Showing papers by "IBM published in 1990"

Light-emitting diodes based on conjugated polymers

Abstract: CONJUGATED polymers are organic semiconductors, the semiconducting behaviour being associated with the π molecular orbitals delocalized along the polymer chain. Their main advantage over non-polymeric organic semiconductors is the possibility of processing the polymer to form useful and robust structures. The response of the system to electronic excitation is nonlinear—the injection of an electron and a hole on the conjugated chain can lead to a self-localized excited state which can then decay radiatively, suggesting the possibility of using these materials in electroluminescent devices. We demonstrate here that poly(p-phenylene vinylene), prepared by way of a solution-processable precursor, can be used as the active element in a large-area light-emitting diode. The combination of good structural properties of this polymer, its ease of fabrication, and light emission in the green–yellow part of the spectrum with reasonably high efficiency, suggest that the polymer can be used for the development of large-area light-emitting displays.

Positioning single atoms with a scanning tunnelling microscope

Abstract: SINCE its invention in the early 1980s by Binnig and Rohrer1,2, the scanning tunnelling microscope (STM) has provided images of surfaces and adsorbed atoms and molecules with unprecedented resolution The STM has also been used to modify surfaces, for example by locally pinning molecules to a surface3 and by transfer of an atom from the STM tip to the surface4 Here we report the use of the STM at low temperatures (4 K) to position individual xenon atoms on a single-crystal nickel surface with atomic pre-cision This capacity has allowed us to fabricate rudimentary structures of our own design, atom by atom The processes we describe are in principle applicable to molecules also In view of the device-like characteristics reported for single atoms on surfaces5,6, the possibilities for perhaps the ultimate in device miniaturization are evident

L-Moments: Analysis and Estimation of Distributions Using Linear Combinations of Order Statistics

Abstract: L-moments are expectations of certain linear combinations of order statistics. They can be defined for any random variable whose mean exists and form the basis of a general theory which covers the summarization and description of theoretical probability distributions, the summarization and description of observed data samples, estimation of parameters and quantiles of probability distributions, and hypothesis tests for probability distributions. The theory involves such established procedures as the use of order statistics and Gini's mean difference statistic, and gives rise to some promising innovations such as the measures of skewness and kurtosis and new methods of parameter estimation

Priority inheritance protocols: an approach to real-time synchronization

Abstract: An investigation is conducted of two protocols belonging to the priority inheritance protocols class; the two are called the basic priority inheritance protocol and the priority ceiling protocol. Both protocols solve the uncontrolled priority inversion problem. The priority ceiling protocol solves this uncontrolled priority inversion problem particularly well; it reduces the worst-case task-blocking time to at most the duration of execution of a single critical section of a lower-priority task. This protocol also prevents the formation of deadlocks. Sufficient conditions under which a set of periodic tasks using this protocol may be scheduled is derived. >

Oscillations in exchange coupling and magnetoresistance in metallic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr.

Abstract: We report the discovery of antiferromagnetic interlayer exchange coupling and enhanced saturation magnetoresistance in two new metallic superlattice systems, Co/Cr and Co/Ru. In these systems and in Fe/Cr superlattices both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance are found to oscillate with the Cr or Ru spacer layer thickness with a period ranging from 12 \AA{} in Co/Ru to \ensuremath{\simeq}18--21 \AA{} in the Fe/Cr and Co/Cr systems.

Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors

Abstract: Using the method of time-domain spectroscopy, we measure the far-infrared absorption and dispersion from 0.2 to 2 THz of the crystalline dielectrics sapphire and quartz, fused silica, and the semiconductors silicon, gallium arsenide, and germanium. For sapphire and quartz, the measured absorptions are consistent with the earlier work below 0.5 THz. Above 1 THz we measure significantly more absorption for sapphire, while for quartz our values are in reasonable agreement with those of the previous work. Our results on high-purity fused silica are consistent with those on the most transparent fused silica measured to date. For the semiconductors, we show that many of the previous measurements on silicon were dominated by the effects of carriers due to impurities. For high-resistivity, 10-kΩ cm silicon, we measure a remarkable transparency together with an exceptionally nondispersive index of refraction. For GaAs our measurements extend the precision of the previous work, and we resolve two weak absorption features at 0.4 and 0.7 THz. Our measurements on germanium demonstrate the dominant role of intrinsic carriers; the measured absorption and dispersion are well fitted by the simple Drude theory.

A statistical approach to machine translation

Abstract: In this paper, we present a statistical approach to machine translation. We describe the application of our approach to translation from French to English and give preliminary results.

Public-key cryptosystems provably secure against chosen ciphertext attacks

Abstract: We show how to construct a public-key cryptosystem (as originally defined by DiNe and Hellman) secure against chosen ciphertezt attacks, given a public-key cryptosystern secure against passive eavesdropping and a noninteractive zero-knowledge proof system in the shared string model. No such secure cryptosystems were known before. A concrete implementation can be based on quadratic residuosity intractability.

Image-directed robotic system for precise robotic surgery including redundant consistency checking

Abstract: A robotic surgical system (10) includes a multiple degree of freedom manipulator arm (14) having a surgical tool (22). The arm is coupled to a controller (24) for controllably positioning the surgical tool within a three dimensional coordinate system. The system further includes a safety monitoring processor (38) for determining the position of the surgical tool in the three dimensional coordinate system relative to a volumetric model. The volumetric model may be represented as a constructive solid geometry (CSG) tree data structure. The system further includes an optical tracking camera system (28, 32) disposed for imaging a region of space that includes at least a portion of the manipulator arm. An output of the camera system is coupled to the processor (38) that processes the volumetric model for determining if the surgical tool is positioned outside of the volumetric model. The system further includes a strain gage (40) for detecting slippage in three dimensions between an immobilized tissue, such as bone, and a reference point (44). The system also includes multiple and redundant safety features for suspending a motion of the surgical tool to prevent the tool from operating outside of the predetermined volume of space.

Superconducting transport properties of grain boundaries in YBa2Cu3O7 bicrystals.

Abstract: Previous work on the superconducting transport properties of individual grain boundaries in thin-film bicrystals of YBa{sub 2}Cu{sub 3}O{sub 7} has been extended to provide a more comprehensive picture of their weak-link characteristics. Grain boundaries with three different geometries have been studied; the transport properties of all three types of boundaries are essentially identical, which implies that the poor superconducting coupling between grains is a result of the intrinsic structural disorder at the boundary. The grain-boundary critical current densities in bicrystal films prepared by evaporation and postannealing and by laser ablation are also in good agreement; this result demonstrates that the transport properties are insensitive to preparation technique and, thus, are not dominated by the diffusion of substrate impurities into the boundary region. High grain-boundary resistivities and low {ital I}{sub {ital c}R{ital n}} products imply that the boundaries act as strong barriers to current flow with locally depressed order parameters. Strong magnetic hysteresis, associated with trapped intragranular flux, is observed; this hysteretic behavior is also responsible for an increase in the grain boundary {ital J}{sub {ital c}} for {ital H}{sub {ital a}{ital p}{ital p}}{gt}300--500 Oe.

Parallel coordinates: a tool for visualizing multi-dimensional geometry

Abstract: A methodology for visualizing analytic and synthetic geometry in RN is presented. It is based on a system of parallel coordinates which induces a non-projective mapping between N-Dimensional and 2-Dimensional sets. Hypersurfaces are represented by their planar images which have some geometrical properties analogous to the properties of the hypersurface that they represent. A point ← → line duality when N = 2 generalizes to lines and hyperplanes enabling the representation of polyhedra in RN. The representation of a class of convex and non-convex hypersurfaces is discussed together with an algorithm for constructing and displaying any interior point. The display shows some local properties of the hypersurface and provides information on the point's proximity to the boundary. Applications to Air Traffic Control, Robotics, Computer Vision, Computational Geometry, Statistics, Instrumentation and other areas are discussed.

Optical stylus and passive digitizing tablet data input system

Abstract: A stylus and table X-Y data input system for a video display system. The pen includes an optical styling having a suitable pickup mechanism and the tablet is passive in nature and provides direct digitized data readout. Absolute positional information is encoded in binary form in the tablet in such a fashion that the pen position upon the tablet is automatically determinable by illuminating a particular area of the tablet and reading off the digitized X-Y coordinate data stored therein. The pen and supporting hardware/software are rotationally insensitive so that the pen may be held in any desired position comfortable to a user. The system provides greatly improved resolution, sampling rate accuracy and general robustness particularly for such applications as text recognition as well as a wide variety of other graphical input uses.

Untraceable Electronic Cash

Abstract: The use of credit cards today is an act of faith on the p a t of all concerned. Each party is vulnerable to fraud by the others, and the cardholder in particular has no protection against surveillance.

Cortical functional architecture and local coupling between neuronal activity and the microcirculation revealed by in vivo high-resolution optical imaging of intrinsic signals.

Abstract: We have shown previously the existence of small, activity-dependent changes in intrinsic optical properties of cortex that are useful for optical imaging of cortical functional architecture. In this study we introduce a higher resolution optical imaging system that offers spatial and temporal resolution exceeding that achieved by most alternative imaging techniques for imaging cortical functional architecture or for monitoring local changes in cerebral blood volume or oxygen saturation. In addition, we investigated the mechanisms responsible for the activity-dependent intrinsic signals evoked by sensory stimuli, and studied their origins and wavelength dependence. These studies enabled high-resolution visualization of cortical functional architecture at wavelengths ranging from 480 to 940 nm. With the use of near-infrared illumination it was possible to image cortical functional architecture through the intact dura or even through a thinned skull. In addition, the same imaging technique proved useful for imaging and discriminating sensory-evoked, activity-dependent changes in local blood volume and oxygen saturation (oxygen delivery). Illumination at 570 nm allowed imaging of activity-dependent blood volume increases, whereas at 600-630 nm, the predominant signal probably originated from activity-dependent oxygen delivery from capillaries. The onset of oxygen delivery started prior to the blood volume increase. Thus, optical imaging based on intrinsic signals is a minimally invasive procedure for monitoring short- and long-term changes in cerebral activity.

Direct Observation and Analysis of Indentation Cracking in Glasses and Ceramics

Abstract: A review of the observations of indentation-induced fracture suggests that there is no simple generalization which may be made concerning crack initiation sequences. Here, we investigate the material dependence of the initiation sequence of indentation cracks (cone, radial, median, half-penny, and lateral) using an inverted tester allowing simultaneous viewing of the fracture process and measurement of the indeter load and displacement during contact. Two normal glasses, two anomalous glasses, and seven crystalline materials are examined. Key results include (i) direct evidence that the surface traces of cracks observed at indentation contacts are those of radial cracks, rather than median-nucleated half-penny cracks (at least for peak contact loads <40 N) and (ii) that, in crystalline materials, radial cracks form almost immediately on loading of the indenter, in anomalous glasses at somewhat greater loads, but in normal glasses during unloading. A detailed consideration of the stress fields arising during indentation contact predicts material-dependent initiation sequences, in agreement with observations, particularly those of radial crack formation on loading for materials with large modulus-to-hardness ratios. In addition, a new, unexplored crack system is demonstrated, the shallow lateral cracks, which appear to be responsible for material removal at sharp contacts.

The state of the art in online handwriting recognition

Abstract: This survey describes the state of the art of online handwriting recognition during a period of renewed activity in the field. It is based on an extensive review of the literature, including journal articles, conference proceedings, and patents. Online versus offline recognition, digitizer technology, and handwriting properties and recognition problems are discussed. Shape recognition algorithms, preprocessing and postprocessing techniques, experimental systems, and commercial products are examined. >

Knowledge and common knowledge in a distributed environment

Abstract: Reasoning about knowledge seems to play a fundamental role in distributed systems. Indeed, such reasoning is a central part of the informal intuitive arguments used in the design of distributed protocols. Communication in a distributed system can be viewed as the act of transforming the system's state of knowledge. This paper presents a general framework for formalizing and reasoning about knowledge in distributed systems. It is shown that states of knowledge of groups of processors are useful concepts for the design and analysis of distributed protocols. In particular, distributed knowledge corresponds to knowledge that is “distributed” among the members of the group, while common knowledge corresponds to a fact being “publicly known.” The relationship between common knowledge and a variety of desirable actions in a distributed system is illustrated. Furthermore, it is shown that, formally speaking, in practical systems common knowledge cannot be attained. A number of weaker variants of common knowledge that are attainable in many cases of interest are introduced and investigated.

The SGML handbook

Abstract: PART ONE, TUTORIALS: Introduction to generalized markup Basic concepts Additional concepts Link in a nutshell PART TWO, OVERVIEW OF THE STANDARD: Introduction Text processing application SGML application SGML document Processing model Storage model Character sets Markup declaration Conformance PART THREE, SGML ANNOTATED PART FOUR, 8879 ANNEXES APPENDICES INDEX COLOPHON.

A variable order Runge-Kutta method for initial value problems with rapidly varying right-hand sides

Abstract: Explicit Runge-Kutta methods (RKMs) are among the most popular classes of formulas for the approximate numerical integration of nonstiff, initial value problems. However, high-order Runge-Kutta methods require more function evaluations per integration step than, for example, Adams methods used in PECE mode, and so, with RKMs, it is expecially important to avoid rejected steps. Steps are often rejected when certain derivatives of the solutions are very large for part of the region of integration. This corresponds, for example, to regions where the solution has a sharp front or, in the limit, some derivative of the solution is discontinuous. In these circumstances the assumption that the local truncation error is changing slowly is invalid, and so any step-choosing algorithm is likely to produce an unacceptable step. In this paper we derive a family of explicit Runge-Kutta formulas. Each formula is very efficient for problems with smooth solution as well as problems having rapidly varying solutions. Each member of this family consists of a fifty-order formula that contains imbedded formulas of all orders 1 through 4. By computing solutions at several different orders, it is possible to detect sharp fronts or discontinuities before all the function evaluations defining the full Runge-Kutta step have been computed. We can then either accpet a lower order solution or abort the step, depending on which course of action seems appropriate. The efficiency of the new algorithm is demonstrated on the DETEST test set as well as on some difficult test problems with sharp fronts or discontinuities.

System for ordering items using an electronic catalogue

Abstract: The disclosed system facilitates the user in electronically ordering items from suppliers. The system is comprised of an Electronic Catlogue and an Electronic Requisition facility. The Electronic Catalogue includes a Public Catalog and a Private Catalogue. The Public Catalog is stored on a publicly available database for access by customer/Requestors. The Private Catalogue is resident on a Customer's computer system and may contain unique pricing data based on pricing agreements. The Electronic Requisition facility is used by the Customer/Requestors to electronically create purchase requisitions based upon the information provided in the catalogues and route the requisitions through the appropriate approval process within he enterprise. Requisitions are then processed through the customer's procurement system and transmitted electronically as purchase orders to Suppliers.

Project GROPEHaptic displays for scientific visualization

Abstract: We began in 1967 a project to develop a haptic+display for 6-D force fields of interacting protein molecules. We approached it in four stages: a 2-D system, a 3-D system tested with a simple task, a 6-D system tested with a simple task, and a full 6-D molecular docking system, our initial goal. This paper summarizes the entire project---the four systems, the evaluation experiments, the results, and our observations. The molecular docking system results are new.Our principal conclusions are:• Haptic display as an augmentation to visual display can improve perception and understanding both of force fields and of world models populated with impenetrable objects.• Whereas man-machine systems can outperform computer-only systems by orders of magnitude on some problems, haptic-augmented interactive systems seem to give about a two-fold performance improvement over purely graphical interactive systems. Better technology may give somewhat more, but a ten-fold improvement does not seem to be in the cards.• Chemists using GROPE-III can readily reproduce the true docking positions for drugs whose docking is known (but not to them) and can find very good docks for drugs whose true docks are unknown. The present tool promises to yield new chemistry research results; it is being actively used by research chemists.• The most valuable result from using GROPE-III for drug docking is probably the radically improved situation awareness that serious users report. Chemists say they have a new understanding of the details of the receptor site and its force fields, and of why a particular drug docks well or poorly.• We see various scientific/education applications for haptic displays but believe entertainment, not scientific visualization, will drive and pace the technology.• The hardware-software system technology we have used is barely adequate, and our experience sets priorities for future development.• Some unexpected perceptual phenomena were observed. All of these worked for us, not against us.

Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions

Abstract: Generally contracted basis sets for second row atoms have been constructed using the Atomic Natural Orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over several atomic states, positive and negative ions, and atoms in an external electric field. The contracted basis sets give virtually identical results as the corresponding uncontracted sets for the atomic properties, which they have been designed to reproduce. The design objective has been to describe the ionization potential, the electron affinity, and the polarizability as accurately as possible. The result is a set of well balanced basis sets for molecular calculations. The starting primitive sets are 17s12p5d4f for the second row atoms Na-Ar. Corresponding ANO basis sets for first row atoms have recently been published.

Oxygen-defect flux pinning, anomalous magnetization and intra-grain granularity in YBa 2 Cu 3 0 7–δ

Abstract: The anomalous magnetization characteristic, intra-grain granularity and the magnitude of the flux pinning in single crystals of YBa2Cu307–δ are shown to be intimately linked. As the nominal oxygen deficiency δ decreases towards zero, the flux pinning declines and the crystals lose their explicitly granular signature. As δ is seldom specifically controlled at levels below ˜0.05 in even the most carefully made materials, small oxygen deficiencies may contribute significantly to both the flux pinning and the weak-link properties.

Network address management for a wired network supporting wireless communication to a plurality of mobile users

Abstract: Apparatus and method for managing bidirectional transmission of information between a wired network and at least one mobile communication unit (10) in wireless communication with the wired network. The wired network is of the type wherein users of the network are each assigned a unique network address such as in, for example, a TCP/IP network. In accordance with the invention there is provided a local gateway (16) coupled between a wireless LAN and the wired network for communication with a mobile communication unit. There is also provided a global gateway (18) coupled to the local gateway and to remote users of the network. The global gateway functions to maintain a plurality of network addresses and, in response to a request for an assignment of a network address from the mobile communication unit, assigns one of the plurality of network addresses to the requesting mobile communication unit. The global gateway also buffers and routes data received from a remote user, the data being directed to an addresss corresponding to the assigned network address, to the mobile communication unit having the assigned address.

Memory Efficient Algorithms for the Verification of Temporal Properties

Abstract: This article addresses the problem of designing memory-efficient algorithms for the verification of temporal properties of finite-state programs. Both the programs and their desired temporal properties are modeled as automata on infinite words (Buchi automata). Verification is then reduced to checking the emptiness of the automaton resulting from the product of the program and the property. This problem is usually solved by computing the strongly connected components of the graph representing the product automaton. Here, we present algorithms that solve the emptiness problem without explicitly constructing the strongly connected components of the product graph. By allowing the algorithms to err with some probability, we can implement them with a randomly accessed memory of size O(n) bits, where n is the number of states of the graph, instead of O(n log n) bits that the presently known algorithms require.

Observation of the photorefractive effect in a polymer.

Abstract: We report the first observation of the photorefractive effect in a polymeric material, the electro-optic polymer bisphenol-A-diglycidylether 4-nitro-1,2-phenylenediamine made photoconductive by doping with the hole-transport agent diethylamino-benzaldehyde diphenylhydrazone. The gratings formed exhibit dynamic writing and erasure, strong electric-field dependence, polarization anisotropy, and estimated space-charge fields up to 26 kV/cm at an applied field of 126 kV/cm. Application of similar concepts should provide a broad new class of easily fabricated photorefractive materials.

Apertureless near field optical microscopy

Abstract: A near field optical microscopy method and apparatus eliminates the necessity of an aperture for scanning a sample surface (18) and greatly reduces the detected background signal. A small dimension tip (14), on the order of atomic dimension, is disposed in close promity to the sample surface (18). A dither motion is applied to the tip (14) at a first frequency in a direction substantially normal (22) to the plane of the sample surface (18). Dither motion is simultaneously applied to the sample (20) at a second frequency in a direction substantially parallel (24) to the plane of the sample surface (18). The amplitude of the motions are chosen to be comparable to the desired measurement resolution. The end (12) of the tip (14) is illuminated by optical energy. The scattered light from the tip (14) and surface (18) is detected at the difference frequency for imaging the sample surface (18) at sub-wavelength resolution without the use of an aperture. Alternatively, the tip (14) is maintained stationary and the sample (20) undergoes motion in the two directions.