3,620 research outputs found
Thermal stress analysis for a wood composite blade
Heat conduction throughout the blade and the distribution of thermal stresses caused by the temperature distribution were determined for a laminated wood wind turbine blade in both the horizontal and vertical positions. Results show that blade cracking is not due to thermal stresses induced by insulation. A method and practical example of thermal stress analysis for an engineering body of orthotropic materials is presented
Thermal-stress analysis for wood composite blade
The thermal-stress induced by solar insolation on a wood composite blade of a Mod-OA wind turbine was investigated. The temperature distribution throughout the blade (a heat conduction problem) was analyzed and the thermal-stress distribution of the blades caused by the temperature distribution (a thermal-stress analysis problem) was then determined. The computer programs used for both problems are included along with output examples
Thermal-stress analysis for a wood composite blade
A thermal-stress analysis of a wind turbine blade made of wood composite material is reported. First, the governing partial differential equation on heat conduction is derived, then, a finite element procedure using variational approach is developed for the solution of the governing equation. Thus, the temperature distribution throughout the blade is determined. Next, based on the temperature distribution, a finite element procedure using potential energy approach is applied to determine the thermal-stress distribution. A set of results is obtained through the use of a computer, which is considered to be satisfactory. All computer programs are contained in the report
Multiplexed communication over a high-speed quantum channel
In quantum information systems it is of particular interest to consider the
best way in which to use the non-classical resources consumed by that system.
Quantum communication protocols are integral to quantum information systems and
are amongst the most promising near-term applications of quantum information
science. Here we show that a multiplexed, digital quantum communications system
supported by comb of vacuum squeezing has a greater channel capacity per photon
than a source of broadband squeezing with the same analogue bandwidth. We
report on the time-resolved, simultaneous observation of the first dozen teeth
in a 2.4 GHz comb of vacuum squeezing produced by a sub-threshold OPO, as
required for such a quantum communications channel. We also demonstrate
multiplexed communication on that channel
Influence of particle size distribution on the proportion of stress-transmitting particles and implications for measures of soil state
It is generally accepted that the use of void ratio and bulk density as measures of soil8state have limitations in the case of gap-graded soils as the finer grains may not 9transmit stress. However, hitherto no one has systematically explored whether this 10issue also emerges for soils with continuous gradings. Building on a number of experimental and discrete element method (DEM) studies that have considered the idea of an effective void ratio for gap-graded or bi-modal soils, this contribution extends consideration of this concept to a broader range of particle size distributions. By exploiting high performance computers, this study considers a range of ideal isotropically compressed samples of spherical particles with linear, fractal and gap-graded (bimodal and trimodal) particle size distributions. The materials’ initial packing densities are controlled by varying the inter-particle coefficient of friction. The results show that even for soils with continuous particle size distributions, a significant proportion of the finer particles may not transmit stress and be inactive. Drawing on ideas put forward in relation to gap-graded soils, both a mechanical void ratio and mechanical bulk density that consider the inactive grains as part of the void space are determined. Even for the linear and fractal gradings considered here, the difference between the conventional measures and the mechanical measures is finite and density dependent. The difference is measurably larger in the looser samples considered. These data highlight a conceptual/fundamental limitation of using the global void ratio26as a measure of state in expressions to predict granular material behaviou
TEM10 homodyne detection as an optimal small displacement and tilt measurements scheme
We report an experimental demonstration of optimal measurements of small
displacement and tilt of a Gaussian beam - two conjugate variables - involving
a homodyne detection with a TEM10 local oscillator. We verify that the standard
split detection is only 64% efficient. We also show a displacement measurement
beyond the quantum noise limit, using a squeezed vacuum TEM10 mode within the
input beam.Comment: 9 pages, 8 figure
“Clip-Stone” Filiation Within the Biliary Tract
A case of cholangitis due to the migration of a metal clip used for surgical cholecystectomy 4 years
earlier, is reported. The diagnostic approach and therapeutic options, either endoscopic or surgical are
discussed. The use of resorbable clips during the performance of laparoscopic cholecystectomy should
avoid this type of complication
Quantum measurements of spatial conjugate variables: Displacement and tilt of a Gaussian beam
We consider the problem of measurement of optical transverse profile
parameters and their conjugate variable. Using multi-mode analysis, we
introduce the concept of detection noise-modes. For Gaussian beams,
displacement and tilt are a pair of transverse profile conjugate variables. We
experimentally demonstrate their optimal encoding and detection with a spatial
homodyning scheme. Using higher order spatial mode squeezing, we show the
sub-shot noise measurements for the displacement and tilt of a Gaussian beam.Comment: 3 page
Can optical squeezing be generated via polarization self-rotation in a thermal vapour cell?
The traversal of an elliptically polarized optical field through a thermal
vapour cell can give rise to a rotation of its polarization axis. This process,
known as polarization self-rotation (PSR), has been suggested as a mechanism
for producing squeezed light at atomic transition wavelengths. In this paper,
we show results of the characterization of PSR in isotopically enhanced
Rubidium-87 cells, performed in two independent laboratories. We observed that,
contrary to earlier work, the presence of atomic noise in the thermal vapour
overwhelms the observation of squeezing. We present a theory that contains
atomic noise terms and show that a null result in squeezing is consistent with
this theory.Comment: 10 pages, 11 figures, submitted to PRA. Please email author for a PDF
file if the article does not appear properl
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