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Презентация была опубликована 2 года назад пользователемГлеб Григорьев

1 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 1 Click Instructions for Viewers MR Symposia 2003 Presentation At any instant during the viewing, the display can be advanced to the NEXT SLIDE/or the Next frame within the same slide by a simple mouse-click. After each mouse-click carefully watch for the change to the next display. Do not make too many Clicks at one instant. When you encounter a HYPERLINK (a green text box with faintblue font color with an underlining) a link-cursor(not an arrow) would appear on placing the cursor over the link and a mouse-click would display the linked slide. Then look for a return link to display again the source slide. Right-Click the mouse and exercise the FULL SCREEN viewing option even at the very beginning

2 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 2 NMRS 2004 Presentation Concerning the Specimen Sample-shape for the Single-Crystal HR PMR Studies S.Aravamudhan Department of Chemistry North Eastern Hill University Shillong (Meghalaya) INDIA 20th February 2004

3 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 3 A recapitualisation from the NMRS2003 presentation Slides 1-6 Bulk Susceptibility Effects In HR PMR Liquids D a = - 4 /3 D b = 2 /3 SOLIDS Single crystal arbitray shape Single Crystal Spherical Shape Induced Fields at the Molecular Site Lorentz Sphere cavity The conclusions earlier had been to find answer to the following questions: 1. Should the Lorentz Sphere be Spherical? For this a study of the convergence characteristics for summing over the lattice (cubic and noncubic) for ellipsoidal inner volume element (counter Lorentz sphere) This was the material at 3rd Alpine Conference Poster Once this question could be adequately answered, the next question was to find the consequences of inhomogeneities arising within the sample. Since even if the bulk susceptibility is the same through out the sample, the resulting induced field distributions will not be homogeneous within the samplefor shapes other than sphere and ellipsoid.

4 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 4 Size of the Cavity and the choice of its location in the Specimen can be varied to sample the induced field over the extent of the specimen Magnetic Field Demagnetization Effects i = i i /R 3 i [1-(3.RR i /R 5 i )] A link to a Web Site containing Features of Demagnetzation Factors Calculations A detailed exposition of this tensor equation Appears in the next slide #5

5 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 5 Isotropic Susceptibility Tensor = Induced field Calculations using these equations and the magnetic dipole model have been simple enough when the summation procedures were applied as described in the previous presentations and expositions. For example, an insight into the induced fields and demagnetization could be gained as depicted in the next slide which otherwise would have been hard to realize and prove so effctively.

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7 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 7 These results could be dated back to the year

8 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 8 for a cubic parameter value of 9:9:9 the inner volume element was given an ellipsoidal shape with varying ellipsoidal shape parameters CZ BY and AX. In most of the cases BY= AX. In the plot referred to here CZ = 1.0 and BY was varied from1.0 to 0.8. This corresponds to the prolate case for the shape of ellipsoid as in the figure. as the shape becomes more ellipsoidal there seems a lot of deviation occurs in the radius range from 18 to 234 units. OR Some Results of the 3rd Alpine POSTER at France in Sept.2003 are summarized in the next three Slides 7-9

9 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 9 Compression of the scale on the Y-axis to 1 division= 1 x units from the value of 2 x units in the lower plot make the cubic case (spherical inner element) value to be all along the zero line !Monotonically increasing deviations from zero line (on the positive side) with increase in ellipticity!! The convergence value does not depend upon the ellipticity of the inner volume element. When the lattice is of cubic type A=B=C, then for all ellipticity including the limiting case of a sphere, the convergence of the lattice sum occurs to zero value. OR

10 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 10 Non-Cubic Cases: With a difference of 3 units in lattice parameters, for the two extreme cases of cubic lattices the summation leads to zero value all through for the various radius values. When the C= 10 and C=7 the convergence values range is far away from zero and the values are from -6 x to +4 x Lower trace the same cubic/noncubic values with ellipsoidal shape 1:0.7. Trends of variation in the x-axis regions of 100 units to 224 units indicate an increased deviation with ellipticity. As noted earlier for the cubic cases the convergence values are independent of the ellipticity even for non-cubic cases. Qualitatively, when the ellipticity ratio changes by 0.1, the convergence value changes at the rate of 4.5 x per 0.1 value change in the ratio. OR After the CUBIC Case...

11 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 11 TOP SHAPE CYLINDER Equatorial (0,7) (0,0) Results of Claculations made for this presentation at NMRS2004

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15 7/23/2015 1:07:27 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 15 END OF Presentation Questions & Comments To End this SHOW make a right-click and click further on the End Show option in the prop-up box.

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