Engineering and fabrication cost considerations for cryogenic wind tunnel models

Design and fabrication cost drivers for cryogenic transonic wind tunnel models are defined. The major cost factors for wind tunnel models are model complexity, tolerances, surface finishes, materials, material validation, and model inspection. The cryogenic temperatures require the use of materials with relatively high fracture toughness but at the same time high strength. Some of these materials are very difficult to machine, requiring extensive machine hours which can add significantly to the manufacturing costs. Some additional engineering costs are incurred to certify the materials through mechanical tests and nondestructive evaluation techniques, which are not normally required with conventional models. When instrumentation such as accelerometers and electronically scanned pressure modules is required, temperature control of these devices needs to be incorporated into the design, which requires added effort. Additional thermal analyses and subsystem tests may be necessary, which also adds to the design costs. The largest driver to the design costs is potentially the additional static and dynamic analyses required to insure structural integrity of the model and support system

The cryogenic wind tunnel concept for high Reynolds number testing

Theoretical considerations indicate that cooling the wind-tunnel test gas to cryogenic temperatures will provide a large increase in Reynolds number with no increase in dynamic pressure while reducing the tunnel drive-power requirements. Studies were made to determine the expected variations of Reynolds number and other parameters over wide ranges of Mach number, pressure, and temperature, with due regard to avoiding liquefaction. Practical operational procedures were developed in a low-speed cryogenic tunnel. Aerodynamic experiments in the facility demonstrated the theoretically predicted variations in Reynolds number and drive power. The continuous-flow-fan-driven tunnel is shown to be particularly well suited to take full advantage of operating at cryogenic temperatures

Analysis of validation tests of the Langley pilot transonic cryogenic tunnel

A pilot transonic cryogenic pressure tunnel has recently been developed and proof tested at the NASA Langley Research Center. In addition to providing an attractive method for obtaining high Reynolds number results at moderate aerodynamic loadings and tunnel power, this unique tunnel allows the independent determination of the effects of Reynolds number, Mach number, and dynamic pressure (aeroelasticity) on the aerodynamic characteristics of the model under test. The proof of concept experimental and theoretical studies are briefly reviewed. Experimental results obtained on both two- and three-dimensional models have substantiated that cryogenic test conditions can be set accurately and that cryogenic gaseous nitrogen is a valid test medium

The Proposed Biological Station at the Tortugas

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Big data-savvy teams’ skills, big data-driven actions and business performance

Prior studies on big data analytics have emphasized the importance of specific big data skills and capabilities for organizational success; however, they have largely neglected to investigate the use of cross-functional teams’ skills and its links to the role played by relevant data-driven actions and business performance. Drawing on the resource-based view (RBV) of the firm and on the data collected from big data experts working in global agrifood networks, we examine the links between the use of big data-savvy (BDS) teams’ skills, big data-driven (BDD) actions and business performance. BDS teams depend on multidisciplinary skills (e.g., computing, mathematics, statistics, machine learning, and business domain knowledge) that help them to turn their traditional business operations into modern data-driven insights (e.g., knowing real time price changes and customer preferences), leading to BDD actions that enhance business performance. Our results, raised from structural equation modelling, indicate that BDS teams' skills that produce valuable insights are the key determinants for BDD actions, which ultimately contribute to business performance. We further demonstrate that those organisations that emphasise BDD actions perform better compared to those that do not focus on such applications and relevant insights

Distinct year-to-year particle flux variations off Cape Blanc during 1988-1991: Relation to δ 18O-deduced sea-surface temperatures and trade winds

Particle fluxes measured from 1988 to 1991 adjacent to a coastal upwelling site off Cape Blanc showed significant interannual variability of fluxes and sea-surface temperatures (SST) deduced from stable oxygen isotope analysis of the planktonic foraminifera Globigerinoides ruber and, partly, of the pteropod Limacina inflata. For the duration of the study period, a decrease in the seasonality of SST\u27s was observed, as well as a significant decrease in the average annual SST from 24.4° to 20.8°C. This cooling trend was mainly the effect of a drastic decrease in the summer to fall SST (from 27.2° to 21.8°C). In comparison, the winter-spring SST decreased only slightly from 20.3° in 1988 to 19.8°C in 1991. Concomitantly, we measured decreasing annual total, carbonate, biogenic opal and lithogenic fluxes and, in contrast, increasing marine organic carbon fluxes. During 1991, when cold SST\u27s prevailed and the trade winds were rather high throughout, annual biogenic and lithogenic fluxes (except organic carbon) were lower by approximately a factor of two compared to the other years. Colder SST\u27s, generally corresponding to stronger trade winds and upwelling intensity, did not result in increased biogenic opal and lithogenic matter sedimentation; but higher marine organic carbon fluxes were recorded. Decreasing summer-fall SST from 1988 to 1991 coincided with decreased carbonate sedimentation maxima which generally occurred during the warm summer season. In the summer of 1989, when SST\u27s were the highest of the four-year sampling period and upwelling was less intense due to weak spring-summer trades, a large sedimentation pulse of pteropod shells was observed. Our data set does not yet provide conclusive evidence that the observed year-to-year flux and SST variations represent larger-scale, periodically occurring climatic variations in the eastern Atlantic but it offers insight into the prevailing large variability in biochemical cycles and processes in the eastern Atlantic

Book Reviews

FEDERAL JUDGES: THE APPOINTING PROCESS. By Harold W. Chase. Minneapolis: University of Minnesota Press. 1972. Pp. xiii, 240. CORPORATE LIB: WOMEN\u27S CHALLENGE TO MANAGEMENT. Edited by Eli Ginzberg and Alice M. Yohalem. Baltimore: Johns Hopkins University Press, 1973. Pp. x, 153. URBAN JUSTICE: LAW AND\u27 ORDER IN AMERICAN CITIES. By Herbert Jacob. Englewood Cliffs: Prentice-Hall, 1973. Pp. viii, 145. THE CONSCIENCE OF A LAWYER. By David Mellinkoff. St. Paul: West Publishing Company, 1973. Pp. x, 304

A Factorization Algorithm for G-Algebras and Applications

It has been recently discovered by Bell, Heinle and Levandovskyy that a large class of algebras, including the ubiquitous $G$-algebras, are finite factorization domains (FFD for short). Utilizing this result, we contribute an algorithm to find all distinct factorizations of a given element $f \in \mathcal{G}$, where $\mathcal{G}$ is any $G$-algebra, with minor assumptions on the underlying field. Moreover, the property of being an FFD, in combination with the factorization algorithm, enables us to propose an analogous description of the factorized Gr\"obner basis algorithm for $G$-algebras. This algorithm is useful for various applications, e.g. in analysis of solution spaces of systems of linear partial functional equations with polynomial coefficients, coming from $\mathcal{G}$. Additionally, it is possible to include inequality constraints for ideals in the input