9,395 research outputs found
Induction motor control system with voltage controlled oscillator circuit
A voltage controlled oscillator circuit is reported in which there are employed first and second differential amplifiers. The first differential amplifier, being employed as an integrator, develops equal and opposite slopes proportional to an input voltage, and the second differential amplifier functions as a comparator to detect equal amplitude positive and negative selected limits and provides switching signals which gate a transistor switch. The integrating differential amplifier is switched between charging and discharging modes to provide an output of the first differential amplifier which upon the application of wave shaping provides a substantially sinusoidal output signal. A two phased version with a second integrator provides a second 90 deg phase shifted output for induction motor control
An archival case study : revisiting the life and political economy of Lauchlin Currie
This paper forms part of a wider project to show the significance of archival material on distinguished economists, in this case Lauchlin Currie (1902-93), who studied and taught at Harvard before entering government service at the US Treasury and Federal Reserve Board as the intellectual leader of Roosevelt's New Deal, 1934-39, as FDR's White House economic adviser in peace and war, 1939-45, and as a post-war development economist. It discusses the uses made of the written and oral material available when the author was writing his intellectual biography of Currie (Duke University Press 1990) while Currie was still alive, and the significance of the material that has come to light after Currie's death
Spitzer IRS Spectroscopy of the 10 Myr-old EF Cha Debris Disk: Evidence for Phyllosilicate-Rich Dust in the Terrestrial Zone
We describe Spitzer IRS spectroscopic observations of the 10 Myr-old star, EF
Cha. Compositional modeling of the spectra from 5 {\mu}m to 35 {\mu}m confirms
that it is surrounded by a luminous debris disk with LD/L\star ~ 10-3,
containing dust with temperatures between 225 K and 430 K characteristic of the
terrestrial zone. The EF Cha spectrum shows evidence for many solid-state
features, unlike most cold, low-luminosity debris disks but like some other
10-20 Myr-old luminous, warm debris disks (e.g. HD 113766A). The EF Cha debris
disk is unusually rich in a species or combination of species whose
emissivities resemble that of finely powdered, laboratory-measured
phyllosilicate species (talc, saponite, and smectite), which are likely
produced by aqueous alteration of primordial anhydrous rocky materials. The
dust and, by inference, the parent bodies of the debris also contain abundant
amorphous silicates and metal sulfides, and possibly water ice. The dust's
total olivine to pyroxene ratio of ~ 2 also provides evidence of aqueous
alteration. The large mass volume of grains with sizes comparable to or below
the radiation blow-out limit implies that planetesimals may be colliding at a
rate high enough to yield the emitting dust but not so high as to devolatize
the planetesimals via impact processing. Because phyllosilicates are produced
by the interactions between anhydrous rock and warm, reactive water, EF Cha's
disk is a likely signpost for water delivery to the terrestrial zone of a young
planetary system.Comment: 21 pages, 10 figures, accepted for publication in The Astrophysical
Journa
On the General Ericksen-Leslie System: Parodi's Relation, Well-posedness and Stability
In this paper we investigate the role of Parodi's relation in the
well-posedness and stability of the general Ericksen-Leslie system modeling
nematic liquid crystal flows. First, we give a formal physical derivation of
the Ericksen-Leslie system through an appropriate energy variational approach
under Parodi's relation, in which we can distinguish the
conservative/dissipative parts of the induced elastic stress. Next, we prove
global well-posedness and long-time behavior of the Ericksen-Leslie system
under the assumption that the viscosity is sufficiently large. Finally,
under Parodi's relation, we show the global well-posedness and Lyapunov
stability for the Ericksen-Leslie system near local energy minimizers. The
connection between Parodi's relation and linear stability of the
Ericksen-Leslie system is also discussed
Accelerating the carbon cycle: the ethics of enhanced weathering
This is the author accepted manuscript. The final version is available from Royal Society via the DOI in this record.Enhanced weathering, in comparison to other geoengineering measures, creates the possibility of a reduced cost, reduced impact way of decreasing atmospheric carbon, with positive knock-on effects such as decreased oceanic acidity. We argue that ethical concerns have a place alongside empirical, political and social factors as we consider how to best respond to the critical challenge that anthropogenic climate change poses. We review these concerns, considering the ethical issues that arise (or would arise) in the large-scale deployment of enhanced weathering. We discuss post-implementation scenarios, failures of collective action, the distribution of risk and externalities and redress for damage. We also discuss issues surrounding âdirty handsâ (taking conventionally immoral action to avoid having to take action that is even worse), whether enhanced weathering research might present a moral hazard, the importance of international governance and the notion that the implementation of large-scale enhanced weathering would reveal problematic hubris. Ethics and scientific research interrelate in complex ways: some ethical considerations caution against research and implementation, while others encourage them. Indeed, the ethical perspective encourages us to think more carefully about how, and what types of, geoengineering should be researched and implemented.European CommissionTempleton World Charity Foundatio
From Usability Studies to User Experience: Designing Library Services at the University of Kansas
The University of Kansas (KU) Libraries first made their discovery tool, Primo (Ex Libris), available to their users in the fall of 2013. Since that time, in spite of many upgrades and improvements, most librarians and library staff are still not using the tool for their own research. Last year, librarians from KU presented their findings at the Charleston Conference using a survey given to KU librarians that asked them to compare Primo to Google Scholar and their favorite databases. Librarians were asked to compare the three and make recommendations for improving Primo. This year, KU librarians designed a much briefer survey and asked all library staff to participate, including student assistants. Library staff were asked to use Primo to conduct research on a topic of their choice and use all aspects of Primo to find relevant results. They were then asked to describe what they used in Primo to lead them to helpful information resources and rank the first 10 results from their final search.
The purpose of this survey is to discern how our colleagues use Primo and how successful they are in retrieving the information they need when using this search tool. This study will help KU Libraries develop training for library staff in the use of this new mode of discovery and access. The search terms used in this study will also be useful in helping the discovery implementation team recreate the searches to test Primo in the future, after scheduled upgrades, in order to detect noticeable improvements or problems with the search results
New evidence on Allyn Young's style and influence as a teacher
This paper publishes the hitherto unpublished correspondence between Allyn Abbott Young's biographer Charles Blitch and 17 of Young's former students or associates. Together with related biographical and archival material, the paper shows the way in which this adds to our knowledge of Young's considerable influence as a teacher upon some of the twentieth century's greatest economists. The correspondents are as follows: James W Angell, Colin Clark, Arthur H Cole, Lauchlin Currie, Melvin G de Chazeau, Eleanor Lansing Dulles, Howard S Ellis, Frank W Fetter, Earl J Hamilton, Seymour S Harris, Richard S Howey, Nicholas Kaldor, Melvin M Knight, Bertil Ohlin, Geoffrey Shepherd, Overton H Taylor, and Gilbert Walker
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