On The Determination of MDI High-Degree Mode Frequencies

The characteristic of the solar acoustic spectrum is such that mode lifetimes get shorter and spatial leaks get closer in frequency as the degree of a mode increases for a given order. A direct consequence of this property is that individual p-modes are only resolved at low and intermediate degrees, and that at high degrees, individual modes blend into ridges. Once modes have blended into ridges, the power distribution of the ridge defines the ridge central frequency and it will mask the true underlying mode frequency. An accurate model of the amplitude of the peaks that contribute to the ridge power distribution is needed to recover the underlying mode frequency from fitting the ridge. We present the results of fitting high degree power ridges (up to l = 900) computed from several two to three-month-long time-series of full-disk observations taken with the Michelson Doppler Imager (MDI) on-board the Solar and Heliospheric Observatory between 1996 and 1999. We also present a detailed discussion of the modeling of the ridge power distribution, and the contribution of the various observational and instrumental effects on the spatial leakage, in the context of the MDI instrument. We have constructed a physically motivated model (rather than some ad hoc correction scheme) resulting in a methodology that can produce an unbiased determination of high-degree modes, once the instrumental characteristics are well understood. Finally, we present changes in high degree mode parameters with epoch and thus solar activity level and discuss their significance.Comment: 59 pages, 38 figures -- High-resolution version at http://www-sgk.harvard.edu:1080/~sylvain/preprints/ -- Manuscript submitted to Ap

Polygonal decompositions of quadrilateral subdivision meshes

We study a polygonal decomposition of the 1-ring neighborhood of a quadrilateral mesh. This decomposition corresponds to the eigenvectors of a matrix with circulant blocks, thus, it is suitable for the study of subdivision schemes. First, we calculate the extent of the local mesh area we have to consider in order to get a geometrically meaningful decomposition. Then we concentrate on the Catmull-Clark scheme and decompose the 1-ring neighborhood into 2n planar 2n-gons, which under subdivision scheme transform into 4n planar n-gons coming in pairs of coplanar polygons and quadruples of parallel polygons. We calculate the eigenvalues and eigenvectors of the transformations of these configurations showing their relation with the tangent plane and the curvature properties of the subdivision surface. Using direct computations on circulant-block matrices we show how the same eigenvalues can be analytically deduced from the subdivision matrix

Prediction of Spot Welding Parameters Using Fuzzy Logic Controlling

The Resistance Spot Welding (RSW) represents one of the most important welding processes. The resistance spot welding quality depends on the process parameters like welding current, electrode force and welding time and their chosen levels. In this work, the experimental part is validated by the simulation part, where the last will be used later for predicting the results for new data with a very acceptable percentage of accuracy. This study presents an experimental work of the resistance spot welding for two similar sheets of Austenitic Stainless Steels (AISI 304) that are intended to be held together in one point by the pressure of the electrodes, with high magnitude of electrical current to be applied, where the resistance spot welding parameters (welding current and welding time) are changeable to show each of the parameter's action on the welded material properties (The Maximum Shear Load that the metal can be subject to besides The Nugget Zone Diameter of the welded contact area). The experimental work in this study delivers genuine and important data that will be the basis for the Fuzzy Logic Controller (FLC), which will be set up then. The Artificial Intelligence (which is presented by the fuzzy logic controller) role is to predict the optimal welded material parameters for any given resistance spot welding parameters, and to discover the probability of expulsion, failure, or breaking in the welding process before it takes place or happens, where in this study, the FLC predicted the optimum value of the maximum shear load for RSW, which occurs at the welding time=20 cycle and the welding current=8 KA, while the estimated optimum value of the Nugget Diameter by FLC for RSW is found at welding time=20 cycle and welding current=8 KA.This prediction will save the metal parts and the electrodes of welding, besides saving the cost and the effor

Qualification of BSO crystals for use onboard the International Space Station

peer reviewedBSO crystals are excellent recording media for use in the holographic instrument of a multiple diagnostic instrument (Fluid Science Laboratory), for monitoring fluid phenomena onboard the ISS. Some experiments have been already presented that showed the potentiality of BSO for this kind of application. Here we present the crystals qualification for use within FSL with respect to gamma rays and protons radiation

Study the Effect of Arabidopsis thaliana Extract on Reducing Blood Glucose Level in Diabetic White Albino Mice

This study was designed to evaluate the effect of aqueous extract of Arabidopsis thaliana seeds on reducing glucose level for white albino mice. Twenty adults mice were used, divided randomly into four groups (five mice per each group). The first group (normal mice) was administrated with 0.1 ml of distilled water as a control, the second group (normal mice) was administrated with 0.1 ml of the plant extract, whereas the third and fourth groups (diabetic mice) were administrated with single dose of alloxan (150 mg/kg of the body weight) to induce diabetes, and the fourth group was administrated with 0.1 ml of the plant extract for 10 days, then blood glucose level was measured for all of the experimental animals (diabetic and non diabetic). Results showed clear increasing in glucose levels in the diabetic mice, while significant reduction was recorded in glucose levels of the normal mice that was treated with the plant extract as compared with the control group. These results indicate that Arabidopsis thaliana seeds aqueous extract possesses a hypoglycemic effect. Key words: Arabidopsis thaliana, glucose level, albino mic

DARWIN fringe sensor (DWARF): concept study

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