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: Biogas Production from a Mix of Cow Manure with corn straw (Zea mays. L)
Abstrak: Biogas merupakan salah satu sumber energi alternatif yang dapat diperbarui karena menggunakan bahan baku yang berasal dari kotoran ternak. Tujuan penelitian ini adalah menganalisis roduksi dan kualitas biogas dari campuran kotoran sapi dengan jerami jagung (Zea mays. L). Penelitian dilakukan dengan 3 perlakuan yaitu kontrol sebanyak 100% kotoran sapi + 0% jerami jagung (S100J0), 75% kotoran sapi + 25% jerami jagung (S75J25), serta 50% kotoran sapi + 50% jerami jagung(S50J50) dan masing-masing 3 kali ulangan dengan analisis data menggunakan rancangan acak lengkap (RAL). Hasil penelitian menunjukkan bahwa campuran biogas kotoran sapi dengan jerami jagung berpengaruh nyata (P>0,05) terhadap produksi biogas yang dihasilkan (S100J0) menghasilkan produksi biogas yang paling tinggi. Suhu harian rata-rata hampir sama untuk semua perlakuan yaitu 27- 29 °C. Kandungan TS, VS awal dan akhir berturut-turut untuk S100J0, S75J25, dan S50J50 14,940; 12,916; dan 13,873. VS awal 12,660; 10,903; dan 10,996. TS akhir 10,643; 7,900; dan 10,550. VS akhir 6,286; 4,546; dan 7,323. Perlakuan S100J0 menghasilkan produksi yang lebih tinggi dan perlakuan penambahan jerami jagung 50% menghasilkan kualitas api yang baik berwarna biru, Biogas is a renewable alternative energy source because it uses raw materials derived from livestock manure. The purpose of this study was to analyze the production and quality of biogas from a mixture of cow dung and corm straw (Zea mays L). The study was conducted with 3 treatments, namely control as much as 0% corn straw or 100% cow dung (S100J0), 75% cow dung + 25% corn straw (S75J30), and 50% cow dung + 50% corn straw (S50J50) and 3 replications each with data analysis using a completely randomized design (CRD). The results showed that the mixture of cow dung biogas and corn straw had a significant effect (P>0,05) on the production of biogas (S100J0) produces the highest biogas production. The average daily temperature was almost the same for all treatments, namely 27-29 0C. The initial and final TS, VS content for S100J0, S75J25, and S50J50 14,940; 12,916; and 13,873. respectively. Initial VS 12,660; 10,903; and 10,996. Final TS 10,643; 7,900; and 10,550, and final VS 6,286; 4,546; and 7,323. The S100J0 treatment resulted in higher production and the addition of 50 % water hyacinth resulted in a good quality blue flame.
Keyword: alternative energy, biogas, corn straw, cow manure

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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