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A “triaxial velocity sensor” consists of three uniaxial velocity sensors, which are nominally identical, orthogonally oriented among themselves, and co-centered at one point in space. A triaxial velocity sensor measures the acoustic particle velocity vector, by its three Cartesian components, individually component-by-component, thereby offering azimuth-elevation two-dimensional spatial directivity, despite the physical compactness that comes with the collocation of its three components. This sensing system’s azimuth-elevation beam-pattern has been much analyzed in the open literature, but only for an idealized case of the three uniaxial velocity sensors being exactly identical in gain. If this nominal identity is violated among the three uniaxial velocity sensors, as may occur in practical hardware, what would happen to the corresponding “spatial matched filter” beam-pattern’s peak direction? How would this effective peak direction deviate from the nominal “look direction”? This paper, by modeling each uniaxial velocity sensor’s gain as stochastic, derives this deviation’s statistical mean and variance, analytically in closed mathematical forms. This analytical derivation is verified by Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

This paper proposes a new radar/sonar processing architecture that enables a low-rate time-sampling rate while still producing a high-resolution range profile over a narrow range-window. This new architecture generalizes the conventional ?stretch processing? architecture (which employs linear frequency modulated (LFM) waveforms that suffer from high range-sidelobes), to nonlinear frequency modulated (NLFM) waveforms, which can lower the range-sidelobes without tapering. Computational results demonstrate both the estimation efficacy and the time-sampling efficiency of the proposed scheme. [ABSTRACT FROM PUBLISHER]

Channel capacity, system versatility and ease of maintenance are factors of prime concern in future generations of wire- less communication systems. As a result, millimeter-wave can offer considerable advantages in providing broadband interface. Nonlinearity and noise effects, including parametric fluctuations, are two significant causes for signal degradation in broadband communication systems. Two methods to assess the performance of an RF channel in a multi-carrier system are described. By measuring the forward transfer function from transmitter IF to receiver IF as the frequency is swept across the channel bandwidth, characteristics such as gain flatness, channel dispersion, and saturation effects are revealed. To evaluate the ability of the communication link in preserving the synchronization between two carriers, their heterodyned spectrum at the receiver IF output is studied. Both measurement methods employ standard equipment and have been found to be effective when applied to a multi-carrier millimeter-wave system with over 1 GHz instantaneous band- width. [ABSTRACT FROM AUTHOR]

New quasi-Bayesian (hybrid) Cramér-Rao bound (CRB) expressions are herein derived for far-field deep-sea direction-of-arrival (DOA) estimation with a nominally linear towed-array that 1) is deformed by spatio-temporally correlated oceanic currents, which have been previously overlooked in the towed-array shape-deformation statistical analysis literature, 2) is deformed by temporally correlated motion of the towing vessel, which is modeled only as temporally uncorrelated in prior literature, and 3) suffers gain-uncertainties and phase-uncertainties in its constituent hydrophones. This paper attempts to bridge an existing literature gap in deformed towed-array DOA-estimation performance analysis, by simultaneously a) incorporating several essential fluid-mechanics considerations to produce a shape-deformation statistical model physically more realistic than those previously used for DOA performance analysis and b) rigorously derive a mathematical analysis to characterize quantitatively and qualitatively the DOA stimation's statistical performance. The derived CRB expressions are parameterized in terms of the towed-array's physically measurable nonidealities for the single-source case. The new hybrid-CRB expressions herein derived are numerically more stable than those in the current literature. [ABSTRACT FROM AUTHOR]

We study a model of two polymers confined to a slit with sticky walls. More precisely, we find and analyse the exact solution of two directed friendly walks in such a geometry on the square lattice. We compare the infinite slit limit, in which the length of the polymer (thermodynamic limit) is taken to infinity before the width of the slit is considered to become large, to the opposite situation where the order of the limits are swapped, known as the half-plane limit when one polymer is modelled. In contrast with the single polymer system we find that the half-plane and infinite slit limits coincide. We understand this result in part due to the tethering of polymers on both walls of the slit. We also analyse the entropic force exerted by the polymers on the walls of the slit. Again the results differ significantly from single polymer models. In a single polymer system both attractive and repulsive regimes were seen, whereas in our two walk model only repulsive forces are observed. We do, however, see that the range of the repulsive force is dependent on the parameter values. This variation can be explained by the adsorption of the walks on opposite walls of the slit. [ABSTRACT FROM AUTHOR]

Kainam Thomas Wong, co-author of the Letter 'Spatial correlation-coefficient across a receiving sensor-array - accounting for propagation loss' on page 1351, offers his insights into his latest work. [ABSTRACT FROM AUTHOR]