A linear circuit analysis program with stiff systems capability

Several existing network analysis programs have been modified and combined to employ a variable topological approach to circuit translation. Efficient numerical integration techniques are used for transient analysis

International Ultraviolet Explorer (IUE) satellite mission analysis

The results are presented of the mission analysis performed by Computer Sciences Corporation (CSC) in support of the International Ultraviolet Explorer (IUE) satellite. The launch window is open for three separate periods (for a total time of 7 months) during the year extending from July 20, 1977, to July 20, 1978. The synchronous orbit shadow constraint limits the launch window to approximately 88 minutes per day. Apogee boost motor fuel was computed to be 455 pounds (206 kilograms) and on-station weight was 931 pounds (422 kilograms). The target orbit is elliptical synchronous, with eccentricity 0.272 and 24 hour period

After the Epidemic: Recent Trends in Youth Violence in the United States

The epidemic of youth violence in the United States peaked in 1993 and has been followed by a rapid, sustained drop. In parallel with our earlier treatment (Cook and Laub 1998), we assess two types of explanation for this drop -- those that focus on 'cohort' effects (including the effects of abortion legalization) and those that focus on 'period' effects (including the effects of the changing crack-cocaine trade). Once again we are able to reject the cohort-type explanations, yet also find contradictions with an account based on the dynamics of crack markets. The 'way out' of this epidemic has not been the same as the 'way in.' The relative importance in homicide of youths, racial minorities, and guns, all of which increased greatly during the epidemic, has remained high during the drop. Arrest patterns tell a somewhat different story, in part because of changing police practice with respect to aggravated assault. Finally, we demonstrate that the rise and fall of youth violence has been narrowly confined with respect to race, sex, and age, but not geography. Given the volatility in the rates of juvenile violence, forecasting rates is a risky business indeed. Effectively narrowing the range of plausible explanations for the recent ups and downs may require a long time horizon, consideration of a broader array of problem behaviors, and comparisons with trends in other countries.

Equivalent damage: A critical assessment

The overall goal of achieving improved life cycle management of aircraft engine, gas turbine components is a major industry thrust. Low cycle fatigue (LCF) crack initiation prediction, an important element of life cycle management as traditionally applied, may be overly conservative in estimating total cyclic life capability. Consequently, there is increasing pressure to improve predictive methods both for crack initiation and for subsequent crack propagation. The utility of equivalent damage concepts for application to hot section components of aircraft engines was studied. Specifically, the topics examined were mean stress, cumulative damage, and multiaxiality. Other factors inherently linked to this study were the basic formulation of damage parameters at elevated temperatures and the fact that hot section components experience severe temperature fluctuations throughout their service lifetime

Nondeterministic Instance Complexity and Proof Systems with Advice

Motivated by strong Karp-Lipton collapse results in bounded arithmetic, Cook and Krajíček [1] have recently introduced the notion of propositional proof systems with advice. In this paper we investigate the following question: Given a language L , do there exist polynomially bounded proof systems with advice for L ? Depending on the complexity of the underlying language L and the amount and type of the advice used by the proof system, we obtain different characterizations for this problem. In particular, we show that the above question is tightly linked with the question whether L has small nondeterministic instance complexity

Faunal Lists of the Tertiary Vertebrata of Nebraska and Adjacent Areas

Mode of access: Internet