Near bottom sediment characterization offshore SW San Clemente Island

Normal incidence, 23.5 kHz seafloor acoustic backscatter data and bottom video were measured with the Deep Tow instrument package of the Scripps Institution of Oceanography in 100 meter water depth south of San Clemente Island, CA. The collected data were processed using an echo envelopesediment characterization method, to derive geoacoustic parameters such as particle mean grain size and the strength of the power law characterizing the roughness energy density spectrum of thesediment-water interface. Two regions, sand and silt, were selected based on available ground truth, perceived along-track sediment homogeneity, data quality and tow fish stability. Distinction between sand and fine grain sediments can be accomplished by creation of feature vectors comprised of mean grain size (MΦ) and interface roughness spectral strength (w2). Estimates for mean grain size and roughness spectral strength (MΦ, w2) were (1.5, 0.0095) for sand, and (6.7, 0.0033) for silt, where MΦ is expressed in PHI units, and w2 has units cm4. These results are consistent with local ground truth measurements and illustrate the potential of this sediment characterization method in survey mode

Time dependent seafloor acoustic backscatter (10-100kHz)

A time-dependent model of the acoustic intensity backscattered by the seafloor is described and compared with data from a calibrated, vertically oriented, echo-sounder operating at 33 and 93 kHz. The model incorporates the characteristics of the echo-sounder and transmitted pulse, and the water column spreading and absorption losses. Scattering from the water–sediment interface is predicted using Helmholtz–Kirchhoff theory, parametrized by the mean grain size, the coherent reflection coefficient, and the strength and exponent of a power-law roughness spectrum. The composite roughness approach of Jackson et al. [J. Acoust. Soc. Am. 79, 1410–1422 (1986)], modified for the finite duration of the transmitted signal, is used to predict backscatter from subbottom inhomogeneities. It depends on the sediment’s volume scattering and attenuation coefficients, as well as the interface characteristics governing sound transmission into the sediment. Estimation of model parameters (mean grain size, roughness spectrum strength and exponent, volume scattering coefficient) reveals ambiguous ranges for the two spectral components. Analyses of model outputs and of physical measurements reported in the literature yield practical constraints on roughness spectrum parameter settings appropriate for echo-envelope-based sediment classification procedures

Remote sensing of sediment characteristics by optimized echo-envelope matching

A sediment geoacoustic parameter estimation technique is described which compares bottom returns, measured by a calibrated monostatic sonar oriented within 15° of vertical and having a 10°–21° beamwidth, with an echo envelope model based on high-frequency (10–100 kHz) incoherent backscattertheory and sediment properties such as: mean grain size, strength, and exponent of the power law characterizing the interface roughness energy density spectrum, and volume scattering coefficient. An average echo envelope matching procedure iterates on the reflection coefficient to match the peak echo amplitude and separate coarse from fine-grain sediments, followed by a global optimization using a combination of simulated annealing and downhill simplex searches over mean grain size, interface roughness spectral strength, and sediment volume scattering coefficient. Error analyses using Monte Carlo simulations validate this optimization procedure. Moderate frequencies (33 kHz) and orientations normal with the interface are best suited for this application. Distinction between sands and fine-grain sediments is demonstrated based on acoustic estimation of mean grain size alone. The creation of feature vectors from estimates of mean grain size and interface roughness spectral strength shows promise for intraclass separation of silt and clay. The correlation between estimated parameters is consistent with what is observed in situ

Presentation of Nostra Aetate Award to Rabbi Irving (Yitz) Greenberg

Barry Sternlicht is chairman and CEO of Starwood Hotels and Resorts

Declaration of Independence: Mary Colum as Autobiographer

I N 1947, ten years before her death at the age of 7I, Mary Catherine Gunning Maguire Colum-Molly to her friends and her husband, the poet-dramatist Padraic Colum-published one ofthe most forthright and powerful protofeminist autobiographies ofthe twentieth century: Life and the Dream, a book that should not be as neglected as it is. What was or is the dream? It was a dream ofmany episodes: the hope ofa free, prosperous, peaceful, united Ireland; the fulfillment ofthe Irish Literary Revival which she so brilliantly chronicles as a participant-witness in the autobiography, and before in her masterwork of literary criticism: From These Roots: Ideas That Made Modern Literature (1937); and perhaps most of all a dream of equality for women in the male-dominated world of AngloIrish- American letters; for Colum never forgot that the Irish writer she admired most, really worshipped, her friend Yeats, had advised her not to follow a career in creative writing, her first love, but to pursue criticism, because women were better at that and a woman could never hope to succeed as a writer of fiction and verse

Summation 1991

1991 Yearbook, Fordham University School of Lawhttps://ir.lawnet.fordham.edu/yearbook/1005/thumbnail.jp