11,912 research outputs found
A water tunnel study of Gurney flaps
Several Gurney flap configurations were tested in the NASA Langley 16 x 24 inch Water Tunnel. These devices provided an increased region of attached flow on a wing upper surface relative to the wing without the flaps. The recirculation region behind the flap was visualized and shown to be consistent with hypotheses stated in previous research. Although the test Reynolds number for this study was several orders of magnitude below those in previous investigations, the effect of the Gurney flaps is in qualitative agreement with them. This is as would be expected from first order effects for high lift devices
Non-integrality of some Steinberg modules
We prove that the Steinberg module of the special linear group of a quadratic
imaginary number ring which is not Euclidean is not generated by integral
apartments. Assuming the generalized Riemann hypothesis, this shows that the
Steinberg module of a number ring is generated by integral apartments if and
only if the ring is Euclidean. We also construct new cohomology classes in the
top dimensional cohomology group of the special linear group of some quadratic
imaginary number rings.Comment: 17 pages. To appear in Journal of Topolog
Graphical Nonbinary Quantum Error-Correcting Codes
In this paper, based on the nonbinary graph state, we present a systematic
way of constructing good non-binary quantum codes, both additive and
nonadditive, for systems with integer dimensions. With the help of computer
search, which results in many interesting codes including some nonadditive
codes meeting the Singleton bounds, we are able to construct explicitly four
families of optimal codes, namely, , ,
and for any odd dimension and a family of nonadditive code
for arbitrary . In the case of composite numbers as
dimensions, we also construct a family of stabilizer codes for odd , whose coding subspace is {\em not} of a dimension
that is a power of the dimension of the physical subsystem.Comment: 12 pages, 5 figures (pdf
The eigenpairs of a Sylvester-Kac type matrix associated with a simple model for one-dimensional deposition and evaporation
A straightforward model for deposition and evaporation on discrete cells of a
finite array of any dimension leads to a matrix equation involving a
Sylvester-Kac type matrix. The eigenvalues and eigenvectors of the general
matrix are determined for an arbitrary number of cells. A variety of models to
which this solution may be applied are discussed.Comment: 7 pages, no figure
Illumination uniformity in endoscopic imaging
Standardised endoscopic digital images were taken and analysed using an image analysis software (National Instruments Vision Assistant version 7.1.1). The luminance plane was extracted and the pixel intensity distribution was determined along a horizontal line at the position of highest average intensity (centroid). The data was exported to MS Excel and the pixel intensity (y-axis) was plotted against pixel position (x-axis). A trendline using a 2nd order polynomial curve was fitted to each data set. The resultant equation for each curve was compared with equations obtained from other images taken under various illumination conditions and settings
Undergraduate Adult Learners’ Acquisition of Credit Through Multiple Means
Using available institutional data, the authors determined the extent to which Penn State’s undergraduate adult learners acquired credit through means in addition to enrolling in other higher education institutions, the frequency with which several means are used, and offered suggestions for improvements to increase adults’ use of these options
Roles of resonance and dark irradiance for infrared photorefractive self-focusing and solitons in bi-polar InP:Fe
This paper shows experimental evidence of photorefractive steady state
self-focusing in InP:Fe for a wide range of intensities, at both 1.06 and
1.55m. To explain those results, it is shown that despite the bi-polar
nature of InP:Fe where one photocarrier and one thermal carrier are to be
considered, the long standing one photocarrier model for photorefractive
solitons can be usefully applied. The relationship between the dark irradiance
stemming out of this model and the known resonance intensity is then discussed
Using dark modes for high-fidelity optomechanical quantum state transfer
In a recent publication [Y.D. Wang and A.A. Clerk, Phys. Rev. Lett. 108,
153603 (2012)], we demonstrated that one can use interference to significantly
increase the fidelity of state transfer between two electromagnetic cavities
coupled to a common mechanical resonator over a naive sequential-transfer
scheme based on two swap operations. This involved making use of a delocalized
electromagnetic mode which is decoupled from the mechanical resonator, a
so-called "mechanically-dark" mode. Here, we demonstrate the existence of a new
"hybrid" state transfer scheme which incorporates the best elements of the
dark-mode scheme (protection against mechanical dissipation) and the
double-swap scheme (fast operation time). Importantly, this new scheme also
does not require the mechanical resonator to be prepared initially in its
ground state. We also provide additional details on the previously-described
interference-enhanced transfer schemes, and provide an enhanced discussion of
how the interference physics here is intimately related to the optomechanical
analogue of electromagnetically-induced transparency (EIT). We also compare the
various transfer schemes over a wide range of relevant experimental parameters,
producing a "phase diagram" showing the the optimal transfer scheme for
different points in parameter space.Comment: 39 pages, 11 figures NJP 14 (Focus issue on Optomechanics
South Platte River Basin
Presented at Competing interests in water resources - searching for consensus: proceedings from the USCID water management conference held on December 5-7, 1996 in Las Vegas, Nevada.Includes bibliographical references.The potential of demand management as a water management tool in the South Platte River basin is limited by a lack of information regarding existing irrigation practices. A study was conducted to obtain information regarding irrigation water use practices in the basin, to determine the frequency of adoption of water conservation practices, and to relate the frequency of adoption of water conserving measures to various demographic factors. The results were based on 285 responses to a voluntary survey sent to a random sample of 1000 irrigators in eight counties within the basin during the winter of 1995. The survey sought information on farming practices, the adoption of water conservation practices, and grower characteristics. Although disincentives for irrigation water conservation appeared to be significant, the results indicated a high rate of adoption. Seventy-four percent of the survey respondents had adopted some type of water conservation measure on their farms. Adoption of various irrigation water conservation practices was associated most frequently with farm size, but factors such as method of irrigation, water source, knowledge of water law, and level of education were also associated with adoption of one or more conservation measures. Respondents indicated that the primary incentive for adopting water conservation measures was "water conservation." The typical reason for conserving water was to improve existing operations. This suggests that in many instances conservation is being used as a method of extending existing supplies on farms operating under water-short decrees
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