Optimization of the Superconducting Linear Magnetic Bearing of a Maglev Vehicle

Considering the need for cost/performance prediction and optimization of superconducting maglev vehicles, we develop and validate here a 3D finite element model to simulate superconducting linear magnetic bearings. Then we reduce the 3D model to a 2D model in order to decrease the computing time. This allows us to perform in a reasonable time a stochastic optimization considering the superconductor properties and the vehicle operation. We look for the permanent magnet guideway geometry that minimizes the cost and maximizes the lateral force during a displacement sequence, with a constraint on the minimum levitation force. The displacement sequence reproduces a regular maglev vehicle operation with both vertical and lateral movements. For the sake of comparison, our reference is the SupraTrans prototype bearing. The results of the optimization suggest that the bearing cost could be substantially reduced, while keeping the same performances as the initial design. Alternatively, the performances could be significantly improved for the same original cost

Le Théâtre

We present preliminary measured responses of a planar superconducting on/off switch operating at millimeter wavelengths. The superconducting switch, comprising three niobium nitride (NbN) bridges, is deposited across the slotline section of a back-to-back unilateral finline. The transmission characteristics of the superconducting switch illuminated by a millimeter source was measured using a superconductor-insulator-superconductor (SIS) tunnel junction as direct detector. The NbN bridges were switched from the superconducting state to the normal state by passing current through the bridges with magnitude that exceeds its critical current value. With this arrangement, we have measured a typical switching dynamic range of approximately 10 dB across the 205-240 GHz band, with the highest dynamic range of ?20 dB at 230 GHz. This demonstrated the successful operation of the multiple NbN bridges as a planar superconducting on/off switch

Attenuation in Rectangular Waveguides with Finite Conductivity Walls

We present a fundamental and accurate approach to compute the attenuation of electromagnetic waves propagating in rectangular waveguides with finite conductivity walls. The wavenumbers kx and ky in the x and y directions respectively, are obtained as roots of a set of transcendental equations derived by matching the tangential component of the electric field (E) and the magnetic field (H) at the surface of the waveguide walls. The electrical properties of the wall material are determined by the complex permittivity ε, permeability μ, and conductivity σ. We have examined the validity of our model by carrying out measurements on the loss arising from the fundamental TE10 mode near the cutoff frequency. We also found good agreement between our results and those obtained by others including Papadopoulos’ perturbation method across a wide range of frequencies, in particular in the vicinity of cutoff. In the presence of degenerate modes however, our method gives higher losses, which we attribute to the coupling between modes as a result of dispersion

Antimicrobial Activities of the Leaves and Fruits of (Cassia fistula)

The biological activity of the extracts of the leaves and fruits of C. fistula tree, was tested against both fungi (Aspergillus niger and Penicillium digitatum), and two bacteria (Staph. aureus and E. coli). From the results it is clear that the leaf extracts were effective against the radial growth of the two fungi. For P. digitatum it was 1.0 mm at 100% concentration compared to 2.2 mm at the control treatment (0.0% concentration) at the 8th day. However, for A. niger it was only 0.5 mm at 100% concentration compared to 2.3 mm at the control treatment (0.0% concentration) at the 8th day. The results also showed that the fruit extracts of C. fistula were also effective in inhibiting the radial  growth of  both fungi, although the extracts are more effective against A. niger than P. digitatum , they gave complete inhibition at all of the concentrations The growth was inhibited even from the second day. The effects of the leaf and fruit extracts of C. fistula were also examined on the fresh and dry weights of both fungi (P. digitatum and A. niger). The leaf extracts were found very effective at their higher concentration compared to the control treatment. However the leaf extracts are better compared to the fruit extracts. The inhibition zone tests were also included in the present study, to evaluate the effect of the leaf and the fruit extracts of the C. fistula tree on inhibiting the growth of two bacteria (the Gram positive, Staph. aureus and the Gram negative, E. coli). The results indicated that the extracts were very effective in inhibiting the growth of the bacterium both bacteria. They gave 10.0 mm 9.0 mm inhibiting zones, for Staph. aureus and 13.0 mm and 11.0 mm inhibiting zones for   E. coli, respectively

Increasing the “region of interest” and “time of interest”, both reduce the variability of blood flow measurements using laser speckle contrast imaging

ObjectiveBoth spatial variability and temporal variability of skin blood flow are high. Laser speckle contrast imagers (LSCI) allow non-contact, real-time recording of cutaneous blood flow on large skin surfaces. Thereafter, the observer can define different sizes for the region of interest (ROI) in the images to decrease spatial variability and different durations over which the blood flow values are averaged (time of interest, TOI) to decrease temporal variability. We aimed to evaluate the impact of the choices of ROI and TOI on the analysis of rest blood flow and post occlusive reactive hyperemia (PORH). Methods Cutaneous blood flow (CBF) was assessed at rest and during PORH. Three different sizes of ROI (1 mm2, 10 mm2 and 100 mm2), and three different TOI (CBF averaged over 1 s, 15 s, and 30 s for rest, and over 1 s, 5 s and 10 s for PORH peak) were evaluated. Inter-subjects and intra-subjects coefficient of variations (inter-CV and intra-CV) were studied. Results The inter-subject variability of CBF is about 25% at rest and is moderately improved when the size of the ROI increases (inter-CV = 31%, for 1 s and 1 mm2 versus inter-CV = 23%, for 15 s and 100 mm2). However, increasing the TOI does not improve the results. The variability of the PORH peak is lower with an inter-CV varying between 11.4% (10 s and 100 mm2) and 21.6% (5 s and 1 mm2). The lowest intra-CV for the CBF at rest was 7.3% (TOI of 15 s on a ROI of 100 mm2) and was 3.1% for the PORH peak (TOI of 10 s on a ROI of 100 mm2). Conclusion We suggest that a size of ROI larger than 10 mm2 and a TOI longer than 1 s are required to reduce the variability of CBF measurements both at rest and during PORH peak evaluations at the forearm level. Many technical aspects such as comparison of laser speckle contrast imaging and laser Doppler imaging or the effect of skin to head distance on recorded values with LCSI are required to improve future studies using this fascinating clinical tool

Measured performance of a 230 GHz prototype focal-plane feedhorn array made by direct drilling of smooth-walled horns

We present the first, complete 230 GHz feedhorn array manufactured by direct drilling of smooth–walled horns into a single plate of aluminium. The horn design process, based on a genetic algorithm, is described and the fabrication process, via direct drilling using shaped drill bits, is presented. We present cross coupling and beam pattern measurements of a close–packed pair of the smooth–walled horns fabricated in a single block of aluminium. We also present a prototype 37 horn array, again fabricated by drilling into a single block. Our measurements show that our designs and fabrication techniques will be robust when applied to large focal arrays of horns consisting of hundreds or thousands of feedhorns. We expect our smooth–walled horn designs and novel manufacturing techniques will offer an attractive, low-cost alternate to traditional horn arrays consisting of electroformed corrugated horns

Optical response of a titanium-based cold-electron bolometer

We present experimental results on the testing of cold-electron bolometer (CEB) detectors comprised of a thin Ti film absorber and two SIN junctions integrated with a planar antenna. The CEB performance was tested in a He-3 sorption cryostat HELIOX-AC-V at bath temperatures of 280-305 mK. The optical response was measured using the hot/cold load method by flipping a Cu reflector opposite a blackbody surface inside a 3 K shield and using a thermal source with variable temperature. In the first experiment, the detector chip was mounted in an optical sample-holder whose aperture was switched towards or away from a blackbody source changing the incident radiation temperature from 3 K to 270 mK. As a result, we measured the optical response to a 3 K/270 mK radiation temperature change. The measured voltage response value for the detector integrated in a double-dipole antenna was Delta V-out = 120 mu V. This corresponds to a noise equivalent power of NEP = V-n/(dV/dP) = 3.5 x 10(-17) W Hz(-1/2), where dV/dP is the voltage to power response obtained from the incoming power estimation based on the Planck formula

CLOVER - A new instrument for measuring the B-mode polarization of the CMB

We describe the design and expected performance of Clover, a new instrument designed to measure the B-mode polarization of the cosmic microwave background. The proposed instrument will comprise three independent telescopes operating at 90, 150 and 220 GHz and is planned to be sited at Dome C, Antarctica. Each telescope will feed a focal plane array of 128 background-limited detectors and will measure polarized signals over angular multipoles 20 < l < 1000. The unique design of the telescope and careful control of systematics should enable the B-mode signature of gravitational waves to be measured to a lensing-confusion-limited tensor-to-scalar ratio r~0.005.Comment: 4 pages, 5 figures. To appear in the proceedings of the XXXVIXth Rencontres de Moriond "Exploring the Universe