Judul: Uji Karakteristik Minyak Nyamplung untuk Modifikasi Kompor Bertekanan
Abstrak: Tamanu (Calophyllum inophyllum L.) has potential as a biofuel producer crop. Tamanu oil has a high viscosity compared with kerosene. Tamanu oil viscosity must be lowered to the equivalent of kerosene to be applied as a substitute for kerosene, especially in pressure stove. In pressure stove, preheating can reduce the viscosity of fuel to achieve the desired viscosity to be sprayed and burned well. Nowadays, pressure stoves generally are made for kerosene fuel. so that, the pressure stove needs to be modified by considering the preheating stage. Thus, the tamanu oil can be used in the modified pressure stove as a subtitute of kerosene. The objective of the study were (1) to simulate the temperature and viscosity change in relation to the length of heating oil pipeline, (2) to modify the heating oil pipeline based on the simulation result, and (3) to test the performance of modified heating oil pipeline. The simulation results show that the oil should be heated to 161.81 °C to obtain the viscosity of tamanu oil close to the viscosity of kerosene, which is using the heating pipe element along the 25 cm. The tamanu oil spraying diameter is 65.67 mm, and the spraying angle is 12.49o. While kerosene as a control has a spraying diameter of 66.75 mm, and the spraying angle is 12.69o. The increasing of spray diameter to temperature follows the equation d = 0.435T + 2.552, with determinant coefficient of 0.961. While the increasing of spray angle to temperature follows the equation θ = 0.082T + 0.51, with determinant coefficient of 0.961. The increase in diameter and angle of spray with increasing oil temperature, due to the increasing temperatures will further lower the viscosity value, surface tension, and density of tamanu oil. According to Ing et al. (2010), viscosity, surface tension, and density are three fluid properties that are influential in forming the droplet. This oil heating element can heat the tamanu oil until 168.5 oC and 164.7 °C for two different data retrieval conditions.
Keyword: 

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.
Keyword: 

Judul: igenvalues and Eigenvectors of Tridiagonal Matrix with Non Constant and Recurrent Diagonal Entries.
Abstrak: Matriks tridiagonal adalah suatu matriks yang mempunyai entri-entri bernilai nol kecuali pada diagonal utama, di bawah diagonal utama (subdiagonal) dan di atas diagonal utama (superdiagonal). Entri pada diagonal utama tidak konstan dan berulang. Setiap entri pada matriks tridiagonal ini adalah bilangan kompleks. Dalam karya ilmiah ini, akan dibuktikan 3 teorema untuk menentukan nilai eigen dengan 2 kasus dan 1 teorema untuk menentukan vektor eigen. Teorema pertama menentukan polinomial karakteristik dari matriks tridiagonal. Polinomial karakteristik dari matriks tridiagonal tersebut digunakan untuk menentukan nilai eigen pada teorema kedua dan ketiga serta menentukan vektor eigen pada teorema keempat
Keyword: