15,022 research outputs found
THERMTRAJ: A FORTRAN program to compute the trajectory and gas film temperatures of zero pressure balloons
A FORTRAN computer program called THERMTRAJ is presented which can be used to compute the trajectory of high altitude scientific zero pressure balloons from launch through all subsequent phases of the balloon flight. In addition, balloon gas and film temperatures can be computed at every point of the flight. The program has the ability to account for ballasting, changes in cloud cover, variable atmospheric temperature profiles, and both unconditional valving and scheduled valving of the balloon gas. The program was verified for an extensive range of balloon sizes (from 0.5 to 41.47 million cubic feet). Instructions on program usage, listing of the program source deck, input data and printed and plotted output for a verification case are included
A unified thermal and vertical trajectory model for the prediction of high altitude balloon performance
A computer model for the prediction of the trajectory and thermal behavior of zero-pressure high altitude balloon was developed. In accord with flight data, the model permits radiative emission and absorption of the lifting gas and daytime gas temperatures above that of the balloon film. It also includes ballasting, venting, and valving. Predictions obtained with the model are compared with flight data from several flights and newly discovered features are discussed
Design of a composite wing extension for a general aviation aircraft
A composite wing extension was designed for a typical general aviation aircraft to improve lift curve slope, dihedral effect, and lift to drag ratio. Advanced composite materials were used in the design to evaluate their use as primary structural components in general aviation aircraft. Extensive wind tunnel tests were used to evaluate six extension shapes. The extension shape chosen as the best choice was 28 inches long with a total area of 17 square feet. Subsequent flight tests showed the wing extension's predicted aerodynamic improvements to be correct. The structural design of the wing extension consisted of a hybrid laminate carbon core with outer layers of Kevlar - layed up over a foam interior which acted as an internal support. The laminate skin of the wing extension was designed from strength requirements, and the foam core was included to prevent buckling. A joint lap was recommended to attach the wing extension to the main wing structure
Exploring eternal stability with the simple harmonic universe
We construct nonsingular cyclic cosmologies that respect the null energy
condition, have a large hierarchy between the minimum and maximum size of the
universe, and are stable under linearized fluctuations. The models are
supported by a combination of positive curvature, a negative cosmological
constant, cosmic strings and matter that at the homogeneous level behaves as a
perfect fluid with equation of state -1 < w < -1/3. We investigate analytically
the stability of the perturbation equations and discuss the role of parametric
resonances and nonlinear corrections. Finally, we argue that Casimir energy
contributions associated to the compact spatial slices can become important at
short scales and lift nonperturbative decays towards vanishing size. This class
of models (particularly in the static limit) can then provide a useful
framework for studying the question of the ultimate (meta)stability of an
eternal universe.Comment: 22 pages, 2 figure
Trade Agreements as Endogenously Incomplete Contracts
We propose a model of trade agreements in which contracting is costly, and as a consequence the optimal agreement may be incomplete. In spite of its simplicity, the model yields rich predictions on the structure of the optimal trade agreement and how this depends on the fundamentals of the contracting environment. We argue that taking contracting costs explicitly into account can help explain a number of key features of real trade agreements.
Winning the Workforce Challenge: A Report on New Jersey's Knowledge Economy
An economic and policy analysis of the New Jersey workforce. The report describes challenges facing workers and policymakers in closing the skills gap, addressing long-term unemployment, ensuring broad-scale economic opportunity, and strengthening government programs
Ground Beetles of Islands in the Western Basin of Lake Erie and the Adjacent Mainland (Coleoptera: Carabidae, Including Cicindelini)
We report 241 species representing 63 genera of ground beetles from the islands of the western basin of Lake Erie and selected mainland sites from a 1991-93 survey, plus specimens examined in public and private collections, and previously published sources. Most species are generally distributed; however, a restricted population of Sphaeroderus schaumii schaumii we rediscovered is no doubt imperiled. Comparison of wing morphotype frequencies of the Lake Erie island species with mainland populations from studies in Ohio and Michigan support a hypothesis that vagility is of increased import in the islands. Regression and correlation analysis show a positive relationship between species number and island area, no correlation between species number and distance from the mainland and an improved fit for a multiple regression which includes collecting effort
- …