Judul: Kualitas Fermentasi Dan Kandungan Nutrien Silase Beberapa Jenis Rumput Yang Dipanen Pada Waktu Berbeda
Abstrak: The aims of the research were to analyze fermentation quality. The research used randomized factorial design (5x3) with factor A was grass sources (Pennisetum purpureum, Pennisetum purputhypoides, Panicum maximum, Brachiaria humidicola, and Paspalum notatum) and factor B was the harvest time (morning, noon, and night). The results showed that grass sources and harvest time significantly (P<0.05) influenced pH, solubility and Water Soluble Carbohydrate (WSC). Solubility, those of pH and WSC from Pennisetum purputhypoides were higher than those of the others, and pH and WSC lost from grass harvested at night were higher than the others silage. There were interaction between grass Pennisetum purputhypoides and time of harvesting. It is concluded that kind and harvesting time of the grass influenced pH, WSC and silage solubility but it did not affect sillage dry matter lost and number of lactic acid bacteria.
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Judul: Uji Kecernaan In vitro Silase Campuran Rumput Gajah (Pennisetum purpureum) dan Lamtoro Merah (Acacia villosa)
Abstrak: The aim of this experiment was to study in vitro digestibility of mixed Pennisetum purpureum and Acacia villosa silage in different proportion. The experiment used factorial block randomized design 3x6 with three replicates. Factor A was the ratio between P. purpureum and A. villosa i.e. A1 = 60% P. purpureum : 40% A. villosa, A2 = 50% P. purpureum : 50% A. villosa, and A3 = 40% P. purpureum and 60% A. villosa. Factor B was incubation times i.e. B1-B6 for 4, 8, 12, 24, 48, and 72 hours. Data were analyzed using analysis of variance (ANOVA), the difference between treatments were tested with polynomial and Duncan test. The result showed that bacterial population, and organic digestibility were influenced by treatments (P<0.05). Ammonia concentrations, and dry matter digestibility were influenced by incubation time (P<0.05). Protozoa populations was influenced by treatments and incubation time (P<0.05). Interaction between two factors was detected (P<0.05) on total VFA concentrations. Methane was reduced by the increased of A. villosa. It is concluded that the addition of 40% of A. villosa cause the highest digestibility and total VFA production but produce the highest methane.
Keyword: P. purpureum, methane, digestibility, A. villosa

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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