15,912 research outputs found
The Skylab radar altimeter
A summary of the significant hardware characteristics of the S-193 altimeter experiment portion of the 1973 Skylab Mission is presented. A detailed discussion of the altimetry, oceanographic, and instrumentation technology objectives are presented along with a discussion of the major experiments associated with these objectives
NASA Wallops Flight Center GEOS-3 altimeter data processing report
The procedures used to process the GEOS-3 radar altimeter data from raw telemetry data to a final user data product are described. In addition, the radar altimeter hardware design and operating parameters are presented to aid the altimeter user in understanding the altimeter data
An atlas of GEOS-3 radar altimeter data for data buoy comparison studies
An atlas is compiled to identify times and dates when GEOS-3 altimeter data was taken in the vicinity of data buoys. The time period covered is from GEOS launch to April 9, 1978. Two buffer areas are considered for each of the various buoy locations to determine the simultaneity of GEOS and buoy data. The two buffer areas are ? or - 0.25 degrees and ? or - 1 degree
IMPACTS ON PROPERTY TAXES OF RECLASSIFYING FLOOD-PRONE CROPLAND IN THE SOUTH DELTA AREA OF MISSISSIPPI
Current tax appraisal procedures for cropland in Mississippi do not account for any negative impacts caused by frequent flooding in some areas of the South Delta. If flood-prone cropland values are significantly below average, the current tax system could generate inequitable tax burdens on owners of flood-prone cropland. A modified system of appraisal may be desirable to produce a more equitable tax structure. The purpose of this study was to evaluate different methods of reclassifying flood-prone cropland in the South Delta and to determine subsequent tax impacts on landowners and county tax revenue. Cropland tax data for Sharkey and Issaquena Counties were collected and different permanent reclassification schemes were proposed. Reclassification schemes were defined by lowering a parcel's capability class assignment by 1, 2, 3, or 4 classes if its elevation was below a specified trigger level. The impact that each reclassification scheme would have on landowners' taxes and the tax base in the affected counties was then estimated. In order to show the impact on tax shifts that would keep the county's tax base from declining, a new, higher millage rate was computed for selected reclassification schemes. After applying the adjusted millage rate to all properties in the county, changes in cropland taxes were reduced. Among the permanent reclassification schemes evaluated in this study, a trigger elevation level of 90 feet appears to offer reasonable tax impacts. Cropland parcels below 90 feet could be reassigned to the lowest capability class if the residents desired to provide the largest tax relief to these property owners. A more conservative reassignment scheme could be selected if desired. A temporary (year-to-year) reclassification system may provide more equitable tax distributions over time but would probably require more administrative costs to implement.Cropland appraisal, property taxes, flood-prone cropland, Land Economics/Use,
An atlas of 1975 GEOS-3 radar altimeter data for hurricane/tropical disturbance studies, volume 1
Geographic locations of 1975 hurricanes and other tropical disturbances were correlated with the closest approaching orbits of the GEOS-3 satellite and its radar altimeter. The disturbance locations and altimeter data were gathered for a seven-month period beginning with GEOS-3 launch in mid-April 1975. Areas of coverage were the Atlantic Ocean, the Carribean, the Gulf of Mexico, the west coast of the continental United States, and the central and western Pacific Ocean. Volume 1 contains disturbance coverage data for the Atlantic Ocean, Gulf of Mexico, and Eastern Pacific Ocean. Central and Western Pacific coverage is documented in Volume II
Scaling behavior in economics: II. Modeling of company growth
In the preceding paper we presented empirical results describing the growth
of publicly-traded United States manufacturing firms within the years
1974--1993. Our results suggest that the data can be described by a scaling
approach. Here, we propose models that may lead to some insight into these
phenomena. First, we study a model in which the growth rate of a company is
affected by a tendency to retain an ``optimal'' size. That model leads to an
exponential distribution of the logarithm of the growth rate in agreement with
the empirical results. Then, we study a hierarchical tree-like model of a
company that enables us to relate the two parameters of the model to the
exponent , which describes the dependence of the standard deviation of
the distribution of growth rates on size. We find that , where defines the mean branching ratio of the hierarchical tree and
is the probability that the lower levels follow the policy of higher
levels in the hierarchy. We also study the distribution of growth rates of this
hierarchical model. We find that the distribution is consistent with the
exponential form found empirically.Comment: 19 pages LateX, RevTeX 3, 6 figures, to appear J. Phys. I France
(April 1997
Instructor perspectives on iteration during upper-division optics lab activities
Although developing proficiency with modeling is a nationally endorsed
learning outcome for upper-division undergraduate physics lab courses, no
corresponding research-based assessments exist. Our longterm goal is to develop
assessments of students' modeling ability that are relevant across multiple
upper-division lab contexts. To this end, we interviewed 19 instructors from 16
institutions about optics lab activities that incorporate photodiodes.
Interviews focused on how those activities were designed to engage students in
some aspects of modeling. We find that, according to many interviewees,
iteration is an important aspect of modeling. In addition, interviewees
described four distinct types of iteration: revising apparatuses, revising
models, revising data-taking procedures, and repeating data collection using
existing apparatuses and procedures. We provide examples of each type of
iteration, and discuss implications for the development of future modeling
assessments.Comment: 4 pages, 1 figure; under revie
Scaling behavior in economics: I. Empirical results for company growth
We address the question of the growth of firm size. To this end, we analyze
the Compustat data base comprising all publicly-traded United States
manufacturing firms within the years 1974-1993. We find that the distribution
of firm sizes remains stable for the 20 years we study, i.e., the mean value
and standard deviation remain approximately constant. We study the distribution
of sizes of the ``new'' companies in each year and find it to be well
approximated by a log-normal. We find (i) the distribution of the logarithm of
the growth rates, for a fixed growth period of one year, and for companies with
approximately the same size displays an exponential form, and (ii) the
fluctuations in the growth rates -- measured by the width of this distribution
-- scale as a power law with , . We find
that the exponent takes the same value, within the error bars, for
several measures of the size of a company. In particular, we obtain:
for sales, for number of employees,
for assets, for cost of goods sold, and
for property, plant, & equipment.Comment: 16 pages LateX, RevTeX 3, 10 figures, to appear J. Phys. I France
(April 1997
Student ownership of projects in an upper-division optics laboratory course: A multiple case study of successful experiences
We investigate students' sense of ownership of multiweek final projects in an
upper-division optics lab course. Using a multiple case study approach, we
describe three student projects in detail. Within-case analyses focused on
identifying key issues in each project, and constructing chronological
descriptions of those events. Cross-case analysis focused on identifying
emergent themes with respect to five dimensions of project ownership: student
agency, instructor mentorship, peer collaboration, interest and value, and
affective responses. Our within- and cross-case analyses yielded three major
findings. First, coupling division of labor with collective brainstorming can
help balance student agency, instructor mentorship, and peer collaboration.
Second, students' interest in the project and perceptions of its value can
increase over time; initial student interest in the project topic is not a
necessary condition for student ownership of the project. Third, student
ownership is characterized by a wide range of emotions that fluctuate as
students alternate between extended periods of struggle and moments of success
while working on their projects. These findings not only extend the literature
on student ownership into a new educational domain---namely, upper-division
physics labs---they also have concrete implications for the design of
experimental physics projects in courses for which student ownership is a
desired learning outcome. We describe the course and projects in sufficient
detail that others can adapt our results to their particular contexts.Comment: 22 pages, 3 tables, submitted to Phys. Rev. PE
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