Showing papers by "University of California, Santa Barbara published in 1991"
Book•
01 Jan 1991TL;DR: The author explains the design and implementation of the Levinson-Durbin Algorithm, which automates the very labor-intensive and therefore time-heavy and expensive process of designing and implementing a Quantizer.
Abstract: 1 Introduction- 11 Signals, Coding, and Compression- 12 Optimality- 13 How to Use this Book- 14 Related Reading- I Basic Tools- 2 Random Processes and Linear Systems- 21 Introduction- 22 Probability- 23 Random Variables and Vectors- 24 Random Processes- 25 Expectation- 26 Linear Systems- 27 Stationary and Ergodic Properties- 28 Useful Processes- 29 Problems- 3 Sampling- 31 Introduction- 32 Periodic Sampling- 33 Noise in Sampling- 34 Practical Sampling Schemes- 35 Sampling Jitter- 36 Multidimensional Sampling- 37 Problems- 4 Linear Prediction- 41 Introduction- 42 Elementary Estimation Theory- 43 Finite-Memory Linear Prediction- 44 Forward and Backward Prediction- 45 The Levinson-Durbin Algorithm- 46 Linear Predictor Design from Empirical Data- 47 Minimum Delay Property- 48 Predictability and Determinism- 49 Infinite Memory Linear Prediction- 410 Simulation of Random Processes- 411 Problems- II Scalar Coding- 5 Scalar Quantization I- 51 Introduction- 52 Structure of a Quantizer- 53 Measuring Quantizer Performance- 54 The Uniform Quantizer- 55 Nonuniform Quantization and Companding- 56 High Resolution: General Case- 57 Problems- 6 Scalar Quantization II- 61 Introduction- 62 Conditions for Optimality- 63 High Resolution Optimal Companding- 64 Quantizer Design Algorithms- 65 Implementation- 66 Problems- 7 Predictive Quantization- 71 Introduction- 72 Difference Quantization- 73 Closed-Loop Predictive Quantization- 74 Delta Modulation- 75 Problems- 8 Bit Allocation and Transform Coding- 81 Introduction- 82 The Problem of Bit Allocation- 83 Optimal Bit Allocation Results- 84 Integer Constrained Allocation Techniques- 85 Transform Coding- 86 Karhunen-Loeve Transform- 87 Performance Gain of Transform Coding- 88 Other Transforms- 89 Sub-band Coding- 810 Problems- 9 Entropy Coding- 91 Introduction- 92 Variable-Length Scalar Noiseless Coding- 93 Prefix Codes- 94 Huffman Coding- 95 Vector Entropy Coding- 96 Arithmetic Coding- 97 Universal and Adaptive Entropy Coding- 98 Ziv-Lempel Coding- 99 Quantization and Entropy Coding- 910 Problems- III Vector Coding- 10 Vector Quantization I- 101 Introduction- 102 Structural Properties and Characterization- 103 Measuring Vector Quantizer Performance- 104 Nearest Neighbor Quantizers- 105 Lattice Vector Quantizers- 106 High Resolution Distortion Approximations- 107 Problems- 11 Vector Quantization II- 111 Introduction- 112 Optimality Conditions for VQ- 113 Vector Quantizer Design- 114 Design Examples- 115 Problems- 12 Constrained Vector Quantization- 121 Introduction- 122 Complexity and Storage Limitations- 123 Structurally Constrained VQ- 124 Tree-Structured VQ- 125 Classified VQ- 126 Transform VQ- 127 Product Code Techniques- 128 Partitioned VQ- 129 Mean-Removed VQ- 1210 Shape-Gain VQ- 1211 Multistage VQ- 1212 Constrained Storage VQ- 1213 Hierarchical and Multiresolution VQ- 1214 Nonlinear Interpolative VQ- 1215 Lattice Codebook VQ- 1216 Fast Nearest Neighbor Encoding- 1217 Problems- 13 Predictive Vector Quantization- 131 Introduction- 132 Predictive Vector Quantization- 133 Vector Linear Prediction- 134 Predictor Design from Empirical Data- 135 Nonlinear Vector Prediction- 136 Design Examples- 137 Problems- 14 Finite-State Vector Quantization- 141 Recursive Vector Quantizers- 142 Finite-State Vector Quantizers- 143 Labeled-States and Labeled-Transitions- 144 Encoder/Decoder Design- 145 Next-State Function Design- 146 Design Examples- 147 Problems- 15 Tree and Trellis Encoding- 151 Delayed Decision Encoder- 152 Tree and Trellis Coding- 153 Decoder Design- 154 Predictive Trellis Encoders- 155 Other Design Techniques- 156 Problems- 16 Adaptive Vector Quantization- 161 Introduction- 162 Mean Adaptation- 163 Gain-Adaptive Vector Quantization- 164 Switched Codebook Adaptation- 165 Adaptive Bit Allocation- 166 Address VQ- 167 Progressive Code Vector Updating- 168 Adaptive Codebook Generation- 169 Vector Excitation Coding- 1610 Problems- 17 Variable Rate Vector Quantization- 171 Variable Rate Coding- 172 Variable Dimension VQ- 173 Alternative Approaches to Variable Rate VQ- 174 Pruned Tree-Structured VQ- 175 The Generalized BFOS Algorithm- 176 Pruned Tree-Structured VQ- 177 Entropy Coded VQ- 178 Greedy Tree Growing- 179 Design Examples- 1710 Bit Allocation Revisited- 1711 Design Algorithms- 1712 Problems
7,015 citations
TL;DR: In this article, the authors describe the mixed mode cracking in layered materials and elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness, showing that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip.
Abstract: Publisher Summary This chapter describes the mixed mode cracking in layered materials. There is ample experimental evidence that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip. An unloaded crack subsequently subject to a combination of modes I and II will initiate growth by kinking in such a direction that the advancing tip is in mode I. The chapter also elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness. The competition between crack advance within the interface and kinking out of the interface depends on the relative toughness of the interface to that of the adjoining material. The interface stress intensity factors play precisely the same role as their counterparts in elastic fracture mechanics for homogeneous, isotropic solids. When an interface between a bimaterial system is actually a very thin layer of a third phase, the details of the cracking morphology in the thin interface layer can also play a role in determining the mixed mode toughness. The elasticity solutions for cracks in multilayers are also elaborated.
3,828 citations
TL;DR: The authors present a fuzzy validity criterion based on a validity function which identifies compact and separate fuzzy c-partitions without assumptions as to the number of substructures inherent in the data.
Abstract: The authors present a fuzzy validity criterion based on a validity function which identifies compact and separate fuzzy c-partitions without assumptions as to the number of substructures inherent in the data. This function depends on the data set, geometric distance measure, distance between cluster centroids and more importantly on the fuzzy partition generated by any fuzzy algorithm used. The function is mathematically justified via its relationship to a well-defined hard clustering validity function, the separation index for which the condition of uniqueness has already been established. The performance of this validity function compares favorably to that of several others. The application of this validity function to color image segmentation in a computer color vision system for recognition of IC wafer defects which are otherwise impossible to detect using gray-scale image processing is discussed. >
3,237 citations
TL;DR: In this article, the authors used the atomic force microscope to measure the forces between a planar surface and an individual colloid particle, a silica sphere of radius 3.5 µm, attached to the force sensor in the microscope and measured in solutions of sodium chloride.
Abstract: THE forces between colloidal particles dominate the behaviour of a great variety of materials, including paints, paper, soil, clays and (in some circumstances) cells. Here we describe the use of the atomic force microscope to measure directly the force between a planar surface and an individual colloid particle. The particle, a silica sphere of radius 3.5 µm, was attached to the force sensor in the microscope and the force between the particle and the surface was measured in solutions of sodium chloride. The measurements are consistent with the double-layer theory1,2 of colloidal forces, although at very short distances there are deviations that may be attributed to hydration forces3–6 or surface roughness, and with previous studies on macroscopic systems4–6. Similar measurements should be possible for a wide range of the particulate and fibrous materials that are often encountered in industrial contexts, provided that they can be attached to the microscope probe.
1,900 citations
TL;DR: In this article, it was shown that low-energy string theory admits a variety of solutions with the structure of an extended object surrounded by an event horizon, whose extremal member is a previously discovered non-singular supersymmetric fivebrane.
1,313 citations
TL;DR: A remarkable oxygen and carbon isotope excursion occurred in Antarctic waters near the end of the Palaeocene (~57.33 Myr ago), indicating rapid global warming and oceanographic changes that caused one of the largest deep-sea benthic extinctions of the past 90 million years.
Abstract: A remarkable oxygen and carbon isotope excursion occurred in Antarctic waters near the end of the Palaeocene (~57.33 Myr ago), indicating rapid global warming and oceanographic changes that caused one of the largest deep-sea benthic extinctions of the past 90 million years. In contrast, the oceanic plankton were largely unaffected, implying a decoupling of the deep and shallow ecosystems. The data suggest that for a few thousand years, ocean circulation underwent fundamental changes producing a transient state that, although brief, had long-term effects on environmental and biotic evolution.
1,220 citations
TL;DR: In this article, the formation processes of neutron stars in interacting binaries, and the subsequent evolution of such systems are discussed, as well as the effect of various types of accretion (from a stellar wind and by Roche-lobe overflow) on the spin evolution of accreting magnetized neutron stars.
1,124 citations
TL;DR: A family of solutions to low-energy string theory representing static, spherically symmetric charged black holes is described, and the extremal charged "black holes" are found to be geodesically complete spacetimes with no event horizons and no singularities.
Abstract: A family of solutions to low-energy string theory representing static, spherically symmetric charged black holes is described. They are labeled by their mass, charge, and asymptotic value of the scalar dilaton. The presence of the dilaton is found to have important consequences. In particular, the extremal charged "black holes" are found to be geodesically complete spacetimes with no event horizons and no singularities. Implications of these new solutions for black-hole thermodynamics and open questions in general relativity are also discussed.
1,103 citations
TL;DR: If a ‘‘dynamical hierarchy’’ of transition probabilities is created which also satisfy the detailed‐balance criterion, then Monte Carlo methods may be utilized to simulate the Poisson process and both static and dynamic properties of model Hamiltonian systems may be obtained and interpreted consistently.
Abstract: Monte Carlo methods are utilized as computational tools in many areas of chemical physics. In this paper, we present the theoretical basis for a dynamical Monte Carlo method in terms of the theory of Poisson processes. We show that if: (1) a ‘‘dynamical hierarchy’’ of transition probabilities is created which also satisfy the detailed‐balance criterion; (2) time increments upon successful events are calculated appropriately; and (3) the effective independence of various events comprising the system can be achieved, then Monte Carlo methods may be utilized to simulate the Poisson process and both static and dynamic properties of model Hamiltonian systems may be obtained and interpreted consistently.
1,039 citations
TL;DR: The properties of an organic molecular ferromagnet with a Curie temperature of 16.1 kelvin are described, where the ferromagnetic state shows no remanence, and the temperature dependence of the magnetization below ;Tc does not follow the behavior expected of a conventional ferromaagnet.
Abstract: The properties of an organic molecular ferromagnet [C(60)TDAE(086); TDAE is tetrakis(dimethylamino)ethylene] with a Curie temperature ;T(c) = 161 kelvin are described The ferromagnetic state shows no remanence, and the temperature dependence of the magnetization below ;T(c) does not follow the behavior expected of a conventional ferromagnet These results are interpreted as a reflection of a three-dimensional system leading to a soft ferromagnet
1,009 citations
TL;DR: In this article, the correlation functions in minimal topological field theories were calculated using the Landau-Ginzburg superpotential and the KdV differential operator, and it was shown that the minimal topology models are in perfect agreement with the matrix models as solved in terms of the kdV hierarchy.
TL;DR: The relative sensitivity of a virus to the inhibitory action of IFN is governed by the qualitative nature and quantitative amount of the individual IFN-regulated cell proteins that may collectively contribute to the inhibition of virus replication.
TL;DR: The toluene extract of the fluffy carbon material produced by resistive heating of graphite contains a variety of molecules larger than C60 and C70 in a total amount of 3 to 4% by weight that are identified as higher fullerenes.
Abstract: The toluene extract of the fluffy carbon material produced by resistive heating of graphite contains a variety of molecules larger than C(60) and C(70) in a total amount of 3 to 4% by weight. Repeated chromatography of this material on neutral alumina has led to the isolation of stable solid samples of C(76), C(84), C(90), and C(94). The characterization, which includes mass spectrometry, (13)C nuclear magnetic resonance, electronic absorption (ultraviolet/visible) and vibrational (infrared) spectroscopy identifies these all-carbon molecules as higher fullerenes. In addition, C(70)O, a stable oxide, has been isolated that is structurally and electronically closely related to D5h-C(70). This compound forms during the resistive heating process and probably has an oxygen atom inserted between two carbon atoms on the convex external surface of the C(70) skeleton.
TL;DR: It was determined that participants have available a single utterance construction format, the compound turn-constructional unit format, which provides the resources needed to complete the utterance-in-progress of another participant, thus allowing for the construction of a single sentence across the talk of two speakers.
Abstract: This article describes how it could be possible for two participants engaged in conversation to jointly produce a single syntactic unit such as a sentence. From an inspection of sentence types that are achieved through such joint production, it was determined that participants have available a single utterance construction format. This format, the compound turn-constructional unit format, may be a component of a socially construed syntax-for-conversation. It can be constituted by a wide range of interactionally relevant features of talk in interaction that reveal an emerging utterance as a multiple component turn-constructional unit. The compound turn-constructional unit format is primarily a resource for turn-taking. It can be used to project the next proper place for speaker change. However, it concomitantly provides the resources needed to complete the utterance-in-progress of another participant, thus allowing for the construction of a single sentence across the talk of two speakers. (Conversation, interaction, recognizable activity)
TL;DR: In this paper, instantons and soliton solutions of heterotic string theory are investigated with an emphasis on the worldsheet point of view, where instantons have the structure of a fivebrane in ten dimensions, the solitons are simply related to the instantons by Wick rotation.
Journal Article•
TL;DR: It is suggested that the antiproliferative activity of the Vinca alkaloids at their lowest effective concentrations in HeLa cells is due to inhibition of mitotic spindle function, and that specific alterations of spindle microtubule dynamics appear to differ among the five VincA congeners.
Abstract: We have used a structure-activity approach to investigate whether the Vinca alkaloids inhibit cell proliferation primarily by means of their effects on mitotic spindle microtubules or by another mechanism or by a combination of mechanisms. Five Vinca alkaloids were used to investigate the relationship in HeLa cells between inhibition of cell proliferation and blockage of mitosis, alteration of spindle organization, and depolymerization of microtubules. Indirect immunofluorescence staining of microtubules and 4,6-diamidino-2-phenylindole staining of chromatin were used to characterize the effects of the drugs on the distributions of cells in stages of the cell cycle and on the organization of microtubules and chromosomes in metaphase spindles. The microtubule polymer was isolated from cells and quantified using a competitive enzyme-linked immunoadsorbent assay for tubulin. We observed a nearly perfect coincidence between the concentration of each Vinca derivative that inhibited cell proliferation and the concentration that caused 50% accumulation of cells at metaphase, despite the fact that the antiproliferative potencies of the drugs varied over a broad concentration range. Inhibition of cell proliferation and blockage of cells at metaphase at the lowest effective concentrations of all Vinca derivatives occurred with little or no microtubule depolymerization or spindle disorganization. With increasing drug concentrations, the organization of microtubules and chromosomes in arrested mitotic spindles deteriorated in a manner that was common to all five congeners. These results indicate that the antiproliferative activity of the Vinca alkaloids at their lowest effective concentrations in HeLa cells is due to inhibition of mitotic spindle function. The results suggest further that the Vinca alkaloids inhibit cell proliferation by altering the dynamics of tubulin addition and loss at the ends of mitotic spindle microtubules rather than by depolymerizing the microtubules. The specific alterations of spindle microtubule dynamics appear to differ among the five Vinca congeners, and such differences may be responsible for differences in the antitumor specificities of the drugs.
TL;DR: In this article, a thin, single-crystal-like film of poly(tetrafluoroethylene) (PTFE) is deposited mechanically on a smooth substrate such as glass.
Abstract: THE formation of highly oriented structures such as single crystals, single-domain liquid crystals and systems comprising uniaxially oriented crystallites is important in many applications of thin films and interfaces, ranging from materials reinforcement to molecular electronics. Of the methods that exist for forming such oriented structures, however, few have sufficient generality to make them applicable to materials of differing chemical composition or physical properties. Here we present a simple and surprisingly versatile method1 for orienting a wide variety of crystalline and liquid-crystalline materials, including polymers, monomers and small organic and inorganic molecules. In our technique, a thin, single-crystal-like film of poly(tetrafluoroethylene) (PTFE) is deposited mechanically on a smooth substrate such as glass. Materials grown on this coated surface from solution, melt or vapour phases show a remarkable degree of alignment.
TL;DR: In this paper, the role of non-deforming particles in reinforcing ductile matrix materials against plastic flow and creep is investigated within the framework of continuum plasticity theory using cell models to implement most of the calculations.
Abstract: A theoretical investigation is made of the role of non-deforming particles in reinforcing ductile matrix materials against plastic flow and creep. The study is carried out within the framework of continuum plasticity theory using cell models to implement most of the calculations. Systematic results are given for the influence of particle volume fraction and shape on the overall behavior of composites with uniformly distributed, aligned reinforcement. The stress-strain behavior of the matrix material is characterized by elastic-perfectly plastic behavior or by power-law hardening behavior of the Ramberg-Osgood type. A relatively simple connection is noted between the asymptotic reference stress for the composite with the power-law hardening matrix and the limit flow stress of the corresponding composite with the elastic-perfectly plastic matrix. The asymptotic reference stress for the composite with the power-law matrix is applicable to steady-state creep. A limited study is reported on the overall limit flow stress for composites with randomly orientated disc-like or needle-like particles when the particles are arranged in a packet-like morphology.
TL;DR: Color patterns of natural populations of guppies (Poecilia reticulata) are a compromise between sexual selection and predation avoidance and relatively less conspicuous at the times and places of maximum predator risk.
TL;DR: Comparisons of the deduced amino acid sequences suggest that three amino acid substitutions produce the approximately 30-nanometer difference in spectral peaks of the pigments underlying human red-green color vision, and red shifts of specific magnitudes are produced by replacement of nonpolar with hydroxyl-bearing amino acids at each of the three critical positions.
Abstract: Variations in the absorption spectra of cone photopigments over the spectral range of about 530 to 562 nanometers are a principal cause of individual differences in human color vision and of differences in color vision within and across other primates. To study the molecular basis of these variations, nucleotide sequences were determined for eight primate photopigment genes. The spectral peaks of the pigments specified by these genes spanned the range from 530 to 562 nanometers. Comparisons of the deduced amino acid sequences of these eight pigments suggest that three amino acid substitutions produce the approximately 30-nanometer difference in spectral peaks of the pigments underlying human red-green color vision, and red shifts of specific magnitudes are produced by replacement of nonpolar with hydroxyl-bearing amino acids at each of the three critical positions.
TL;DR: In this article, the authors argue that firms use debt to protect the wealth of shareholders from the threat of unionization under U.S. labor law and present empirical evidence that strongly supports this hypothesis.
Abstract: This paper argues that firms use debt to protect the wealth of shareholders from the threat of unionization. Under U. S. labor law the firm cannot prohibit its workers from attempting to form a collective bargaining unit. Debt policy offers a method of reducing the impact of this monopoly right on shareholders. By issuing debt, the firm credibly reduces the funds that are available to a potential union. Empirical evidence that strongly supports this hypothesis is presented.
TL;DR: In this article, the space-time dynamics of fivebrane solitons in heterotic and type II string theories are described in terms of supersymmetric low-energy field theories which live on the (5+1)-dimensional soliton worldbranes.
TL;DR: In this article, the authors used the near bottom ARGO imaging system to visually and acoustically survey the narrow ( < 200 m wide) axial zone of the fast-spreading East Pacific Rise (EPR) along 83 km of its length (9°09′-54′N), and systematically mapped the distribution of hundreds of hydrothermal features relative to other fine-scale volcanic and tectonic features of the ridge crest.
TL;DR: It is reported that some rodents have a retinal mechanism that is maximally sensitive to ultraviolet light, which was thought not to exist in the eyes of mammals.
Abstract: HIGH sensitivity to near-ultraviolet light is a fundamental feature of vision in many invertebrates1,2 Among vertebrates there are some amphibians, birds and fishes that are also sensitive to near-ultraviolet wavelengths3–6 This sensitivity can be achieved through a class of cone photoreceptor containing an ultraviolet-sensitive pigment7–9 Although these receptors were thought not to exist in the eyes of mammals, we now report that some rodents have a retinal mechanism that is maximally sensitive to ultraviolet light
TL;DR: In this article, a model of the number of weekly bus trips taken as a function of various exogenous variables, some of which are under the control of the public transit authority, is presented.
Abstract: SUMMARY This paper examines a class of maximum-likelihood regression estimators for count data from truncated samples. Estimators for the truncated Poisson and negative binomial distributions are illustrated. Simulation results are given to illustrate the magnitude of the bias that may result from the failure to account for overdispersion in truncated samples. An empirical application based upon the number of recreational fishing trips taken by a sample of Alaskan fishermen is provided. the number of bus trips taken per week and other variables which might be related to that behaviour, such as attitudinal and demographic variables. Given these data we seek to construct a model of the number of weekly bus trips taken as a function of various exogenous variables, some of which are under the control of the public transit authority. Due to the choice-based sampling scheme employed, no observations are made of individuals making zero bus trips, since a criterion for sample inclusion is that at least one bus trip be made. The dependent variable in our model, the number of bus trips taken that week, is truncated at zero, taking on only positive values. More generally, two common types of sampling schemes are likely to give rise to samples of truncated counts: surveys which ask 'participants' about the number of 'participation occasions' and samples drawn from administrative records where inclusion in such a database is predicated on having engaged in the activity of interest. Examples of the first type include on-site sampling plans, surveys of owners of a particular home appliance (e.g. from warranty
TL;DR: In this paper, the authors survey the theory and evidence on the relationship between savings and investment and find that there is a positive correlation between saving and investment rates in both the short and long runs.
TL;DR: In this article, the coefficients of the identity operator are determined by the elements of the matrix S which implements modular transformations on the torus and the other coefficients are related to the matrix implementing duality transformation on the conformal blocks of the four-point functions on the sphere.
TL;DR: A proposed general framework learning to live with errors in spatial databases and the traditional and modern look at Tissot's indicatrix are proposed.
Abstract: Error modelling for the map overlay operation modelling error in overlaid categorical maps user considerations in landscape characterization knowledge-based approaches to determining and correcting areas of unreliability in geographical databases observations and comments on the generation and treatment of error in digital GIS data developing confidence limits on errors of suitability analyses in geographical information systems distance calculations and errors in geographical databases inclusion of accuracy data in a feature based, object- orientated data model accuracy and bias issues in surface representation modelling error in objects and fields frame independence spatial analysis modelling locational uncertainty via hierarchical tesselation minimum cross-entropy convex decompositions of pixel-indexed stochastic matrices - a geographical application of the Ising model the traditional and modern look at Tissot's indicatrix real data and real problems - dealing with large spatial databases the small number problems and the accuracy of spatial databases demand point approximations for location problems modelling realibility on statistical surfaces by polygon filtering scale-independent spatial analysis the effect of data aggregation on a poisson model of Canadian migration statistical methods for inference between incompatible zonal systems statistical effect of spatial data transformations - a proposed general framework learning to live with errors in spatial databases.