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Abstrak :
ABSTRAK
The results of a computer simulation investigation delineating the limits of resolution, sensitivity, and accuracy of the depth-resolved surface-coil spectroscopy (DRESS), volume-selective excitation (VSE), and image-selected in vivo spectroscopy (ISIS) methods for achieving spatially localized NMR spectroscopy are presented. A computer program, which numerically solves the Bloch equations for variable input parameters, is used to simulate the spatial localization afforded by each technique. Because the numerical solution of the Bloch equations describes the behavior of the bulk magnetization with great precision, the simulations provide an obejective and realistic means of evaluating the performance of the individual localization schemes and reveal nuances and limitations not discussed in the original experimental papers. The results of this computer simulation study should encourage the optimization of localization methodology for use in specific applications.

Abstrak :
Alloy FeSi adalah bahan yang digunakan sebagai inti dalam transformator. Material ini merupakan material softmagnetik, yang memiliki sifat antara lain : Magnetisasi saturasinya tinggi( Ms>1.27 T ), koersivitasnya rendah( Hc<10 A/m ), permeabilitasnya tinggi(10.000-200.000) dan lain-lain. Dalam penelitian ini, dipelajari efek penambahan Si pada Fe, dan efek impuritas Fe terhadap nilai temperatur Curienya. Alloy Fe1-xSix(x=0,1,2,3,4 wt) dipreparasi dengan metode arcmelting furnace dalam kondisi argon. Fe yang digunakan memiliki tingkat kemurnian yang berbeda, yaitu: 99,98% dan 99,5%. Studi temperatur Curie ini dikaitkan dengan mikrostrukturnya. Difraksi sinar X digunakan untuk meneliti struktur kristal dan fase. Sedangkan studi metalografi digunakan untuk melihat distribusi dan ukuran grain. Penambahan %Si pada Fe menghasilkan penurunan temperatur Curie dan meningkatkan impuritasnya.

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FeSi alloys are softmagnetic materials which are used as core transformer. These alloys posses high saturation magnetization(Ms > 1,27 T), low coercivity(Hc < 10A/m) and high permeability (10.000-200.000). In this thesis we studied the effect of Si addition in Fe and the impurity of Fe on its curie temperature. Fe100-xSix(x=1,2,3,4 at%) have been prepared by using arc-melting furnace in argon environment. Two kinds of Fe which has impurity of 99.98% and 99.5% were used in this study. The Curie temperature of these alloys decreases with increasing of Si content in Fe-structure.