HAL/S programmer's guide

HAL/S is a programming language developed to satisfy the flight software requirements for the space shuttle program. The user's guide explains pertinent language operating procedures and described the various HAL/S facilities for manipulating integer, scalar, vector, and matrix data types

HAL/S programmer's guide

This programming language was developed for the flight software of the NASA space shuttle program. HAL/S is intended to satisfy virtually all of the flight software requirements of the space shuttle. To achieve this, HAL/s incorporates a wide range of features, including applications-oriented data types and organizations, real time control mechanisms, and constructs for systems programming tasks. As the name indicates, HAL/S is a dialect of the original HAL language previously developed. Changes have been incorporated to simplify syntax, curb excessive generality, or facilitate flight code emission

Characterization of a Rijke Burner as a Tool for Studying Distribute Aluminum Combustion

As prelude to the quantitative study of aluminum distributed combustion, the current work has characterized the acoustic growth, frequency, and temperature of a Rijke burner as a function of mass flow rate, gas composition, and geometry. By varying the exhaust temperature profile, the acoustic growth rate can be as much as tripled from the baseline value of approximately 120 s-1• At baseline, the burner operated in the third harmonic mode at a frequency of 1300 Hz, but geometry or temperature changes could shift operation to a second mode. During oscillatory combustion, center-line temperatures in the exhaust rose by as much as 80 K when compared to the non-oscillating case. With oscillations, the mean flow of gases in the boundary slowed with a consequent decrease in heat transfer to the walls. The information gained in this study will aid in refining burner modeling efforts and allow interpretation of planned aluminum combustion studies in hopes of gaining a greater understanding of distributed combustion as a driving mechanism in the combustion instability of solid propellant rocket motors

Examination of the Combustion Morphology of Ziconium Carbide Using Scanning Electron Microscopy

Calculation of viscous particle damping of acoustic combustion instability in solid propellant motors requires an understanding of the combustion behavior of added particles and oxides. A simple hydrogen/oxygen flame was used to ignite carefully sieved zirconium carbide particles which were impacted on slides at different levels below the burner. Scanning electron microscopy revealed that zirconium carbide has a complex heterogeneous combustion morphology. Initially, particles are partly vitreous and crystalline with a complex surface area. Upon ignition, particles round, but soon wrinkle as zirconium oxide deposits on the surface. Such morphology information is useful to refine viscous damping calculations

U.S. and U.K. Interest Rates 1890 - 1934: New Evidence on Structural Breaks

This paper presents econometric evidence on whether the founding of the Federal Reserve in 1914 caused a structural change from level-stationarity to difference-stationarity in U.S. and U.K. short-term nominal interest rates. We develop new econometric tests that allow for parameter transitions to test for a break of this kind and undertake a grid search analysis of dates and speeds for the change. We find that U.S. nominal interest rates most likely evolved rapidly to difference-stationarity in June 1917. For the U.K. we fail to reject the null that U.K. interest rate series follow a difference stationary process over the entire period 1890-1934. Our analysis differs from previous research on this topic in that we take care to explore statistical uncertainty around parameter estimates, and incorporate higher order dynamics into our econometric analysis.

New approaches for estimating risk from exposure to diethylstilbestrol.

A subgroup from a National Institute of Environmental Health Sciences, workshop concerned with characterizing the effects of endocrine disruptors on human health at environmental exposure levels considered the question, If diethylstilbestrol (DES) were introduced into the market for human use today and likely to result in low-dose exposure of the human fetus, what would be required to assess risk? On the basis of an analysis of the quality of data on human DES exposure, the critical times and doses for inducing genital tract malformations and cancer must be determined. This would be facilitated through analysis of the ontogeny of estrogen receptor expression in the developing human genital tract. Models of low-dose estrogenic effects will have to be developed for human and rodent genital tract development. Mouse models offer many advantages over other potential animal models because of the wealth of the earlier literature, the availability of sensitive end points, the availability of mutant lines, and the possibility of generating genetically engineered model systems. Through multidisciplinary approaches, it should be possible to elucidate the cellular and molecular mechanisms of endocrine disruption elicited by estrogens during development and facilitate an assessment of risk to humans