Ferdy S. Rondonuwu

Low Writing Field on Perpendicular Nano-ferromagnetic

For heat-assisted magnetic recording, magnetization reversal probabilities of nano-Pt/MnSb multilayer film with perpendicular magnetic anisotropy under thermal pulse activation were investigated numerically by solving the Landau-Lifshift Gilbert Equation. Magnetic parameters of nano-Pt/MnSb multilayer were used with anisotropy energy of 3 × 10 5 erg/cc and saturation magnetization of 2100 G, which offer more than 10 y data stability at room temperature. Scheme of driven magnetic field and thermal pulse on writing mechanism was designed closely to real experiment. This study found that the chosen material is potential to be used as a high density magnetic storage that requires low writing field less than two-hundreds Oersted through definite heating and cooling interval. The possibility of writing data with a zero driven magnetic field also became an important result. Further study is recommended on the thickness of media and thermal pulse design as the essential parameters of the reversal magnetization.

Construction of calibration model for sweetness degree on fructose using the Fourier-transform near-infrared spectroscopy and singular value decomposition analysis

Measuring the sweetness degree of fruit generally performed by refractometer with sweetness degree expresses in 0Brix. Brix meters measure sample sweetness within seconds and are easy to operate; yet it can’t differentiate composition of sugar contents (glucose, fructose, sucrose). Sugar absorption appears on near-infrared region so that Fourier-transform near-infrared spectroscopy enables us to measure sugar spectrum of near-infrared absorption for different kind of sugar. This research reports the model of sweetness degree’s measurement using fructose and their various concentration of 0 -10 grams each in 100 grams of solutions. Singular value decomposition (SVD) analysis technique was used in constructing the ideal data training based on the measurement of spectrum for 15 kinds of concentrations. Validation inspections show that fructose and concentration predicted by the technique of Fourier-transform near-infrared spectroscopy and SVD analysis showed the high level of consistency to that of actual on...

Classification of Stevia rebaudiana Using Near Infrared Spectroscopy and Multivariate Data Analysis

Stevia rebaudiana leaf contains stevioside and rebaudioside A as main diterpene glycosides. These compounds are used as natural sweetener and potentially as drug candidate of diabetes type 2. Rapid and nondestructive method for S. rebaudiana leaves (n = 23) classification based on geographical area and main diterpene glycosides content was carried out using near infrared spectroscopy combined with multivariate data analysis. Linear discriminant analysis (LDA) was applied to discriminate S. rebaudiana leaves based on geographical area. Principal component analysis (PCA) was established to classify S. rebaudiana leaves based on main diterpene glycosides content. HPLC analysis was used as reference data to divide PCA result into groups. LDA model correctly classified 95% of the S. rebaudiana leaves based on geographical area. PCA model correctly classified 95% and 90% of S. rebaudiana leaves based on rebaudioside A and stevioside content, respectively. The classification method using near infrared spectroscopy combined with multivariate data analysis demonstrate potential use of the classification method established as quality control technique of S. rebaudiana leaves.