Daniel U. Campos-Delgado

Automatic classification of atherosclerotic plaques imaged with intravascular OCT.

Intravascular optical coherence tomography (IV-OCT) allows evaluation of atherosclerotic plaques; however, plaque characterization is performed by visual assessment and requires a trained expert for interpretation of the large data sets. Here, we present a novel computational method for automated IV-OCT plaque characterization. This method is based on the modeling of each A-line of an IV-OCT data set as a linear combination of a number of depth profiles. After estimating these depth profiles by means of an alternating least square optimization strategy, they are automatically classified to predefined tissue types based on their morphological characteristics. The performance of our proposed method was evaluated with IV-OCT scans of cadaveric human coronary arteries and corresponding tissue histopathology. Our results suggest that this methodology allows automated identification of fibrotic and lipid-containing plaques. Moreover, this novel computational method has the potential to enable high throughput atherosclerotic plaque characterization.

Geometry-Based Statistical Modeling of Non-WSSUS Mobile-to-Mobile Rayleigh Fading Channels

In this paper, we present a novel geometry-based statistical model for small-scale non-wide-sense stationary uncorrelated scattering (non-WSSUS) mobile-to-mobile (M2M) Rayleigh fading channels. The proposed model builds on the principles of plane wave propagation to capture the temporal evolution of the propagation delay and Doppler shift of the received multipath signal. This is different from existing non-WSSUS geometry-based statistical channel models, which are based on a spherical wave propagation approach, that in spite of being more realistic is more mathematically intricate. By considering an arbitrary geometrical configuration of the propagation area, we derive general expressions for the most important statistical quantities of nonstationary channels, such as the first-order probability density functions of the envelope and phase, the four-dimensional (4-D) time-frequency correlation function (TF-CF), local scattering function (LSF), and time-frequency-dependent delay and Doppler profiles. We also present an approximate closed-form expression of the channels 4-D TF-CF for the particular case of the geometrical one-ring scattering model. The obtained results provide new theoretical insights into the correlation and spectral properties of non-WSSUS M2M Rayleigh fading channels.

First-order statistics analysis of two new geometrical models for non-WSSUS mobile-to-mobile channels

In this paper, we analyze the first-order (FO) statistics of two new geometry-based statistical models for small-scale nonstationary time-frequency (TF) dispersive mobile-to-mobile (M2M) fading channels. We derive exact analytic expressions for the joint and marginal probability density functions (PDFs) of the envelope and phase of both models. In addition, we analyze the asymptotic behavior of these PDFs as the number of multipath components of the received signal approaches infinity. The obtained results are of practical relevance, as they can be used as a benchmark to investigate the influence of the small-scale fading statistics of nonstationary channels on the M2M communication systems performance.

Quadratic blind linear unmixing

Spectral unmixing is the process of breaking down data from a sample into its basic components and their abundances. Previous work has been focused on blind unmixing of multi-spectral fluorescence lifetime imaging microscopy (m-FLIM) datasets under a linear mixture model and quadratic approximations. This method provides a fast linear decomposition and can work without a limitation in the maximum number of components or end-members. Hence this work presents an interactive software which implements our blind end-member and abundance extraction (BEAE) and quadratic blind linear unmixing (QBLU) algorithms in Matlab. The options and capabilities of our proposed software are described in detail. When the number of components is known, our software can estimate the constitutive end-members and their abundances. When no prior knowledge is available, the software can provide a completely blind solution to estimate the number of components, the end-members and their abundances. The characterization of three case studies validates the performance of the new software: ex-vivo human coronary arteries, human breast cancer cell samples, and in-vivo hamster oral mucosa. The software is freely available in a hosted webpage by one of the developing institutions, and allows the user a quick, easy-to-use and efficient tool for multi/hyper-spectral data decomposition.

A generalized model-based controller for the n-level CHB multilevel converter used as a shunt active filter

This paper presents the modeling and control design of a single-phase cascaded H-bridge multilevel converter used as a shunt active filter in the general case of n-levels. Based on a general model, a controller is proposed to compensate harmonic distortion and reactive power caused by nonlinear loads. For this, the controller must guarantee tracking of the line current towards an appropriately defined reference. In the proposed approach, the current reference has been selected to be proportional to the line voltage. The proposed controller also includes voltage loops to guarantee regulation and balance of the involved capacitor voltages. Simulation results are presented to assess the performance of the proposed controller.

Rigid Multimodal/Multispectral Image Registration Based on the Expectation-Maximization Algorithm

In this paper, we present a novel methodology for multimodal/multispectral rigid image registration. The proposed approach is formulated by using the Expectation-Maximization (EM) technique in order to estimate a geometric transformation that aligns the multiparametric images to register. In this approach, the images alignment relies on hidden stochastic random variables which allow to compare the multiparametric intensity values between images of different modalities. The methodology is basically composed by an EM-technique approach, where at each step, a new estimation of the joint conditional multispectral intensity distribution and the rigid transformation are computed. The proposed algorithm was tested with different kinds of medical images; our results show that the proposed methodology is a good alternative for rigid multimodal/multispectral registration.

Adaptive Impedance Control of Robot Manipulators with Parametric Uncertainty for Constrained Path–Tracking

Abstract The main impedance control schemes in the task space require accurate knowledge of the kinematics and dynamics of the robotic system to be controlled. In order to eliminate this dependence and preserve the structure of this kind of algorithms, this paper presents an adaptive impedance control approach to robot manipulators with kinematic and dynamic parametric uncertainty. The proposed scheme is an inverse dynamics control law that leads to the closed-loop system having a PD structure whose equilibrium point converges asymptotically to zero according to the formal stability analysis in the Lyapunov sense. In addition, the general structure of the scheme is composed of continuous functions and includes the modeling of most of the physical phenomena present in the dynamics of the robotic system. The main feature of this control scheme is that it allows precise path tracking in both free and constrained spaces (if the robot is in contact with the environment). The proper behavior of the closed-loop system is validated using a two degree-of-freedom robotic arm. For this benchmark good results were obtained and the control objective was achieved despite neglecting non modeled dynamics, such as viscous and Coulomb friction.

A Novel Geometrical Model for Non-Stationary MIMO Vehicle-to-Vehicle Channels

Abstract A novel geometry-based statistical model for non-stationary multiple-input multiple-output (MIMO) vehicle-to-vehicle (V2V) Rayleigh fading channels is presented in this paper. The proposed model seeks to provide new insights into the non-stationary characteristics of MIMO V2V channels stemming from the time-varying propagation delays of the received multipath signal. To achieve this goal, the temporal evolution of the propagation delays is characterized following a simple, although theoretically sound, plane-wave propagation approach. The modelling framework presented here allows obtaining generic expressions for the space-time-frequency cross-correlation function of the MIMO V2V channel, unveiling in the process important features of the channels correlation and stationary properties. The obtained results show that as a consequence of the time-varying character of the propagation delays, the elements of the MIMO channel matrix are non-wide-sense stationary uncorrelated scattering (non-WSSUS) random processes, as well as pairwise jointly non-wide-sense stationary (non-WSS). The particular cases where the proposed MIMO V2V channel model can be considered quasi-WSS are also discussed for the sake of completeness.

Fault tolerant controller for a generalized n-level CHB multilevel converter

This paper presents a model-based fault tolerant control strategy for open-circuit faults (OCFs) in the switching devices of a cascade H-bridge converter with n-levels (CHB-nL). In this study, we address the application of the CHB-nL converter as a single-phase active filter. The OCFs are modeled as additive signals into the subsystems describing the dynamics of each H-bridge in the converter. For diagnosis purposes, a bank of nonlinear proportional-integral (PI) observers are suggested to estimate the OCF profiles, independently of the operating point of the converter. Based on the estimated components, fault detection, isolation and reconfiguration is achieved. Furthermore, no additional sensors are needed to carry out the diagnosis media besides the ones used for control purposes. To validate the ideas proposed in this work, an experimental evaluation is carried out for a single OCF condition. The experimental results are used to confirm that the current tracking, voltage regulation and balance objectives can be obtained despite of OCFs in the active filter and highly distorted load currents.

Closed-loop pre-equalization for multiuser multicarrier MIMO systems under QoS restrictions

In this paper, a closed-loop pre-equalization approach for multiuser multicarrier code division multiple access (MC-CDMA) systems under a multiple-input multiple-output (MIMO) framework is presented. This work investigates the impact and limitations of combining the robustness of a feedback scheme with the degrees of freedom available in the system, given in terms of the number of subcarriers and multiple antennas, while satisfying the quality of service (QoS) requirements. Simulation results show that the derived closed-loop pre-equalization scheme takes advantage of the spatial diversity, induced by the transmit antennas, to yield a notable power reduction while achieving the objective QoS under a severe system operation. Further investigations are required to identify the impact of the receive antennas in the MIMO system.