect and replace approaches because of threshold based decisions of the latter. However, robustness of the former is lower. We solve this problem by including a correction mechanism that checks the fuzzy noise degree of the output and replaces it with a robust colour vector either when noise has not been properly reduced or when a colour artefact has been introduced. We carry out a thorough study of the method parameter setting and give a convenient and robust setting. Experimental results show that our approach is very robust in front of four different types of impulse noise.

Nonlinear effects in the radiation force generated by amplitude-modulated focused beams

Harmonic Motion Imaging (HMI) uses an amplitude-modulated (AM) beam to induce an oscillatory radiation force before, during and after ablation. In this paper, the findings from a numerical analysis of the effects related with the nonlinear propagation of AM focused ultrasonic beams in water on the radiation force and the location of its maxima will be presented. The numerical modeling is performed using the KZK nonlinear parabolic equation. The radiation force is generated by a focused transducer with a gain of 18, a carrier frequency of 1 MHz and a modulation frequency of 25 kHz. The modulated excitation generates a spatially-invariant force proportional to the intensity. Regarding the nonlinear wave propagation, the force is no longer proportional to the intensity, reaching a factor of eight between the nonlinear and linear estimations. Also, a 9 mm shift in the on-axis force peak occurs when the initial pressure increased from 1 to 300 kPa. This spatial shift, due to the nonlinear effects, becomes dyna...

Numerical study of nonlinear, transcranial focused ultrasound wave propagation for blood-brain barrier (BBB) opening

Focused ultrasound (FUS) techniques for Blood-Brain Barrier opening are emerging for localized and safe brain drug delivery. In this work, a transcranial FUS field is computed by a numerical approach entailing nonlinear wave propagation in the time domain in order to determine the position of the true focus and the existence of reflections and resonances. A transducer with a curvature radius of 90 mm, and an aperture of 80 mm was simulated at a central frequency of 500 kHz. The computational method was a Finite-Difference Time-Domain (FDTD) implemented on nonlinear fluid model over a 2D Axis-symmetric domain. The boundary conditions were derived from the apparent density measurements based on a 3D CT scan acquisition performed on a Macaca mulatta primate. The study shows that nonlinear propagation shifts the peak pressure 3 mm away from the transducer when the pressure in the transducer increases from 2 kPa to 70 kPa. The focal shift is mainly due to the presence of the skull and dependent on the incidence angle of the ultrasonic beam. This study proposes a FDTD nonlinear numerical approach to study the propagation of ultrasonic waves through the skull, showing that nonlinear propagation can affect the position of the focal peak.