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Fourier transform methods are the standard way for determining time-domain pulse structure and arrival time from a set of continuous wave (discrete frequency) underwater acoustic model calculations. This technique requires a large number of computer model runs at closely spaced frequencies, often making it computationally expensive. It has the advantages of including the correct attenuation at each frequency component, and of correctly treating continuity requirements at the water/sediment interface. Direct time-domain computer models are not as accurate for ocean bottoms with strong attenuation over a large bandwidth of frequencies. In this work the frequency-domain/Fourier approach is optimized for maximum efficiency at a given level of acceptable imprecision. Techniques are presented to improve the efficiency of the individual frequency component calculations, and to avoid running many of the frequencies. Efficiencies at individual frequencies are gained through intelligent selection of grid parameters in the ocean acoustic model (a parabolic equation model). Further improvements are achieved through intelligent zero padding schemes, and by interpolating envelope functions at the receiver location in order to estimate (and hence avoid running) up to 90% of the calculations required by the Nyquist sampling theorem. The effects of the various approximations are shown in the examples., See also ADM202806. Proceedings of the Oceans 2009 MTS/IEEE Conference held in Biloxi, Mississippi on 26-29 October 2009. Copyright belongs to the Marine Technology Society. The original document contains color images.

Our work addresses the link between internal solitary waves and acoustics. The location of the study is in the Yellow Sea south of the Shandong peninsula. Previously in this region, we have performed internal solitary wave generation and propagation simulations with the Lamb nonhydrostatic model. The model parameters were tuned to SAR data. Here, we consider variations of solitary wave characteristics in parameter space. We introduce scaling parameters for a two-layer analogue configuration. This analogue is applied to predicted numerical solutions with the full nonlinear nonhydrostatic Lamb model in the first of the above-mentioned references. Variations of density difference across the pycnocline, tidal forcing and topographic height arc considered. Characteristics of solitary waves are analyzed as the parameters deviate from a tuned case to data. Changes of solitary wave functional form, amplitude, wavelength, and phase speed are tracked. We consider oceanographic and acoustical parameters that describe the physical ocean-acoustic environment and its associated variability. For certain source, receiver, and acoustical frequency configurations, a redistribution of acoustical energy to higher modes can occur and result in acoustical intensity loss in the presence of solitary wave trains. This will be considered in part B., Published in Nonlinear Analysis, v71 p e1807-e1817, 2009. The original document contains color images. All DTIC reproductions will be in black and white.

Large amplitude ocean solitons can interfere with underwater acoustic signals that pass through the solitons. This can disrupt underwater acoustic communications and produce erroneous measurements in ocean acoustic experiments. Recently a simulation method has been developed that links certain properties of the soliton with properties of the affected acoustic signals. This can be used as a "feedback method" to determine if acoustic signals are likely to be affected in ocean regions where solitons may be present. Results from ocean model and acoustic model simulations are given to illustrate the method., See also ADM002047. Presented at the MTS/IEEE Oceans 2007 Conference held in Vancouver, Canada on 29 Sep -4 Oct 2007. Published in the MTS/IEEE Oceans 2007 Conference Proceedings, Oct 2007. The original document contains color images.

We present new results from a joint ocean-acoustic modeling study of solitary wave generation in the Strait of Messina, their propagation in the Tyrrhenian Sea & subsequent shoaling in the Gulf of Gioia. The nonhydrostatic 3D EULAG model is used for the oceanographic predictions. The simulations are initialized w/ measured temp. & salinity profiles from an October 1995 survey of the Messina region and forced w/ semidiurnal tidal magnitudes predicted by a barotropic tidal model. Parameter sensitivity studies are performed. The predicted solitary wave trains are compared w/ CTD chain measurements. The model results & data are examined through a wavelet analysis. The wavelengths are tracked by the spines (maximum intensity for each wavelength) at various times. From the slope of the variations, phase speeds are derived as a function of wavelength. For the parameters extracted from CTD measurements & existing tidal conditions, phase speed distribution for wavelengths ranging from about 0.6m to 1.6km are obtained. The model predicted phase speed magnitudes range from 0.85m/s to 0.93m/s. The phase speeds derived from data range from 0.77m/s to 0.88m/s. The model predicted phase speed vs. wavelength distribution derived from data. The shoaling of the solitary waves in the Gulf of Gioia is studied. Calculations of the acoustical field are conducted along the solitary wave propagation path, w/ the parabolic (PE) acoustical model., Published in Ocean Modelling, v18 p97-121, 2007. The original document contains color images. All DTIC reproductions will be in black and white.

Since its national debut in 1987, Fresh Air with Terry Gross has been a highly acclaimed and much adored weekday magazine among public radio listeners. Each week, nearly 4.8 million people turn to Peabody Award-winning host Terry Gross for insightful conversations with the leading voices in contemporary arts and issues. The renowned program reaches a global audience, with over 620 public radio stations broadcasting Fresh Air, and 3 million podcast downloads each week. Fresh Air has broken the mold of 'talk show' by weaving together superior journalism and intimate storytelling from modern-day intellectuals, politicians and artists alike. Through probing questions and careful research, Gross's interviews are lauded for revealing a fresh perspective on cultural icons and trends. Her thorough conversations are often complemented by commentary from well-known contributors. Fresh Air is produced at WHYY-FM in Philadelphia and broadcast nationally by NPR., (1.) Writer MICHAEL PATRICK HEARN. He's edited 'The Annotated Wizard of Oz: A Centennial Edition' (W.W. Norton). The book commemorates the 100th anniversary of the publication of L. Frank Baum's classic 'The Wonderful Wizard of Oz.' Back in 1900, the first 10,000 copies printed of Baum's book sold out in two weeks. Baum wrote 14 Oz books in all. (2.) Critic MAUREEN CORRIGAN reviews 'The Complete Letters of Oscar Wilde' edited by Merlin Holland and Rupert Hart-Davis. (Henry Holt) The volume includes over 1500 letters. November 21, 2000 marked the 100th anniversary of Wilde's death.(3.) Columnist STANLEY BING (a pseudonym) satirizes the corporate world in his columns for Fortune and Esquire Magazines. He revels his true identity in this interview. His book 'Lloyd—what Happened: A Novel of Business' followed the aspirations of an executive who was climbing the corporate ladder. BING's newest book is 'What Would Machiavelli Do? The Ends Justify the Means' (Harperbusiness) a satirical how-to book for the Machiavellian-minded in the corporate world. (4.) Rock critic KEN TUCKER reviews the debut C-D from singer-songwriter Nelly Furtado, called 'Whoa, Nelly.'

Low-frequency ocean acoustic propagation can be affected by backscatter from rough ocean bottoms and by compressional-shear wave conversions within the ocean bottom. Numerical simulations have been performed that include the effects of such backscattering and loss mechanisms. A full-wave range- dependent finite-element ocean seismo-acoustic computer model (SAFE) was used together with a simulated rough ocean bottom structure that supported compressional and shear wave speeds as well as compressional and shear wave attenuations. Step-periodic changes in depth and range along the water-bottom interface were used to simulate ocean-bottom roughness. A numerical example was used to illustrate the combined effects of ocean-bottom shear and roughness, and to give insight into these complicated processes.... Acoustic waves, Elastic waves, Seismic waves., Pub. in Math Modelling and Scientific Computing, v2 p780-785 1993.

Wave propagation through randomness models much ocean acoustic behavior. Random sound speed introduces non-linearity in the differential equations for the ensemble averages. This leads to results which can be significantly different than if an averaged volume parameters, such as sound speed, are used in a deterministic equation. We examine some theoretical aspects of randomness in the normal mode and parabolic equations. As an example, transmission losses in several specific examples are computed where differences result., Pub. in Mathematical Modelling and Scientific Computing in Science and Technology, v2 p798-803, 1993. Pres. at the International Conference on Mathematical Modelling and Scientific Computing in Science and Technology (8th) held in College Park, MD in April 1991.

Perhaps the most important and encouraging results of this PE workshop were that underwater acoustic parabolic equation (PE) models from both the 6.1 basic research modeling community and the 6.3 Navy operational modeling community were applied to the same set of test problems--each test problem designed to push the PE models to their limits--and each of the two communities' PE models did extremely well, given the requirements and constraints imposed by each community. The PE models developed by the 6.1 basic research modeling community were able to produce results for the test case problems that were benchmark accurate. This is a definite requirement, since the basic research community uses these models to identify, to isolate, and to understand the physical mechanisms involved in underwater acoustic propagation and scattering in highly complex underwater environments. The 6.3 Navy operational community is also interested in accurate model predictions, but the need for computational speed, portability, and the ability to run a computer in the field (micro or desk-top) is also of utmost importance-to the extent that trade-offs among accuracy, speed, and portability must be optimized. The results from this workshop demonstrate that the under water acoustic PE models used by both modeling communities are performing at their expected levels. Underwater acoustics, Ocean wave characteristics, Environmental technology