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Oceanic Engineering, IEEE Journal of

Issue 3 • Date Jul 1989

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Displaying Results 1 - 8 of 8
  • Radar backscattering from artificially grown sea ice

    Publication Year: 1989 , Page(s): 259 - 264
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    Fine-resolution X-band backscatter measurements were made at the US Army Cold Region Research and Engineering Laboratory in Jan. 1987. Backscatter data were collected from unmodified smooth ice and snow-covered ice and from ice from which the snow had been removed (slightly roughened ice). The results indicate that vertically polarized returns were consistently higher than horizontally polarized echoes from both the slightly roughened and snow-covered saline ice. A 6.5-cm-thick dry snow layer altered the σo of the original smooth-surfaced saline ice only slightly, but introduced a noticeable volume scattering component. It is shown that although substantial agreement exists between the bare first-year ice measurements and commonly used surface-scatter model predictions, a complete model of first-year ice must include a volume-scatter contribution View full abstract»

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  • Comments on `Theory and application of calibration techniques for an NDBC directional wave measurements buoy' by K.E. Steele, et al.: nonlinear effects

    Publication Year: 1989 , Page(s): 268 - 272
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    For original paper see ibid., vol. OE-10, no.4, p.382-96 (1985). The authors of the above mentioned paper present an extensive set of linear calibration techniques that are applied to National Data Buoy Center wave-buoy sensor spectral output before calculating and disseminating directional wave spectra. The commentators identify and estimate the nonlinear effects that produce biases still present in the output, due both to wave nonlinearities themselves and to constraints on the buoy and mooring system to the driving forces. Simple models show that these nonlinearities can produce spectral energy biases of 5-15% at and above the spectral peak frequency, and even greater errors below it. NDBC presently records wave data from vertically stabilized and fixed accelerometers and slope sensors. Calculations show that these sensors all incur bias due to wave nonlinearities: this is greater for vertically stabilized accelerometers and least for slope sensors. Effects of the resulting inconsistencies between the different sensors are most pronounced below the spectral peak where the nonlinear terms dominate; these effects are illustrated with measured data View full abstract»

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  • On underwater sound scattering by surface waves

    Publication Year: 1989 , Page(s): 245 - 247
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    An angular-scattering approach is outlines that provides insight into some of the elementary acoustics involved in the perturbation theory. In the past, the comparison of predictions with experiment has been based mainly on propagation-loss measurements in surface ducts. Here the absorption is subtracted from total attenuation and the remainder is ascribed to scatter loss View full abstract»

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  • Observations of the von Karman constant over open-ocean waves

    Publication Year: 1989 , Page(s): 248 - 253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    Forty-six open-ocean observations of the von Karman constant k , estimated from the momentum flux, wind velocity, and air temperature differences observed at the Argus Island tower, yielded an average value of 0.40±0.18 for |Ri|⩽0.014, where Ri is the gradient Richardson number. This average value agrees with the determinations of k over land by U. Hogstrom (1988) and S.F. Zhang et al. (1988). Scatter in these oceanic data sets may be due in part to ocean-wave influence as well as to instrumental and statistical variability View full abstract»

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  • Dependence of microwave sea returns on wind-friction velocity under varied atmospheric stability conditions

    Publication Year: 1989 , Page(s): 254 - 258
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    Microwave sea returns under varied atmospheric conditions and sea states were measured by W.C. Keller et al. (1985). The author has examined quantitative variations of these returns with the wind-friction velocity, incorporating modifications of the atmospheric stability, and has also compared features of sea returns and wind-stress coefficients varying with the stability length. Implications for the inception of fine sea-surface structures by wind and their probable saturation and corrections of stability effects of the wind-stress coefficient are discussed. It is shown that trends based on radar returns at low and high winds can be resolved only with simultaneous measurements of fine sea-surface structures View full abstract»

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  • Sharkbite on the SL submarine lightwave cable system: history, causes and resolution

    Publication Year: 1989 , Page(s): 230 - 237
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (860 KB)  

    The nature of the sharkbite phenomenon is presented. The physical nature of the faults and their location along the OPTICAN-1 route are described. The morphology of the shark teeth recovered, and the identification and nature of the sharks believed responsible are discussed. A hypothesis as to the cause of the attacks, based on the findings of previous shark-sensory research, is detailed. The methods and results of an experimental program aimed at verifying this hypothesis are summarized. The results of development programs aimed at resolving this problem are presented. Two avenues were pursued: the first was the development of a mechanically protected SL deep-water, repeated lightwave trunk cable for use in areas of high sharkbite risk; the second was the development of a methodology to assess the sharkbite risk in different areas of the world's oceans. The resultant algorithm, for use in specifying the amount of protected cable to be deployed in an SL system is detailed View full abstract»

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  • Improved time-delay estimates of underwater acoustic signals using beamforming and prefiltering techniques

    Publication Year: 1989 , Page(s): 238 - 244
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    Passive sonar systems that localize broadband sources of acoustic energy estimate the difference in arrival times (or time delays) of an acoustic wavefront at spatially separated hydrophones, The output amplitudes from a given pair of hydrophones are cross-correlated, and an estimate of the time delay is given by the time lag that maximizes the cross correlation function. Often the time-delay estimates are corrupted by the presence of noise. By replacing each of the omnidirectional hydrophones with an array of hydrophones, and then cross-correlating the beamformed outputs of the arrays, the author shows that the effect of noise on the time-delay estimation process is reduced greatly. Both conventional and adaptive beamforming methods are implemented in the frequency domain and the advantages of array beamforming (prior to cross-correlation) are highlighted using both simulated and real noise-field data. Further improvement in the performance of the broadband cross-correlation processor occurs when various prefiltering algorithms are invoked View full abstract»

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  • The uniqueness of the Practical Salinity Scale (1978): testing the scale with natural seawaters

    Publication Year: 1989 , Page(s): 265 - 267
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The scale provides a precisely defined, unambiguous method that is universally applicable to all waters for determining the practical salinity from measurements of conductivity, temperature, and pressure. In the terminology of standards, it is highly desirable to have a scale that is also unique. The authors questioned whether measurements performed on a particular water sample at different temperatures would lead to the same value of practical salinity. They have investigated this problem by examining the behavior of natural seawaters from several oceans and conclude that the PSS provides a unique scale for salinity measurements for these waters within the bounds ±0.001 in salinity View full abstract»

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Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca