Judul: Produksi Gas Bio Dari Campuran Kotoran Sapi Perah Dengan Kompos Jerami Padi Pada  Rasio C/N Yang Berbeda
Abstrak: Biogas is a renewable energy which can be used as alternative fuel instead of fuel such as oil and natural gas. Biogas is gases mixture that produced from organic fermentation processing by bacteria in anaerobic condition. The fermentation process for biogas production affected by C/N ratio. The optimum C/N Ratio is very important because related to metabolic activity of organism. Additional of rice straw can increase C/N ratio. The purpose of this research was to know production rates of biogas from dairy manure mixture with composted rice straw on different C/N ratio. The results showed that dairy manure mixture with compost rice straw on different C/N ratio very significant (P<0,01) to biogas production. The mixture between rice straw that composted by EM4 activator with dairy manure on C/N ratio 30 resulted highest biogas production. Keywords: Biogas, Ratio C/N, Dairy manure, Compost rice straw.
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Judul: Biogas Production from a Mix of Cow Mature with Odot Grass (Pennisetum purpureum cv. Mott)
Abstrak: Biogas merupakan salah satu sumber energi alternatif yang dapat diperbarui karena menggunakan bahan baku yang berasal dari kotoran ternak. Penelitian bertujuan untuk menganalisis produksi biogas dari campuran rumput odot dan kotoran sapi. Penelitian dilakukan dengan 3 perlakuan yaitu 100 % kotoran sapi (kontrol), 70% kotoran sapi +30% rumput odot, dan 50% kotoran sapi +50% rumput odot. Hasil penelitian menunjukkan bahwa campuran biogas kotoran sapi dengan rumput odot sangat nyata (P<0,05) terhadap produksi biogas yang dihasilkan nilai produksi berturut-turut untuk K₁₀₀R₀, K₇₀R₃₀, dan K₃₀E₃₀ sebesar 191,3500; 99.0067 dan 0,0000. Rasio C/N bahan tiap perlakuan sebesar 27,52; 25,32 dan 23,85. Temperature harian rata-rata hampir sama untuk semua perlakuan yaitu 27-29°C. Nilai pH tiap perlakuan sebesar 5,90-7,27; 5,00-7,00 dan 4,77-6,70. Kandungan TS, VS awal dan akhir tiap perlakuan adalah TS awal 11,014; 11,007; dan 11,195; TS akhir 6,960; 6,794; dan 6,714; VS awal 8,838; 8,965; dan 9,309; VS akhir 5,734; 5,728; dan 5.831. Nyala api biogas dengan campuran rumput odot (K₁₀₀R₀) dan (K₇₀R₃₀) menghasilkan biogas berwarna biru sedangkan (K₅₀R₅₀) tidak menghasilkan nyala api., Biogas is one of the alternative energy sources that can be updated because it uses raw materials derived from livestock manure. The research aims to analyze biogas production from a mixture of odot grass and cow manure. The study was conducted with 3 treatments namely 100% cow manure (control), 70% cow manure + 30% odot grass, and 50% cow manure + 50% odot grass. The results showed that the mixture of cow manure biogas with odot grass was very real (P<0.05) against the production of biogas produced successive production values for K₁₀₀R₀, K₇₀R₃₀, and K₃₀E₃₀ 191.3500; 99,0067 and0.0000. TheC/N ratio of each treatmentis 27.52; 25.32 and 23.85. The average daily temperature is about the same for all treatments which is 27-29°C. The pH value of each treatment is 5.90-7.27; 5.00-7.00 and 4.77-6.70. The content of TS, VS the initial and final of each treatment is the initial TS of 11,014; 11,007; and 11,195;final TS6,960; 6,794; and 6,714;initial VS8,838;8,965; and 9,309; final VS of 5734; 5,728; and 5,831. Biogas flames with a mixture of odot grass (K₁₀₀R₀) dan (K₇₀R₃₀) produce blue biogas flames (K₅₀R₅₀) do not produce flames
Keyword: Biogas, Cow Manure, Fermentation, Odot Grass, Production

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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