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Formal Reports

Report of results of completed projects or major milestones either in scientific terms or in terms acceptable to a wider audience. Note: Unless linked to the full text, reports are only available to NATO member nations from designated distribution centres. 


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Retrieving ray convergence in a flux-like formulation Retrieving ray convergence in a flux-like formulation

Date added: 10/01/2012
Date modified: 10/26/2012
Filesize: Unknown

Retrieving ray convergence in a flux-like formulation. Harrison, Christopher H. CMRE-FR-2012-006. October 2012.

The energy flux formulation of propagation is closely related to the incoherent mode sum, and its simplicity has led to development of efficient computational algorithms for reverberation and target echo strength, but it lacks the effects of convergence or modal interference. By starting with the coherent mode sum and rejecting the most rapid interference but retaining beats on a scale of a ray cycle distance it is shown that convergence can be included in a hybrid formulation. Furthermore only minimal extra computation is required. Three solutions are offered by evaluating the cross terms in the modal intensity using Taylor expansions. In the most efficient approach the double summation of the cross terms is reduced to a single numerical sum by solving the other one analytically. The other two solutions are a local range average and a local depth average. Examples are given for three environments: a shallow refracting duct, a uniform gradient upward refracting duct, and the deep water Munk profile. Favourable comparisons are made between these three solutions and also the wave model Orca with, and without, spatial averaging. As a by-product it is shown that the running range average is very close to the mode solution with fringes extracted, given a relation between averaging window size and effective number of modes which, in turn, is related to the waveguide invariant.

Numerical modelling of wave-current interactions in the Sea of Marmara. Numerical modelling of wave-current interactions in the Sea of Marmara.

Date added: 10/01/2010
Date modified: 08/10/2012
Filesize: Unknown

Numerical modelling of wave-current interactions in the Sea of Marmara. Chiggiato, J.; Rixen, M.; Besiktepe, S. NURC-FR-2010-015. October 2010

The synchronous 2-way coupled modelling system ROMS/SWAN has been configured in a realistic application in order to test wave-current interaction parameterizations for use in ocean modelling. Inclusion of these interactions is expected to improve model performance and representation of the dynamics of the upper ocean. The case study discussed here is an indirect assessment of the impact of these parameterizations in model simulations using available observations. The TSS09 trial provided the opportunity to test this modelling system thanks to the concurrent measurement of wind field, wave field and upper circulation as seen by surface lagrangian drifters. All these data have been used for model validation. The numerical exercise focuses on a selected windstorm during TSS09. Model results from the control run (i.e., no wave current interactions) show a fairly good agreement with known Marmara Sea hydrography and available observations. The inclusion of wave-current interactions physics weakly impacts on model results, without showing overall improvements, even if model results do show sensitivity to the inclusion of such parameterizations. The Marmara Sea is a very challenging natural laboratory, because of its limited size, the need for very high meteorological forcing and the impact of the outflow of the straits in the general hydrodynamics. This makes very difficulty to assess wave-current interactions physics implemented in the models because of the major impact of uncertainties associated to other driving mechanisms in the area.

Countermeasure effectiveness: how much protection is enough?. Countermeasure effectiveness: how much protection is enough?.

Date added: 11/01/2010
Date modified: 08/10/2012
Filesize: Unknown

Countermeasure effectiveness: how much protection is enough?. Kessel, R.T. NURC-FR-2010-016. November 2010

Among the foremost system requirements for protective countermeasures is their overall effectiveness. In practice, effectiveness is limited by socioeconomic and technical feasibility, forcing security providers to settle for admittedly imperfect countermeasures. The question, then, is how much countermeasure effectiveness is enough? The answer would constitute a minimum requirement for countermeasures to achieve. It is addressed from two vantage points: 1) risk analysis methodologies and 2) the attacker's perspective, with emphasis on the latter owing to the insight it provides. It is shown with examples (9/11, WMD, suicide attack, Mumbai) how the rational pursuit of objectives by the attacker imposes an upper bound on the risk that the mastermind behind an attack is willing to tolerate, which in turn constitutes a lower bound on the effectiveness of countermeasures when deterrence is taken into account. It is shown how low- to moderate-performance countermeasures can be effective owing to deterrence, and how the perspective adopted toward a countermeasure -whether from a defender's risk analysis, the attacker's expectation of success, or the audience at a security demonstration- changes the countermeasure effectiveness requirements. The prospect of 'over deterrence' is also considered. Practical implications are drawn throughout.

The multi-sensor PHD in a multi-target environment: optimality and applications The multi-sensor PHD in a multi-target environment: optimality and applications

Date added: 06/01/2012
Date modified: 09/06/2012
Filesize: Unknown

The Multi-sensor PHD in a multi-target environment: optimality and applications. Braca, Paolo ; Marano, Stefano ; Matta, Vincenzo ; Willett, Peter. NURC-FR-2012-003. June 2012

Optimal and efficient multi-sensor multi-target tracking in the presence of an unknown number of targets can be still considered an open problem, despite the existence of many working solutions introduced in the recent years [1, 2]. In the present work, authors prove a theorem which states that the multi-sensor probability hypothesis density (MS-PHD) is asymptotically optimal [3]. Computer experiments corroborate the theoretical analysis, and real-world applications (e.g. MSA, ASW) are also presented.

Non-Lethal Response Technologies for Port Protection: 2009 Survey Report and Options Non-Lethal Response Technologies for Port Protection: 2009 Survey Report and Options

Date added: 02/01/2010
Date modified: 06/21/2012
Filesize: Unknown

Non-Lethal Response Technologies for Port Protection: 2009 Survey Report and Options. Kessel, R. NURC-FR-2010-006. February 2010.

In defensive security measures during operations other than war, low levels of force may be required to meet obligations to warn, prove hostile intent, and use proportional force. Non-lethal response technologies are therefore being considered for use in port protection, especially for the enforcement of security exclusion zones above and under the water in the vicinity of protected assets, to counter underwater intruders and small boats. Concepts for non-lethal capabilities and technology readiness assessment are given here, followed by a review of selected response technologies for port protection, including an underwater air gun and sparker, marine mammals, above and underwater loud hailing devices, dazzlers, boat entanglement barriers, and projected energy. The intent was familiarization with new technologies that could be operational within 3 to 5 years, and identification of gaps where further research is required to advance them toward fielded capability. The review and context given here should be of interest to security providers, technology developers, system integrators, and researchers.

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