Little research has been conducted on how differing spatial resolutions or classification techniques affect image-driven identification and categorization of slum neighborhoods in developing nations. This study assesses the correlation between satellite-derived land cover and census-derived socioeconomic variables in Accra, Ghana to determine whether the relationship between these variables is altered with a change in spatial resolution or scale. ASTER and Landsat TM satellite images are each used to classify land cover using spectral mixture analysis (SMA), and land cover proportions are summarized across Enumeration Areas in Accra and compared to socioeconomic data for the same areas. Correlation and regression analyses compare the SMA results with a Slum Index created from various socio-economic data taken from the Census of Ghana, as well as to data derived from a “hard” per-pixel classification of a 2.4 m Quickbird image. Results show that the vegetation fraction is significantly correlated with the Slum Index (Pearson’s r ranges from −0.33 to −0.51 depending on which image-derived product is compared), and the use of a spatial error model improves results (multivariate model pseudo-R2 ranges from 0.37 to 0.40 by image product). We also find that SMA products derived from ASTER are a sufficient substitute for classification products derived from higher spatial resolution QB data when using land cover fractions as a proxy for slum presence, suggesting that SMA might be more cost-effective for deriving land cover fractions than the use of high-resolution imagery for this type of demographic analysis.

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tncreased Interest In using workstatlons and small processors for distnbuted transaction processing raises the question of how to Implement the logs needed for transactron recovery Although logs can be rmplemented wrth data wntten to duplexed disks on each processing node, this paper argues there are advantages tf log data is wntten to multtple log server nodes A simple analysts Of expected loggrng loads leads to the conclusion that a hrgh performance, microprocessor based processing node can Support a log server if it uses efficient communication protocols and low IateflCy, non volatile storage to buffer log data The buffer IS needed to reduce the processing time per log record and to Increase throughput to the logging disk An interface to the log servers usmg simple, robust, and efficient protocols IS presented Also described are the disk data structures that the log servers use This paper concludes with a brief dkscusslon of remammg design issues, the status of a prototype Implementatron, and plans for its completion

Weighted voting is used as the basis for a replication technique for directories. This technique affords arbitrarily high data availability as well as high concurrency. Efficient algorithms are presented for all of the standard directory operations. A structural property of the replicated directory that permits the construction of an efficient algorithm for deletion is proven. Simulation results are presented and the system is modeled and analyzed. The analysis agrees well with the simulation, and the space and time performance are shown to be good for all configurations of the system.