The limitations and potential of AVHRR GAC data for continental scale fire studies

Global Area Coverage (GAC) data from the Advanced Very High Resolution Radiometer (AVHRR) are available on a daily basis, dating back to July 1981. The AVHRR's 3·55–3·93 μm channel is suitable for detection of terrestrial hot spots, such as bushfires. The long-term archives and global cover make the GAC a potentially valuable data source for large scale fire studies. However, these data are sampled spatially through a combination of line skipping and averaging. This study shows that the sampling affects the sensitivity of GAC for fire detection in relation to ecosystem and season. The GAC are found to provide a reasonable measure of fire activity in grassland and open b'ush savannah, but to perform poorly in the forest margins. Overall at least 79 per cent of fires detected with non-sampled AVHRR data are missed by the GAC. This severely limits the use of GAC data for quantitative fire studies. The GAC does appear to provide a reasonable measure of fire calendar (i.e., variations in fire activity with time) and on a continental scale successfully identifies the main regions of fire activity. The potential of these data for continental scale fire studies is illustrated through the preliminary analysis of 277 GAC mosaics of Africa for the period September 1988 to August 1989.     

FACTORS AFFECTING THE COMPARATIVE ADVANTAGES OF SEQUENTIAL AND BATCHED DECISION MAKING

Whether to batch-process data or to randomly update files in real-time is a common design choice faced by information system analysts. A related (but different) problem is whether or not decisions should be batch processed. Though this latter problem is undoubtedly of greater managerial concern it has received less attention. This paper discusses considerations relevant to the optimal batching and timing of decisions and illustrates these by examples. A simple illustrative mathematical model of the problem is developed and optimized. This topic is of interest to MIS designers since their systems may include automated decision making and always support the decision making process.     

EFFECTS of FEED MOISTURE and BARREL TEMPERATURE ON the RHEOLOGICAL PROPERTIES of EXTRUDED COWPEA MEAL1

Decorticated cowpea meal was adjusted to 20, 30, and 40% moisture and extruded in a Wayne pilot-scale extruder at barrel temperatures of 150, 175 and 200°C. the resulting products were subjected to rheological evaluation using the Instron Universal Testing Machine equipped with standard tensile jaws, the Warner-Bratzler shear device and the Kramer Shear Press. Regression equations relating rheological properties to feed moisture and barrel temperature were computed from the data, and response surfaces were generated from these models. Tensile strength of extrudates was greatest for the dense products produced in the low moisture-low temperature region and declined at higher moistures and temperatures. Shear strength as determined by either the Warner-Bratzler or Kramer devices exhibited a ridge of high values extending from 20%-150°C to 30%-200°C, and declined for brittle, expanded products made at low moisture and high temperature and for soft products made at high moisture.     

Effect of Feed Moisture and Barrel Temperature on Physical Properties of Extruded Cowpea Meal

Whole cowpeas were decorticated, adjusted to moisture contents of 20, 30 and 40%, chopped into coarse meals and extruded on a Wayne pilot-scale extrudel (19 mm × 475 mm barrel, 5:1 compression screw, 4.76 mm i.d. die) at barrel temperatures of 150°, 175° and 200°C. Measured product temperatures ranged from 130-164°C. Product moistures ranged from 10–34% and were affected mainly by initial moisture. Expansion at the die was highest for 20% moisture extrudates (1.7–1.9), and lowest for 40% samples (0.9- 1.3). The 20%-150° extrudate was dense (0.45 g/cm³) and twisted. The 20%-175° product was highly expanded (0.23 g/cm³). Other products were intermediate in density. Tristimulus color values were determined.     

Measurement of Mobility and Zeta Potential of Beta-Alumina Suspensions in Various Solvents

Mobilities and zeta potentials of β -alumina particles have been measured in 1-pentanol, nitromethane, and dichloromethane media. The effects of grinding, aging, water content, and acid solute content were observed; all of these variables were critical. The charge on the β -alumina particles could be either positive or negative, depending on the suspension conditions.