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SUMMARY This paper presents implementation techniques for the coupled wavenumber integration approach that is occasionally used in the underwater acoustics community to address larger scale problems in seismo-acoustics. This numerically efficient method is suitable for detailed wavefield representation of the long, thin waveguide propagating geometries such as those within subducting plate. It therefore represents an attractive alternative to ray-based solutions and finite element methods when thin layers with strong velocity contrast are expected. This wavefield modelling technique is based upon range-dependent wavenumber integration combined with Kirchhoff approximation. Examples of the details of the propagating wavefield with a dipping slab-like structure and the effects of low-velocity layers (LVLs) are presented. These results include the propagation of the wavefield through the wedge and through very LVLs as a function of setups of different complexity as well as a function of horizontal range. By identifying the existence of a sediment-like layer, the presence of a source within and the effects of the changes in the receiver range location, we demonstrate the ability of the coupled wavenumber technique to capture the physics associated with LVLs configuration, and provide classification features for effective identification of these, often intricate, subducted slab structure characteristic.

The design of the actuating mechanism of a biologically inspired flapping wing UAV is addressed. Several configurations able to reproduce the desired flapping-wing kinematics are analyzed and an optimization study is conducted to select the best configuration. The optimization results are used as the starting point for the design of the different structural components of the flapping mechanism. During the mechanism design stage, the linkages are optimized to match the desired wing’s motion during a flapping cycle. A structural and durability analysis is then conducted to verify that the mechanism and its components are able to withstand the aerodynamic and inertial loads.

One of the current Integrated Marine Mammal Monitoring and Protection System (IMPAS) directions is concentrated on the design and development of the active sonar modality representing just one component of the global system. The active sonar was designed, built, and tested during the Marine Mammal Active Sonar Test (MAST 04), producing whale detections and whale tracks. The experiment was conducted in January 2004 off the coast of California. One of the objectives of the current work is to distinguish whale backscattered responses from the ones generated by the environmental clutter in a waveguide. Furthermore, the work aims to identify and analyze the target signature features that are necessary for enhanced active sonar detection and classification of marine mammals. Over the years there have been very few documented attempts to capture and analyze the backscattering response of whales using an active sonar system. Nevertheless, whales, mostly owing to their size, their motion, and the aspect dependence of their backscattered field, possess desirable properties that help distinguish their scattered response from clutter and other environment related false alarms. As an initial step, data collected during the MAST 04 experiment are presented, and gray whale target strength measurements are obtained. Results are compared to the previously published whale target strengths. Additionally, an investigation is conducted in an effort to provide whale feature identification points suitable for automated detection and classification, as means of relating gray whale active acoustic signatures to their inherent characteristics and their motion.

Life consumption evaluation presently represents a high priority topic for Industry and University. In the specific work of this paper, we performed an analysis about the effects of thermal transients on life consumption of steam turbine rotors and an optimization of the thermal transient during runups. This kind of operation, more and more recurrent in power generation, produces a stress in the mechanical elements that could compromise their integrity. The work was developed in its larger part in the MGMV laboratory of the University of Genova, using the equipment (hardware and software) present in this structure, in cooperation with industry. The study moves from a classification of the damage mechanism and from a description of the most important manufacturing technologies of turbine rotors. Then, after a glance at the most important commercial software for estimating life consumption, a classification is given referring to the checks that Ansaldo, the industrial collaborator, performs during its service interventions. Finally, the paper reports the calculation module developed according to the specifications given by the industrial collaborator; the software was developed in Matlab and needs as input the characteristic constants of the rotor and the temperature measurements (with high precision transducers) at the inlet of the HP and IP sections of the turbine. This study confirms that thermal transients are very important to define the rotor’s residual life; the results could help the manufacturer, who designed the machines, and the operators, who run the power plant, to ensure a correct use of the installation, without unexpected failures that could create an economical damage connected with a missed production.

For active sonar systems, transmission Loss (TL) and reverberation level (RL) are key parameters derived from the acoustic fields predicted by models and used to assess sonar performance. The existing propagation and scattering models may be appropriate for applications in the deep ocean or open littorals, but sonar operators are increasingly being asked to perform tasks including navigation or detection in significantly more confined waterways such as rivers or ports. Physics-based models are generally not available for predicting the acoustic field in such highly geometrically constrained and dynamic 3D environments often characterized by highly variable azimuthal boundaries such as irregularly shaped port geometries, piers, and breakwaters that may also have high large tidally driven depth variations over short time periods. They also may be populated with large scattering objects such as deep draft vessels and mooring dolphins. A virtual source research model capable of predicting the three-dimensiona...