Substantial Space Savings Research Articles

Compact Preservation of Scrambled CD-Rom Data

When preserving CD-ROM discs, data sectors are often read in a so-called “scrambled mode” in order to preserve as much data as possible. This scrambled data is later unscrambled and further processed into a standard CD-ROM disc image. The process of converting the scrambled data into a standard CD-ROM disc image is potentially lossy, but standard CD-ROM disc images exhibit much higher software compatibility and have greater usability compared to the scrambled data from which they are derived. Consequently, for preservation purposes, it is often necessary to store both the scrambled data and the corresponding standard disc image, resulting in greatly increased storage demands compared to storing just one or the other. Here, a method that enables compact storage of scrambled data alongside the corresponding (unscrambled) standard CD-ROM disc image is introduced. The method produces a compact representation of the scrambled data that is derived from the unscrambled disc image. The method allows for (1) storage of the standard unscrambled disc image in unmodified form, (2) easy reconstruction of the scrambled data as needed, and (3) a substantial space savings (in the typical case) compared to storing the scrambled data using standard data compression techniques.

Le Problème De L'Optimisation De L'Entreposage Partage: Méthodes Exacte Et Heuristique

The shared storage assignment policy, contrary to the dedicated one, allows a rack slot to receive units from different products or classes of products. This type of storage can lead to substantial savings in space and travel time. We focus on the problem of minimizing travel time for the context where motion cycles are simple, non-interleaved, and where information is available at the beginning of the horizon. We propose and apply an exact method for medium size problems. Then, we propose and analyse a very efficient heuristic method for large scale problems.

Increased sump capacity – A model study

Increasing pump sump capacity by mere addition of more pumps is limited by the generation of vortices. In most cases the costs for changing sump dimensions to increase capacity are prohibitive. In a sump model for which three pumps would satisfy the Hydraulic Institute Standards, three arrangements were tested with five pumps to determine their acceptance for the increased load. These arrangements were the echelon, the inverted "Vee," and the upright "Vee" as shown in the paper. At this 67% higher pumping rate, the echelon and the inverted "Vee" arrangements were found acceptable. Besides increasing the capacity of existing sumps, adoption of these arrangements could yield substantial space savings in new pumping pits.

On the space optimizing effect of eliminating single productions from LR parsers

Single productions in the syntax of a programming language usually have no semantic significance, and thus parsers can be modified so that they do not perform reductions by single productions. In this paper we show that the basic method developed by Pager for eliminating all undesired single productions from LR parsers can cause a quadratic increase in the number of states of the parser. We then define an improvement of Pager's basic method such that generally smaller parsers are produced; in fact, even a quadratic decrease in the number of states is possible. This improvement is further evaluated by giving a sequence of practically motivated grammars for which substantial savings in space are obtained. We also characterize this improvement by a grammatical condition under which it is guaranteed that no increase in the number of states can occur. This condition is compared with a similar condition derivable in the case of Pager's original method.

Converting from Hard Copy to Microfilm:

An administrative experiment in an industrial R&D from laboratory was conducted to evaluate the effectiveness of converting Chemical Abstracts from hard copy to microfilm. A brief training session on the use of Chemical Abstracts was also conducted in an attempt to increase user (and potential user) awareness of the abstracts and to alter attitudes and behavior toward the abstracts in a positive way. The results of the experiment indicate that substantial space savings in search and photocopy time, and intermediate-to-long-range cost savings can be realized by converting Chemical Abstracts from hard copy to microfilm. Scientists and engineers, however, perceived the microfilm as less accessible and less easy to use than the hard copy, and were less satisfied with the microfilm than they were with the hard copy. The training session, moreover, while generally perceived to be well conducted, informative, and valuable, was not influential in increasing utilization rates for the microfilm in the short run. The small number of individuals who attended the training session and used the microfilm during the trial period precluded linking the training session with users' attitudes toward the abstracts.

Fast electrometer amplifier for astronomical photometry

A compact, inexpensive, and reliable electrometer which will respond to frequencies from dc to a few kilohertz is described. The high megohm feedback resistors are shared with a built-in calibration and zero suppression current source, resulting in substantial savings in space and money.