Showing papers in "American Scientist in 1972"

Detection of soil moisture by remote surveillance

Abstract: Three general regions of the electromagnetic spectrum are being used in feasibility studies of remote sensing of soil moisture - the short-wave region, the thermal of long-wave region, and radar or micro-wave region. Simple solarimeters have been used to correlate albedo values (ratio of reflected incoming solar radiation depends on the amount of water in surface soil) gravimetrically measured water-content values of soil layers. Albedo values could also be used to delineate the three classical stages of soil drying. Studies have suggested that a thermal inertia concept could be used to monitor soil moisture, i.e. soil temperatures are measured when they are maximum and minimum and the difference between them is related to water content. The governing principle of microwave radiation techniques derives from the fact that the dielectric constant of water at microwave frequencies is quite large (80) whereas that of dry soil is typically less than 5. A wide range of wavelengths has been used in feasibility studies of soil-moisture detection by microwave techniques - from fractions of a centimeter to tens of centimeters - and the depth of the soil layer monitored has varied from a few millimeters to a few centimeters. Microwave techniques however, suffer from the need to know surface temperatures in order to resolve moisture-induced emittance changes, and albedo techniques always require specific knowledge of the soil type viewed. Cloud-cover (encountered in satellite based programs), salinity, and the presence of vegetation also create problems for these techniques. Some of the primary benefits of remote detection of soil moisture include the ability to predict crop yields, pest outbreaks, plant disease. It could also be an aid in the management of crops and rangelands.

Speech cues and sign stimuli.

Abstract: DOCUMENT REE.UME

Traffic flow and control: theory and applications

Abstract: Because of the omnipotence of the automobile in society today, it is necessary to understand the process which converts traffic into the menace it can become. It is only during the last decade or so that the scientific method has been applied on a large scale in developing a traffic science. This new science has addressed questions related to understanding traffic processes and to optimizing these processes through proper design and control. Some examples of both basic and applied research are discussed here, omitting applications of network theory to transportation planning.

From simulation model to public policy

Abstract: In Urban Dynamics, Jay W. Forrester constructs a simulation model of the housing, industry, and population of a single urban area. From this model he draws conclusions about the relative effectiveness of various public policies. This paper discusses both the original Forrester model and an adaptation of it which can be used to simulate any number of urban areas. The latter model is used to show that the effectiveness of the policies can be strongly dependent on whether they are applied nationally or only to individual urban areas. This result calls into question the usefulness of a model of a single area in the evaluation of national urban policy.