Manipulación acustica del orden y dinámica molecular en estructuras mesomorficas de organización lamelar. Acoustic manipulation of molecular order and dynamics in mesomorphic structures of lamellar organization.

El control de propiedades hidrodinámicas capaces de influir en la mecánica de ruptura y poración de sistemas lamelares o membranas es de fundamental interés para diferentes aplicaciones biotecnológicas. Resulta de particular interés la conexión entre los procesos microscópicos relacionados al tipo de moléculas o unidades básicas, el orden determinado en el auto-ensamblado de las mismas y la dinámica local del sistema, con las propiedades físicas que determinan el comportamiento macroscópico bajo estimulación acústica. Resultados logrados recientemente sugieren la existencia de resonancias hidrodinámicas que podrian ser utilizadas para lograr la inestabilidad del sistema a baja potencia acústica. Se realizaran estudios experimentales utilizando principalmente técnicas que combinan resonancia magnética nuclear (RMN) y la sonicación de la muestra. También se realizarán estudios teóricos y simulaciones numéricas que permitan modelar los sistemas bajo estudio. Se propone dar continuidad al desarrollo de una técnica de relaxometría magnética nuclear en la cual se estimula acústicamente a la muestra durante el proceso de relajación magnética nuclear, y continuar la implementación de técnicas de RMN con resolución espacial que permitan complementar los estudios mencionados. Se espera comprender los mecanismos físicos que determinan la estabilidad de fases lamelares, logrando un modelo verificable y consistente que permita relacionar las propiedades mecánicas e hidrodinámicas con las propiedades de orden y dinámica molecular. Asimismo, se espera lograr avances en el desarrollo de las técnicas experimentales involucradas. La importancia del proyecto radica en el enfoque del problema. A diferencia de casi la totalidad de los estudios reportados, nuestro interés se enfoca en mecanismos de interacción entre la membrana y el campo acústico que sean eficientes a baja potencia acústica, en un régimen donde los gradientes térmicos y la cavitación sean despreciables.

Acoustic emission analysis of the effect of a 2D wedge shaped blade on the compact bone cutting process

Surgeons may use a number of cutting instruments such as osteotomes and chisels to cut bone during an operative procedure. The initial loading of cortical bone during the cutting process results in the formation of microcracks in the vicinity of the cutting zone with main crack propagation to failure occuring with continued loading. When a material cracks, energy is emitted in the form of Acoustic Emission (AE) signals that spread in all directions, therefore, AE transducers can be used to monitor the occurrence and development of microcracking and crack propagation in cortical bone. In this research, number of AE signals (hits) and related parameters including amplitude, duration and absolute energy (abs-energy) were recorded during the indentation cutting process by a wedge blade on cortical bone specimens. The cutting force was also measured to correlate between load-displacement curves and the output from the AE sensor. The results from experiments show AE signals increase substantially during the loading just prior to fracture between 90% and 100% of maximum fracture load. Furthermore, an amplitude threshold value of 64dB (with approximate abs-energy of 1500 aJ) was established to saparate AE signals associated with microcracking (41 – 64dB) from fracture related signals (65 – 98dB). The results also demonstrated that the complete fracture event which had the highest duration value can be distinguished from other growing macrocracks which did not lead to catastrophic fracture. It was observed that the main crack initiation may be detected by capturing a high amplitude signal at a mean load value of 87% of maximum load and unsteady crack propagation may occur just prior to final fracture event at a mean load value of 96% of maximum load. The author concludes that the AE method is useful in understanding the crack initiation and fracture during the indentation cutting process.

Instrumentation and software for the VERITAS Project and the detection of TeV Gamma-Ray Emission from the BL Lacertae Object 1ES1959+650

Transmission of Cherenkov light through the atmosphere is strongly influenced by the optical clarity of the atmosphere and the prevailing weather conditions. The performance of telescopes measuring this light is therefore dependent on atmospheric effects. This thesis presents software and hardware developed to implement a prototype sky monitoring system for use on the proposed next-generation gamma-ray telescope array, VERITAS. The system, consisting of a CCD camera and a far-infrared pyrometer, was successfully installed and tested on the ten metre atmospheric Cherenkov imaging telescope operated by the VERITAS Collaboration at the F.L. Whipple Observatory in Arizona. The thesis also presents the results of observations of the BL Lacertae object, 1ES1959+650, made with the Whipple ten metre telescope. The observations provide evidence for TeV gamma-ray emission from the BL Lacertae object, 1ES1959+650, at a level of more than 15 standard deviations above background. This represents the first unequivocal detection of this object at TeV energies, making it only the third extragalactic source seen at such levels of significance in this energy range. The flux variability of the source on a number of timescales is also investigated.

Robust acoustic and semantic modeling in a telephone-based spoken dialog system

Magdeburg, Univ., Fak. für Elektrotechnik und Informationstechnik, Diss., 2009

Estudio de las diferentes alternativas para mejorar la respuesta de los filtros BAW (Bulk Acoustic Wave) con topología en escalera

Los requisitos de los dispositivos empleados en los nuevos sistemas de telecomunicaciones son: unas avanzadas prestaciones, reducido tamaño y bajo coste. Actualmente, se utilizan filtros basados en la tecnología SAW para trabajar a frecuencias de microondas. Dado los inconvenientes que presentan dicho tipo de filtros, se pretende substituirlos por filtros basados en tecnología BAW. La topología en escalera es hasta el momento la más extendida para diseñar estos filtros.

Could cell membranes produce acoustic streaming? Making the case for synechococcus self-propulsion

Sir James Lighthill proposed in 1992 that acoustic streaming occurs in the inner ear, as part of the cochlear amplifier mechanism. Here we hypothesize that some of the most ancient organisms use acoustic streaming not only for self-propulsion but also to enhance their nutrient uptake. We focus on a motile strain of Synechococcus, a yanobacteria whose mechanism for self-propulsion is not known. Molecular motors could work like piezoelectric transducers acting on the crystalline structure surrounding the outer cell membrane. Our calculations show that a traveling surface acoustic wave (SAW)could account for the observed velocities. These SAW waves will also produce a non-negligible Stokes layer surrounding the cell: motion within this region being essentially chaotic. Therefore, an AS mechanism would be biologically advantageous, enhancing localized diffusion processes and consequently, chemical reactions. We believe that acoustic streaming, produced by nanometer scale membrane vibrations could be widespread in cell biology. Other possible instances are yeast cells and erythrocytes. Flows generated by acoustic streaming may also be produced by silica coated diatoms along their raphe. We note that microelectromechanical (MEMS) acoustic streaming devices were first introduced in the 1990’s. Nature may have preceded this invention by 2.7 Gyr.

Underwater Gigamosaicing

El procés de fusió de dues o més imatges de la mateixa escena en una d'única i més gran és conegut com a Image Mosaicing. Un cop finalitzat el procés de construcció d'un mosaic, els límits entre les imatges són habitualment visibles, degut a imprecisions en els registres fotomètric i geomètric. L'Image Blending és l'etapa del procediment de mosaicing a la que aquests artefactes són minimitzats o suprimits. Existeixen diverses metodologies a la literatura que tracten aquests problemes, però la majoria es troben orientades a la creació de panorames terrestres, imatges artístiques d'alta resolució o altres aplicacions a les quals el posicionament de la càmera o l'adquisició de les imatges no són etapes rellevants. El treball amb imatges subaquàtiques presenta desafiaments importants, degut a la presència d'scattering (reflexions de partícules en suspensió) i atenuació de la llum i a condicions físiques extremes a milers de metres de profunditat, amb control limitat dels sistemes d'adquisició i la utilització de tecnologia d'alt cost. Imatges amb il·luminació artificial similar, sense llum global com la oferta pel sol, han de ser unides sense mostrar una unió perceptible. Les imatges adquirides a gran profunditat presenten una qualitat altament depenent de la profunditat, i la seva degradació amb aquest factor és molt rellevant. El principal objectiu del treball és presentar dels principals problemes de la imatge subaquàtica, seleccionar les estratègies més adequades i tractar tota la seqüència adquisició-procesament-visualització del procés. Els resultats obtinguts demostren que la solució desenvolupada, basada en una Estratègia de Selecció de Límit Òptim, Fusió en el Domini del Gradient a les regions comunes i Emfatització Adaptativa d'Imatges amb baix nivell de detall permet obtenir uns resultats amb una alta qualitat. També s'ha proposat una estratègia, amb possibilitat d'implementació paral·lela, que permet processar mosaics de kilòmetres d'extensió amb resolució de centímetres per píxel.

A new method for geoelectrical investigations underwater

A new electrical method is proposed for determining the apparent resistivity of multi-earth layers located underwater. The method is based on direct current geoelectric sounding principles. A layered earth model is used to simulate the stratigraphic target. The measurement array is of pole-pole type; it is located underwater and is orientated vertically. This particular electrode configuration is very useful when conventional electrical methods cannot be used, especially if the water depth becomes very important. The calculated apparent resistivity shows a substantial quality increase in the measured signal caused by the underwater targets, from which little or no response is measured using conventional surface electrode methods. In practice, however, different factors such as water stratification, underwater streams or meteorological conditions complicate the interpretation of the field results. A case study is presented, where field surveys carried out on Lake Geneva were interpreted using the calculated apparent resistivity master-curves.

Diseño de filtros Bulk Acoustic Wave con topología en escalera de altas prestaciones

Degut als avenços als dispositius de telecomunicacions durant l’última dècada, els filtres integrats en aquests dispositius requereixen de millors prestacions, baix cost i, per sobre de tot, requereixen unes dimensions el més reduïdes possibles. Tot i que avui dia encara s’utilitzen el filtres SAW en aquests dispositius, cada cop més s’estan substituint pels filtres amb tecnologia BAW, ja que tenen millors prestacions. En l’actualitat la topologia BAW més extensa i utilitzada és la topologia en escala. En aquest projecte s’ha portat a terme un estudi en profunditat de les limitacions dels filtres en escala. A partir de les limitacions detectades s’ha presentat una nova estructura de disseny per aquest tipus de filtres que redueix les dimensions d’aquests i millora considerablement algunes de les limitacions de l’estructura convencional. Paral·lelament s’ha desenvolupat una metodologia sistemàtica pròpia pel disseny de la nova estructura.

Evaluation of monoenergetic imaging to reduce metallic instrumentation artifacts in computed tomography of the cervical spine.

OBJECT Monoenergetic imaging with dual-energy CT has been proposed to reduce metallic artifacts in comparison with conventional polychromatic CT. The purpose of this study is to systematically evaluate and define the optimal dual-energy CT imaging parameters for specific cervical spinal implant alloy compositions. METHODS Spinal fixation rods of cobalt-chromium or titanium alloy inserted into the cervical spine section of an Alderson Rando anthropomorphic phantom were imaged ex vivo with fast-kilovoltage switching CT at 80 and 140 peak kV. The collimation width and field of view were varied between 20 and 40 mm and medium to large, respectively. Extrapolated monoenergetic images were generated at 70, 90, 110, and 130 kiloelectron volts (keV). The standard deviation of voxel intensities along a circular line profile around the spine was used as an index of the magnitude of metallic artifact. RESULTS The metallic artifact was more conspicuous around the fixation rods made of cobalt-chromium than those of titanium alloy. The magnitude of metallic artifact seen with titanium fixation rods was minimized at monoenergies of 90 keV and higher, using a collimation width of 20 mm and large field of view. The magnitude of metallic artifact with cobalt-chromium fixation rods was minimized at monoenergies of 110 keV and higher; collimation width or field of view had no effect. CONCLUSIONS Optimization of acquisition settings used with monoenergetic CT studies might yield reduced metallic artifacts.

Vision-based localization of an underwater robot in a structured environment

This paper presents a vision-based localization approach for an underwater robot in a structured environment. The system is based on a coded pattern placed on the bottom of a water tank and an onboard down looking camera. Main features are, absolute and map-based localization, landmark detection and tracking, and real-time computation (12.5 Hz). The proposed system provides three-dimensional position and orientation of the vehicle along with its velocity. Accuracy of the drift-free estimates is very high, allowing them to be used as feedback measures of a velocity-based low-level controller. The paper details the localization algorithm, by showing some graphical results, and the accuracy of the system

A behavior-based scheme using reinforcement learning for autonomous underwater vehicles

This paper presents a hybrid behavior-based scheme using reinforcement learning for high-level control of autonomous underwater vehicles (AUVs). Two main features of the presented approach are hybrid behavior coordination and semi on-line neural-Q_learning (SONQL). Hybrid behavior coordination takes advantages of robustness and modularity in the competitive approach as well as efficient trajectories in the cooperative approach. SONQL, a new continuous approach of the Q_learning algorithm with a multilayer neural network is used to learn behavior state/action mapping online. Experimental results show the feasibility of the presented approach for AUVs