Previous studies have shown that, when presented in rapid stream (i.e., RSVP paradigm), word recognition speed for strings of three-letter words increases approximately 10% with large letter spacing, both in the fovea and the periphery (up to 10° eccentricity). A possible explanation is that small spacing may cause features of individual characters to overlap with one another, thus reducing text legibility, impeding letter and word recognition, and slowing down the reading process. In contrast, increasing letter spacing reduced the crowding effect until it was so wide that the word shape information is disrupted, or extends beyond the visual span, and thus slows down the reading.

The hypothesis is that using a contrast-enhancing filter (CEF) on a computer display will improve display legibility, reading speed and visual comfort. Twenty subjects performed reading tasks, letter counting tasks, and legibility measurements on eight display conditions: a cathode ray tube (CRT) and liquid crystal display (LCD) matched for size and luminance – each at high luminance, with two different CEFs and a lower luminance to match one of the CEFs. The CEFs decreased both luminance and contrast when applied to the displays with the brightness set high, although the contrast was better with the filters compared to a matched luminance display without a filter. The legibility measurements support the positive effect of the CEFs due to improved contrast but the larger negative effect due to reduction in luminance results in a net loss of legibility. Performance on the reading and letter counting tasks was not improved with the CEFs.

The science objectives for the Near Earth Asteroid Rendezvous (NEAR) Magnetometer Experiment (MAG) are to measure a possible magnetic field of 433 Eros to 5 nT accuracy and secondarily to detect asteroid-solar wind interaction signatures. Because the MAG sensor is body mounted, achieving this accuracy required detailed analysis of spacecraft magnetic fields during cruise. Sources of magnetic contamination identified prior to launch and during cruise are: propulsion latch valves, fixed 190 nT residual held, solar arrays and power harness, variable 15 to 60 nT field, power distribution terminal board, /spl sim/30 nT field with 5 nT variations, power shunting circuitry, 1-5 nT variations, the MAG sensor survival heater, 6 nT steps and attitude control momentum wheels, and 1 nT amplitude at 0.5 to 10 Hz from each of four wheels. Analysis of cruise data was used to create accurate /spl plusmn/1 nT models for the fixed and variable fields with signals below 0.5 Hz to provide correction of the raw data. The spacecraft field corrections and MAG calibration were validated with data from the Earth swing-by of January 1997. Comparison of solar wind magnetic held measurements from the WIND spacecraft and NEAR from January 22-24, 1997, before and after the Earth swing-by maneuver, confirm that the resulting NEAR magnetic field measurements are accurate to 1-2 nT.

Designing cost-effective architectures over wide area networks is becoming increasingly important with the rapid growth of client/server applications (e.g., WWW) over private and public wide-area networks. This paper presents a heuristic algorithm that can be used to (1) design cost-effective client/server architectures in an wide-area network environment; (2) analyze the tradeoffs between network transport cost and information storage cost; and (3) dynamically determine which server should be the default for a user. The algorithm works by determining server locations and default server assignments so that total network cost can be minimized. The algorithm can handle many realistic network parameters that cannot be taken into account easily by other approaches in the literature. These parameters include arbitrary physical and logical network topologies; physical and logical user groups; arbitrary number, capacity, and locations of servers; and arbitrary geographical distributions of user demands. Furthermore, the algorithm has a low time complexity of O(N/sup 3/). Quantitative analysis using the algorithm provides new insight into the design of client/server systems over wide-area networks. For example, a small number of servers could provide cost savings close to that achievable with large number of servers. Furthermore, cost savings using multiple servers can be made virtually insensitive to the ratio of transport cost to storage cost.

We have developed a simple direct execution architecture for a 32 bit Forth microprocessor. The processor can directly access a linear address space of over 4 gigawords. Two instruction types are defined; a subroutine call, and a user defined microcode instruction. On-chip stack caches allow most Forth primitives to execute in a single cycle.