Judul: Biogas from a Mixture of Banana Stalks and Chicken  Manure
Abstrak: Usaha peternakan ayam ras petelur menghasilkan kotoran yang dapat mencemari lingkungan jika tidak ditangani dengan baik. Pengolahan kotoran ayam ras petelur perlu dilakukan untuk mengurangi dampak negatif bagi lingkungan. Biogas merupakan teknologi yang dapat menghasilkan sumber bahan bakar alternatif yang dapat diperbaharui karena menggunakan bahan baku yang berasal dari kotoran ternak. Tujuan penelitian ialah menganalisis potensi biogas dari campuran kotoran ayam ras petelur dan batang pisang. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) 3 perlakuan yaitu kontrol (K100B0: 100% kotoran ayam), perlakuan 1 (K70B30: kotoran ayam 70% dan batang pisang 30%) dan perlakuan 2 (K50B50: kotoran ayam 50% dan batang pisang 50%) yang disimpan dalam digester yang berukuran 30 liter selama 35 hari. Parameter yang diamati pada penelitian ini adalah pH, total solid (TS), volatile solid (VS), uji nyala api dan volume gas. Produksi biogas yang diindikasikan oleh TS dan VS awal dan akhir pada perlakuan 1 dan 3 lebih tinggi (P>0,05) daripada kontrol. Nyala api pada perlakuan 1 dan perlakuan 2 lebih lama dan api yang dihasilkan berwarna biru dengan kandungan metana lebih tinggi daripada yang kontrol. Hasil penelitian ini mengindikasikan potensi yang tinggi pemanfaatan kotoran ayam ras petelur dan batang pisang sebagai bahan pembuatan biogas., Layer chicken production produces manure that could be pollute the environment if those are not handled properly. Waste treatment, therefore, need to be done to minimize the negative impact of manure pollution to the environment. Biogas is an alternative technologies to produce a renewable energy by using raw materials derived from livestock manure. This research objective is to analyze the the potency of layer chicken manure and banana stalks as raw material for biogas production. The study used completely randomized design. There were 3 treatments in this study, namely control (K100B0: 100% layer chicken manure), treatment 1 (K70B30: 70% chicken manure and 30% banana stalks), and treatment 2 (K50B50: 50% chicken manure and 50% banana stalks) using a digester with a volume of 30 liter, and incubated for 35 days. Parameter measured in this study were pH, total solid (TS), volatile solid (VS), flame, and gas volume. The treatment groups (K70B30 and K50B50) produced higher (P>0.05) biogas production compared to control group that was indicated by higher initial and final TS and VS content. The methane content and flame produced by treatment groups (K70B30 and K50B50) were longer than the control (K100B0). Those above results show the high potency of layer chicken manure and banan stalks as materials for biogas
Keyword: banana stalks, biogas, layer chicken manure, pH, total solid, volatile solid, flame, gas volume

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: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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