Computer program predicts thermal and flow transients experienced in a reactor loss- of-flow accident

Program analyzes the consequences of a loss-of-flow accident in the primary cooling system of a heterogeneous light-water moderated and cooled nuclear reactor. It produces a temperature matrix 36 x 41 /x,y/ which includes fuel surface temperatures relative to the time the pump power was lost

High-temperature Adhesive Development and Evaluation

High-temperature adhesive systems are evaluated for short and long-term stability at temperatures ranging from 232C to 427C. The resins selected for characterization include: NASA Langley developed polyphenylquinoxaline (PPQ), and commercially available polyimides (PI). The primary method of bond testing is single lap shear. The PPQ candidates are evaluated on 6A1-4V titanium adherends with chromic acid anodize and phosphate fluoride etch surface preparations. The remaining adhesives are evaluated on 15-5 PH stainless steel with a sulfuric acid anodize surface preparation. Preliminary data indicate that the PPQ adhesives tested have stability to 3000 hours at 450F with chromic acid anodize surface preparation. Additional studies are continuing to attempt to improve the PPQ's high-performance by formulating adhesive films with a boron filler and utilizing the phosphate fluoride surface preparation on titanium. Evaluation of the polyimide candidates on stainless-steel adherends indicates that the FM-35 (American Cyanamid), PMR-15 (U.S. Polymeric/Ferro), TRW partially fluorinated polyimide and NR 150B2S6X (DuPont) adhesives show sufficient promise to justify additional testing

The bearable lightness of being

How are philosophical questions about what kinds of things there are to be understood and how are they to be answered? This paper defends broadly Fregean answers to these questions. Ontological categories-such as object, property, and relation-are explained in terms of a prior logical categorization of expressions, as singular terms, predicates of varying degree and level, etc. Questions about what kinds of object, property, etc., there are are, on this approach, reduce to questions about truth and logical form: for example, the question whether there are numbers is the question whether there are true atomic statements in which expressions function as singular terms which, if they have reference at all, stand for numbers, and the question whether there are properties of a given type is a question about whether there are meaningful predicates of an appropriate degree and level. This approach is defended against the objection that it must be wrong because makes what there depend on us or our language. Some problems confronting the Fregean approach-including Frege's notorious paradox of the concept horse-are addressed. It is argued that the approach results in a modest and sober deflationary understanding of ontological commitments

Evaluation of absorption cycle for space station environmental control system application Interim report

Zero-gravity absorption refrigeration system design and performance testing for space station environmental control applicatio

Evaluation of high temperature structural adhesives for extended service, phase 4

The evaluation of three phenylquinoxaline polymers as high temperature structural adhesives is presented. These included an experimental crisskubjabke oiktner (X-PQ) and two experimental materials (PPQ-2501) and (PPQ-HC). Lap shear, crack extension, and climing drum peel specimens were fabricated from all three polymers, and tested after thermal, combined thermal/humidity, and stressed Skydrol exposure. All three polymers generally performed well as adhesives at initial test temperatures from 219K (-67 F) to 505K (450 F) and after humidity exposure. The 644K (700 F) cured test specimens exhibited superior Skydrol resistance and thermal stability at 505K (450 F) when compared to the 602K (625 F) cured test specimens

Stabilizing unstable periodic orbits in the Lorenz equations using time-delayed feedback control

For many years it was believed that an unstable periodic orbit with an odd number of real Floquet multipliers greater than unity cannot be stabilized by the time-delayed feedback control mechanism of Pyragus. A recent paper by Fiedler et al uses the normal form of a subcritical Hopf bifurcation to give a counterexample to this theorem. Using the Lorenz equations as an example, we demonstrate that the stabilization mechanism identified by Fiedler et al for the Hopf normal form can also apply to unstable periodic orbits created by subcritical Hopf bifurcations in higher-dimensional dynamical systems. Our analysis focuses on a particular codimension-two bifurcation that captures the stabilization mechanism in the Hopf normal form example, and we show that the same codimension-two bifurcation is present in the Lorenz equations with appropriately chosen Pyragus-type time-delayed feedback. This example suggests a possible strategy for choosing the feedback gain matrix in Pyragus control of unstable periodic orbits that arise from a subcritical Hopf bifurcation of a stable equilibrium. In particular, our choice of feedback gain matrix is informed by the Fiedler et al example, and it works over a broad range of parameters, despite the fact that a center-manifold reduction of the higher-dimensional problem does not lead to their model problem.Comment: 21 pages, 8 figures, to appear in PR

lnfluence of Salt Creek rootstock on composition and quality of Shiraz grapes and wine

Salt Creek rootstock modified the composition and quality of Shiraz grapes and wine. At harvest, grapes from vines grown on Salt Creek stock had a higher pH and higher levels of titratable acidity, malate and potassium and a lower level of soluble solids than grapes from vines grown on their own roots. Wines made from these grapes showed similar differences in composition. In addition, wines made from vines on Salt Creek had lower concentrations of phenolic compounds, anthocyanins (total and ionised) and chloride than wines from ungrafted vines. The Salt Creek wines were less dense in colour, duller in hue and had a greater "chemical age". Sensory evaluations also revealed differences between the wines. Wines from vines on Salt Creek were scored lower than the wines from ungrafted vines. Only part of the difference was due to colour. Der Einfluß der Unterlage Salt Creek auf die Zusammensetzung und Qualität von Trauben und Wein der Sorte ShirazDie Unterlage Salt Creek modifizierte die Zusammensetzung und Qualität der Trauben und des Weines der Rebsorte Shiraz. Bei der Ernte hatten die Trauben auf Salt-Creek-Unterlage einen höheren pH-Wert und höhere Gehalte an titrierbarer Säure, Malat und Kalium, aber weniger lösliche Trockensubstanz als die Trauben wurzelechter Shiraz-Reben. Die aus diesen Trauben hergestellten Weine zeigten in ihrer Zusammensetzung ähnliche Unterschiede. Darüber hinaus hatten Weine von Pfropfreben niedrigere Konzentrationen an phenolischen Verbindungen, Anthocyanen (insgesamt und ionisiert) sowie Chloriden als Weine von wurzelechten Reben. Die Salt-Creek-Weine hatten eine weniger intensive Färbung, einen stumpferen Farbton und ein höheres „chemisches Alter". Auch bei der sensorischen Prüfung wurden Unterschiede zwischen diesen Weinen festgestellt. Die Weine von Reben auf Salt Creek wurden niedriger bewertet als Weine von wurzelechten Reben. Die unterschiedliche Beurteilung war nur teilweise auf Färbungsunterschiede zurückzuführen

The environment and host haloes of the brightest z~6 Lyman-break galaxies

By studying the large-scale structure of the bright high-redshift Lyman-break galaxy (LBG) population it is possible to gain an insight into the role of environment in galaxy formation physics in the early Universe. We measure the clustering of a sample of bright (-22.7<M_UV<-21.125) LBGs at z~6 and use a halo occupation distribution (HOD) model to measure their typical halo masses. We find that the clustering amplitude and corresponding HOD fits suggests that these sources are highly biased (b~8) objects in the densest regions of the high-redshift Universe. Coupled with the observed rapid evolution of the number density of these objects, our results suggest that the shape of high luminosity end of the luminosity function is related to feedback processes or dust obscuration in the early Universe - as opposed to a scenario where these sources are predominantly rare instances of the much more numerous M_UV ~ -19 population of galaxies caught in a particularly vigorous period of star formation. There is a slight tension between the number densities and clustering measurements, which we interpret this as a signal that a refinement of the model halo bias relation at high redshifts or the incorporation of quasi-linear effects may be needed for future attempts at modelling the clustering and number counts. Finally, the difference in number density between the fields (UltraVISTA has a surface density ~1.8 times greater than UDS) is shown to be consistent with the cosmic variance implied by the clustering measurements.Comment: 19 pages, 8 figures, accepted MNRAS 23rd March 201

Quantum Monte Carlo calculations of neutron-alpha scattering

We describe a new method to treat low-energy scattering problems in few-nucleon systems, and we apply it to the five-body case of neutron-alpha scattering. The method allows precise calculations of low-lying resonances and their widths. We find that a good three-nucleon interaction is crucial to obtain an accurate description of neutron-alpha scattering.Comment: 4 pages, 2 figures, submitted to Physical Review Letter