Judul: Pengaruh perajangan dan lama pengukusan pada ekstraksi terhadap mutu gambir (Uncaria gambir Roxb.)
Abstrak: Penelitian ini bertujuan untuk mempelajari pengaruh perajangan dan lama pengukusan daun gambir (Uncaria gambir Roxb) terhadap rendemen dan mutu gambir yang dihasilkan dan untuk memperoleh kondisi ekstraksi yang optimum. Tahapan proses ekstraksi yang dilakukan adalah pera- jangan, pengukusan, pengepressan, penguapan dan penge- ringan. Pelarut yang digunakan pada proses ekstraksi ada- lah air. Rancangan percobaan yang digunakan adalah Rancangan Acak Lengkap Faktorial dengan dua kali ulangan. yang diteliti adalah ukuran perajangan dalam empat Faktor taraf percobaan yaitu 0.5 1 cm, 2 3 cm, 4 6 cm, tidak di- rajang dan faktor lama pengukusan dalam empat taraf yaitu 30 menit, 45 menit, 60 menit dan 75 menit. Pengamatan di- lakukan terhadap rendemen gambir, kadar air, kadar cate- chin, kadar abu, kadar bahan tidak larut dalam air dan kadar bahan tidak larut dalam alkohol. Hasil analisis sidik ragam menunjukkan bahwa interaksi ukuran perajangan dan lama pengukusan berpengaruh nyata terhadap rendemen, kadar catechin, kadar bahan tidak larut dalam air dan kadar bahan tidak larut dalam alkohol. Rendemen gambir yang diperoleh dari daun yang dirajang lebih tinggi dibandingkan dengan daun yang tidak dirajang. 10.32 Rendemen gambir tertinggi yang diperoleh persen pada ukuran perajangan 0.5 adalah 1 cm dan lama pengukusan 30 menit dengan kadar catechin 75.82 persen. Rendemen gambir yang diperoleh berkisar antara 7.79 sampai 10.32 persen, kadar catechin berkisar antara 65.06 sampai 75.82 persen, kadar kadar bahan tidak larut dalam air 3.50 sampai 4.92 persen, kadar bahan tidak larut dalam alkohol antara 11.17 sampai 13.47 persen, kadar air antara 9.47 sampai 11.34 persen dan kadar abu 4.55 sampai 6.20 persen. Nilai yang diperoleh memenuhi spesifikasi mutu yang di tetapkan oleh Departemen Perdagangan untuk kualitas ekspor, dengan tingkat mutu yang lebih baik dibandingkan gambir cipte mili hasil pengolahan secara tradisional.
Keyword: 

Judul: Kajian Pembuatan Gambir Bubuk Dari Daun Gambir (Uncaria Gambir Roxb.) Kering Menggunakan Spray Dryer
Abstrak: Gambier is the sap of dried leaves and twigs extracts of gambier plant (Uncaria gambir Roxb.) The main chemical components contained in gambier are catechin and tannin. Both of these chemical compounds contribute to the usefulness and high added value. Indonesia is the highest producer and exporter of gambier in the world. Indonesian gambier export has some problems caused by low and different quality of gambier. On the other hand, extraction that has been done by local people did not support to produce high quality of gambier. Delay in fresh leaf gambier extraction can cause the decreasing of gambier quality. The further study of gambier extraction must be done to find the right method to produce high quality of gambier. Drying leaves is one method to keep the quality of gambier. This study aims to determine the influence of type and concentration solvent for the yield, catechin content, and the quality of gambier powder that are extracted by organic solvents from dried gambier leaves, and to measure the effect of difference shelf-life in the quality of gambier powder. The extraction of dried gambier leaves had been done by some stages, that were reduction gambier leaves size using Hammer Mill, solvent extraction in Shaker Waterbath at 500C for 90 minutes, maceration for 3 x 24 hours, filtering, and drying using Spray Dryer. Type of solvent used were ethanol, methanol, and isopropanol at concentration 100%, 75%, and 50%. The effect of difference shelf-life had been done by using ethanol 96% at initial week, first week, second week, third week, and fourth week. Based on calculations on yield gambier, it were obtain that ethanol at a concentration of 75% gave the highest yield gambier (13,43%). Type of solvent significantly affected the yield of gambier, whereas the concentration in each solvent did not affect significantly to the yield of gambier. Analysis of catechin content in the product showed that the highest levels of catechin was obtained in the solvent isopropanol 100% (93.47% db), and the lowest of catechin content in the solvent was ethanol 50% (24,36% db). Solvent type and concentration of each solvent gave a significant effect on the concentration of catechin in gambier powder. The extraction used ethanol, methanol, dan isopropanol at concentration 100% gave the first quality of gambier. The extraction used isopropanol 75% gave the second quality of gambier. Whereas, the extraction used etanol and methanol at 75% and 50%, and also isopropanol at 50% is not qualified. Quality analysis of gambier powder showed that the product had water content from 3,47% to 6,23%, ash content was from 0,54% db to 4,66% db, insoluble material in water content was from 13,04% db to 37,93% db, insoluble material in alcohol content was from 3,96% db to 11,96% db, and had brownish yellow color to greenish brown color. Water content, ash content, insoluble material in alcohol content, and color of gambier powder had qualified as the first quality of gambier, whereas the content of insoluble material in water was not qualified.
Keyword: 

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.
Keyword: