Airborne lidar observations of Arctic polar stratospheric clouds

Polar stratospheric clouds (PSC's) have been detected repeatedly during Arctic and Antarctic winters since 1978/1979 by the SAM II (Stratospheric Aerosol Measurement II) instrument aboard the NIMBUS-7 satellite. PSC's are believed to form when supercooled sulfuric acid droplets freeze, and subsequently grow by deposition of ambient water vapor as the local stratospheric temperature falls below the frost point. In order to study the characteristics of PSC's at higher spatial and temporal resolution than that possible from the satellite observations, aircraft missions were conducted within the Arctic polar night vortex in Jan. 1984 and Jan. 1986 using the NASA Langley Research Center airborne dual polarization ruby lidar system. A synopsis of the 1984 and 1986 PSC observations is presented illustrating short range spatial changes in cloud structure, the variation of backscatter ratio with temperature, and the depolarization characterics of cloud layers. Implications are noted with regard to PSC particle characteristics and the physical process by which the clouds are thougth to form

Visualization of back pain data-A 3-D solution

Traditional approaches to gathering and visualizing pain data rely on two-dimensional (2-D) human body models, where different types of sensation are recorded with various monochrome symbols. We proposean alternative that uses a three-dimensional (3-D) representation of the human body, which can be marked in color to visualize and record pain data

SAGE 2 satellite data set validation

The results of a validation study of data obtained by the Stratospheric Aerosol and Gas Experiment 2 satellite experiment (SAGE 2) are given. Preliminary SAGE 2 data have been available for the period October, 1984 to May, 1985. In addition, the results of two correlative experimental measurement series have been studied in detail, as well as climatological data obtained by other techniques, including ground-based and airborne lidar. The study shows the SAGE 2 data to be of great potential value to studies of the microphyiscs of stratospheric aerosols, the chemistry of trace gases and stratospheric dynamics. A small number of unidentified errors in the current preliminary data set are described. These will be removed from the next version of the data set which is anticipated to be of archival quality

New geometries for high spatial resolution hall probes

The Hall response function of symmetric and asymmetric planar Hall effect devices is investigated by scanning a magnetized tip above a sensor surface while simultaneously recording the topography and the Hall voltage. Hall sensor geometries are tailored using a Focused Ion Beam, in standard symmetric and new asymmetric geometries. With this technique we are able to reduce a single voltage probe to a narrow constriction 20 times smaller than the other device dimensions. We show that the response function is peaked above the constriction, in agreement with numerical simulations. The results suggest a new way to pattern Hall sensors for enhanced spatial resolution.Comment: 12 pages, 5 figures, submitted to Journal of Applied Physic

Expertise in map comprehension: processing of geographic features according to spatial configuration and abstract roles

Expertise in topographic map reading is dependent on efficient processing of geographical information presented in a standardised map format. Studies have supported the proposition that expert map readers employ cognitive schemas in which prototypical configurations held in long term memory are employed during the surface search of map features to facilitate map comprehension. Within the experts’ cognitive schemas, it is assumed that features are grouped according to spatial configurations that have been frequently encountered and these patterns facilitate efficient chunking of features during information processing. This thesis investigates the nature of information held in experts’ cognitive schemas. It also proposes that features are grouped in the experts’ schemas not only by their spatial configurations but according to the abstract and functional roles they perform. Three experiments investigated the information processing strategies employed by firstly, skilled map readers engaged in a map reproduction task and secondly, expert map readers engaged in a location comparison exercise. In the first and second experiments, skilled and novice map readers studied and reproduced a town map and a topographic map. Drawing protocols and verbal protocols provided insights into their information processing strategies. The skilled map readers demonstrated superior performance for reproducing contour related data with evidence of the use of cognitive schemas. For the third experiment, expert and novice map readers compared locations within map excerpts for similarities of boundary extents. Eye-gaze data and verbal protocols provided information on the features attended to and the participants’ search patterns. The expert group integrated features into their cognitive schemas according to the abstract roles they performed significantly more frequently than the novices. Both groups employed pattern recognition to integrate features for some of the locations. Within a similar experimental design the second part of the third experiment examined whether experts also integrated the abstract roles of remote features and village grouping concepts within their cognitive schemas. The experts again integrated the abstract roles of physical features into their schemas more often than novices but this strategy was not employed for either the remote feature or grouping categories. Implications for map design and future Geographic Information Systems are discussed

SAGE measurements of the stratospheric aerosol dispersion and loading from the Soufriere Volcano

Explosions of the Soufriere volcano on the Caribbean Island of St. Vincent reduced two major stratospheric plumes which the stratospheric aerosol and gas experiment (SAGE) satellite tracked to West Africa and the North Atlantic Ocean. The total mass of the stratospheric ejecta measured is less than 0.5% of the global stratospheric aerosol burden. No significant temperature or climate perturbation is expected. It is found that the movement and dispersion of the plumes agree with those deduced from high altitude meteorological data and dispersion theory. The stratospheric aerosol dispersion and loading from the Soufrier volcano was measured

A new nickel-base wrought superalloy for applications up to 1033 K (1400 F)

Alloy was melted from high purity raw materials and cast ingots extruded at 1422 K. Material was hot rolled to 0.013 m diameter bar stock. Partial solution heat-treatment followed by aging produced structure of fine gamma prime precipitate reinforcing gamma matrix containing coarser blocky gamma prime particles. Alloy can be processed by powder metallurgy

Development of a global model for atmospheric backscatter at CO2 wavelengths

The effect of aerosol microphysical processes on the backscatter from an aerosol plume undergoing long-range atmospheric transport was studied. A numerical model which examines the effects of coagulation and sedimentation on an aerosol size distribution is under development and the initial results for a single homogeneous layer were obtained. Use was made of the SAGE/SAM II data set to study the global variation of aerosol concentration and, hence, to predict the variation of Beta sub CO2. Computer programs were written to determine the mean, median, and the probability distribution of the measured aerosol extinction as a function of altitude, latitude and geographical conditions. The first data sets analyzed in this way are under study. Data was used to study aerosol behavior over the U.S.A. and the Pacific Ocean

SAGE 1 and SAM 2 measurements of 1 micron aerosol extinction in the free troposphere

The SAGE 1 and SAM 2 satellite sensors were designed to measure, with global coverage, the 1 micron extinction produced by the stratospheric aerosol. In the absence of high altitude cloud, similar measurements may be made for the free tropospheric aerosol. Median extinction values in the Northern Hemisphere, for altitudes between 5 and 10 km, are found to be one-half to one order of magnitude greater than values at corresponding latitudes in the Southern Hemisphere. In addition, a seasonal increase by a factor of 1.5 yields 2 is observed in both hemispheres in local spring and summer. Following major volcanic eruptions, a long-lived enhancement of the aerosol extinction is observed for altitudes above 5 km

Excessive Strand End Slip in Prestressed Piles

This paper presents the results of a research project that investigated excessive strand end slip observed recently in some prestressed piles. From measurements taken in the field, it is apparent that the problem o excessive initial strand slip is independent of pile shape and size. Strand end slip is evident in piles of different manufacturers in different states in the Southeast. Excessive strand end slip was found in both the top and bottom of the cross section of the piles, although the top portion of the cross section generally exhibited much higher initial slip. Several preventive measures can be adopted to reduce the excessive strand end slip. These preventive measures include: a) proper concrete mixture proportioning to reduce top bar effect; b) use of higher-strength concrete with the lowest possible slump and setting time; c) assessment of the condition of the strands prior to installation to insure excellent bond characteristics; d) gradual release of prestress, with an optimal release sequence; and e) use of adequate vibration to ensure consolidation. The strand end slip measured at five prestressing plants in the Southeast is considerably higher than the allowable end slip and is expected to affect the pile performance. If the strand slip theory is adopted, the strand development length increases substantially due to the excessive strand end slip. A top bar effect factor similar to the one used in reinforced concrete design is recommended. To maintain the excellent quality of precast and prestressed concrete products, manufacturers should adopt a dynamic quality control process that follows the rapid changes in the industry. More tests are necessary to ensure excellent quality, such as the Moustafa or an equivalent test, to assess the bond capabilities of the strands, end slip measurements, and direct measurement of the transfer length. Installation of piles should proceed in a manner to alleviate the top bar effects by placing piles alternately in their best and worst directions