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.
Keyword: 

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.
Keyword: