Judul: Kendali Mutu Rimpang Temulawak (Curcuma xanthorrhiza) menggunakan Fotometer Jinjing dengan Analisis Kemometrik
Abstrak: Temulawak (Curcuma xanthorrhiza) is widely used herb in Indonesia. The complex composition of the herbal extract requires quality control in the evaluation. This study aimed to develop portable photometer as a quality control device for temulawak rhizome age 9 months based on quality diversity of stem rhizome and branch rhizome that was combined with pattern recognition techniques (PCA & PLSDA) and compare the result of the analysis with high performance liquid chromatography (HPLC) method. PCA analysis on portable photometer data with 8 filters was able to classify stem rhizome and branch rhizome with just 2 main components. Curcuminoid content of stem rhizome was higher than the branch rhizome in plant 2, 4, and 8, and its grouping was in accordance with PCA analysis result using 3 filters (blue-green, green-yellow, and yellow) only on stem fresh rhizome samples. The grouping formed a PLSDA model with plant 2, 4, and 8 were in group A and the curcuminoid content fell into that respective range. It indicates that portable photometer as an alternative instrument cannot provide quantitative results based on differences of stem and branch rhizomes, but fairly informative in grouping stem rhizome and branch rhizome.
Keyword: temulawak, quality control, portable photometer, curcuminoid, chemometric

Judul: Evaluasi Kadar Kurkuminoid Rimpang Temulawak (Curcuma xanthoriza Roxb.) Menggunakan Analisis Citra Berbasis Red Green Blue
Abstrak: Turmeric (Curcuma xanthoriza Roxb.) is one of the important natural product in Indonesia. Quality of turmeric is dictated by content of curcuminoid. The curcuminoid content could be determined by spectrophotometry, titration volumetry, or chromatography, but those analytical methods are destructive to the material and need long time. One of rapid and nondestrucive method is image analysis. The objectives of this research were to evaluate content of curcuminoid using image analysis based on red green blue (RGB). Picture taking for image analysis was using USB Digital Microscope with enlargement 800x and curcuminoids were measured using spectrophotometry Uv-Vis at wavelength of 420 nm. The data showed that RGB value is equivalent with the content of curcuminoid. The result can be used as parameter to differentiate turmeric with harvest age 3, 6, and 9 months. The obtained equation of predicted content of curcuminoid is y = - 0,22 - 0,0062 R + 0,0643 G - 0,0330 B, R² = 96,1%.
Keyword: turmeric., RGB, curcuminoid, image analysis

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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