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Tajdari, F. (author), Berkhoff, A.P. (author), de Boer, A. (author)This paper focuses on extensive numerical and experimental investigations of a thin sandwich acoustic source. Due to an energy inefficient actuation design, a thin sandwich acoustic source that was proposed in an early study is redesigned and reconstructed in the current research. The thin acoustic source in the present paper is actuated by long...article 2020
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- Tajdari, F. (author), Berkhoff, A.P. (author), van der Zee, R.A.R. (author), de Boer, A. (author) article 2020
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Tajdari, F. (author), Berkhoff, A.P. (author), de Boer, A. (author)This paper studies an acoustic source with a relatively small thickness and a high bending stiffness. The acoustic source operates in the low frequency, quasi-static regime. The focus of the current study is on the actuation part in order to design an appropriate excitation mechanism. A flexural mechanism is modeled in combination with a...article 2020
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Ochoa, P.A. (author), Groves, R.M. (author), Bernedictus, R. (author)A reliable damage diagnostic by ultrasonic guided wave (GW) based structural health monitoring (SHM) can only be achieved if the physical interactions between wave propagation, the SHM system and environmental factors are fully understood. The purpose of this research was to gain knowledge about the effects of high-amplitude low-frequency...article 2020
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Bosschaart, C. (author)The Royal Netherlands Navy operates a low-frequency active sonar consisting of a combination of a towed sonar source and receiver array in order to detect and classify objects underwater. The operation involves transmitting high power underwater sound towards an object and detecting the echo reflected by the object. Operating a towed source at...conference paper 2019
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Behringer, A. (author), Beerens, S.P. (author), van der Spek, E. (author), Sprik, R. (author)Wideband low frequency transducers are crucial enablers for building underwater communication networks. The use of low frequencies promises long range communication ranges, but most low-frequency transducers are large, lack directionality and have limited bandwidth. The aim of this study is to tackle these limitations. We take a novel approach...conference paper 2019
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van der Eerden, F.J.M. (author), Wessels, P.W. (author), Basten, T.G.H. (author), Botteldooren, D. (author), van Rentherghem, T. (author), de Coensel, B. (author)A long-term monitoring project, with 12 months of continuous operation time, is described where the sound sources within a large industrial area as well as the sound levels in the nearby residential area are measured. The sources in the industrial area may give rise to complaints from the neighboring residential areas, at several kilometers...conference paper 2017
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Heaney, K.D. (author), Prior, M. (author), Campbell, R.L. (author)The ocean is nearly transparent to low frequency sound permitting the observation of distant events such as earthquakes or explosions at fully basin scales. For very low frequency the ocean acts as a shallow-water waveguide and lateral variability in bathymetry can lead to out-of-plane effects. In this paper, data from the International...article 2017
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Wang, Y. (author), Kostić, D. (author), Jansen, S.T.H. (author), Nijmeijer, H. (author)The use of redundant sensors brings a rich diversity of information, nevertheless fusing different sensors that run at vastly different frequencies into a proper estimate is still a challenging sensor fusion problem. Instead of using the size-varying measurements and thereby the size-varying filters during each sampling period, we propose to...conference paper 2014
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Koeman, T. (author), van den Brandt, P.A. (author), Slottje, P. (author), Schouten, L.J. (author), Goldbohm, R.A. (author), Kromhout, H. (author), Vermeulen, R. (author)Purpose: To investigate the association between exposure to occupational extremely low-frequency magnetic fields (ELF-MF) and the risk of a priori selected cancer outcomes within the prospective Netherlands Cohort Study. Methods: 120,852 men and women aged 55-69 years at time of enrollment in 1986 were followed up (17.3 years) for incident lung,...article 2014
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Koeman, T. (author), Offermans, N.S.M. (author), Christopher-De Vries, Y. (author), Slottje, P. (author), van den Brandt, P.A. (author), Goldbohm, R.A. (author), Kromhout, H. (author), Vermeulen, R. (author)Background: In epidemiological studies, occupational exposure estimates are often assigned through linkage of job histories to job-exposure matrices (JEMs). However, available JEMs may have a coding system incompatible with the coding system used to code the job histories, necessitating a translation of the originally assigned job codes. Since...article 2013
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Hunter, A.J. (author), van Vossen, R. (author), Quesson, B.A.J. (author), Beckers, A.L.D. (author)The remediation of underwater unexploded ordnance (UXO) requires a capability to detect and classify objects on or beneath the seafloor. This can be facilitated partly by use of modern high-frequency imaging sonar. However, this technology is limited in two respects: 1) the high frequencies employed by these systems cannot penetrate into the...conference paper 2013
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Cristol, X. (author), Jespers, S. (author), Chalindar, B. (author), Juhel, B. (author), Dybedal, J. (author), Eidem, E.J. (author), Ivansson, S. (author), van Vossen, R. (author), Ainslie, M.A. (author), Andersson, B.L. (author), Colin, M.E.G.D. (author), Pihl, J. (author)The European Defence Agency project RUMBLE-2 (ref.[1]) offered the opportunity for investigating experimentally acoustic reverberation at about 1.kHz, under grazing incidence (less than about 20°), from very porous clayey seafloors of a continental shelf (mean grain size spanning from about 7 to 10 in units); the instrument was an operational,...conference paper 2012
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Abrahamsson, L. (author), Andersson, B.L. (author), Ivansson, S. (author), Pihl, J. (author), Chalindar, B. (author), Cristol, J.X. (author), Juhel, B. (author), Eidem, E.J. (author), Dybedal, J. (author), Olsen, G.K. (author), Ainslie, M.A. (author), Benders, F.P.A. (author), Colin, M.E.G.D. (author), van Vossen, R. (author)An operational low-frequency active sonar system has been used in the EDA (European Defence Agency) project Rumble-2 to collect reverberation data at sea trials in the North Sea. Using a fast ray model for the forward computations, the reverberation data are inverted to determine bottom parameters: Lambert back-scattering parameter μ and sound...conference paper 2012
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van Vossen, R. (author), Quesson, B.A.J. (author), Beckers, A.L.D. (author), Zampolli, M. (author), Colin, M.E.G.D. (author), Hunter, A.J. (author)Naval mines, underwater improvised explosive devices (UW-IEDs), and underwater unexploded ordnance (UW-UXO) are concerns for harbour security. In conditions without burial, existing commercial systems, such as the REMUS unmanned underwater vehicle equipped with a (very) high frequency side scan sonar (900/1800 kHz), may be deployed for detection...conference paper 2012
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Beerens, S.P. (author), Benders, F.P.A. (author)Several navies are operating or procuring low-frequency active sonar systems (LFAS) as the primary part of their ASW capability. Since LFAS is a relatively new sensor with a performance strongly depending on environmental conditions, the proper operational sensor settings, such as depth and pulse type, that provide optimum performance are not...conference paper 2012
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Beckers, A.L.D. (author), van Vossen, R. (author), Vlaming, G. (author)Naval mines and underwater improvised explosive devices in harbors can halt or block maritime transport, causing local disruptions that can impact national and regional economies considerably. Securing harbors against such threats is implemented in the Netherlands through cooperation between civil and military authorities. Existing commercial...article 2012
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Jespers, S. (author), Juhel, B. (author), Chalindar, B. (author), Cristol, X. (author), Dybedal, J. (author), Eidem, E.J. (author), Ivansson, S. (author), van Vossen, R. (author), Ainslie, M.A. (author), Andersson, B.L. (author), Benders, F.P.A. (author), Colin, M.E.G.D. (author), Olsen, G.K. (author), Pihl, J. (author)The safety of the deployment of naval forces requires a correct estimation of sonar performances. The quality of these performances strongly depends on the knowledge of the environmental data, especially in shallow water environments where the acoustic field is particularly influenced by the interaction with the seabed sediment whose acoustic...conference paper 2012
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Hunter, A.J. (author), van Vossen, R. (author), Quesson, B.A.J. (author), Colin, M.E.G.D. (author), Zampolli, M. (author), Beckers, A.L.D. (author)Sidescan high-frequency (HF) sonar (i.e., with frequencies higher than 100 kHz) is ideally suited for providing high-resolution images of the seafloor. However, since sound does not penetrate into the sediment at these frequencies, such systems cannot be used for the detection of buried objects, such as naval mines, improvised explosive devices ...conference paper 2012
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van Vossen, R. (author), Colin, M. (author), Benders, F. (author), Ainslie, M.A. (author), Eidem, E.J. (author), Chalindar, B. (author), Juhel, B. (author), Dybedal, J. (author), Olsen, G.K. (author), Ivansson, S. (author), Abrahamsson, L. (author)Accurate environmental information is required for obtaining reliable predictions for the performance of low-frequency active sonar (LFAS) systems. This environmental information is, however, often unreliable or unavailable. For example, the acoustic seabed parameters relevant for the scattering and reflection of sound at the seabed are commonly...conference paper 2011