http://hdl.handle.net/2117/3362 2013-06-20T02:09:20Z http://hdl.handle.net/2117/18640 Title: Micro-mechanical damage in tool steels analyzed by acoustic emission technique Authors: Picas Anfruns, Ingrid; Martínez González, Eva; Casellas, Daniel; Romeu Garbí, Jordi Abstract: The carbides in tool steels act as hard particles and dictate the wear resistance. The origin of failure of these steels is mostly related with the carbide cracking, as a nucleation site of final cracks. This paper shows the acoustic emission (AE) signals related with the nucleation (carbide cracking) and the crack growth (in the metallic matrix) during a monotonic bending test of a tool steel obtained by ingot metallurgy routes (DIN 1.2379). The paper presents a relationship between the frequency spectrum of AE signals obtained and the microscopic images during the test. 2013-04-05T11:01:05Z http://hdl.handle.net/2117/18544 Title: Self-video recording for the integration and assessment of generic competencies Authors: Masip Álvarez, Albert; Hervada Sala, Carme; Pàmies Gómez, Teresa; Arias Pujol, Antoni; Jaen Fernandez, Carles; Rodríguez Sorigué, M. Cristina; Romero Durán, David; Nejjari Akhi-Elarab, Fatiha; Álvarez del Castillo, María Dolores; Roca Lefler, Marta; Hernández Farràs, Jorge; Montferrer Liñan, Raul Abstract: This document presents the use of a self-video-recording service for the integration and assessment of certain generic competences (oral and written communication, teamwork and third (English) language) in all degree programs related to the Industrial area at the Terrassa School of Engineering (EET). The resulting service allows to carry out the assessment through active and collaborative learning methodologies using ICT as a support, becoming an educational resource where students are encouraged to evaluate their own activity, individually and in groups (co-evaluation), and with which the faculty can enhance certain sections of the syllabus while also evaluating generic competences. This paper outlines the rationale and design of the system based on self-recording-video that assists work on some generic competences. A preliminary experience has taken place and it has been carried out by volunteer students and some professors from the promoting team. It consisted of following all steps to obtain the video-recording as a result and fulfil the further assessment. Preparing the defence of the final project career, explaining the way a problem is faced are examples of use of the service endowed to assist the assessment of some generic competences. A good number of students and professors have participated in this preliminary experiment carried out on some subjects and in which oral effective communication will be assessed. A specific rubric for the assessment of generic competences has been used both for students and faculty. There is a summary of qualitative feedback from both students and instructors, and where several issues related to improving the self-assessment and self-video-recording system, are discussed. Finally, a survey is proposed, whose results will be helpful for its improvement. 2013-04-02T14:02:57Z http://hdl.handle.net/2117/18181 Title: New siren tones optimised for increased detectability distances of emergency vehicles Authors: Balastegui Manso, Andreu; Romeu Garbí, Jordi; Clot Razquin, Arnau; Martín Román, Sara-Regina Abstract: Sirens from emergency vehicles are particularly annoying for people living in the vicinities of emergency centres. In order to reduce their discomfort, the present work computes the optimal output power and frequency content of the sirens by taking into account the car noise reduction, the background noise inside the car and the hearing threshold. The combination of these parameters gives rise to frequency windows where the sirens are more effective, hence new siren tones are proposed and their annoyance is assessed through a jury test procedure. The new tones can either increase the detectability distance by 40% without increasing their annoyance or reduce their sound pressure level by 3 dB while keeping their effectiveness in being detected. 2013-03-11T16:09:47Z http://hdl.handle.net/2117/17598 Title: Some analytical aspects of viscoelastic Lamb’s problem for improving its numerical evaluation Authors: Arcos Villamarín, Robert; Romeu Garbí, Jordi; Clot Razquin, Arnau; Genesca Francitorra, Meritxell Abstract: Two analytical modifications of the original viscoelastic time-harmonic Lamb’s problem expressions are presented with the aim of improving their numerical integration efficiency. Firstly, a new change of variable in the Lamb’s problem integrands is proposed, which allows a standardization of the integration sampling vector and a complete spatialfrequency field solution after performing only one numerical integration/transformation. Secondly, the Lamb’s problem static integrands are modified and introduced into the original integrands to reduce their spectral content at high wavenumbers and, therefore, the sampling vector lengths needed to avoid aliasing. 2013-02-07T16:13:13Z http://hdl.handle.net/2117/17597 Title: On the use of a linear microphone array to measure wind turbine aerodynamic noise Authors: Genesca Francitorra, Meritxell; Romeu Garbí, Jordi; Pàmies Gómez, Teresa; Solé, Jaume Abstract: A linear microphone array is shown to be a simple tool to locate aerodynamic sound sources on a horizontal axis wind turbine. This paper discusses the capabilities and limitations of a linear microphone array to locate sound sources and measure aerodynamic noise on the blades of a horizontal axis wind turbine rotor. Compared with a planar microphone array, a linear array requires fewer microphones to achieve the same resolution, a simpler structure to support it and a simpler signal processing algorithm. For a linear array, areas exist in the rotor plane where the sources cannot be located unambiguously. For certain applications, it is not necessary to map the whole rotor plane. This paper also shows the result of an experimental test aimed at locating and measuring aerodynamic sound sources on the three blades of a wind turbine. Each blade received a different surface treatment, with the goal of comparing their relative sound emission levels. The test was carried out with a 10.32 m linear microphone array, placed horizontally near the ground, extending parallel to the rotor plane. The results show that for all three blades, most of the noise is generated in the outer 25% of the blade span, with a maximum occurring just after the blade has passed the horizontal position going downwards. Results also show that tripped blade is the noisiest of the three, whereas the smoothest, polished blade is clearly the quietest. Copyright © 2012 John Wiley & Sons, Ltd. 2013-02-07T15:53:52Z http://hdl.handle.net/2117/17438 Title: Impacto acústico generado como consecuencia de la implantación de un skate park Authors: Jiménez Diaz, Santiago; Romeu Garbí, Jordi; Alsina Sánchez, Antoni Abstract: Un skate park es una instalación singular formada por un conjunto de elementos y obstáculos, fuentes sonoras potenciales, que se imlpanta en un entorno urbano abierto. El estudio de impacto acústico de este tipo de actividad no se puede realizar por evaluación de una actividad respecto de los receptores será diferente en cada caso. El cálculo por simulación permite incluir todas estas variables, pero requiere tener previamente la potencia acústica radiada y la directividad de cada fuente sonora (actividad del patinador sobre el elemento y obstáculo) de que consta la instalación del skate park. Una vez caracterizadas las fuentes de ruido, usando los datos topográficos y meteorólogicos del lugar, se determinan mediante simulación informática, los niveles de inmisión sonora procedentes de las diferentes fuentes del skate park que llegan a la fachada de los receptores. 2013-01-21T13:49:43Z http://hdl.handle.net/2117/14718 Title: Acelerómetros y sensores de vibración Authors: Romeu Garbí, Jordi; Genesca Francitorra, Meritxell 2012-01-20T16:40:00Z http://hdl.handle.net/2117/14717 Title: On the power and frequency of auditory signals on emergency vehicles Authors: Balastegui Manso, Andreu; Romeu Garbí, Jordi; Clot Razquin, Arnau; Martín Román, Sara-Regina Abstract: Sirens from emergency vehicles are particularly annoying for people living in the vicinities of hospitals. The power regulations for sirens vary for different countries as well as it does their frequency content. In order to reduce their annoyance the present work computes the optimal output power and frequencies of the siren by taking into account the car's sound insulation, the background noise inside the car and the masked threshold of hearing. The combination of these parameters gives rise to frequency windows where the sirens are more effective, so new tones are proposed and their annoyance is assessed through a jury test procedure. 2012-01-20T16:18:43Z http://hdl.handle.net/2117/14357 Title: Estimating the rate and luminosity function of all classes of GRBs Authors: Balastegui Manso, Andreu; Canal, Ramon; Ruiz-Lapuente, Pilar Abstract: The aim of the present work is to estimate the rate and luminosity functions of short, intermediate and long gamma-ray bursts (GRBs) by fitting their intensity distributions wih parameterized explosion rates and luminosity functions. The results show that the parameters of the rate and luminosity function for long GRBs can be calculated with an accuracy of 10-30%. However, some parameters of intermediate and short GRBs have large uncertainties. An important conclusion is that there was initially a large outburst in the frequency of long GRBs, and consequently a large outburst in the star-formation rate, if they come from collapsars. Finally, a simulated intensity distribution has been constructed to test the ability of the method to recover the simulated parameters. 2011-12-29T14:50:10Z http://hdl.handle.net/2117/13449 Title: Aplicación de la técnica de emisión acústica (EA) para auscultación en diversos tipos de materiales y estructuras Authors: Martínez González, Eva; Gallego Molina, Antolino; Infantes Vázquez, Cristobal; Benavent Climent, Amadeo; Morillas Romero, Leandro; Martínez Jequier, José; Juanes, Javier; Valea Pérez, Ángel 2011-10-06T08:40:24Z http://hdl.handle.net/2117/12017 Title: Analysis of fracture resistance of tool steels by means of acoustic emission Authors: Martínez González, Eva; Picas Anfruns, Ingrid; Casellas Padró, Daniel; Romeu Garbí, Jordi Abstract: The automotive manufacturers currently use advanced high-strength steels (AHSS) to produce lightweight vehicles with increased safety performance. While showing excellent strengthto-weight ratios, AHSS have several limitations due to the high loads required in cold forming and cutting processes, which lead to accelerated wear and premature fracture of tools. Thus, new tool materials with improved mechanical behavior ought to be developed with regard to the tool failure mechanisms. The aim of this work is to shed light on the fracture mechanisms acting in tools (i.e. crack nucleation and propagation) applying the acoustic emission (AE) technique. Bending tests using two different tool steels were monitored in order to establish a relationship between AE signals and fracture events. 2011-03-22T13:06:33Z http://hdl.handle.net/2117/10834 Title: Planes específicos para la reducción de la contaminación acústica de la ciudad de Terrassa Authors: Jiménez Diaz, Santiago; Romeu Garbí, Jordi; Genesca Francitorra, Meritxell; Alsina Sánchez, Antoni Abstract: La Directiva 2002/49 sobre evaluación y gestión del ruido ambiental contempla la adopción de planes de acción, tomando como base los resultados de los mapas estratégicos del ruido, con vistas a prevenir y reducir el ruido ambiental. El mapa estratégico de ruido de la aglomeración de Terrassa, pone de manifiesto las zonas donde se superan los índices de ruido, en las cuales sería necesario elaborar planes específicos de actuación. En este trabajo se presentan las actuaciones propuestas y realizadas así como, los resultados y el coste/beneficio obtenidos. 2010-12-29T15:56:30Z http://hdl.handle.net/2117/10329 Title: Mapas estratégicos de ruido en Catalunya Authors: Jiménez Diaz, Santiago; Romeu Garbí, Jordi; Pàmies Gómez, Teresa; Majó Torrent, Maite Abstract: La Directiva 2002/49 sobre evaluación y gestión del ruido ambiental demanda en caso de aglomeraciones, una serie de datos que hay que comunicar a la Comisión, entre los que se encuentran: el número de personas cuyas viviendas están expuestas a cada rango de valores Lden y de Lnight en dBA. En este trabajo se presentan los criterios contemplados en la delimitación de las aglomeraciones en el interior del territorio de Catalunya, así como las metodologías utilizadas en la estimación de los niveles sonoros y de la población expuesta a los diferentes indicadores de ruido, así como, los resultados obtenidos. 2010-11-16T18:58:36Z http://hdl.handle.net/2117/10317 Title: CATdBTren project: a complete model for the assessment of vibration impact from new railway infrastructures Authors: Alarcón Rovira, Gabriel; Palacios Higueras, José Ignacio; Romeu Garbí, Jordi; Balastegui Manso, Andreu; Arcos Villamarín, Robert; Sánchez Venegas, Ángel Abstract: The prediction of vibration impact remains as a complex challenge for designers of new railway infrastructures. Due to the large quantity of parameters involved in the generation, transmission and reception of the vibration waves, it would be necessary to develop a complete study for each potential receiver, which would include: source, soil and building characterization, infrastructure vibration behaviour modelling and, finally, countermeasures influence prediction. This process can turn out to be very costly in terms of both time and money. Therefore, it is usually done only for areas very likely to suffer high vibration levels or for high sensitive buildings (hospital, educational). The CATdBTren project, which has been awarded with R&D funding from the Catalonia Government, is aimed to develop a new prediction tool for evaluating the vibration impact from new railway infrastructures as well as to develop new types of fastening systems having high vibration isolation properties. That tool is intended to be user-friendly and to produce results with average accuracy, so it still will be required detailed studies of problematic areas. In this sense, the software will model the contact forces caused by high-speed, conventional and underground rolling stock. Moreover, it will model the infrastructure’s vibration transmission behaviour, ground vibration propagation, terrain-foundation coupling and building vibration mechanism. The CATdBTren prediction tool will be also capable of estimating the influence of the rolling stock, rail and wheel roughness, fastening system, substructure, soil vibration propagation properties and building characteristics, all in the final vibration impact. 2010-11-16T15:31:16Z http://hdl.handle.net/2117/10176 Title: Two step optimization of transducer locations in single input single output tonal global active noise control in enclosures Authors: Palacios Higueras, José Ignacio; Romeu Garbí, Jordi; Balastegui Manso, Andreu Abstract: Global active control of sound can be achieved inside enclosures under low modal acoustic fields. However, the performance of the system depends largely on the localization of the elements of the control system. For a purely acoustic active control system in which secondary acoustic sources (loudspeakers) and pressure transducers (microphones) as error sensors are used, several optimization strategies have been proposed. These strategies usually rely on partial approximation to the problem, focusing on the study of number and localization of secondary sources without considering error transducers, or selecting the best positions of secondary sources and error transducers of an initial set of candidate locations for these elements. The strategy presented here for tonal global active noise control of steady states comprises two steps; the first is rather common for this sort of problem and its goal is to find the best locations for secondary sources and their strengths by minimizing the potential energy of the enclosure. The second step is the localization of the error transducer, which ensures the results of the first step. It is analytically demonstrated that for a single input single output system, the optimum location of error transducers is at a null pressure point of the optimally attenuated acoustic field. It is also shown that in a real case, the optimum position is that of a minimum of the optimally attenuated acoustic field. Finally, a numerical validation of this principle is carried out in a parallelipedic enclosure. 2010-11-08T14:25:47Z