10,702 research outputs found
Development of a prototype multi-processing interactive software invocation system
The Interactive Software Invocation System (NASA-ISIS) was first transported to the M68000 microcomputer, and then rewritten in the programming language Path Pascal. Path Pascal is a significantly enhanced derivative of Pascal, allowing concurrent algorithms to be expressed using the simple and elegant concept of Path Expressions. The primary results of this contract was to verify the viability of Path Pascal as a system's development language. The NASA-ISIS implementation using Path Pascal is a prototype of a large, interactive system in Path Pascal. As such, it is an excellent demonstration of the feasibility of using Path Pascal to write even more extensive systems. It is hoped that future efforts will build upon this research and, ultimately, that a full Path Pascal/ISIS Operating System (PPIOS) might be developed
Turbulence measurements using the laser Doppler velocimeter
The photomultiplier signal representing the axial velocity of water within a glass pipe is examined. It is shown that with proper analysis of the photomultiplier signal, the turbulent information that can be obtained in liquid flows is equivalent to recent hot film studies. In shear flows the signal from the laser Doppler velocimeter contains additional information which may be related to the average shear
Predictability and hierarchy in Drosophila behavior
Even the simplest of animals exhibit behavioral sequences with complex
temporal dynamics. Prominent amongst the proposed organizing principles for
these dynamics has been the idea of a hierarchy, wherein the movements an
animal makes can be understood as a set of nested sub-clusters. Although this
type of organization holds potential advantages in terms of motion control and
neural circuitry, measurements demonstrating this for an animal's entire
behavioral repertoire have been limited in scope and temporal complexity. Here,
we use a recently developed unsupervised technique to discover and track the
occurrence of all stereotyped behaviors performed by fruit flies moving in a
shallow arena. Calculating the optimally predictive representation of the fly's
future behaviors, we show that fly behavior exhibits multiple time scales and
is organized into a hierarchical structure that is indicative of its underlying
behavioral programs and its changing internal states
An operating system for future aerospace vehicle computer systems
The requirements for future aerospace vehicle computer operating systems are examined in this paper. The computer architecture is assumed to be distributed with a local area network connecting the nodes. Each node is assumed to provide a specific functionality. The network provides for communication so that the overall tasks of the vehicle are accomplished. The O/S structure is based upon the concept of objects. The mechanisms for integrating node unique objects with node common objects in order to implement both the autonomy and the cooperation between nodes is developed. The requirements for time critical performance and reliability and recovery are discussed. Time critical performance impacts all parts of the distributed operating system; e.g., its structure, the functional design of its objects, the language structure, etc. Throughout the paper the tradeoffs - concurrency, language structure, object recovery, binding, file structure, communication protocol, programmer freedom, etc. - are considered to arrive at a feasible, maximum performance design. Reliability of the network system is considered. A parallel multipath bus structure is proposed for the control of delivery time for time critical messages. The architecture also supports immediate recovery for the time critical message system after a communication failure
Creation of entanglement in a scalable spin quantum computer with long-range dipole-dipole interaction between qubits
Creation of entanglement is considered theoretically and numerically in an
ensemble of spin chains with dipole-dipole interaction between the spins. The
unwanted effect of the long-range dipole interaction is compensated by the
optimal choice of the parameters of radio-frequency pulses implementing the
protocol. The errors caused by (i) the influence of the environment,(ii)
non-selective excitations, (iii) influence of different spin chains on each
other, (iv) displacements of qubits from their perfect locations, and (v)
fluctuations of the external magnetic field are estimated analytically and
calculated numerically. For the perfectly entangled state the z component, M,
of the magnetization of the whole system is equal to zero. The errors lead to a
finite value of M. If the number of qubits in the system is large, M can be
detected experimentally. Using the fact that M depends differently on the
parameters of the system for each kind of error, varying these parameters would
allow one to experimentally determine the most significant source of errors and
to optimize correspondingly the quantum computer design in order to decrease
the errors and M. Using our approach one can benchmark the quantum computer,
decrease the errors, and prepare the quantum computer for implementation of
more complex quantum algorithms.Comment: 31 page
Direct comparison of Viking 2.3-GHz signal phase fluctuation and columnar electron density between 2 and 160 solar radii
The relationship between solar wind induced signal phase fluctuation and solar wind columnar electron density has been the subject of intensive analysis during the last two decades. In this article, a sizeable volume of 2.3-GHz signal phase fluctuation and columnar electron density measurements separately and concurrently inferred from Viking spacecraft signals are compared as a function of solar geometry. These data demonstrate that signal phase fluctuation and columnar electron density are proportional over a very wide span of solar elongation angle. A radially dependent electron density model which provides a good fit to the columnar electron density measurements and, when appropriately scaled, to the signal phase fluctuation measurements, is given. This model is also in good agreement with K-coronameter observations at 2 solar radii (2r0), with pulsar time delay measurements at 10r0, and with spacecraft in situ electron density measurements at 1 AU
Dynamical Stability and Quantum Chaos of Ions in a Linear Trap
The realization of a paradigm chaotic system, namely the harmonically driven
oscillator, in the quantum domain using cold trapped ions driven by lasers is
theoretically investigated. The simplest characteristics of regular and chaotic
dynamics are calculated. The possibilities of experimental realization are
discussed.Comment: 24 pages, 17 figures, submitted to Phys. Rev
Meanfield treatment of Bragg scattering from a Bose-Einstein condensate
A unified semiclassical treatment of Bragg scattering from Bose-Einstein
condensates is presented. The formalism is based on the Gross-Pitaevskii
equation driven by classical light fields far detuned from atomic resonance. An
approximate analytic solution is obtained and provides quantitative
understanding of the atomic momentum state oscillations, as well as a simple
expression for the momentum linewidth of the scattering process. The validity
regime of the analytic solution is derived, and tested by three dimensional
cylindrically symmetric numerical simulations.Comment: 21 pages, 10 figures. Minor changes made to documen
Influence of External Fields and Environment on the Dynamics of Phase Qubit-Resonator System
We analyze the dynamics of a qubit-resonator system coupled with a thermal
bath and external electromagnetic fields. Using the evolution equations for the
set of Heisenberg operators, that describe the whole system, we derive an
expression for the resonator field, accounting for the resonator-drive,-bath,
and -qubit interaction. The renormalization of the resonator frequency, caused
by the qubit-resonator interaction, is accounted for. Using solutions for the
resonator field, we derive the equation describing qubit dynamics. The
influence of the qubit evolution during the measurement time on the fidelity of
a single-shot measurement is studied. The relation between the fidelity and
measurement time is shown explicitly. Also, an expression describing relaxation
of the superposition qubit state towards its stationary value is derived. The
possibility of controlling this state, by varying the amplitude and frequency
of drive, is shown.Comment: 15 page
Soviet Comrades\u27 Courts
A major aspect of Soviet criminal law reform since 1959 has been the transfer of certain judicial functions to Comrades\u27 Courts, which are nonprofessional tribunals established to try petty offenses in enterprises, apartment houses, collective farms, universities, and elsewhere. These are called social, rather than state, agencies, because they are not staffed by civil servants but by volunteers and because they are conceived to perform a persuasive rather than a coercive function. Apart from their practical importance, they play an important part in symbolizing the theory that in the new period of expanded construction of communism there will be a decline in the use of formal and coercive sanctions and an increase in the use of informal and popular instruments of self-government. Under communism itself, the first stage of which, according to the 1961 Party Program, is to be achieved by 1980, this process of the dying out of the state, it is said, will be accelerated, as crime gradually disappears and such remnants of the past as the spirit of individualism and money-grubbing, the psychology of private property, and moral callousness cease to exist
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