Economic Benefits of American Lobster Fishery Management Regulations

A simulation model is used to compare measures for future management identified in the American lobster fishery management plan; specifically, increases in the minimum legal size and a modest reduction in aggregate fishing mortality are evaluated. The analysis differs from previous work in that the distributional aspects of the alternative management regulations are quantified. The results indicate that (1) both an increased minimum size and a reduction in fishing mortality are economically justified in the sense that net benefits are positive; (2) increasing the minimum size without an adjunct regulation to prohibit entry will cause present fishermen to suffer an initial short-term reduction in revenues for which there will be no long-term gain; (3) because increased minimum size can be justified on the basis of consumer benefits alone, arguments favoring its increase to prevent recruitment failure are moot as far as a test of national economic efficiency is concerned; and (4) a program of effort reduction which reduces by 20% the fraction of available lobsters captured annually is projected to generate SI of producer benefits for every pound of lobster landed. Reducing the annual harvest fraction by 20% results in a level of fishery benefits greater than increasing the minimum size to 89 mm (3^-in.), and increases the coincidence of short-run costs and long-term benefits among those impacted by fishery management.Environmental Economics and Policy, Resource /Energy Economics and Policy,

Direct and Inverse Problems Pertaining to the Scattering of Elastic Waves in the Rayleigh (Long Wavelength) Regime

It is well known that in the scattering of elastic waves from localized inhomogeneities the scattering amplitude2A is proportional to the square of the frequency win the Rayleigh {long wavelength) regime, i.e., A= A2w + ... This talk deals with the problem of (1) extracting A2 from experimental scattering data, (2) calculating A2 for an assumed scatterer and (3) deducing the properties of the scatterer from a set of values of A2 measured for various transducer configurations. A review of experimental and theoretical results for A2 will be presented for the case.of spheroidal voids and the remaining discrepancies between the two kinds of results will be discussed. The inverse problem (i.e., deducing the scatterer properties from the scattering measurements) will be discussed in detail. The probabilistic inverse problem, which provides the appropriate framework for the interpretation of real data, will be covered at greater length. In the case in which it is assumed that the scatterer is an ellipsoid void, \those size, shape and orientation are unknown a priori, a number of computational results involving best estimates and associated measures of significance will be given. Analogous results will be derived for parameters related to fracture mechanics

Deterministic and Probabilistic Inversion at Long Wavelengths

In contrast with the scalar wave case, the scattering of elastic waves in the long wavelength limit yields data containing a surprising amount of information concerning the nature of the scatterer. We will consider both deterministic and probabilistic versions of the inversion problem pertaining to the above scattering problem. The deterministic version provides theoretical insight into the blindspots of an optimal inversion procedure in the hypothetical limit of zero measurement error. The probabilistic version is appropriate for the interpretation of real data containing errors and possible inconsistencies. In the former category our-discussion will start with a review of earlier results obtained by Kohn and Rice, Gubernatis, and the author. Some new results dealing with ellipsoidal inclusions will be discussed

Exact Solution of Probabilistic Inverse Problem Pertaining to the Scattering of Elastic Waves from General Inhomogeneities

Probabilistic inversion methodology (e.g., finding the most probable inhomogeneity given the measurements) has been applied to many inverse scattering problems with either Gaussian or non-Gaussian statistical models of possible scatterers. All of our past investigations have dealt either with weak inhomogeneities, for which the Born approximation is valid, or with highly reflective scatterers, for which the Kirchhoff approximation is presumed to be adequate. In this paper we consider an approach to the general probabilistic inversion problem involving strong inhomogeneities by the application of the Pontryagin maximum principle generalized to 3D space. The key feature of the present approach to inverse scattering is the treatment of the wave equation, relating each scattered field to each incident field and the state of the inhomogeneity, as a continuous set of side conditions. This set of side conditions is handled by the Lagrange multiplier method, Our procedure, in analogy with that of Pontryagin, is to first determine the most probable state of the inhomogeneity given both the scattered wave fields and the conjugate Lagrange multiplier fields. The final stationarization with respect to both fields yields finally a set of nonlinear coupled integral equations defined on the localization domain

A Design For Maintaining Maritime Superiority

The United States Navy will be ready to conduct prompt and sustained combat incident to operations at sea. Our Navy will protect America from attack and preserve America’s strategic influence in key regions of the world

A code-division, multiple beam sonar imaging system

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1989In this thesis, a new active sonar imaging concept is explored using the principle of code-division and the simultaneous transmission of multiple coded signals. The signals are sixteen symbol, four-bit, non-linear, block Frequency-Shift Keyed (FSK) codes, each of which is projected into a different direction. Upon reception of the reflected waveform, each signal is separately detected and the results are inverted to yield an estimation of the spatial location of an object in three dimensions. The code-division sonar is particularly effective operating in situations where the phase of the transmitted signal is perturbed by the propagation media and the target Most imaging techniques presently used rely on preservation of the phase of the received signal over the dimension of the receiving array. In the code-division sonar, spatial resolution is obtained by using the combined effects of code-to-code rejection and the a-priori knowledge of which direction each code was transmitted. The coded signals are shown to be highly tolerable of phase distortion over the duration of the transmission. The result is a high-resolution, three-dimensional image, obtainable in a highly perturbative environment Additionally, the code-division sonar is capable of a high frame rate due to the simplicity of the processing required. Two algorithms are presented which estimate the spatial coordinates of an object in the ensonified aperture of the system, and the performance of the two is compared for different signal to noise levels. Finally, the concept of code-division imaging is employed in a series of experiments in which a code-division sonar was used to image objects under a variety of conditions. The results of the experiments are presented, showing the resolution capabilities of the system

Time Domain Born Approximation

The time domain Born approximation for ultrasonic scattering from volume flaws in an elastic medium is described. Results are given both for the direct and the inverse problem. The time domain picture leads to simple intuitive formulas which we illustrate by means of several simple examples. Particular emphasis is given to the front surface echo and its use in reconstructing the properties of the flaw