Hybrid LZW compression

The Science Data Management and Science Payload Operations subpanel reports from the NASA Conference on Scientific Data Compression (Snowbird, Utah in 1988) indicate the need for both lossless and lossy image data compression systems. The ranges developed by the subpanel suggest ratios of 2:1 to 4:1 for lossless coding and 2:1 to 6:1 for lossy predictive coding. For the NASA Freedom Science Video Processing Facility it would be highly desirable to implement one baseline compression system which would meet both of these criteria. Presented here is such a system, utilizing an LZW hybrid coding scheme which is adaptable to either type of compression. Simulation results are presented with the hybrid LZW algorithm operating in each of its modes

Selecting Windows

Covers double-hung, horizontal sliding, casement, awning, jalousie, top-hinged, and fixed windows. Includes patio doors and skylights

The Nature and Measurement of Secondary School Students\u27 Attitudes Toward Reading

In recent years attitudinal goals have increasingly become a planned facet of school curricula. As a result teachers have become more involved in assessing students\u27 attitudes toward what is being taught. Reading is certainly one area that receives considerable attention in this respect. Secondary teachers and administrators have come to realize that improving students\u27 attitudes toward reading is every bit as important as improving their reading comprehension, word recognition and word analysis skills

Arms Control and Heavy Missiles

The governing concept infnsing US nuclear strategy over the past two decades has been mutual assnred destruction (MAD). This concept postulates that once the United States and the Soviet Union achieved an invulnerable second-strike capabi Ii ty, stabi Ii ty would result. By definition the doctrine required that each side be able to offer a genuine threat to the other in the form of an invulnerable second-strike capability. Thns, if either side\u27s second-strike capability became vulnerable it would be necessary to reestablish an invulnerable retaliatory force