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7-Level asymmetric multilevel current source inverter with predictive control
(2018-01) Cossutta, Pablo; Aguirre, Miguel Pablo; Muñoz, Javier; Rivera, Marco; Melín, Pedro; Rohten, Jaime
"In this paper a 7-Level Asymmetric Multilevel Current Source Inverter is presented. The topology considers two Current Source Inverters that follow a 1:2 ratio to generate the multilevel current waveform. A Model Predictive Control is used to track the internal current and voltage references as well as to keep the asymmetric ratio between the DC currents even during transient conditions. To properly use the predictive algorithm, the modelling equations of the presented topology are systematically obtained in continuous and discrete time domains, considering the characteristic constraints of a Current Source Inverter. Simulated dynamic tests are presented in order to prove the feasibility of the asymmetric approach and the properness of the predictive control technique."
Acoustical renovation of “Nuestra Señora de la Paz”
(2016-09) Del Solar Dorrego, Fernando; Gardella, Pablo
"Church “Nuestra Señora de la Paz” is located in Pilar, province of Buenos Aires, Argentina. It has an octagonal floor plan and an internal volume of 2500 m3 with bare sidewalls and little ornamentation. Excessive reverberation (4 seconds at mid-band frequencies), and an inappropriate sound system impaired speech intelligibility making ceremonies almost unintelligible. The church also suffered from thermal problems due to insufficient thermal insulation on the roof. Measurements (reverberation time, impulse responses and STI) were carried out and subsequent analysis revealed the significance of these problems. A holistic acoustical and thermal renovation was proposed and a new sound system was designed to address these issues. Subsequent measurements validated the effectiveness of the proposed renovations."
Advertise your A/D converter, a SP teaching strategy
(2010-03) Saint-Nom, Roxana
"The goal of this paper is to invite the reader to consider role-playing as a method to train Signal Processing students for professional functions they would undertake in their future careers. Interaction, communication skills and learning purposes of SP concepts are key elements of this approach. An example applied to Analog to Digital converters is detailed, to show the advantages of this technique and the enthusiasm awakened."
Aggregation languages for moving object and places of interest
(2008) Gómez, Leticia Irene; Kuijpers, Bart; Vaisman, Alejandro Ariel
"We address aggregate queries over GIS data and moving object data, where non-spatial information is stored in a data warehouse. We propose a formal data model and query language to express complex aggregate queries. Next, we study the compression of trajectory data, produced by moving objects, using the notions of stops and moves. We show that stops and moves are expressible in our query language and we consider a fragment of this language, consisting of regular expressions to talk about temporally ordered sequences of stops and moves. This fragment can be used not only for querying, but also for expressing data mining and pattern matching tasks over trajectory data."
An alternative approach to the state observation problem for Lipschitz continuous systems with controls
(2010-07) Hernández, Santiago M.; García Galiñanes, Rafael
"In the present work we propose an alternative approach to the state observation problem for Lipschitz continuous systems with open-loop controls. We construct an observer based on a concept of observability weaker than that of the instantaneous observability. The resulting observation algorithm is then applicable under mild assumptions about the considered dynamical system".
Analysis of invariants for efficient bounded verification
(2010-07) Galeotti, Juan Pablo; Rosner, Nicolás; López Pombo, Carlos G.; Frías, Marcelo
"SAT-based bounded veri cation of annotated code consists of translating the code together with the annotations to a propositional formula, and analyzing the formula for speci cation violations using a SAT-solver. If a violation is found, an execution trace exposing the error is exhibited. Code involving linked data structures with intricate invariants is particularly hard to analyze using these techniques. In this article we present TACO, a prototype tool which implements a novel, general and fully automated technique for the SAT-based analysis of JML-annotated Java sequential programs dealing with complex linked data structures. We instrument code analysis with a symmetry-breaking predicate that allows for the parallel, automated computation of tight bounds for Java elds. Experiments show that the translations to propositional formulas require signi cantly less propositional variables, leading in the experiments we have carried out to an improvement on the e ciency of the analysis of orders of magnitude, compared to the non instrumented SAT-based analysis. We show that, in somecases, our tool can uncover bugs that cannot be detected by state-of-the-art tools based on SAT-solving, model checking or SMT-solving."
An analysis of the suitability of test-based patch acceptance criteria
(2017-07) Zemín, Luciano; Gutiérrez Brida, Simón; Godio, Ariel; Cornejo, César; Degiovanni, Renzo; Regis, Germán; Aguirre, Nazareno; Frías, Marcelo
"Program repair techniques attempt to fix programs by looking for patches within a search space of fix candidates. These techniques require a specification of the program to be repaired, used as an acceptance criterion for fix candidates, that often also plays an important role in guiding some search processes. Most tools use tests as specifications, which constitutes a risk, since the incompleteness of tests as specifications may lead one to obtain spurious repairs, that pass all tests but are in fact incorrect. This problem has been identified by various researchers, raising concerns about the validity of program fixes. More thorough studies have been proposed using different sets of tests for fix validation, and resorting to manual inspection, showing that while tools reduce their program fixing rate, they are still able to repair a significant number of cases. In this paper, we perform a different analysis of the suitability of tests as acceptance criteria for automated program fixes, by checking patches produced by automated repair tools using a bug-finding tool, as opposed to previous works that used tests or manual inspections. We develop a number of experiments in which faulty programs from a known benchmark are fed to the program repair tools GenProg, Angelix, AutoFix and Nopol, using test suites of varying quality and extension, including those accompanying the benchmark. We then check the produced patches against formal specifications using a bug-finding tool. Our results show that, in general, automated program repair tools are significantly more likely to accept a spurious program fix than producing an actual one, in the studied scenarios. "
Application of robust control to a cryogenic current comparator
(2017-06) Bierzychudek, Marcos E.; Götz, Martin; Sánchez-Peña, Ricardo; Iuzzolino, Ricardo; Drung, Dietmar
"This paper describes the implementation of a digital robust controller in a cryogenic current comparator. The controller was designed applying H∞ control theory and it was programmed in a home-made digital unit. Experimental comparisons of the new robust controller with the conventional analog integrator have showed a significant improvement of stability robustness and noise rejection in the system."
Application of robust control to a cryogenic current comparator
(2016-07) Bierzychudek, Marcos E.; Götz, Martin; Sánchez-Peña, Ricardo; Tonina, Alejandra; Iuzzolino, Ricardo; Drung, Dietmar
"We describe the design and implementation of an H ∞ controller for PTB's 14-bit cryogenic current comparator (CCC). Measurement results obtained using either the newly implemented digital H ∞ controller or the conventional analog integrator are consistent. In a wide frequency range, the system's noise figure is improved when using the new controller."
Artificial Pancreas: first clinical trials in Argentina
(2017-07) Sánchez-Peña, Ricardo; Colmegna, Patricio; Grosembacher, Luis; Breton, Marc; De Battista, Hernán; Garelli, Fabricio; Belloso, Waldo H.; Campos-Náñez, Enrique; Simonovich, Ventura; Beruto, Valeria; Scibona, Paula; Cherñavvsky, Daniel
"The first clinical trials using an Artificial Pancreas (AP) in Latin America have been defined in 2 stages. The first stage was carried out in November 2016 with the UVA controller (developed by the Center for Diabetes Technology and already clinically tested), and the second will be performed during the first semester of 2017 with the ARG (Automatic Regulation of Glucose) algorithm (developed by ITBA, UNQ, and UNLP in Argentina). Both tests are based on the DiAs (Diabetes Assistant) from the UVA, and are performed in the HIBA on 5 patients with Type 1 Diabetes Mellitus (T1DM), for 36 hours. For the first stage, Open-Loop (OL) insulin boluses were applied before meals and patient's physical activity was included. On the other hand, for the second stage, patients will not be involved in physical activity, but no OL insulin boluses will be injected before meals. In this work, experimental results from the first stage with the UVA controller, and preliminary results with the ARG control algorithm tested on the UVA/Padova simulator are presented. Due to the final paper deadline, the experimental results from the second stage are not included here, but will be presented at the IFAC World Congress."
Automated workarounds from Java Program specifications based on SAT solving
(2017) Uva, Marcelo; Ponzio, Pablo; Regis, Germán; Aguirre, Nazareno; Frías, Marcelo
"The failures that bugs in software lead to can sometimes be bypassed by the so called workarounds: when a (faulty) routine fails, alternative routines that the system offers can be used in place of the failing one, to circumvent the failure. Previous works have exploited this workarounds notion to automatically recover from runtime failures in some application domains. However, existing approaches that compute workarounds automatically either require the user to manually build an abstract model of the software under consideration, or to provide equivalent sequences of operations from which workarounds are computed, diminishing the automation of workaround-based system recovery. In this paper, we present two techniques that automatically compute workarounds from Java code equipped with formal specifications, avoiding abstract software models and user provided equivalences. These techniques employ SAT solving to compute workarounds on concrete program state characterizations. The first employs SAT solving to compute traditional workarounds, while the second directly exploits SAT solving to circumvent a failing method, building a state that mimics the (correct) behaviour of this failing routine. Our experiments, based on case studies involving implementations of collections and a library for date arithmetic, enable us to show that the techniques can effectively compute workarounds from complex contracts in an important number of cases, in time that makes them feasible to be used for run time repairs."
Automatic detection of reverse‑triggering related asynchronies during mechanical ventilation in ARDS patients using flow and pressure signals
(2019) Rodríguez, Pablo Oscar; Tiribelli, Norberto; Gogniat, Emiliano; Plotnikow, Gustavo A.; Fredes, Sebastián; Fernández Ceballos, Ignacio; Pratto, Romina A.; Madorno, Matías; Ilutovich, Santiago; San Román, Eduardo; Bonelli, Ignacio; Guaymas, María; Raimondi, Alejandro C.; Maskin, Luis Patricio; Setten, Mariano
"Asynchrony due to reverse-triggering (RT) may appear in ARDS patients. The objective of this study is to validate an algo-rithm developed to detect these alterations in patient–ventilator interaction. We developed an algorithm that uses flow and airway pressure signals to classify breaths as normal, RT with or without breath stacking (BS) and patient initiated double-triggering (DT). The diagnostic performance of the algorithm was validated using two datasets of breaths, that are classified as stated above. The first dataset classification was based on visual inspection of esophageal pressure (Pes) signal from 699 breaths recorded from 11 ARDS patients. The other classification was obtained by vote of a group of 7 experts (2 physicians and 5 respiratory therapists, who were trained in ICU), who evaluated 1881 breaths gathered from recordings from 99 sub-jects. Experts used airway pressure and flow signals for breaths classification. The RT with or without BS represented 19% and 37% of breaths in Pes dataset while their frequency in the expert’s dataset were 3% and 12%, respectively. The DT was very infrequent in both datasets. Algorithm classification accuracy was 0.92 (95% CI 0.89–0.94, P < 0.001) and 0.96 (95% CI 0.95–0.97, P < 0.001), in comparison with Pes and experts’ opinion. Kappa statistics were 0.86 and 0.84, respectively. The algorithm precision, sensitivity and specificity for individual asynchronies were excellent. The algorithm yields an excellent accuracy for detecting clinically relevant asynchronies related to RT."
Automatically identifying sufficient object builders from Module APIs
(2019) Ponzio, Pablo; Bengolea, Valeria; Politano, Mariano; Aguirre, Nazareno; Frías, Marcelo
"Various approaches to software analysis (e.g. test input generation, software model checking) require engineers to (manually) identify a subset of a module’s methods in order to drive the analysis. Given a module to be analyzed, engineers typically select a subset of its methods to be considered as object builders to define a so-called driver, that will be used to automatically build objects for analysis, e.g., combining them non-deterministically, randomly, etc. This requires a careful inspection of the module and its API, since both the relative exhaustiveness of the analysis (leaving important methods out may systematically avoid generating different objects), as well as its efficiency (the different bounded combinations of methods grows exponentially as the number of methods increases), are affected by the selection. We propose an approach for automatically selecting a set of builders from a module’s API, based on an evolutionary algorithm that favors sets of methods whose combinations lead to producing larger sets of objects. The algorithm also takes into account other characteristics of these sets of methods, trying to prioritize the selection of methods with less and simpler parameters. As the implementation of this evolutionary mechanism requires in principle handling and comparing large sets of objects, and this grows very quickly both in terms of space and running times, we employ an abstraction of sets of objects, called field extensions, that involves using the field values of the objects in the set instead of the actual objects, and enables us to effectively implement our mechanism. An experimental assessment on a benchmark of stateful classes shows that our approach can automatically identify sets of builders that are sufficient (can be used to create any instance of the module) and minimal (do not contain superfluous methods), in a reasonable time."
Autonomic modulation during a cognitive task using a wearable device
(2019) Bonomini, Maria Paula; Val-Calvo, Mikel; Díaz-Morcillo, Alejandro; Ferrández Vicente, José Manuel; Fernández-Jover, Eduardo
"Heart-brain interaction is by nature bidirectional, and then, it is sensible to expect the heart, via the autonomic nervous system (ANS), to induce changes in the brain. Respiration can originate differentiated ANS states reflected by HRV. In this work, we measured the changes in performance during a cognitive task due to four autonomic states originated by breath control: at normal breathing (NB), fast breathing (FB), slow breathing (SB) and control phases. ANS states were characterized by temporal (SDNN) and spectral (LF and HF power) HRV markers. Cognitive performance was measured by the response time (RT) and the success rate (SR). HRV parameters were acquired with the wristband Empatica E4. Classification was accomplished, firstly, to find the best ANS variables that discriminated the breathing phases (BPH) and secondly, to find whether ANS parameters were associated to changes in RT and SR. In order to compensate for possible bias of the test sets, 1000 classification iterations were run. The ANS parameters that better separated the four BPH were LF and HF power, with changes about 300% from controls and an average classification rate of 59.9%, a 34.9% more than random. LF and HF explained RT separation for every BPH pair, and so was HF for SR separation. The best RT classification was 63.88% at NB vs SB phases, while SR provided a 73.39% at SB vs NB phases. Results suggest that breath control could show a relation with the efficiency of certain cognitive tasks. For this goal the Empatica wristband together with the proposed methodology could help to clarify this hypothesis."
Autonomous vehicles for outdoor multidomain mapping
(2018-06) Garberoglio, Leonardo; Moreno, Patricio; Mas, Ignacio; Giribet, Juan I.
"In the last years, progress has been made attempting to replace a unique, complex and expensive vehicle equipped with several sensors such as LIDAR, RGB cameras, thermal sensor, etc. with a group of small vehicles, each of them carrying one sensor. There are several advantages of these segmented architectures, for instance this allows a reduction in the cost of the vehicles (several small vehicles can be less expensive than one big vehicle), the flexibility to choose for a mission only those vehicles with the appropriate sensors, the robustness of the system since it can acquire information even if one vehicle fails, among others. The advantage of segmented architectures is even more noticeable if the vehicles carrying those different sensors, have different characteristics or environments for operations, e.g. aerial, terrestrial or aquatic vehicles. In this work, we present the experimental results obtained with an ASV (Autonomous Surface Vehicle) and a UAV (Unmanned Aerial Vehicle) that cooperate to obtain a topographic survey of the terrain. The ASV is equipped with a LIDAR, meanwhile the UAV is equipped with a monocular RGB camera. The data acquired is post-processed in order to obtain a detailed map of the coastline of a creek and the surrounding area."
Avances y desafíos: el caso de la Biblioteca del Instituto Tecnológico de Buenos Aires (ITBA)
(2016) Rizzo, Gabriela; de Tezanos, Mariana
"Se ofrece un breve panorama de la Biblioteca del ITBA con la intención de compartir la experiencia de trabajo desde 2012 hasta 2016. Para esto, se proporciona una síntesis de los avances, problemas y desafíos presentes en todas las áreas de la Biblioteca. Finalmente, se establecen lineamientos a futuro."
Biodisponibilidad de elementos potencialmente tóxicos en suelos del margen del arroyo Morón, Prov. de Buenos Aires
(2019-06) Pacheco Rudz, Erika O.; Kucher, Hernán; Torri, Silvana I.; Bertini, Liliana María
"El objetivo de este trabajo fue evaluar la biodisponibilidad de ciertos elementos potencialmente tóxicos (EPT) en los suelos aledaños en un tramo rectificado del arroyo Morón. Para ello se llevó a cabo un muestreo de la llanura de inundación del cauce y del dique artificial contiguo. Se realizó un fraccionamiento secuencial para los EPT (Cu, Zn, Cr, Ni, Cd y Pb) y se midió el pH y la conductividad eléctrica de las muestras. Se observó que dichos elementos se encontraron mayormente asociados a la fracción inorgánica por lo que su disponibilidad es baja. En la llanura de inundación se encontraron valores bajos de Cu y Zn, mientras que la concentración de Cd, Cr, Ni y Pb se incrementó, con respecto a las muestras del área del dique; atribuyendo estas diferencias a los cambios en la concentración de los EPT estudiados en el cuerpo de agua a partir de la rectificación del arroyo."
Bounded exhaustive search of alloy specification repairs
(2021) Gutiérrez Brida, Simón; Regis, Germán; Zheng, Guolong; Bagher, Hamid; Nguyen, Thanh Vu; Aguirre, Nazareno; Frías, Marcelo
"The rising popularity of declarative languages and the hard to debug nature thereof have motivated the need for applicable, automated repair techniques for such languages. However, despite significant advances in the program repair of imperative languages, there is a dearth of repair techniques for declarative languages. This paper presents BeAFix, an automated repair technique for faulty models written in Alloy, a declarative language based on first-order relational logic. BeAFix is backed with a novel strategy for bounded exhaustive, yet scalable, ex ploration of the spaces of fix candidates and a formally rigorous, sound pruning of such spaces. Moreover, different from the state of-the-art in Alloy automated repair, that relies on the availability of unit tests, BeAFix does not require tests and can work with assertions that are naturally used in formal declarative languages. Our experience with using BeAFix to repair thousands of real world faulty models, collected by other researchers, corroborates its ability to effectively generate correct repairs and outperform the state-of-the-art."
A characterization of iISS for time-varying impulsive systems
(2018-12) Haimovich, Hernán; Mancilla-Aguilar, J. L.
"Most of the existing characterizations of the integral input-to-state stability (iISS) property are not suitable for time varying or switched (nonlinear) systems. Previous work by the authors has shown that in such cases where converse Lyapunov theorems for stability are not available, iISS-Lyapunov functions may not exist. In these cases, the iISS property can still be characterized as the combination of global uniform asymptotic stability under zero input (0-GUAS) and uniformly bounded energy input-bounded state (UBEBS). This paper shows that such a characterization remains valid for time-varying impulsive systems, under an appropriate condition on the number of impulse times on each finite time interval."
A characterization of strong iISS for time-varying impulsive systems
(2019-09) Haimovich, Hernán; Mancilla-Aguilar, J. L.; Cardone, Paula
"For general time-varying or switched (nonlinear) systems, converse Lyapunov theorems for stability are not available. In these cases, the integral input-to-state stability (iISS) property is not equivalent to the existence of an iISS-Lyapunov function but can still be characterized as the combination of global uniform asymptotic stability under zero input (0-GUAS) and uniformly bounded energy input-bounded state (UBEBS). For impulsive systems, asymptotic stability can be weak (when the asymptotic decay depends only on elapsed time) or strong (when such a decay depends also on the number of impulses that occurred). This paper shows that the mentioned characterization of iISS remains valid for time-varying impulsive systems, provided that stability is understood in the strong sense. "

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