AN ANALYSIS ON THE EFFECTS OF ADDITIVE MANUFACTURING (AM) ON F/A-18E/F READINESS

This research paper focuses on the Boeing F/A-18E and the F/A-18F Super Hornet aviation depot level repairable (AVDLR) parts process and the potential effects of additive manufacturing (AM) on that process. The motivation for study was spurred by recent reports indicating that the F/A-18E/F is experiencing decreased operational readiness due to increases in maintenance-related impacts related to parts availability, long lead times, and increased parts failure frequency. This study aimed to determine the requirements for interjecting AM into the Intermediate level repair process in order to make a significant impact on  F/A-18E/F depot-level repairable part lead times. More specifically, this research analyzes the potential impact of various AM production levels on overall lead times. Facilitation of this research project was accomplished through mathematical modeling and by conducting simulations based on various assumptions and probability distributions. Eight simulations were conducted, each with different AM production time assumptions. Resultant outputs reflected 19 different scenarios simulating 0%–90% production of AM at the Intermediate Maintenance level. Results indicate that AM has the potential to decrease overall expected lead time averages if AM production can be kept to less than approximately 30 days.Lieutenant, United States NavyLieutenant, United States NavyLieutenant Commander, United States NavyApproved for public release. Distribution is unlimited

The controversy in the γγ→ρρ\gamma\gamma\to\rho\rho process: potential scattering or qqqˉqˉqq\bar{q}\bar{q} resonance ?

The $\gamma\gamma\to\rho^0\rho^0\to 4 \pi$ reaction shows a broad peak at 1.5 GeV in the $(J^P,J_z)=(2^+,2)$ channel which has no counterpart in the $\rho^+\rho^-$ channel. This "resonance" is considered as a candidate for a $qq\bar q\bar q$ state in the "s-channel". We show, however, that it can also be explained by potential scattering of $\rho^0\rho^0$ via the $\sigma$- exchange in the "t-channel".Comment: 12 pages, latex, 3 postscript figures, to appear in Zeitschrift fur Physi

Verkörperte Techniken und technisierte Verkörperungen – Zur multimodalen Koordination von Handlungen und Wissen

Der Beitrag versucht, die Verhältnisse von Körpern, Technik und Wissen empirisch auszuloten und fragt nach ihrer konstitutiven Bedeutung für soziale Situationen. Entgegen einer vermeintlichen Dichotomie behandeln wir Körper, Objekte und Technik als Ensemble, indem Technik und dingliche Materialitäten durch verkörperte Praktiken zur Koordinierung sozialer Situationen eingesetzt werden. Wie sich anhand verschiedener Felder des Sports, der Bildung oder schlicht im Alltag aufzeigen lässt, werden spezifische Körpertechniken und technisierte Wissensbestände nicht nur in Körper eingeschrieben, sondern darüber hinaus körperlich externalisiert und somit im Interaktionsverlauf für die Situationsteilnehmer lokal sichtbar gemacht. Die empirische Grundlage bilden videobasierte Aufzeichnungen aus drei verschiedenen Projekten zur (1) Herstellung von Körperwissen im Trampolinturnen, (2) zur Besprechung einer Konstruktionszeichnung im Ingenieursstudium (3) zur Aushandlung von Ordnung im Straßenverkehr. Im Fallvergleich wird deutlich, dass die analytische Trennung von Körpern und Technik für die Aushandlung jeweiliger situativer Ordnungen aus Sicht der Handelnden kaum nachvollziehbar ist. Vielmehr verschränken sich die 'Grenzen' innerhalb der Praxis alltäglicher, verkörperter Technik- und Dingverwendung

Mysterium Corpus: The Solo Piano Music of Alexander Scriabin

This article introduces the Mysterium corpus, the complete published oeuvre of Alexander Scriabin’s 207 solo piano works, and makes the corpus available in Humdrum’s kern format. Scriabin’s music presents distinct challenges, specifically in relation to his use of complex rhythmic and metric explorations and the idiosyncratic ways in which he notated his compositional ideas. While this sidetdataset is focused on Scriabin, the methodological challenges explored in the article may shed light on the encoding process for other related late-tonal and early post-tonal repertoires. As such, this article provides a case study of methodological considerations involved in systematically translating messy musical notations into a symbolic encoding of the musical data. Finally, this article provides descriptive statistics of the corpus, especially focusing on Scriabin’s treatment of meter and two harmonies (i.e., the dominant-seventh chord with lowered fifth, and the “Mystic” chord), and discusses the applicability of the Mysterium corpus for future research

Glutaconate CoA-transferase from Acidaminococcus fermentans: the crystal structure reveals homology with other CoA-transferases

AbstractBackground: Coenzyme A-transferases are a family of enzymes with a diverse substrate specificity and subunit composition. Members of this group of enzymes are found in anaerobic fermenting bacteria, aerobic bacteria and in the mitochondria of humans and other mammals, but so far none have been crystallized. A defect in the human gene encoding succinyl-CoA: 3-oxoacid CoA-transferase causes a metabolic disease which leads to severe ketoacidosis, thus reflecting the importance of this family of enzymes. All CoA-transferases share a common mechanism in which the CoA moiety is transferred from a donor (e.g. acetyl CoA) to an acceptor, (R)-2-hydroxyglutarate, whereby acetate is formed. The transfer has been described by a ping-pong mechanism in which CoA is bound to the active-site residue of the enzyme as a covalent thiol ester intermediate. We describe here the crystal structure of glutaconate CoA-transferase (GCT) from the strictly anaerobic bacterium Acidaminococcus fermentans. This enzyme activates (R)-2-hydroxyglutarate to (R)-2-hydroxyglutaryl-CoA in the pathway of glutamate fermentation. We initiated this project to gain further insight into the function of this enzyme and the structural basis for the characteristics of CoA-transferases.Results: The crystal structure of GCT was solved by multiple isomorphous replacement to 2.55 Å resolution. The enzyme is a heterooctamer and its overall arrangement of subunits can be regarded as an (AB)4tetramer obeying 222 symmetry. Both subunits A and B belong to the open α/β-protein class and can be described as a four-layered α/α/β/α type with a novel composition and connectivity of the secondary structure elements. The core of subunit A consists of seven α/β repeats resulting in an all parallel central β sheet, against which helices pack from both sides. In contrast, the centre of subunit B is formed by a ninefold mixed β sheet. Inboth subunits the helical C terminus is folded back onto the N-terminal domain to form the third layer of helices.Conclusions: The active site of GCT is located at the interface of subunits A and B and is formed by loops of both subunits. The funnel-shaped opening to the active site has a depth and diameter of about 20 Å with the catalytic residue, Glu54 of subunit B, at the bottom. The active-site glutamate residue is stabilized by hydrogen bonds. Despite very low amino acid sequence similarity, subunits A and B reveal a similar overall fold. Large parts of their structures can be spatially superimposed, suggesting that both subunits have evolved from a common ancestor

An Empirical Study on the Practical Impact of Prior Beliefs over Policy Types

Many multiagent applications require an agent to learn quickly how to interact with previously unknown other agents. To address this problem, researchers have studied learning algorithms which compute posterior beliefs over a hypothesised set of policies, based on the observed actions of the other agents. The posterior belief is complemented by the prior belief, which specifies the subjective likelihood of policies before any actions are observed. In this paper, we present the first comprehensive empirical study on the practical impact of prior beliefs over policies in repeated interactions. We show that prior beliefs can have a significant impact on the long-term performance of such methods, and that the magnitude of the impact depends on the depth of the planning horizon. Moreover, our results demonstrate that automatic methods can be used to compute prior beliefs with consistent performance effects. This indicates that prior beliefs could be eliminated as a manual parameter and instead be computed automatically

Age, composition and spatial distribution of sandy loess in north-eastern Germany (Fläming, Brandenburg)

The sandy loess deposits in the lowlands of northern Germany present a valuable sedimentary archive for late Weichselian periglacial geomorphodynamics. While other aeolian sediments from the Late Quaternary, especially loess deposits and sand dunes, have been studied and dated in some detail in the last decades, sandy loess has received less scientific attention with respect to its genesis, composition, age and provenance as well as distribution patterns. In this study, we present detailed results for three sediment sections located on the Fläming ridge in the south of the state of Brandenburg. According to our results from luminescence dating, the sandy loess deposits of this area were deposited during the late MIS 2 (19–14 ka) with a highly variable thickness of at least up to 4 m, followed by a deposition of periglacial coversands shortly thereafter. The sandy loess deposits display a homogeneous geochemical composition and grain size characteristics similar to loess sections in the main loess areas to the west and south. Furthermore, we analysed a large dataset of geological drill data and performed a spatial interpolation of sandy loess distribution in the Western Fläming. Despite the strongly dissected modern landscape of the Fläming ridge which is partly the result of intense Holocene soil erosion processes, general patterns of the original loess distribution could be deduced. Based on these findings, we were able to identify the low-lying areas to the north and north-east of the study area to be the most likely source areas for the sandy loess as a result of katabatic winds originating from the Fennoscandian Ice Shield. Thereby, this study yields important insights regarding aeolian transport and deposition patterns under periglacial conditions in the Central European Lowlands

Belief and Truth in Hypothesised Behaviours

There is a long history in game theory on the topic of Bayesian or "rational" learning, in which each player maintains beliefs over a set of alternative behaviours, or types, for the other players. This idea has gained increasing interest in the artificial intelligence (AI) community, where it is used as a method to control a single agent in a system composed of multiple agents with unknown behaviours. The idea is to hypothesise a set of types, each specifying a possible behaviour for the other agents, and to plan our own actions with respect to those types which we believe are most likely, given the observed actions of the agents. The game theory literature studies this idea primarily in the context of equilibrium attainment. In contrast, many AI applications have a focus on task completion and payoff maximisation. With this perspective in mind, we identify and address a spectrum of questions pertaining to belief and truth in hypothesised types. We formulate three basic ways to incorporate evidence into posterior beliefs and show when the resulting beliefs are correct, and when they may fail to be correct. Moreover, we demonstrate that prior beliefs can have a significant impact on our ability to maximise payoffs in the long-term, and that they can be computed automatically with consistent performance effects. Furthermore, we analyse the conditions under which we are able complete our task optimally, despite inaccuracies in the hypothesised types. Finally, we show how the correctness of hypothesised types can be ascertained during the interaction via an automated statistical analysis.Comment: 44 pages; final manuscript published in Artificial Intelligence (AIJ