Showing papers by "University of Rhode Island published in 1982"
01 Sep 1982
TL;DR: In this paper, the frequency estimation performance of the forward-backward linear prediction (FBLP) method was improved for short data records and low signal-to-noise ratio (SNR) by using information about the rank M of the signal correlation matrix.
Abstract: The frequency-estimation performance of the forward-backward linear prediction (FBLP) method of Nuttall/Uhych and Clayton, is significantly improved for short data records and low signal-to-noise ratio (SNR) by using information about the rank M of the signal correlation matrix. A source for the improvement is an implied replacement of the usual estimated correlation matrix by a least squares approximation matrix having the lower rank M. A second, related cause for the improvement is an increase in the order of the prediction filter beyond conventional limits. Computationally, the recommended signal processing is the same as for the FBLP method, except that the vector of prediction coefficients is formed from a linear combination of the M principal eigenvectors of the estimated correlation matrix. Alternatively, singular value decomposition can be used in the implementation. In one special case, which we call the Kumaresan-Prony (KP) case, the new prediction coefficients can be calculated in a very simple way. Philosophically, the improvement can be considered to result from a preliminary estimation of the explainable, predictable components of the data, rather than attempting to explain all of the observed data by linear prediction.
1,072 citations
TL;DR: In this paper, the estimation procedure presented here makes use of "backward prediction" in addition to singular value decomposition (SVD) for accurate estimation of closely spaced frequencies of sinusoidal signals in noise.
Abstract: We have presented techniques [1] - [6] based on linear prediction (LP) and singular value decomposition (SVD) for accurate estimation of closely spaced frequencies of sinusoidal signals in noise. In this note we extend these techniques to estimate the parameters of exponentially damped sinusoidal signals in noise. The estimation procedure presented here makes use of "backward prediction" in addition to SVD. First, the method is applied to data consisting of one and two exponentially damped sinusoids. The choice of one and two signal components facilitates the comparison of estimation error in pole damping factors and pole frequencies to the appropriate Cramer-Rao (CR) bounds and to traditional methods of linear prediction. Second, our method is applied to an example due to Steiglitz [8] in which the data consists of noisy values of the impulse response samples (composed of many exponentially damped sinusoids) of a linear system having both poles and zeros. The poles of the system are accurately determined by our method and the zeros are obtained subsequently, using Shanks' method.
881 citations
TL;DR: Stages of change interacted with the processes of change in the cessation of smoking behavior, and verbal and behavioral processes were seen as important in making the decision to change while action processes were critical for breaking the actual smoking habit.
791 citations
TL;DR: Oceanic macroaggregates sampled from the Sargasso Sea are associated with bacterial and protozoan populations up to four orders of magnitude greater than those present in samples from the surrounding water.
Abstract: Oceanic macroaggregates (marine snow and Rhizosolenia mats) sampled from the Sargasso Sea are associated with bacterial and protozoan populations up to four orders of magnitude greater than those present in samples from the surrounding water. Filamentous, curved, and spiral bacteria constituted a higher proportion of the bacteria associated with the particles than were found among bacteria in the surrounding water. Protozoan populations were dominated numerically by heterotrophic microflagellates, but ciliates and amoebas were also observed. Macroaggregates are highly enriched heterotrophic microenvironments in the oceans and may be significant for the cycling of particulate organic matter in planktonic food chains.
259 citations
TL;DR: Concentrates of the picoplankton from the euphotic zone of estuarine and oceanic waters were examined by transmission electron microscopy and the most ubiquitous microalga was a scaled, non‐flagellated prasinophyte that is probably the smallest known photo‐trophic eucaryote and has not heretofore been described.
Abstract: Concentrates of the picoplankton (0.2–2.0 μm) sized fraction from the euphotic zone of estuarine and oceanic waters were examined by transmission electron microscopy. In addition to the numerous phototrophic procaryotes (chroococcoid cyanobacteria) previously reported, small phototrophic eucaryotes were observed in 20 of 25 samples examined. Micromonas pusilla (Butcher) Manton and Parks, a 1 × 1.5 μm flagellate, was abundant in estuarine samples in summer. Similar sized cells of non-flagellated chlorophytes, either Nannochloris Naumann or Chlorella Beijerinck, were observed sporadically in many samples. The most ubiquitous microalga was a scaled, non-flagellated prasinophyte that occurred at 9 of 15 different locations on 15 of 20 sampling dates in water samples from Iceland to the Caribbean Sea, This tiny alga (0.5 to 1.0 μm in diam.) is probably the smallest known photo-trophic eucaryote and has not heretofore been described. Enrichment cultures using conventional techniques on several cruises yielded only the Chlorella-type of green alga, as well as numerous isolates of unicellular chroococcoid cyanobacteria.
254 citations
TL;DR: LP estimation of frequencies can be greatly improved at low SNR by singular value decomposition (SVD) of the LP data matrix, as is done in Pisarenko's method and its variants.
Abstract: Linear-prediction-based (LP) methods for fitting multiple-sinusoid signal models to observed data, such as the forward-backward (FBLP) method of Nuttall [5] and Ulrych and Clayton [6], are very ill-conditioned. The locations of estimated spectral peaks can be greatly affected by a small amount of noise because of the appearance of outliers. LP estimation of frequencies can be greatly improved at low SNR by singular value decomposition (SVD) of the LP data matrix. The improved performance at low SNR is also better than that obtained by using the eigenvector corresponding to the minimum eigenvalue of the correlation matrix, as is done in Pisarenko's method and its variants.
238 citations
TL;DR: In this paper, the metal-nutrient relationship observed for nickel and cadmium in the deep ocean is continued at the interface between seawater and oxidizing pore water.
223 citations
TL;DR: In this article, a set of 35 basaltic glass samples dredged from the Mid-Atlantic Ridge between 28° and 53°N latitude were analyzed and the helium concentrations and helium isotopic ratios were determined.
208 citations
01 Jun 1982
TL;DR: A new method is presented for estimating the signal component of a noisy record of data by assuming the approximate value of rank of a matrix which is formed from the samples of the signal is assumed to be known or obtainable from singular value decomposition (SVD).
Abstract: A new method is presented for estimating the signal component of a noisy record of data. Only a little prior information about the signal is assumed. Specifically, the approximate value of rank of a matrix which is formed from the samples of the signal is assumed to be known or obtainable from singular value decomposition (SVD).
204 citations
TL;DR: In this paper, 13 runs were made in a small recirculating flume to simulate the deposition of the climbingripple sequences commonly present in fine-grained facies of fluvial and deltaic deposits.
Abstract: Thirteen runs were made in a small recirculating flume to simulate the deposition of the climbingripple sequences commonly present in fine-grained facies of fluvial and deltaic deposits. These sequences consist of intergradational climbing-ripple cross laminae and draped laminae. The experiments were based on the assumption that stratification type depends mainly on near-bottom flow structure and uniform sediment fallout from an overloaded flow. Various combinations of curves of velocity versus time and of sediment feed versus time in runs lasting from 45 to 840 min were used in an exploratory program; conditions for each run were selected on the basis of experience in previous runs. The runs verified that Type A (erosional-stoss) climbing ripples are produced by aggradation rates that are small relative to ripple migration rate, and Type B (depositional-stoss) climbing ripples are produced by aggradation rates that are large relative to ripple migration rate. Draped lamination results from continued fallout of sediment from suspension after ripple migration ceases or almost ceases. Comparison of geometric details of the ripple stratification produced in the flume runs with that in natural sequences, supplemented by considerations on maximum and minimum migration rates of ripples, suggests times of no more than a few tens of hours for the deposition of the climbing-ripple portions of sequences 10-20 cm thick. Runs in which deposition of a 20 cm sequence took more than 10 h produced such atypical features of ripple geometry as sharp crests, planar lee-side laminae, and angular toeset-foreset contacts.
191 citations
TL;DR: In this article, a theoretical analysis is presented for the spread of a viscous liquid flowing under its own hydrostatic pressure on a horizontal surface in order to model lava dome formation, and two situations are considered in detail: the spreading of a constant volume of liquid and the case where the amount of liquid is continually increased.
TL;DR: In this paper, the ground state properties of the one-dimensional spin-s (12⩽s <∞) anisotropic XYZ antiferromagnet in a magnetic field of arbitrary direction were studied.
Abstract: This is a study of the ground-state properties of the one-dimensional spin-s (12⩽s<∞) anisotropic XYZ antiferromagnet in a magnetic field of arbitrary direction. It provides the first rigorous results for the general case of this model in non-zero field. By exact calculations we find the existence of an ellipsoidal surface h = hN in field space where the ground state is of the classical two-sublattice Neel type with non-zero antiferromagnetic long-range order. At hN there are no correlated quantum fluctuations. We give upper and lower bounds for the critical field hc where antiferromagnetic long-range order is suppressed by the field. The zero-temperature phase diagrams are discussed for a few representative cases.
TL;DR: Histological examination of the retinas revealed that the distance between cones decreased as the animals grew, suggesting that the larger retinas could resolve smaller objects, and correlated behavioral and anatomical results suggest that improved visual resolution contributes to improved predation.
Abstract: Planktivorous sunfish of various sizes were studied to ascertain whether growth-related changes in the retina are related to the ability to capture small planktonic crustaceans. Behaviorally, the larger fish detected and captured crustaceans that subtended smaller visual angles. Histological examination of the retinas revealed that the distance between cones, measured in minutes of visual angle, decreased as the animals grew, suggesting that the larger retinas could resolve smaller objects. These correlated behavioral and anatomical results suggest that improved visual resolution contributes to improved predation. This finding provides a selective advantage for the continuous retinal growth noted in many fish.
TL;DR: Oxygen isotope analyses of planktonic foraminifera from an anoxic basin (Orca Basin) in the northwestern Gulf of Mexico record a negative isotopic anomaly of 3.6 as discussed by the authors.
TL;DR: In this article, the pore waters from the MANOP siliceous and calcareous ooze sites in the central Pacific Ocean were recovered by shipboard squeezing and centrifuging techniques and an in situ harpoon sampler.
TL;DR: In this article, the authors investigated the stability of gravity currents, in a rotating system, that are infinitely long and uniform in the direction of flow and for which the current depth vanishes on both sides of the flow.
Abstract: We investigate the stability of gravity currents, in a rotating system, that are infinitely long and uniform in the direction of flow and for which the current depth vanishes on both sides of the flow. Thus, owing to the role of the Earth's rotation in restraining horizontal motions, the currents are bounded on both sides by free streamlines, or sharp density fronts. A model is used in which only one layer of fluid is dynamically important, with a second layer being infinitely deep and passive. The analysis includes the influence of vanishing layer depth and large inertial effects near the edges of the current, and shows that such currents are always unstable to linearized perturbations (except possibly in very special cases), even when there is no extremum (or gradient) in the potential vorticity profile. Hence the established Rayleigh condition for instability in quasi-geostrophic models, where inertial effects are assumed to be vanishingly small relative to Coriolis effects, does not apply. The instability does not depend upon the vorticity profile but instead relies upon a coupling of the two free streamlines. The waves permit the release of both kinetic and potential energy from the mean flow. They can have rapid growth rates, the e-folding time for waves on a current with zero potential vorticity, for example, being close to one-half of a rotation period. Though they are not discussed here, there are other unstable solutions to this same model when the potential vorticity varies monotonically across the stream, verifying that flows involving a sharp density front are much more likely to be unstable than flows with a small ratio of inertial to Coriolis forces.Experiments with a current of buoyant fluid at the free surface of a lower layer are described, and the observations are compared with the computed mode of maximum growth rate for a flow with a uniform potential vorticity. The current is observed to be always unstable, but, contrary to the predicted behaviour of the one-layer coupled mode, the dominant length scale of growing disturbances is independent of current width. On the other hand, the structure of the observed disturbances does vary: when the current is sufficiently narrow compared with the Rossby deformation radius (and the lower layer is deep) disturbances have the structure predicted by our one-layer model. The flow then breaks up into a chain of anticyclonic eddies. When the current is wide, unstable waves appear to grow independently on each edge of the current and, at large amplitude, form both anticyclonic and cyclonic eddies in the two-layer fluid. This behaviour is attributed to another unstable mode.
TL;DR: In this paper, the authors measured the SrCa ratio of seawater during the last 75 million years and found that the ratio has increased to its present value by 10-15% during the Cenozoic and that minima occurred between 55-45 Ma and 10-5 Ma, when the ratio was 15-25% less than at present.
TL;DR: In this paper, concentrations of 40 elements in 11 desert soils from Africa and North America have been determined as a function of particle size by neutron activation, and most elements were within a factor of 2-3 of crustal rock proportions, suggesting that bulk crustal rocks is an acceptable reference material for calculating aerosol-crust enrichment factors.
TL;DR: In this paper, the authors studied the oscillatory behavior of equations of the forms (y′(t) + ∑i = 1nPiy(t − τi) = 0 and (**) y′ (t) − ∑I = 1npiy (t + τi), where pi and τi, i = 1, 2,…, n, are positive constants.
TL;DR: The effect of ammonia uptake by one organ on the uptake of that nutrient by another organ was determined for the seagrass Zostera marina L. under laboratory conditions, showing that leaves had a greater affinity for ammonia than roots.
Abstract: The effect of ammonia uptake by one organ on the uptake of that nutrient by another organ was determined for the seagrass Zostera marina L. under laboratory conditions. Leafy shoots with roots attached were incubated in two-compartment chambers, with the roots in one compartment and the leaves in the other. Rates of ammonia uptake were compared when roots and leaves were supplied with ammonia separately and simultaneously. Root uptake of ammonia had no influence on the rate of ammonia uptake by leaves. However, leaf uptake of ammonia caused a 77% decrease in the maximum rate of ammonia uptake by roots. The Ks values for ammonia uptake by leaves and roots were 9.2 and 104 μM respectively, showing that leaves had a greater affinity for ammonia than roots.
TL;DR: Theoretical and experimental results for a quasi-equilibrium regime are given in this paper, where the leading edge of a boundary jet is not carried by the nose but is deflected backwards (detrained) and left behind the propagating nose.
Abstract: When light rotating fluid spreads over heavier fluid in the vicinity of a vertical wall (coast) a boundary jet of width Λ forms, the leading edge or nose of which propagates with speed ĉ along the coast. A certain fraction 8 of the boundary transport is not carried by the nose but is deflected backwards (detrained) and left behind the propagating nose. Theoretical and experimental results for Λ,ĉ, and δ are given for a quasi-equilibrium (constant-ĉ) regime. Over longer time intervals the laboratory observations suggest that the nose slows down and stagnates, whereupon the trailing flow separates from the coast and an intermittent boundary current forms. These processes may be relevant to the mixing of oceanic coastal currents and the maintenance of the mean current.
TL;DR: In this article, the authors used reverse-phase liquid chromatography employing C18 Sep-Pak cartridges (Waters Associates) to extract dissolved organic matter (DOM) and dissolved copper-organic complexes from the estuarine waters of Narragansett Bay, RI.
TL;DR: The system presented here offers a simple, rapid test to determine whether a specific genetic alteration in a bacterium results in enhanced, reduced, or unchanged colonizing ability, and might prove to be of value as a part of the clinical testing of antibiotics.
Abstract: Male CD-1 mice, fed streptomycin in their drinking water, were used to study colonization of the mouse intestine by both fecal Escherichia coli strains isolated from healthy humans and Escherichia coli K12 strains which are routinely used as hosts for recombinant DNA. Prior to use in mice, all the strains were made resistant to streptomycin. Several facts emerged from these studies: (a) Strains isolated from different healthy humans colonized the mouse intestine with equal ability (approximately 10(8) cells/g feces), but may have colonized biochemically distinct sites. (b) K12 strains tested had, at most, one hundredth the colonizing ability of human fecal strains. (c) Rifampicin-resistant mutants of strains which contain one or no plasmids were poor colonizers relative to their parents. (d) Rifampicin-resistant mutants of strains which contain six or more plasmids retained the colonizing abilities of their parents. (e) Introduction of the F-amp or pJBK5 plasmid into HS-4, a human fecal strain which does not normally carry these plasmids, reduced its colonizing ability 1000-fold. (f) Strains used in this study colonized the mouse caecum and colon exclusively. The system presented here offers a simple, rapid test to determine whether a specific genetic alteration in a bacterium (e.g. antibiotic resistance) results in enhanced, reduced, or unchanged colonizing ability. Such a test might prove to be of value as a part of the clinical testing of antibiotics.
01 Mar 1982
TL;DR: The feasibility of robots employing vision to acquire randomly oriented cylinders has been demonstrated for the first time and robots with such capabilities can be applied to enhance automation applications, especially in small batch production.
Abstract: The feasibility of robots employing vision to acquire randomly oriented cylinders has been demonstrated for the first time. An experimental robot system using vision and a parallel jaw gripper was able to acquire randomly oriented cylindrical workpieces piled in bins. Binary image analysis was adequate to guide the gripper into the multilayered, piles. Complementary information was provided by simple sensors on the gripper. Experiments were performed using titanium cylinders 6 cm × 15 cm diameter and 7.6 cm × 3 cm diameter. Cycle times to acquire a cylinder and deliver it to a receiving chute ranged from 8 to 10 s when a single supply of one-size cylinders was used. By using a dual supply bin configuration with one bin of each size and overlapping arm motion and image analysis tasks, the cycle times for one cylinder from alternate bins ranged from 5.5 to 7.5 s per piece. In the future robots with such capabilities can be applied to enhance automation applications, especially in small batch production.
TL;DR: Methods available for measuring biofilm accumulation are presented and their use in both laboratory studies and in the field for continuous monitoring of biofilm processes is discussed.
TL;DR: The study compared 38 maintainers and 24 relapsers who had quit smoking on their own to suggest that successful self-changers relied more on inner-directed, experiential processes of change, while the relapser relied moreon environmental change processes.
Abstract: The study compared 38 maintainers and 24 relapsers who had quit smoking on their own. The results suggest that successful self-changers relied more on inner-directed, experiential processes of change, while the relapsers relied more on environmental change processes. Successful changers experienced markedly higher levels of self-efficacy, while relapsers reported least confidence in coping with situations that evoke negative emotions. The maintainers experience high congruence between their basic self-concepts and their concepts of self as non-smokers. The relapsers see themselves as more anxious, dependent, and helpless in their role as smokers. The results are discussed in terms of how greater reliance on experiential processes of self-change can lead to more successful attempts at cessation of smoking than reliance on environmental processes of change.
TL;DR: The atmospheric impact of volcanic eruptions on the earth's climate is not simply related to the volume of erupted material, but relfects the chemistry of the magma, specifically the concentration of the volatile constituents SO/sub 2/, H/sub 1/S, and to a lesser extent Cl and F as discussed by the authors.
Abstract: The atmospheric impact of volcanic eruptions on the earth's climate is not simply related to the volume of erupted material, but relfects the chemistry of the magma, specifically the concentration of the volatile constituents SO/sub 2/, H/sub 2/S, and to a lesser extent Cl and F. Ice cores extracted by drilling reveal peak acidity values in the 1783 ice layer are higher than any others in the last thousand years and correspond to a global fallout of 100 x 10/sup 9/ kg of H/sub 2/SO/sub 4/ from the Laki eruption. Analyses indicate that the magma contained 800 to 1000 parts per million of S before eruption and that only 150 ppm were retained by the volcanic deposits, or 85% released to the atmosphere. Volcanoes deposit two types of aerosols - volcanic ash, which is so coarse it settles out of the atmosphere in a few days, and sulfates. Sulfates are mainly in the form of liquid H/sub 2/SO/sub 4/ droplets which absorb incoming solar radiation and cause cooling at the earth's surface. The Laki event resulted in a two-hundredfold increase in atmospheric S loading over that which is usually emitted by volcanoes. The results from Laki indicate that the Smore » content of the Magma and the erupted volume are the critical parameters in determining the impact of a volcanic eruption on climate. 19 references, 1 figure, 2 tables.« less