Xerox (United States)

By reducing the costs of coordination, information technology will lead to an overall shift toward proportionately more use of markets—rather than hierarchies—to coordinate economic activity.

Two different formal definitions of gray-scale reconstruction are presented. The use of gray-scale reconstruction in various image processing applications discussed to illustrate the usefulness of this transformation for image filtering and segmentation tasks. The standard parallel and sequential approaches to reconstruction are reviewed. It is shown that their common drawback is their inefficiency on conventional computers. To improve this situation, an algorithm that is based on the notion of regional maxima and makes use of breadth-first image scannings implemented using a queue of pixels is introduced. Its combination with the sequential technique results in a hybrid gray-scale reconstruction algorithm which is an order of magnitude faster than any previously known algorithm.

This paper presents the use of B-splines as a tool in various digital signal processing applications. The theory of B-splines is briefly reviewed, followed by discussions on B-spline interpolation and B-spline filtering. Computer implementation using both an efficient software viewpoint and a hardware method are discussed. Finally, experimental results are presented for illustrative purposes in two-dimensional image format. Applications to image and signal processing include interpolation, smoothing, filtering, enlargement, and reduction.

A general theory of stochastic transport in disordered systems has been developed. The theory is based on a generalization of the Montroll-Weiss continuous-time random walk (CTRW) on a lattice. Starting from a general mobility formalism, specialized $\stackrel{\mathrm{\ifmmode\acute\else\textasciiacute\fi{}}}{\mathrm{t}}$o hopping conduction, an exact expression for the conductivity $\ensuremath{\sigma}(\ensuremath{\omega})$ for the CTRW process is derived. The frequency dependence of $\ensuremath{\sigma}(\ensuremath{\omega})$ is determined by the Fourier transform of the zeroth and second spatial moments of the function $\ensuremath{\psi}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{s}},t)$, which is equal to the probability per unit time that the displacement and time between hops is $\stackrel{\ensuremath{\rightarrow}}{\mathrm{s}}$, $t$. The conductivity corresponding to characteristically different types of hopping distributions is discussed, as well as the basic approximation in adopting a CTRW on a lattice to transport in disordered solids.

In statistical relational learning, the link prediction problem is key to automatically understand the structure of large knowledge bases. As in previous studies, we propose to solve this problem through latent factorization. However, here we make use of complex valued embeddings. The composition of complex embeddings can handle a large variety of binary relations, among them symmetric and antisymmetric relations. Compared to state-of-the-art models such as Neural Tensor Network and Holographic Embeddings, our approach based on complex embeddings is arguably simpler, as it only uses the Hermitian dot product, the complex counterpart of the standard dot product between real vectors. Our approach is scalable to large datasets as it remains linear in both space and time, while consistently outperforming alternative approaches on standard link prediction benchmarks.

The UNAFold software package is an integrated collection of programs that simulate folding, hybridization, and melting pathways for one or two single-stranded nucleic acid sequences. The name is derived from “Unified Nucleic Acid Folding.” Folding (secondary structure) prediction for single-stranded RNA or DNA combines free energy minimization, partition function calculations and stochastic sampling. For melting simulations, the package computes entire melting profiles, not just melting temperatures. UV absorbance at 260 nm, heat capacity change (Cp), and mole fractions of different molecular species are computed as a function of temperature. The package installs and runs on all Unix and Linux platforms that we have looked at, including Mac OS X. Images of secondary structures, hybridizations, and dot plots may be computed using common formats. Similarly, a variety of melting profile plots is created when appropriate. These latter plots include experimental results if they are provided. The package is “command line” driven. Underlying compiled programs may be used individually, or in special combinations through the use of a variety of Perl scripts. Users are encouraged to create their own scripts to supplement what comes with the package. This evolving software is available for download at http://www.bioinfo.rpi.edu/applications/hybrid/download.php .

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Harvey Scher, Richard Zallen; Critical Density in Percolation Processes. J. Chem. Phys. 1 November 1970; 53 (9): 3759–3761. https://doi.org/10.1063/1.1674565 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioThe Journal of Chemical Physics Search Advanced Search |Citation Search

The effective-mass approximation for shallow acceptor states in cubic semiconductors with degenerate valence bands is reformulated. The Hamiltonian is written as the sum of a spherical term and a cubic corection, thus pointing out the relevance of the spherical symmetry in the acceptor problem and the strong similarity to the case of atoms with the spin-orbit interaction. Without the introduction of any explicit representation of the Hamiltonian, the present formulation yields a meaningful classification of the acceptor states and reduces the eigenvalue problem to simple radial Hamiltonians. These radial Hamiltonians are explicitly given for the most improtant acceptor states and are shown to apply also to the description of the exciton problem. The variational method is used in the numerical calculation. The resulting eigenvalues, eigenfunctions, and related quantities are given as functions of the relevant parameters. The theoretical ionization energies are compared with available experimental data.

The low-lying particlelike excitations of a model linearly conjugated diatomic polymer, ${(A=B)}_{x}$, are found to be pairs of either spin-0 or spin-\textonehalf{} solitons with irrational charge values. The charge values and excitation energies are calculated as functions of the difference of the energy levels of the atomic $p$ orbitals of the two atomic constitutents of the unit cell. The phonon spectrum of the uniform polymer is also calculated.

Abstract The experimental manifestations of dispersive (non-Gaussian) transient transport in disordered solids are discussed and compared with the predictions of theoretical treatments. The mathematical equivalence of the two theoretical approaches based on the formalisms of continuous-time random-walk (CTRW) and generalized multiple-trapping is demonstrated. Several transport mechanisms are discussed, viz. extended state motion with multiple trapping, hopping and trap-controlled hopping. Experimental studies on the chalcogenide glasses a-Se and a-As2Se3 are emphasized but results for organic solids and a-SiO2 are included. There is independent evidence that transport occurs by a hopping process for the organic systems, but not such clear evidence exists for the inorganic solids. Nevertheless, on the basis of the temperature behaviour of the transit time dispersion and the values of parameters obtained from numerical analysis, we argue that hopping is also the microscopic transport mechanism in the inorganic solids. For a-As2Se3 and a-SiO2 the hopping time distribution function assumes the algebraic form ω(t) ∼ t −(1+α) where 0 < α < 1 and α ∼ const. For the organic systems and a-Se, more complicated time and temperature dependences of the distribution function are necessary to fit the data at all temperatures. In this context the observation of a transition from dispersive to non-dispersive transport as a function of increasing temperature in a-Se and poly-(N-vinylcarbazole) (PVK) is of particular interest. The subtle role played by local morphology in generating a transit time dispersion is demonstrated by comparing PVK and its brominated derivative 3Br-PVK. A special section will be devoted to time-dependent electrical phenomena of metal semiconductor surfaces. That discussion will include a description of the experimental procedures necessary to identify the nature of contacts and their influence on the interpretation of steady-state conductivity data.

The authors review the theory of semiconductor superlattice electronic structure. First a survey of theoretical methods is presented. These methods can be divided into two general classes: the supercell approach in which the superlattice is viewed as a material with a large unit cell, and the boundary-condition approach in which bulk wave functions in the constituent semiconductors are matched at the superlattice interfaces. Supercell approaches are essentially the same as conventional band-structure methods. They can only be applied to thin-layer superlattices because of numerical cost. The authors discuss problems of interface matching that occur in various boundary-condition methods and relate these methods to each other. A particular boundary-condition method is used to discuss the electronic structure of various III-V semiconductor superlattices. Emphasis is placed on discussing the qualitatively different behavior that can arise because of different energy-band lineups, strain conditions, and growth orientations. The authors compare the results of three commonly used boundary-condition methods and find generally good agreement.

Predicting the future health information of patients from the historical Electronic Health Records (EHR) is a core research task in the development of personalized healthcare. Patient EHR data consist of sequences of visits over time, where each visit contains multiple medical codes, including diagnosis, medication, and procedure codes. The most important challenges for this task are to model the temporality and high dimensionality of sequential EHR data and to interpret the prediction results. Existing work solves this problem by employing recurrent neural networks (RNNs) to model EHR data and utilizing simple attention mechanism to interpret the results. However, RNN-based approaches suffer from the problem that the performance of RNNs drops when the length of sequences is large, and the relationships between subsequent visits are ignored by current RNN-based approaches. To address these issues, we propose Dipole, an end-to-end, simple and robust model for predicting patients' future health information. Dipole employs bidirectional recurrent neural networks to remember all the information of both the past visits and the future visits, and it introduces three attention mechanisms to measure the relationships of different visits for the prediction. With the attention mechanisms, Dipole can interpret the prediction results effectively. Dipole also allows us to interpret the learned medical code representations which are confirmed positively by medical experts. Experimental results on two real world EHR datasets show that the proposed Dipole can significantly improve the prediction accuracy compared with the state-of-the-art diagnosis prediction approaches and provide clinically meaningful interpretation.

Bayou's anti-entropy protocol for update propagation between weakly consistent storage replicas is based on pair-wise communication, the propagation of write operations, and a set of ordering and closure.

An analytic solution of the "conventional" multiple-trapping problem is obtained for a small quantity of charge moving through a spatially varying, but time-independent, electric field and an arbitrary distribution of traps. The solution is shown to apply to cases of microscopic hopping as well as free-translation through extended states. The solution for a discrete set of traps, simply characterized by their mean times for capture and release (${\ensuremath{\tau}}_{i} \mathrm{and} {\ensuremath{\tau}}_{r,i}$, respectively) appears in the form of convolutions of modified Bessel functions of order unity, but for a uniform electric field and a continuum of traps satisfying the relation ${\ensuremath{\tau}}_{i}^{\ensuremath{-}1}={\ensuremath{\tau}}_{r,i}^{\ensuremath{-}\ensuremath{\alpha}}$ with the ${\ensuremath{\tau}}_{r,i}$ uniformly spaced on a logarithmic scale, the solution reduces to a simple algebraic form which is identical to the one obtained by Scher and Montroll for their power-law waiting-time distribution function $\ensuremath{\psi}(t)\ensuremath{\sim}{t}^{\ensuremath{-}(1+\ensuremath{\alpha})}$. A general equivalence between trapping and continuous-time random walk (CTRW) is further established which shows that $\ensuremath{\psi}(t)$ can always be constructed from capture and release kinetics, and vice versa. The new trapping solution (and its equivalence to CTRW) is illustrated by reinterpreting transit-time data on $a\ensuremath{-}{\mathrm{As}}_{2}{\mathrm{Se}}_{3}$. A trap density satisfying ${N}_{i}\ensuremath{\propto}{\ensuremath{\nu}}_{i}^{\ensuremath{\alpha}\ensuremath{-}1}$ for ${10}^{11}&lt;{\ensuremath{\nu}}_{i}&lt;{10}^{14}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ is obtained, where ${\ensuremath{\nu}}_{i}$ is the coefficient of ${\ensuremath{\tau}}_{r,i}={\ensuremath{\nu}}_{i}^{\ensuremath{-}1}\mathrm{exp}(\frac{{\ensuremath{\epsilon}}_{i}}{\mathrm{kT}})$ and ${\ensuremath{\epsilon}}_{i}=0.65$ eV (for all traps) is the activation energy for release. With the plausible assumption that the microscopic mobility and capture processes are similarly activated (if at all), a trap density for the half-decade interval of ${\ensuremath{\nu}}_{i}$ around 7 \ifmmode\times\else\texttimes\fi{} ${10}^{11}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ is found to satisfy $(\frac{{N}_{i}}{{N}_{\ensuremath{\nu}}})=4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}{\ensuremath{\mu}}_{0}$ (${\mathrm{cm}}^{2}$/V sec), where ${N}_{i}$ and ${N}_{\ensuremath{\nu}}$ are concentrations of traps and transport states, respectively, and ${\ensuremath{\mu}}_{0}$ is the prefactor in $\ensuremath{\mu}={\ensuremath{\mu}}_{0}\mathrm{exp}(\ensuremath{-}\frac{{\ensuremath{\Delta}}_{\ensuremath{\mu}}}{\mathrm{kT}})$. Both hopping and extendedstate motion are compatible with these results, but the most plausible tentative view is hopping with ${N}_{i}\ensuremath{\sim}{10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ and ${\ensuremath{\mu}}_{0}=0.2 \mathrm{to} 0.002$ ${\mathrm{cm}}^{2}$/V sec. Additional photo- and dark-conduction data could significantly reduce the range of plausible values.

The HiPAC project is investigating active, time-constrained database management. An active DBMS is one which automatically executes specified actions when specified conditions arise. HiPAC has proposed Event-Condition-Action (ECA) rules as a formalism for active database capabilities. We have also developed an execution model that specifies how these rules are processed in the context of database transactions. The additional functionality provided by ECA rules makes new demands on the design of an active DBMS. In this paper we propose an architecture for an active DBMS that supports ECA rules. This architecture provides new forms of interaction, in support of ECA rules, between application programs and the DBMS. This leads to a new paradigm for constructing database applications.

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A description is given of the Xerox 8010 Star information system, which was designed as an office automation system. The idea was that professionals in a business or organization would have workstations on their desks and would use them to produce, retrieve, distribute, and organize documentation, presentations, memos, and reports. All of the workstations in an organization would be connected via Ethernet and would share access to file servers, printers, etc. The distinctive features of Star are identified, and changes to the original design are examined. A history of Star development is included. Some lessons learned from designing Star are related.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

N-version programing is defined as the independent generation of N2 2 functionally e quivalent prograns fran the sme initial specification. A methodology of N-version programing has been devised and three types of special mechanisms have been identified t hat are needed to coordinate the execution of an N-version software unit and to canpare the correspondent results generated by each version. Two experiments have been conducted to test the feasibility of N-version programing. The results o f these experiments are discussed. In addition, constraints are identified that must be met for effective application of N-version programing.

New, nonlinear, charged elementary excitations are predicted to occur for weakly pinned Fröhlich charge-density-wave condensates at low temperatures.Received 19 November 1975DOI:https://doi.org/10.1103/PhysRevLett.36.432©1976 American Physical Society

In a previous paper the effective-mass Hamiltonian for shallow acceptor states was separated into a spherical term and a cubic contribution. Neglecting the latter term, a spherical model was formulated which explained the main features of the experimental acceptor spectra. Here the effects of the cubic term are studied using perturbation theory, and all the details of the observed spectra are reproduced. As in the case of the spherical model, the eigenvalue problem is reduced to simple radial Hamiltonians which are explicitly given for the most important acceptor states. These Hamiltonians are solved numerically and the resulting eigenvalues are tabulated as functions of the relevant parameters. The predicted spectra are in good agreement with available experimental data for acceptors in Ge, InSb, and GaAs, but not for acceptors in Si, where the unusual strength of the cubic term makes the present analysis unsatisfactory.