Engine Data Interpretation System (EDIS), phase 2

A prototype of an expert system was developed which applies qualitative constraint-based reasoning to the task of post-test analysis of data resulting from a rocket engine firing. Data anomalies are detected and corresponding faults are diagnosed. Engine behavior is reconstructed using measured data and knowledge about engine behavior. Knowledge about common faults guides but does not restrict the search for the best explanation in terms of hypothesized faults. The system contains domain knowledge about the behavior of common rocket engine components and was configured for use with the Space Shuttle Main Engine (SSME). A graphical user interface allows an expert user to intimately interact with the system during diagnosis. The system was applied to data taken during actual SSME tests where data anomalies were observed

Density Functional Calculations On First-Row Transition Metals

The excitation energies and ionization potentials of the atoms in the first transition series are notoriously difficult to compute accurately. Errors in calculated excitation energies can range from 1--4 eV at the Hartree-Fock level, and errors as high as 1.5eV are encountered for ionization energies. In the current work we present and discuss the results of a systematic study of the first transition series using a spin-restricted Kohn-Sham density-functional method with the gradient-corrected functionals of Becke and Lee, Yang and Parr. Ionization energies are observed to be in good agreement with experiment, with a mean absolute error of approximately 0.15eV; these results are comparable to the most accurate calculations to date, the Quadratic Configuration Interaction (QCISD(T)) calculations of Raghavachari and Trucks. Excitation energies are calculated with a mean error of approximately 0.5eV, compared with \sim 1\mbox{eV} for the local density approximation and 0.1eV for QCISD(T). These gradient-corrected functionals appear to offer an attractive compromise between accuracy and computational effort.Comment: Journal of Chemical Physics, 29, LA-UR-93-425

Did the Bundesbank React to Stock Price Movements?

In this paper, we investigate the relationship between stock returns and short-term interest rates. Identification of the stock return-interest rate relation is solved by using a new technique that relies on the heteroskedasticity of shocks to stock market returns. We suggest some improvements to the identification technique and its justification, as well as providing some new findings. In particular, we ask whether the Bundesbank, prior to the European Central Bank taking responsibility for monetary policy in 1999, reacted systematically to stock price movements. In contrast to the results for the US, our empirical findings for the 1985 - 1998 period show a positive, but statistically insignificant, parameter for the relationship between German stock returns and short-term interest rates at the daily frequency. The same result is found at the monthly frequency. Nevertheless, the confidence bands are wide enough that we cannot entirely exclude the possibility of a reaction at lower frequencies. The results are extremely robust to alternative methods used to identify changes in heteroskedasticity. The evidence is, therefore, inconsistent with the hypothesis of a systematic reaction of the Bundesbank to every wiggle in German stock prices. Both the historical and institutional evidence are supportive of this conclusion. -- In diesem Diskussionspapier untersuchen wir den Zusammenhang zwischen Aktienkursveränderungen und Veränderungen der kurzfristigen Zinssätze. Die ökonometrische Identifikation dieses Zusammenhangs erfolgt mit Hilfe eines neuen Verfahrens, das die Heteroskedastie von Aktienkursveränderungen ausnutzt. Wir schlagen einige Verbesserungen und Rechtfertigungen zu diesem Verfahren vor und liefern neue empirische Befunde. Im Vordergrund der Betrachtungen steht die Frage, ob die Bundesbank vor der Übernahme der geldpolitischen Entscheidungen durch die Europäische Zentralbank im Jahre 1999 systematisch auf Veränderungen der Aktienkurse reagiert hat. Im Unterschied zu den verfügbaren Ergebnissen für die Vereinigten Staaten von Amerika, finden wir auf Basis von Tagesdaten zwar einen positiven, aber statistisch nicht signifikanten Parameter für die Reaktion des kurzfristigen Zinssatzes auf Änderungen des Aktienkurses. Auf der Grundlage von Monatsdaten ist der Parameter ebenfalls positiv und statistisch insignifikant. Die Konfidenzintervalle sind aber sehr breit, so dass eine Reaktion auf der niedrigeren Frequenz nicht völlig ausgeschlossen werden kann. Die empirischen Resultate sind sehr robust gegenüber unterschiedlichen Modellspezifikationen. Die empirische Evidenz widerspricht somit der These einer systematischen Reaktion der Bundesbank auf jede Bewegung am Aktienmarkt, was durch die historischen und institutionellen Gegebenheiten gestützt wird.

Asset Prices in Taylor Rules: Specification, Estimation, and Policy Implications for the ECB

This paper estimates standard and extended Taylor rules for core countries in the euro area, namely France, Germany and Italy, as well as for the ECB. Forward, backward and forecast-based rules are estimated for a variety of samples since the late 1970s. We are particularly interested in the impact of adding asset prices to the standard Taylor rule specification. Since forward-looking Taylor rules are usually estimated via GMM we perform extensive tests for over-identifying restrictions and instrument relevance, a practice generally eschewed in previous work. We find that asset prices can be highly relevant as instruments rather than as separate arguments in policy rules. Backwardlooking Taylor rules, however, cannot be rejected outright. Forecast-based rules perform best using the root mean squared error metric but produce coefficients implying that central banks may be too aggressive at fighting inflation. Encompassing tests are therefore required to select the ?best? policy rule and these suggest that policy rules need to have a mix of forward and forecast-based elements. Furthermore too aggressive reactions to stock prices in particular would have led to an implausible monetary policy. Hence, asset prices appear at best to serve as indicators of the direction of interest rates and not as a variable that the ECB directly reacts to. --reaction function,asset prices

Seven for Seven: \u3ci\u3eThe Voyage of the\u3c/i\u3e Dawn Treader and the Literary Tradition

Examines the motif of the seven cardinal sins within Voyage, linking each of the seven lost lords of Narnia to a particular vice and showing how the crew of the Dawn Treader resists the vices to which they succumbed. This essay is meant to be read with Schuknecht, Mattison “C.S. Lewis’s Debt to Dante” in the same issue, as each comments on the other

Quasirandom Load Balancing

We propose a simple distributed algorithm for balancing indivisible tokens on graphs. The algorithm is completely deterministic, though it tries to imitate (and enhance) a random algorithm by keeping the accumulated rounding errors as small as possible. Our new algorithm surprisingly closely approximates the idealized process (where the tokens are divisible) on important network topologies. On d-dimensional torus graphs with n nodes it deviates from the idealized process only by an additive constant. In contrast to that, the randomized rounding approach of Friedrich and Sauerwald (2009) can deviate up to Omega(polylog(n)) and the deterministic algorithm of Rabani, Sinclair and Wanka (1998) has a deviation of Omega(n^{1/d}). This makes our quasirandom algorithm the first known algorithm for this setting which is optimal both in time and achieved smoothness. We further show that also on the hypercube our algorithm has a smaller deviation from the idealized process than the previous algorithms.Comment: 25 page

Facultative Altitudinal Movements by Mountain White-Crowned Sparrows (Zonotrichia Leucophrys Oriantha) in the Sierra Nevada

Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) winter in Mexico and often arrive in the vicinity of their breeding grounds in the Sierra Nevada well before nesting is possible. Arrival at Tioga Pass, California (elevation 3,030 m), usually occurs in early May, but residual winter snow and adverse weather can delay nesting for weeks. We used radiotelemetry to determine whether prebreeding Mountain White-crowned Sparrows engaged in weather-related altitudinal movements during the waiting period between the end of spring migration and onset of breeding during 1995-2001, with a range of residual winter snowpacks. Interannual variation in arrival date and onset of egg laying was 18 and 41 days, respectively. We tracked females for two years and males for all seven years. During spring snowstorms (which occurred in four years), radiomarked individuals moved to lower elevation sites, where they often remained for several days. Departing birds left Tioga Pass by early afternoon and returned early in the morning after storms. More frequent storms during tracking increased the likelihood of facultative altitudinal movements, but heavier residual winter snowpack did not. Warm days increased the likelihood of birds returning to Tioga Pass from low elevation. This study demonstrates that facultative altitudinal movement behavior can be a common feature of spring arrival biology in montane-breeding birds. Received 1 November 2002, accepted 30 June 2004.Integrative Biolog