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- Acoustic emission and reception unit (AERU)Publication . Saleiro, MárioThis document describes a data acquisition/data generation system, which consists of a portable waterproof case with all the integrated electronics. It features a high power battery, a precision DAQ board, a state-of-the-art GPS board and a complete computer system. Acquired data can be stored in the internal hard drive and download into another storage device or directly to another computer using the Ethernet connection. It is intended to be used with the Portable Acoustic Source Unit (PASU) for acoustic data transmission and with single or multiple hydrophones for acoustic data acquisition. The system also features a easy and ready-to-use graphical user interface that allows the user to use the system using the integrated LCD touch screen. A user manual is included as an installation, setup and maintenance guide for the system and its practical applications. The developed hardware and software is described in detail. Detailed schematics and designs can be found in the final section of this document, which can be used to further develop the system, perform maintenance, purchase spare parts or perform any type of modifications. A support equipment named OCU (Outdoor Communications Unit) is also described in this document. The OCU consists of a waterproof case that can be used to supply the AERU or the PASU and to add wireless connectivity to the AERU it can also provide a handy solution to charge the batteries of the AOB2 buoys in a wet deck environment. ACKNOWLEDGMENT:
- Acoustic maritime rapid environmental assessment 2004 during the MREA'04 sea trialPublication . Jesus, S. M.; Soares, C.; Felisberto, P.; Silva, A.; Farinha, L.; Martins, C.Environmental inversion of acoustic signals for bottom and water column properties is being proposed in the literature as an interesting concept for complementing direct hydrographic and oceanographic measurements for Rapid Environmental Assessment (REA). The acoustic contribution to REA can be cast as the result of the inversion of ocean acoustic properties to be assimilated into ocean circulation models specifically tailored and calibrated to the scale of the area under observation. Traditional ocean tomography systems and methods for their requirements of long and well populated receiving arrays and precise knowledge of the source/receiver geometries are not well adapted to operational Acoustic REA (AREA). The Acoustic Oceanographic Buoy (AOB) was proposed as an innovative concept that responds to the operational requirements of AREA. That concept includes the development of water column and geo-acoustic inversion methods being able to retrieve environmental true properties from signals received on a drifting network of acoustic-oceanographic sensors - the AOBs. An AOB prototype and a preliminary version of the inversion code, was tested at sea during the Maritime Rapid Environmental Assessment 2003 (MREA’03) sea trial and was reported in [1]. On a separate register it should be noted that the characterization of the environment between the source and the receiver also contributes to the identification of the acoustic channel response and therefore provides a basis for fulfilling the objectives of project NUACE1. The present report describes the data sets and results gathered during the MREA’04 sea trial that took place from 29 March to 19 April 2004 off the west coast of Portugal, south of Lisboa (Portugal), with the objectives of testing an improved version of the individual AOB and its functionality in a simple network. The acoustic part of the experiment lasted for four days between April 7 and April 10, 2004 and involved the transmission and reception of pre-coded signals along range-dependent and range-independent acoustic tracks.
- Acoustic oceanographic buoy (version 1)Publication . Silva, A.; Martins, C.; Jesus, S. M.One of the known impairements in the application of ocean acoustic tomography in operational scenarios has been the size, weight and difficulty of operation of actual ocean going equipment, such as hydrophone arrays and acoustic sources. The Acoustic Oceanographic Buoy - AOB is meant to be, at its final stage, an easy to deploy and easy to maintain autonomous vertical array that puts together in a single system acoustic and non-acoustic sensors, self-storing of geotime and GPS referred data, on the buoy preprocessing capabilities and network seamless integrability and data online transfer via a wireless lan high speed link. These capabilities make the AOB a versatile system for a variety of applications such as ocean tomography, underwater communications, rapid environmental assessment (REA), passive and multistatic sonar and underwater target tracking. The AOB version 1 described in this report was developed between 2003 and 2004 and tested at sea during the MREA’03 and MREA’04 sea trials.
- Acoustic oceanographic buoy (version 2)Publication . Zabel, F.; Martins, C.This report describes an underwater acoustic data acquisition system, which uses a surface buoy and an underwater array of acoustic and non-acoustic sensors. The surface buoy includes a digital storage unit for the acquired data, a communications system for remote monitoring and data transmission, a digital processing unit for pre-processing of acquired data and a battery power supply. A user manual is included as an installation, setup and maintenance guide for the system and its practical applications. The developed hardware and software is described in detail. Detailed schematics and designs can be found in the final section of this document, these can be used to develop the system, perform maintenance, purchase spare parts or perform any type of modifications.
- Acoustic oceanographic buoy data report Makai Ex 2005Publication . Jesus, S. M.; Silva, A.; Zabel, F.It is now well accepted in the underwater acoustic scientific community that below, say, 1 kHz acoustic propagation models are accurate enough to be able to predict the received acoustic field up to the point of allowing precise and reliable source tracking in range and depth with only limited environmental information. This results from a large number of studies both theoretical and with real data, carried out in the last 20 years. With the event of underwater communications and the necessity to increase the signal bandwidth for allowing higher communication rates, the frequency band of interest was raised to above 10 kHz. In this frequency band the detailed knowledge of the environment - acoustic signal interplay is reduced. The purpose of the MakaiEx sea trial is to acquire data in a complete range of frequencies from 500 Hz up to 50 kHz, for a variety of applications ranging from high-frequency tomography, coherent SISO and MIMO applications, vector - sensor, active and passive sonar, etc...The MakaiEx sea trial, that took place off Kauai I. from 15 September - 2 October, involved a large number of teams both from government and international laboratories, universities and private companies, from various countries. Each team focused on its specific set of objectives in relation with its equipment or scientific interest. The team from the University of Algarve (UALg) focused on the data acquired by their receiving Acoustic Oceanographic Buoy - version 2 (AOB2) during six deployments in the period 15 - 27 September. This report describes the AOB2 data set as well as all the related environmental and geometrical data relative to the AOB2 deployments. The material described herein represents a valuable data set for supporting the research objectives of projects NUACE1, namely to fulfill NUACE’s task 3 and 4 and RADAR2, namely its tasks 2 and 3 devoted to the developement and testing of a field of sonobuoys.
- Acoustic Oceanographic Buoy Test during the MREA’03 Sea TrialPublication . Jesus, S. M.; Silva, A.; Soares, C.Environmental inversion of acoustic signals for bottom and water column properties is being proposed in the literature as an interesting concept for complementing direct hydrographic and oceanographic measurements for Rapid Environmental Assessment (REA). The acoustic contribution to REA can be cast as the result of the inversion of ocean acoustic properties to be assimilated into ocean circulation models specifically tailored and calibrated to the scale of the area under observation. Traditional ocean tomography systems and methods for their requirements of long and well populated receiving arrays and precise knowledge of the source/receiver geometries are not well adapted to operational Acoustic REA (AREA). An innovative concept that responds to the operational requirements of AREA is being proposed under a Saclantcen JRP jointly submitted by the the Universit´e Libre de Bruxelles (ULB), SiPLAB/CINTAL at University of Algarve, the Instituto Hidrogr´afico (IH) and the Royal Netherlands Naval College (RNLNC) and approved by Saclantcen in 2003 under the 2004 SPOW. That concept includes the development of water column and geo-acoustic inversion methods being able to retrieve environmental true properties from signals received on a drifting network of Acoustic-Oceanographic Buoys (AOB). A prototype of an AOB and a preliminary version of the inversion code, was tested at sea during the Maritime Rapid Environment Assessment’2003 sea trial (MREA’03) and is described in this report together with the results obtained.
- Afinal o que são e como se calculam os quartis?Publication . Fernandes, Susana; Pinto, Mónica MartinsImaginemos que queremos calcular os quartis de um conjunto de dados. Se consultarmos vários manuais de matemática do ensino básico e do ensino secundário e sebentas de estatística do ensino superior encontramos diferentes definições e fórmulas para o cálculo dos quartis, que algumas vezes conduzem a resultados diferentes. Se recorrermos a meios tecnológicos para determinar o valor dos quartis do mesmo conjunto de dados, usando uma máquina de calcular, uma folha de cálculo ou um programa estatístico, pode acontecer ficarmos com mais algumas respostas diferentes. Afinal o que são e como se calculam os quartis? Neste texto abordaremos esta questão, considerando apenas dados discretos não agrupados. Salientamos que no ensino superior se ensinam formas de cálculo dos quartis distintas das apresentadas nos ensinos básico e secundário, o que confunde os alunos e gera neles uma certa desconfiança relativamente à estatística. Argumentamos que o método introduzido no ensino superior é preferível e apresentamos uma proposta de uniformização do cálculo dos quartis em todos os níveis de ensino.
- Análise custo-benefício ex-ante dos investimentos em Scuts: o caso da Scut da Beira InteriorPublication . Pereira, Alfredo; Pereira, Rui; Andraz, Jorge MiguelA análise custo-benefício ex-ante do projecto de investimento na SCUT da Beira Interior aponta no sentido de este projecto demonstrar um valor financeiro e microeconómico muito positivo. Partindo da comparação de resultados entre cenários com e sem a existência da SCUT mostra-se que a além de ser financeiramente viável para o concessionário, a existência desta SCUT permite ganhos consideráveis em termos de redução dos tempos de viagem, de sinistralidade, e de impactes ambientais comparativamente com as vias alternativas. De acordo com a informação desponível calculamos que a taxa de rentabilidade interna financeira da SCUT para o concessionário é de 14,5%, correspondendo a um valor actual líquido de 456.443 mil euros (a preços de 1998), enquanto a taxa interna de rentabilidade microeconómicos é de 22,40%, correspondendo a um valor actual líquido de 2.109.831 mil euros (a preços de 1998).
- Análise custo-benefício ex-ante dos investimentos em scuts: o caso da scut das Beiras Litoral e AltaPublication . Pereira, Alfredo; Pereira, Rui; Andraz, Jorge MiguelA análise custo-benefício ex-ante do projecto de investimento na SCUT da Beira Litoral e Alta aponta no sentido de este projecto demonstrar um valor financeiro e microeconómico muito positivo. Partindo da comparação de resultados entre cenários com e sem a existência da SCUT mostra-se que a além de ser financeiramente viável para o concessionário, a existência desta SCUT permite ganhos consideráveis em termos de redução dos tempos de viagem, de sinistralidade, e de impactes ambientais comparativamente com as vias alternativas.
- Análise custo-benefício ex-ante dos investimentos em Scuts: o caso da Scut do grande PortoPublication . Pereira, Alfredo; Pereira, Rui; Andraz, Jorge MiguelO presente trabalho tem como objectivo a apresentação do projecto de investimento na SCUT do Grande Porto, uma auto-estrada em regime de portagem sem cobrança aos utilizadores, e a sua avaliação financeira e microeconómica numa base ex-ante.