5,049 research outputs found
Symmetry causes a huge conductance peak in double quantum dots
We predict a huge interference effect contributing to the conductance through
large ultra-clean quantum dots of chaotic shape. When a double-dot structure is
made such that the dots are the mirror-image of each other, constructive
interference can make a tunnel barrier located on the symmetry axis effectively
transparent. We show (via theoretical analysis and numerical simulation) that
this effect can be orders of magnitude larger than the well-known universal
conductance fluctuations and weak-localization (both less than a conductance
quantum). A small magnetic field destroys the effect, massively reducing the
double-dot conductance; thus a magnetic field detector is obtained, with a
similar sensitivity to a SQUID, but requiring no superconductors.Comment: 5pages 3 figures and an appendix ONLY in arXiv versio
Cold-air investigation of a 4 1/2 stage turbine with stage-loading factor of 4.66 and high specific work output. 2: Stage group performance
The stage group performance of a 4 1/2 stage turbine with an average stage loading factor of 4.66 and high specific work output was determined in cold air at design equivalent speed. The four stage turbine configuration produced design equivalent work output with an efficiency of 0.856; a barely discernible difference from the 0.855 obtained for the complete 4 1/2 stage turbine in a previous investigation. The turbine was designed and the procedure embodied the following design features: (1) controlled vortex flow, (2) tailored radial work distribution, and (3) control of the location of the boundary-layer transition point on the airfoil suction surface. The efficiency forecast for the 4 1/2 stage turbine was 0.886, and the value predicted using a reference method was 0.862. The stage group performance results were used to determine the individual stage efficiencies for the condition at which design 4 1/2 stage work output was obtained. The efficiencies of stages one and four were about 0.020 lower than the predicted value, that of stage two was 0.014 lower, and that of stage three was about equal to the predicted value. Thus all the stages operated reasonably close to their expected performance levels, and the overall (4 1/2 stage) performance was not degraded by any particularly inefficient component
Cold air investigation of 4 1/2-stage turbine with stage loading factor of 4.66 and high specific work output. 1: Overall performance
The turbine developed design specific work output at design speed at a total pressure ratio of 6.745 with a corresponding efficiency of 0.855. The efficiency (0.855)was 3.1 points lower than the estimated efficiency quoted by the contractor in the design report and 0.7 of a point lower than that determined by a reference prediction method. The performance of the turbine, which was a forced vortex design, agreed with the performance determined by the prediction method to about the same extent as did the performance of three reference high stage loading factor turbines, which were free vortex designs
Design and cold-air test of single-stage uncooled turbine with high work output
A solid version of a 50.8 cm single stage core turbine designed for high temperature was tested in cold air over a range of speed and pressure ratio. Design equivalent specific work was 76.84 J/g at an engine turbine tip speed of 579.1 m/sec. At design speed and pressure ratio, the total efficiency of the turbine was 88.6 percent, which is 0.6 point lower than the design value of 89.2 percent. The corresponding mass flow was 4.0 percent greater than design
Herschel Observations of a Newly Discovered UX Ori Star in the Large Magellanic Cloud
The LMC star, SSTISAGE1C J050756.44-703453.9, was first noticed during a
survey of EROS-2 lightcurves for stars with large irregular brightness
variations typical of the R Coronae Borealis (RCB) class. However, the visible
spectrum showing emission lines including the Balmer and Paschen series as well
as many Fe II lines is emphatically not that of an RCB star. This star has all
of the characteristics of a typical UX Ori star. It has a spectral type of
approximately A2 and has excited an H II region in its vicinity. However, if it
is an LMC member, then it is very luminous for a Herbig Ae/Be star. It shows
irregular drops in brightness of up to 2 mag, and displays the reddening and
"blueing" typical of this class of stars. Its spectrum, showing a combination
of emission and absorption lines, is typical of a UX Ori star that is in a
decline caused by obscuration from the circumstellar dust. SSTISAGE1C
J050756.44-703453.9 has a strong IR excess and significant emission is present
out to 500 micron. Monte Carlo radiative transfer modeling of the SED requires
that SSTISAGE1C J050756.44-703453.9 has both a dusty disk as well as a large
extended diffuse envelope to fit both the mid- and far-IR dust emission. This
star is a new member of the UX Ori subclass of the Herbig Ae/Be stars and only
the second such star to be discovered in the LMC.Comment: ApJ, in press. 9 pages, 5 figure
Nothing Happens Unless First a Dream: Demystifying the Academic Library Job Search and Acing the Application Process
Academic library positions can be highly desirable for both new librarians and experienced librarians interested in transitioning into a different setting. Yet for both novice and experienced librarians alike, landing an interview for an academic librarian position can feel intimidating and overwhelming. Applicants may have difficulty understanding tenure track requirements, no academic library experience, no coursework in relevant areas, and may be competing with a large pool of qualified candidates. When academic job openings ask for years of academic library experience and library school specializations suggest that the path you pick is the path you keep until retirement, it begins to feel as though finding a position in an academic library is an insurmountable endeavor. As three librarians who have successfully made the move into an academic setting, we can attest that although the way may be unclear, this goal is not impossible to achieve. This paper will explain some of the facets unique to the academic setting with which applicants might not be familiar, how to tailor application materials to an academic position and why this is crucial for success, and how to acclimate to new responsibilities and expectations
Scientific investigations in the Gulf of Mexico and Caribbean Sea during the 1974-1975 Calypso cruise, parts 1 and 2
The distribution and concentrations of the standing crop of phytoplankton and nutrient salts in the Gulf of Mexico and the Caribbean Sea were investigated to provide ground truth for correlating temperature and chlorophyll-a measurements with observations from NASA U-2 aircraft equipped with specially designed sensors for measuring ocean color phenomena. The physical, chemical, and biological data obtained is summarized. Sampling procedures and methods used for determining plant pigments, species composition of phytoplankton, nutrient salt analysis, and the euphotic zones are described
Rheological transitions in the middle crust:insights from Cordilleran metamorphic core complexes
High-strain mylonitic rocks in Cordilleran metamorphic
core complexes reflect ductile deformation in the middle crust, but in many
examples it is unclear how these mylonites relate to the brittle detachments
that overlie them. Field observations, microstructural analyses, and
thermobarometric data from the footwalls of three metamorphic core complexes
in the Basin and Range Province, USA (the Whipple Mountains, California; the
northern Snake Range, Nevada; and Ruby Mountains–East Humboldt Range,
Nevada), suggest the presence of two distinct rheological transitions in the
middle crust: (1) the brittle–ductile transition (BDT), which depends on
thermal gradient and tectonic regime, and marks the switch from discrete
brittle faulting and cataclasis to continuous, but still localized, ductile
shear, and (2) the localized–distributed transition, or LDT, a deeper, dominantly
temperature-dependent transition, which marks the switch from localized
ductile shear to distributed ductile flow. In this model, brittle normal
faults in the upper crust persist as ductile shear zones below the BDT in
the middle crust, and sole into the subhorizontal LDT at greater depths.<br><br>In metamorphic core complexes, the presence of these two distinct
rheological transitions results in the development of two zones of ductile
deformation: a relatively narrow zone of high-stress mylonite that is
spatially and genetically related to the brittle detachment, underlain by a
broader zone of high-strain, relatively low-stress rock that formed in the
middle crust below the LDT, and in some cases before the detachment was
initiated. The two zones show distinct microstructural assemblages,
reflecting different conditions of temperature and stress during
deformation, and contain superposed sequences of microstructures reflecting
progressive exhumation, cooling, and strain localization. The LDT is not
always exhumed, or it may be obscured by later deformation, but in the
Whipple Mountains, it can be directly observed where high-strain mylonites
captured from the middle crust depart from the brittle detachment along a
mylonitic front
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Comparative study of design: application to Engineering Design
A recent exploratory study examines design processes across domains and compares them. This is achieved through a series of interdisciplinary, participative workshops. A systematic framework is used to collect data from expert witnesses who are practising designers across domains from engineering through architecture to product design and fashion, including film production, pharmaceutical drugs, food, packaging, graphics and multimedia and software. Similarities and differences across domains are described which indicate the types of comparative analysis we have been able to do from our data. The paper goes further and speculates on possible lessons for selected areas of engineering design which can be drawn from comparison with processes in other domains. As such this comparative design study offers the potential for improving engineering design processes. More generally it is a first step in creating a discipline of comparative design which aims to provide a new rich picture of design processes
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