Cryogenic fluid flow instabilities in heat exchangers

Analytical and experimental investigation determines the nature of oscillations and instabilities that occur in the flow of two-phase cryogenic fluids at both subcritical and supercritical pressures in heat exchangers. Test results with varying system parameters suggest certain design approaches with regard to heat exchanger geometry

Perceiving animacy from shape

Superordinate visual classification—for example, identifying an image as “animal,” “plant,” or “mineral”—is computationally challenging because radically different items (e.g., “octopus,” “dog”) must be grouped into a common class (“animal”). It is plausible that learning superordinate categories teaches us not only the membership of particular (familiar) items, but also general features that are shared across class members, aiding us in classifying novel (unfamiliar) items. Here, we investigated visual shape features associated with animate and inanimate classes. One group of participants viewed images of 75 unfamiliar and atypical items and provided separate ratings of how much each image looked like an animal, plant, and mineral. Results show systematic tradeoffs between the ratings, indicating a class-like organization of items. A second group rated each image in terms of 22 midlevel shape features (e.g., “symmetrical,” “curved”). The results confirm that superordinate classes are associated with particular shape features (e.g., “animals” generally have high “symmetry” ratings). Moreover, linear discriminant analysis based on the 22-D feature vectors predicts the perceived classes approximately as well as the ground truth classification. This suggests that a generic set of midlevel visual shape features forms the basis for superordinate classification of novel objects along the animacy continuum

Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. II. A Short-period Companion Orbiting an F Star with Evidence of a Stellar Tertiary and Significant Mutual Inclination

We report the discovery via radial velocity (RV) measurements of a short-period (P = 2.430420 ± 0.000006 days) companion to the F-type main-sequence star TYC 2930-00872-1. A long-term trend in the RV data also suggests the presence of a tertiary stellar companion with P > 2000 days. High-resolution spectroscopy of the host star yields T_(eff) = 6427 ± 33 K, log g = 4.52 ± 0.14, and [Fe/H] = –0.04 ± 0.05. These parameters, combined with the broadband spectral energy distribution (SED) and a parallax, allow us to infer a mass and radius of the host star of M_1 = 1.21 ± 0.08 M_☉ and R_1 = 1.09^(+0.15)_(–0.13) R_☉. The minimum mass of the inner companion is below the hydrogen-burning limit; however, the true mass is likely to be substantially higher. We are able to exclude transits of the inner companion with high confidence. Further, the host star spectrum exhibits a clear signature of Ca H and K core emission, indicating stellar activity, but a lack of photometric variability and small v sin I suggest that the primary's spin axis is oriented in a pole-on configuration. The rotational period of the primary estimated through an activity-rotation relation matches the orbital period of the inner companion to within 1.5 σ, suggesting that the primary and inner companion are tidally locked. If the inner companion's orbital angular momentum vector is aligned with the stellar spin axis as expected through tidal evolution, then it has a stellar mass of ~0.3-0.4 M_☉. Direct imaging limits the existence of stellar companions to projected separations <30 AU. No set of spectral lines and no significant flux contribution to the SED from either companion are detected, which places individual upper mass limits of M_([2,3]) ≾ 1.0 M_☉, provided they are not stellar remnants. If the tertiary is not a stellar remnant, then it likely has a mass of ~0.5-0.6 M_☉, and its orbit is likely significantly inclined from that of the secondary, suggesting that the Kozai-Lidov mechanism may have driven the dynamical evolution of this system

Shallow grooves in journal improve air bearing performance

Bearing designs, which shape the surface to create artificial fluid-film wedges in the absence of any applied radial load, generate radial restoring forces to keep journals from whirling. Helical- or herringbone-grooved journals or rotors show most promise of stable operation, with no sacrifice in load capacity

Informational Complexity and the Flow of Knowledge across social boundaries

Scholars from a variety of backgrounds – economists, sociologists, strategists, and students of technology management – have sought a better understanding of why some knowledge disperses widely while other knowledge does not. In this quest, some researchers have focused on the characteristics of the knowledge itself (e.g., Polanyi, 1966; Reed and DeFillippi, 1990; Zander and Kogut, 1995) while others have emphasized the social networks that constrain and enable the flow of knowledge (e.g., Coleman et al., 1957; Davis and Greve, 1997). This chapter examines the interplay between these two factors. Specifically, we consider how the complexity of knowledge and the density of social relations jointly influence the movement of knowledge. Imagine a social network composed of patches of dense connections with sparse interstices between them. The dense patches might reflect firms, for instance, or geographic regions or technical communities. When does knowledge diffuse within these dense patches circumscribed by social boundaries but not beyond them? Synthesizing social network theory with a view of knowledge transfer as a search process, we argue that knowledge inequality across social boundaries should reach its peak when the underlying knowledge is of moderate complexity. To test this hypothesis, we analyze patent data and compare citation rates across three types of social boundaries: within versus outside the firm, geographically near to versus far from the inventor, and internal versus external to the technological class. In all three cases, the disparity in knowledge diffusion across these borders is greatest for knowledge of an intermediate level of complexity.evolutionary economics, informational complexity, knowledge flow, social boundaries

Factorization Approach for Top Mass Reconstruction at High Energies

Using effective theories for jets and heavy quarks it is possible to prove that the double differential top-antitop invariant mass distribution for the process $e^+e^-\to t\bar t$ in the resonance region for c.m. energies $Q$ much larger than the top mass can factorized into perturbatively computable hard coefficients and jet functions and a non-perturbative soft function. For invariant mass prescriptions based on hemispheres defined with respect to the thrust axis the soft function can be extracted from massless jet event shape distributions. This approach allows in principle for top mass determinations without uncertainties from hadronization using the reconstruction method and to quantify the top mass scheme dependence of the measured top quark mass value.Comment: Talk given at 2007 International Linear Collider Workshop (LCWS07 and ILC07), Hamburg, Germany, 30 May - 3 Jun 2007, 7 pages, 4 figures, title modifie

"It Isn't Race or Nation Governs Movement": New Writers' Press and the Transnational Scope of Irish Experimental Poetry in the 1960s and 1970s

In this paper, I seek to contribute to the resurrection from critical obscurity of an overlooked tradition in contemporary Irish poetry: namely, that of small-press poetic experimentalism. Taking as a case study the Dublin-based New Writers’ Press (NWP, established 1967), I will interrogate the absence of virtually any mention of small Irish experimental presses in critical narratives of late modernist poetry of the British Isles in the 1960s and 1970s. By using an array of insights gleaned from the many letters, typescripts and other ephemera in the NWP archive housed at the National Library of Ireland, such absences in scholarship are explored in the context of what the press’ founding editors faced in navigating the small Irish poetry market of the mid-twentieth century. Through this archival lens, the reasons why a cohesive avant-garde network of British and Irish poetic experimentalists never materialised are analysed, and an argument for how Irish poetic experiments of the last half century have not received anywhere near the same degree of critical attention as those of their British counterparts will emerge. In the first half of this paper, I focus on the Irish commercial poetry scene in the 1950s and 1960s, ultimately illustrating how narrow and competitive it was in comparison to the British market, as well as the peculiar individual context of an Irish campus magazine, Trinity College’s Icarus (1950-). This will in turn suggest that the absence of presses such as NWP from critical accounts of late modernist poetic experimentalism may well be due to editorial decisions made by those Irish presses themselves. In the second half of this paper, I foreground some important archival evidence to review a number of instances in NWP’s history in which it comes close to forging alliances with presses within the more cohesive British experimental scene, though it never manages to do so. Drawing on this evidence, I present an archival basis for counterarguments to the possible conclusion that the responsibility for the general absence of Irish presses from narratives of small-press experimentalism lies with those Irish presses themselves

Top Mass Measurements from Jets and the Tevatron Top-Quark Mass

Theoretical issues are discussed for the measurement of the top-mass using jets, including perturbative and non-perturbative effects that relate experimental observables to the Lagrangian mass, and appropriate choices for mass schemes. Full account for these issues is given for e+e--> t-tbar using a factorization theorem for event shapes for massive quarks. Implications for the Tevatron top-mass measurement are discussed. A mass-scheme, the "MSR-mass", is introduced which allows for a precise description of observables sensitive to scales R << m, but at the same time does not introduce perturbative matching uncertainties in conversion to the MSbar mass.Comment: 7 pages, proceedings for the International Workshop on Top Quark Physics, and the 2nd Workshop on Theory, Phenomenology and Experiment in Heavy Flavor Physics, 2008. v2: reference added, language in section 5 improve