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: Biogas Production from A Combination of Sheep and Dairy Cattle Manure
Abstrak: Tingginya populasi domba dan sapi perah di Jawa barat akan menghasilkan kotoran ternak yang berlimpah. Kotoran ternak dapat mencemari lingkungan jika tidak dikelola dengan benar. Biogas dapat diproduksi dari kotoran domba dan kotoran sapi perah melalui fermentasi anaerob. Penelitian bertujuan menganalisis produksi biogas dari kombinasi kotoran domba dan kotoran sapi perah. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan tiga perlakuan dan tiga kali ulangan tiap perlakuan. Perlakuan pada penelitian ini yaitu D100S0 (100% kotoran domba dan 0% kotoran sapi perah), D50S50 (50% kotoran domba dan 50% kotoran sapi perah), dan D25S75 (25% kotoran domba dan 75% kotoran sapi perah). Nilai TS akhir setelah fermentasi anaerobik semua perlakuan berbeda nyata (P<0,05). Volume biogas dan lama nyala api perlakuan D50S50 berbeda nyata daripada D100S0 dan D25S75. Suhu harian biogas mengalami fluktuasi antara 2629 °C. Nilai pH pada rentang 6,698,13 melebihi kondisi netral. Penggunaan kotoran domba sebagai biogas menghasilkan warna nyala api biru sedikit kemerahan. Hasil penelitian menyimpulkan bahwa kotoran domba berpotensi menghasilkan biogas., The high population of sheep and dairy cattle in West Java will produce high manure production. Animal manure can pollute the environment if not managed properly. Biogas can be produced from sheep manure and dairy cattle manure through anaerobic fermentation. This study aimed to analyze biogas production from a combination of sheep and dairy cattle manure. This study used a completely randomized design (CRD) with three treatments and three replications for each treatment, including D100S0 (100% sheep manure and 0% dairy cattle manure), D25S75 (25% sheep manure and 75% dairy cattle manure), and D50S50 (50% sheep manure and 50% dairy cattle manure). The final TS after anaerobic fermentation differed for all treatment (P<0,05). The biogas volume and flame duration of D50S50 differed (P<0,05) than D100S0 and D25S75. The daily biogas temperature fluctuates between 26-29 °C. The pH value in the range of 6,69-8,13 exceeded neutral conditions. The use of sheep manure as biogas produces a slightly reddish-blue flame. To conclude, sheep manure has the potential to produce biogas.
Keyword: biogas, kotoran domba, kotoran sapi perah

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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