Judul: Uji Daya Tahan Motor Bakar Diesel Berbahan Bakar Minyak Nyamplung (Calophyllum inophyllum L.)
Abstrak: Tamanu oil is one of alternative fuel for diesel engine which has close characteristics to diesel fuel. However, the viscosity of tamanu oil is much higher than petroleum diesel fuel, so it is necessary to lower down its viscosity for better atomization in fuel injection to get better combustion process. From previous research, diesel engine can operate well with pre-heated tamanu oil fuel in a short period. The objective of this study was to test the endurance of diesel engine with tamanu oil as its fuel. After endurance test, carbon deposit in engine component and lubricating oil quality were analyzed. An 8 HP diesel engine mounted to an electric generator and operated using tamanu oil for 50 hours with 2 kW load. The results showed that component of diesel engine such as piston, cylinder head, and injector still work well and seems normally. Specific fuel consumption for petroleum diesel fuel was 0.34 l/HP/hour and for tamanu oil fuel was 0.44 l/HP/hour. The weight of carbon on the diesel engine components when using tamanu oil fuel was 23.51% lower than using petroleum diesel fuel. The viscosity, total base number (TBN), and sulfated ash content of lubricating oil after 50 hours operation were 13.93 cSt, 1.063 mg KOH/g, 1.19 %weight for petroleum diesel fuel, and 15.57 cSt, 1.258 mg KOH/g, 1.42 %weight for tamanu oil fuel. The analysis of metal content showed that tamanu oil fuel resulted higher friction and wear, due to metal content of Fe, Cu, and Al exceed the maximum standard. FTIR (Fourier Transform Infra Red) analysis showed that soot content, oxidation, nitration, and sulfation of lubricating oil when using tamanu oil fuel are higher than using petroleum diesel fuel, but still below the allowable standard limit. It shows that lubricating oil contamination from fuel and combustion process residu when using tamanu oil fuel are higher than using petroleum diesel fuel. Regression analysis of lubricating oil properties shows that lubricating oil when using tamanu oil fuel have shorter life than using petroleum diesel fuel.
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Judul: Rancang Bangun Elemen Pemanas Bahan Bakar Minyak Nyamplung Untuk Motor Bakar Diesel dengan Memanfaatkan Panas Gas Buang
Abstrak: Tamanu oil is one of biosolar substituter as diesel engine fuel. High viscosity of tamanu oil becomes main obstacle in direct using of tamanu oil as diesel engine fuel. Heater element is made to decrease tamanu oil viscosity. Heater element is benefitted high temperature of diesel engine exhaust gas as reheating source. Optimum temperature which is needed to reduce tamanu oil viscosity of 3-5 cSt is 110 Celcius degree (biosolar viscosity of 30oC is 5-7 cSt). IV design of element heater has optimum tamanu oil reheating. There are four kind of tamanu oil that has different treatment. degumming neutralization (N4) tamanu oil has best quality with the lowest viscosity of 30cSt in 30oC. Tamanu oil (N4) usage as fuel occur reduction power of 12.26 %, torsion of 9.59 %, power maximum of diesel engine is 5.39 kW and maximum torsion of 123.74 Nm. Maximum power of diesel engine using biosolar is 5.99 kW and maximum torsion of 144.53 Nm. But then, tamanu oil can replace biosolar (fossil energy), without made as biodiesel first and mixed with biosolar.
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Judul: Kajian frieze groups untuk klasifikasi dan konstruksi desain berdasarkan simetri pada pola
Abstrak: Frieze groups adalah konsep matematika untuk mengklasifikasikan desain pada dua dimensi permukaan yang berulang-ulang dalam satu arah berdasarkan simetri pada pola. Frieze groups merupakan grup yang mempertahankan bentuk pola. Pergerakan bentuk pola terdiri dari translasi, refleksi dan rotasi 180o. Tujuan dari karya ilmiah ini adalah mengkaji sifat Frieze group, mengkaji penggunaan Frieze group dalam mengklasifikasikan simetri pada pola dan mengkonstruksi pola dengan menggunakan software tesselmania. Hasil yang telah diperoleh, bahwa jenis Frieze groups merupakan subgroup dari grup pergerakan pola. Selain itu dapat dilihat dari sifat isomorfik berbagai jenis Frieze groups. Untuk mengkonstruksi sebuah bentuk pola dapat menggunakan salah satu software untuk membentuk sebuah pola bidang datar (dua dimensi) yaitu tesselmania.
Keyword: Frieze groups, Simetri, Pola