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 the Combination of Dairy Cow Manure and Layer Chicken Manure
Abstrak: Banyaknya populasi sapi perah dan ayam petelur di Jawa Barat dapat menghasilkan kotoran berlebih. Kotoran sapi perah memiliki C/N ratio dan kadar air yang tinggi dan kotoran ayam petelur memiliki keunggulan nutrisi dan protein yang tinggi. Biogas dapat dihasilkan dari kotoran sapi dan ayam petelur melalui fermentasi anaerobik. Tujuan penelitian adalah menganalisis produksi biogas dari kombinasi kotoran sapi dan ayam. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan tiga level perlakuan dan tiga ulangan. Perlakuan pada penelitian adalah S100A0 (100% kotoran sapi dan 0% kotoran ayam), S80A20 (80% kotoran sapi dan 20% kotoran ayam), dan S60A40 (60% kotoran sapi dan 40% kotoran ayam). Nilai TS awal dan TS akhir setiap perlakuan berbeda nyata (P<0,05). Volume biogas, kandungan metana, dan panjang nyala api bervariasi berdasarkan variasi level perlakuan S100A0 dibandingkan dengan S80A20 dan S60A40. Hasil analisis menunjukkan bahwa jika kotoran sapi dipadukan dengan kotoran ayam dengan takaran S60A40 menghasilkan biogas yang lebih maksimal., The high population of dairy cows and laying hens in West Java can result in excess manure. Dairy cow manure has a high C/N ratio and moisture content, while chicken manure from laying hens has high nutritional and protein advantages. Biogas can be produced from the manure of both dairy cows and laying hens through anaerobic fermentation. The research aims to analyze the biogas production from the combination of dairy cow and chicken manure. This study uses a Completely Randomized Design (CRD) with three treatment levels and three replications. The treatments in the study are S100A0 (100% dairy cow manure and 0% chicken manure), S80A20 (80% dairy cow manure and 20% chicken manure), and S60A40 (60% dairy cow manure and 40% chicken manure). The initial and final TS values of each treatment were significantly different (P <0.05). Biogas volume, methane content, and flame length varied based on the treatment level variations of S100A0 compared to S80A20 and S60A40. The analysis results indicate that when dairy cow manure is combined with chicken manure in the proportion of S60A40, it produces optimal biogas.
Keyword: Kotoran sapi perah, Kotoran ayam petelur, biogas, dairy cow manure, laying hen 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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