32,509 research outputs found
Logic circuit detects both present and missing negative pulses in superimposed wave trains
Pulse divide and determination network provides a logical determination of pulse presence within a data train. The network uses digital logic circuitry to divide positive and negative pulses, to shape the separated pulses, and to determine, by means of coincidence logic, if negative pulses are missing from the pulse train
Docking and Curtons\u27 Crisis in higher education: A plan to save small liberal arts colleges in America (book review)
Data compression system
A data compression system is described in which TV PCM data for each line scan is received in the form of a succession of multibit pixel words. All or selected bits of each word are compressed by providing difference values between successive pixel words and coding the difference values of a selected number of pixel words forming a block into a fundamental sequence (FS). The FS, based on its length and the number of words per block, is either transmitted as the compressed data or is used to generate a code FS or its complement is used to generate a code FS bar. When the code FS is generated, its length is compared with the original block PCM and only if the former is the shorter of the two is the code transmitted. Selected bits per pixel word may be compressed, while the remaining bits may be transmitted directly, or some of them may be omitted altogether
Dynamics of exploding magma chambers: Implications for K-T volcanism and mass extinctions
Although it is well known that unconfined chemical explosives may yield pressures to several megabars on detonation in air, the explosive literature has yet to be accessed by some contributors to the volcanological literature who've indicated that pressures in excess of the overburden and/or tensile cannot be obtained. Idealized ballistic assessments of pressures internal to volcanoes yield pressures in the hundreds of kilobar range upon correction by addition of friction, etc. Previous assessments of exploding magma chamber pressure have been made from the characteristics of the Mt. St. Helens explosion. A variety of methods yield pressures of similar value: at least hundreds of kilobars. Such results are consistent with free energy requirements for quench supersaturation explosion, a process occurring in solidifying industrial melts. Several reviews of geochemical literature emphasize the carbon event at the Cretaceous-Tertiary (K-T) boundary as being an indicator of a massive dump of CO2 derived from the mantle and entering the atmosphere by extensive global volcanism. Oxygen isotope data indicates extreme warming at the end of the Cretaceous which is consistent with a greenhouse effect attending the CO2 event. Reaction rate equations for the quench supersaturation explosion mechanism indicated, are consistent with the rise in pressure to 30 kbar on solidification of magmatic melts, these pressures limited by the strength of the experimental apparatus
Mission science value-cost savings from the Advanced Imaging Communication System (AICS)
An Advanced Imaging Communication System (AICS) was proposed in the mid-1970s as an alternative to the Voyager data/communication system architecture. The AICS achieved virtually error free communication with little loss in the downlink data rate by concatenating a powerful Reed-Solomon block code with the Voyager convolutionally coded, Viterbi decoded downlink channel. The clean channel allowed AICS sophisticated adaptive data compression techniques. Both Voyager and the Galileo mission have implemented AICS components, and the concatenated channel itself is heading for international standardization. An analysis that assigns a dollar value/cost savings to AICS mission performance gains is presented. A conservative value or savings of 4.5 million for Galileo, and as much as $7 to 9.5 million per mission for future projects such as the proposed Mariner Mar 2 series is shown
The code word Wiggle - TV data compression
Information preserving data compression systems with coding algorithm developed for noiseless channel condition
RPV application of a globally adaptive rate controlled compressor
A globally adaptive image compression structure is introduced for use in a tactical RPV environment. The structure described would provide an operator with the flexibility to dynamically maximize the usefulness of a limited and changing data rate. The concepts would potentially simplify system design while at the same time improving overall system performance
An air-bearing weight offload system for ground test of heavy LSS structures
The capability and use of the Gravity Offload Facility (GOF) are discussed. Briefly explained are the: truss and base casting; carriage assembly; carriage weldment; vertical lift axis control; lifting cylinder; payload gimbal; motion base layout; and control processor
Design and Implementation of an Extensible Variable Resolution Bathymetric Estimator
For grid-based bathymetric estimation techniques, determining the right resolution at which to work is essential. Appropriate grid resolution can be related, roughly, to data density and thence to sonar characteristics, survey methodology, and depth. It is therefore variable in almost all survey scenarios, and methods of addressing this problem can have enormous impact on the correctness and efficiency of computational schemes of this kind. This paper describes the design and implementation of a bathymetric depth estimation algorithm that attempts to address this problem by combining the computational efficiency of locally regular grids with piecewise-variable estimation resolution to provide a single logical data structure and associated algorithms that can adjust to local data conditions, change resolution where required to best support the data, and operate over essentially arbitrarily large areas as a single unit. The algorithm, which is in part a development of CUBE, is modular and extensible, and is structured as a client-server application to support different implementation modalities. The algorithm is called “CUBE with Hierarchical Resolution Techniques”, or CHRT
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