Browsing by Author "Guarini Hermann, Marcelo Walter"

Now showing 1 - 19 of 19
  • Thumbnail Image
    Item
    A DAC reconstruction filter for narrowband long distance Communications
    (IEEE, 2014) Aldunate Varela, Joaquín Pablo; Feres Ducci, Carlos Jose; Vlahoyiannatos, Spyros; Oberli Graf, Christian Robert; de Villers-Grandchamps Zaldivar, Jean-Paul Idesbald; Guarini Hermann, Marcelo Walter
    There are applications that require long-range, low data rate and low power consumption communications that could be implemented with wireless sensor networks equipped with multiple antennas. We are implementing a transceiver for that purpose. The transceiver requires a specific reconstruction filter which isn't commercially available for our target technology, XFAB XH018. An integrated active DAC reconstruction filter was designed and implemented on the target technology using Synopsys design tools. This document present the design, implementation and testing of the reconstruction filter. The filter achieved the design requirements.
  • Thumbnail Image
    Item
    A fuzzy logic based model computes cardiac output from the radial arterial pressure waveform
    (IEEE, 1994) Urzua Urzua, Jorge; Guarini Hermann, Marcelo Walter; Cipriano, Aldo; Matus Acuña, Marcelo Enrique; Lee, J.; Salinas, C.; Olmedo Hidalgo, Juan Carlos; Lema F., Guillermo; Canessa, Roberto
    An interactive scheme for the development of a fuzzy logic based model has been implemented and applied to build a model that is able to determine cardiac output from radial arterial pressure. It was built using as input radial pressure waveforms from patients in whom cardiac output was simultaneously measured by thermodilution. The scheme was programmed in C language in an Apollo workstation under Unix. Input variables were area under the curve, ratio between systolic and diastolic pressure, and pulse frequency. To determine fuzzy sets and membership functions the authors used 149 pressure waveforms. To test the model, the authors used 6 waveforms not used in building the model. Correlation between predicted cardiac output with measured flow was 0.98.<>
  • No Thumbnail Available
    Item
    A low-cost altitude control system for the Kadet Senior radio-controlled airplane
    (2003) Abusleme Hoffman, Ángel Christian; Cipriano, Aldo; Guarini Hermann, Marcelo Walter
    In automatic control education, real examples always improve students' learning and motivation. Considering this fact, a hardware-in-the-loop, low-cost altitude control system for a radio-controlled (RC) airplane has been developed to improve automatic control education. This system constitutes a high-impact demonstrator for teaching automatic control topics, applied to a real-life problem. The airplane has an altitude sensor; students can safely remotely control this variable in a computer real-time environment. This paper addresses the system analysis and description, controller design, and real demonstrations. This device was tested in a basic automatic control course for undergraduate electrical engineering students and received good results; students reacted with curiosity and enthusiasm and encouraged the lecturers to design more experiences like this one.
  • No Thumbnail Available
    Item
    A model of internal control may improve the response time of an automatic arterial pressure controller
    (IEEE, 2000) Urzua Urzua, Jorge; Sauma Santis, Enzo Enrique; Cipriano, Aldo; Guarini Hermann, Marcelo Walter
    A simplified model for the arterial pressure control system was implemented on a personal computer using Matlab Simulink(R). Model responses to variations of systemic vascular resistance were comparable to those predicted by physiology. Computer simulation suggested that including this model of the internal pressure control system within the design of an external controller would achieve better arterial pressure control and faster response than previous systems.
  • Thumbnail Image
    Item
    A Model of Internal Control May Improve the Response Time of An Automatic Arterial Pressure Controller
    (1999) Urzúa Urzúa, Jorge; Cipriano, Aldo; Guarini Hermann, Marcelo Walter; Zapata, Patricio
  • No Thumbnail Available
    Item
    A simple index for ventriculoarterial coupling
    (1993) Urzúa Urzúa, Jorge; Lema F., Guillermo; Guarini Hermann, Marcelo Walter; Cipriano, Aldo; Meneses Riquelme, Gladys Elena; Matus Acuña, Marcelo Enrique
  • No Thumbnail Available
    Item
    Chebyshev series for designing RF pulses employing an optimal control approach
    (2004) Ulloa Allendes, José Luis; Guarini Hermann, Marcelo Walter; Guesalaga Meissner, Andrés; Irarrazaval Barros, Pablo
    Magnetic resonance imaging (MRI) provides bidimensional images with high definition and selectivity. Selective excitations are achieved applying a gradient and a radio frequency (RF) pulse simultaneously. They are modeled by the Bloch differential equation, which has no closed-form solution. Most methods for designing RF pulses are derived from approximation of this equation or are based on iterative optimization methods. The approximation methods are only valid for small tip angles and the optimization-based algorithms yield better results, but they are computationally intensive. To improve the solutions and to reduce processing time, a method for designing RF pulses using a pseudospectral approach is presented. The Bloch equation is expanded in Chebyshev series, which can be solved using a sparse linear algebraic system. The method permits three different formulations derived from the optimal control theory, minimum distance, minimum energy, or minimum time, which are solved as algebraic constrained minimization problems. The results were validated through simulated and real experiments of 90/spl deg/ and 180/spl deg/ RF pulses. They show improvements compared to the corresponding solutions obtained using the Shinnar-Le Roux method. The minimum time formulation produces the best performance for 180/spl deg/ pulses, reducing the excitation length in 4% and the RF pulse energy in 3%.
  • Thumbnail Image
    Item
    Cuantificación de la calidad perceptual de imágenes estáticas
    (2008) Prieto Cifuentes, Francisco; Guarini Hermann, Marcelo Walter; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Los nuevos métodos para reconstruir imágenes médicas representan un avance importante para la capacidad de diagnóstico clínico, sin embargo es necesario validarlos midiendo la calidad de las imágenes por ellos producidos. Algo similar ocurre con las técnicas de compresión de imágenes. Ambos métodos, reconstrucción y compresión, requieren de métricas para evaluar las distorsiones que se introducen en las imágenes y el grado de esas distorsiones producto de los algoritmos. La métrica utilizada en forma estándar ha sido el error cuadrático medio (RMSE del inglés Root Mean Squared Error), pero esta métrica no refleja necesariamente la forma en que el sistema visual humano (SVH) percibe las imágenes. En este trabajo se han desarrollado tres nuevos enfoques alternativos al RMSE, de los que se obtuvieron cinco nuevas métricas que logran una correlación mayor con la percepción subjetiva de observadores. Estas métricas incorporan algunas características del SVH. Para validar estas métricas se realizaron experimentos que reflejan la correlación entre las métricas y la calificación subjetiva. Las métricas presentan buenos desempeños, y por su facilidad de implementación y adecuación al SVH se recomienda su uso en áreas de reconstrucción y compresión de imágenes. Además, pueden ser el punto de partida de nuevos desarrollos en esta línea de investigación.
  • Thumbnail Image
    Item
    Diseño e implementación en FPGA de un módem de banda base para redes inalámbricas de sensores.
    (2012) Pérez Díaz, Héctor; Oberli Graf, Christian Robert; Guarini Hermann, Marcelo Walter; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Diversos avances tecnológicos han permitido el desarrollo de dispositivos microelectrónicos altamente eficientes y de muy bajo costo. En los últimos años, esta tecnología ha sido utilizada para desarrollar pequeños microcontroladores, transceptores de radio y sensores para medir variables físicas, cada uno de ellos en un solo circuito integrado. La combinación de estos componentes en un nodo ha establecido un área de desarrollo en comunicaciones que emerge rápidamente, conocida como redes inalámbricas de sensores. Las aplicaciones de redes de sensores requieren que los nodos operen aisladamente y para extender su vida útil es importante minimizar el consumo energético de las comunicaciones entre nodos. La incorporación de tecnología de múltiples antenas en transmisión y recepción permitiría disminuir el consumo energético de un enlace manteniendo su desempeño, solución que hasta ahora no ha sido explorada.
  • Thumbnail Image
    Item
    Enhancement of Visual Perception Through Dynamic Cues: An Application to Mammograms
    (IEEE, 2007) Plett Heckmann, Johannes Alberto; Guarini Hermann, Marcelo Walter; Irarrázaval Mena, Pablo
    Images often contain very small and hardly detectable objects or patterns, which can be of grave importance for diagnosis. In this paper we present a new method for aiding medical doctors in diagnosis of such images by adding artificial movement to the static images, in order to utilize the motion sensitivity of the human visual system. This technique permits detection of lesions not just by intensity, structure and texture differences with its surroundings, but by motion as well. Statistical analysis of experimental tests with both radiologists and non-radiologists show improved detection rate of microcalcifications in mammograms, raising it on average by 20.8% for non-radiologists and by 8.4% for radiologists.
  • No Thumbnail Available
    Item
    Fuzzy control for the Kadet senior radiocontrolled airplane
    (IEEE, 2001) Abusleme Hoffman, Ángel Christian; Cipriano, Aldo; Guarini Hermann, Marcelo Walter
    Three control strategies for the longitudinal dynamics of a Kadet Senior radiocontrolled airplane are analyzed and compared through simulation of a global nonlinear mathematical model. The first strategy uses a PID controller for the speed and two PID cascade controllers for the climb rate and altitude. The second strategy is a control system based on fuzzy logic. The third strategy consists of a hybrid system with a PID controller for the climb rate and fuzzy controllers for the speed and altitude.
  • No Thumbnail Available
    Item
    Fuzzy modelling of pulp density in a mineral grinding plant
    (IEEE, 1994) Cipriano, Aldo; Ramos, M.; Munoz, C.; Guarini Hermann, Marcelo Walter; Guesalaga, A.
    This paper describes an identification algorithm of fuzzy models and its application to the modeling of the pulp density in a mineral grinding plant. The parameters of the fuzzy model are estimated using information obtained from a process simulator. The performance of the fuzzy model is only slightly superior to that of a conventional linear model
  • Thumbnail Image
    Item
    Implementación de procesador banda base MIMO
    (2015) Venegas Jara, Joaquín Andrés; Guarini Hermann, Marcelo Walter; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Actualmente no existe un desarrollo adecuado o suficiente de la tecnología en el ámbito de las comunicaciones de ancho de banda angosto y largo alcance. Sin embargo, este segmento de las comunicaciones se muestra especialmente adecuado para las redes inalámbricas de sensores que cubren grandes extensiones geográficas. Varios autores han propuesto utilizar algoritmos que emplean múltiples antenas (conocida como MIMO por sus siglas en inglés) para minimizar la potencia total transmitida. No obstante, el desarrollo de las plataformas experimentales que permiten validar las investigaciones han apuntado en la dirección de esquemas de gran ancho de banda como WiMAX o LTE. Esta tesis propone una metodología para diseñar e implementar un procesador banda base y comprobar su funcionamiento en un dispositivo programable, en este caso una FPGA, para la investigación en redes inalámbricas de sensores MIMO. El procesador fue diseñado bajo las especificaciones del test bed desarrollado en el Laboratorio de Tecnologías Inalámbricas (LATINA) de la Pontificia Universidad Católica de Chile (PUC). El procesador propuesto incluyó las características mínimas de un transceptor comercial, tales como: registros de configuración, interfaz de comunicación y procesamiento de señales en banda-base. Además, utilizando algoritmos desarrollados por investigadores en LATINA que solucionan aspectos de sincronización mediante el uso mútliples antenas, se diseñó una arquitectura de procesamiento que permitirá la posterior comprobación empírica de técnicas MIMO. Finalmente, para validar el procesador se desarrolló en FPGA un emulador de canal discreto como medio para realizar simulaciones de Monte Carlo, y así comparar bajo un medio controlado la tasa de error de bit para distintas razones de señal a ruido entre la implementación y las simulaciones realizadas en MATLAB.
  • Thumbnail Image
    Item
    In silico evaluation of a control system and algorithm for automated insulin infusion in the ICU setting
    (2010) Ortiz, José L.; Guarini Hermann, Marcelo Walter; Borzone, Gisella; Olmos Coelho, Pablo Roberto
    Abstract Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity and mortality not only in diabetic patients but also in those non-diabetics who become transiently hyperglycemic. Taking advantage of a recently marketed subcutaneous glucose sensor we designed an Automatic Insulin Infusion System (AIIS) for inpatient treatment, and tested its stability under simulated clinical conditions. Methods The system included: reference glucose, glucose sensor, insulin and glucose infusion controllers and emergency infusion logic. We carried out computer simulations using Matlab/Simulink®, in both common and worst-case conditions. Results The system was capable of controlling glucose levels without entering in a phase of catastrophic instability, even under severe simulated challenges. Care was taken to include in all simulations the 5-10 minute delay of the subcutaneous glucose signal when compared to the real-time serum glucose signal, a well-known characteristic of all subcutaneous glucose sensors. Conclusions When tested in-Silico, a commercially available subcutaneous glucose sensor allowed the stable functioning of a proportional-derivative Automatic Insulin Infusion System, which was able to maintain glucose within acceptable limits when using a well-established glucose response model simulating a patient. Testing of the system in vivo using animal models is now warranted.Abstract Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity and mortality not only in diabetic patients but also in those non-diabetics who become transiently hyperglycemic. Taking advantage of a recently marketed subcutaneous glucose sensor we designed an Automatic Insulin Infusion System (AIIS) for inpatient treatment, and tested its stability under simulated clinical conditions. Methods The system included: reference glucose, glucose sensor, insulin and glucose infusion controllers and emergency infusion logic. We carried out computer simulations using Matlab/Simulink®, in both common and worst-case conditions. Results The system was capable of controlling glucose levels without entering in a phase of catastrophic instability, even under severe simulated challenges. Care was taken to include in all simulations the 5-10 minute delay of the subcutaneous glucose signal when compared to the real-time serum glucose signal, a well-known characteristic of all subcutaneous glucose sensors. Conclusions When tested in-Silico, a commercially available subcutaneous glucose sensor allowed the stable functioning of a proportional-derivative Automatic Insulin Infusion System, which was able to maintain glucose within acceptable limits when using a well-established glucose response model simulating a patient. Testing of the system in vivo using animal models is now warranted.Abstract Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity and mortality not only in diabetic patients but also in those non-diabetics who become transiently hyperglycemic. Taking advantage of a recently marketed subcutaneous glucose sensor we designed an Automatic Insulin Infusion System (AIIS) for inpatient treatment, and tested its stability under simulated clinical conditions. Methods The system included: reference glucose, glucose sensor, insulin and glucose infusion controllers and emergency infusion logic. We carried out computer simulations using Matlab/Simulink®, in both common and worst-case conditions. Results The system was capable of controlling glucose levels without entering in a phase of catastrophic instability, even under severe simulated challenges. Care was taken to include in all simulations the 5-10 minute delay of the subcutaneous glucose signal when compared to the real-time serum glucose signal, a well-known characteristic of all subcutaneous glucose sensors. Conclusions When tested in-Silico, a commercially available subcutaneous glucose sensor allowed the stable functioning of a proportional-derivative Automatic Insulin Infusion System, which was able to maintain glucose within acceptable limits when using a well-established glucose response model simulating a patient. Testing of the system in vivo using animal models is now warranted.Abstract Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity and mortality not only in diabetic patients but also in those non-diabetics who become transiently hyperglycemic. Taking advantage of a recently marketed subcutaneous glucose sensor we designed an Automatic Insulin Infusion System (AIIS) for inpatient treatment, and tested its stability under simulated clinical conditions. Methods The system included: reference glucose, glucose sensor, insulin and glucose infusion controllers and emergency infusion logic. We carried out computer simulations using Matlab/Simulink®, in both common and worst-case conditions. Results The system was capable of controlling glucose levels without entering in a phase of catastrophic instability, even under severe simulated challenges. Care was taken to include in all simulations the 5-10 minute delay of the subcutaneous glucose signal when compared to the real-time serum glucose signal, a well-known characteristic of all subcutaneous glucose sensors. Conclusions When tested in-Silico, a commercially available subcutaneous glucose sensor allowed the stable functioning of a proportional-derivative Automatic Insulin Infusion System, which was able to maintain glucose within acceptable limits when using a well-established glucose response model simulating a patient. Testing of the system in vivo using animal models is now warranted.
  • Thumbnail Image
    Item
    Motion estimation applied to reconstruct undersampled dynamic MRI
    (2007) Prieto Vásquez, Claudia; Guarini Hermann, Marcelo Walter; Hajnal, Joseph V.; Irarrázaval Mena, Pablo
    Magnetic Resonance Imaging (MRI) has become an important tool for dynamic clinical studies. Regrettably, the long acquisition time is still a challenge in dynamic MRI. Several undersampled reconstruction techniques have been developed to speed up the acquisition without significantly compromising image quality. Most of these methods are based on modeling the pixel intensity changes. Recently, we introduced a new approach based on the motion estimation of each object element (obel, a piece of tissue). Although the method works well, the outcome is a trade off between the maximum undersampling factor and the motion estimation accuracy. In this work we propose to improve its performance through the use of additional data from multiple coils acquisition. Preliminary results on cardiac MRI show that further undersampling and/or improved reconstruction accuracy is achieved using this technique. Furthermore, an approximation of the vector field of motion is obtained. This method is appropriate for sequences where the obels' intensity through time is nearly constant.
  • Thumbnail Image
    Item
    Optimal CCD readout by digital correlated double sampling
    (2016) Alessandri Amenábar, Cristóbal; Abusleme Hoffman, Ángel Christian; Guzmán Carmine, Christian Dani; Passalacqua, I.; Alvarez, E.; Guarini Hermann, Marcelo Walter
  • Thumbnail Image
    Item
    Reconstruction of undersampled dynamic images by modeling the motion of object elements
    (2007) Prieto Vásquez, Claudia; Batchelor, Philip G.; Hill, D.L.G.; Hajnal, Joseph V.; Guarini Hermann, Marcelo Walter; Irarrázaval Mena, Pablo
    Dynamic MRI is restricted due to the time required to obtain enough data to reconstruct the image sequence. Several undersampled reconstruction techniques have been proposed to reduce the acquisition time. In most of these techniques the nonacquired data are recovered by modeling the temporal information as varying pixel intensities represented in time or in temporal frequencies. Here we propose a new approach that recovers the missing data through a motion estimation of the object elements ('' obels,'' or pieces of tissue) of the image. This method assumes that an obel displacement through the sequence has lower bandwidth than fluctuations in pixel intensities caused by the motion, and thus it can be modeled with fewer parameters. Preliminary results show that this technique can effectively reconstruct (with root mean square (RMS) errors below 4%) cardiac images and joints with undersampling factors of 8 and 4, respectively. Moreover, in the reconstruction process an approximation of the motion vectors is obtained for each obel, which can be used to quantify dynamic information. In this method the motion need not be confined to a part of the field of view (FOV) or to a portion of the temporal frequency. It is appropriate for dynamic studies in which the obels' motion model has fewer parameters than the number of acquired samples.
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item