Judul: Perbaikan Karakteristik Biodiesel Jarak Pagar   Pada Suhu Rendah Melalui Kombinasi Campuran Dengan Berbagai Jenis Minyak Nabati
Abstrak: The limitation of biodiesels as fuel is that it will form crystal or gel at low temperature, which it can cause restriction in combustion process. Cold flow properties of biodiesel are affected by fatty acid composition in vegetable oil. Unsaturated fatty acid has lower cloud point and pour point than saturated one, but it more suceptible to oxidation. Blending of biodiesels with different fatty acid compositions was expected to improve low temperature properties of biodiesel. The objective of this research is to decrease the value of cloud point and pour point of Jatropha biodiesel. The preliminary research was to determine the best compotition which has lowest cloud point and pour point. Blending Jatropha biodiesel was done with Soybean biodiesel, Rapeseed biodiesel, Palm biodiesel, and Coconut biodiesel. Concentration of Jatropha biodiesel start from 10% (v/v) to 100% (v/v) with increment 10% (v/v). The Main research divided into three step that is determination of the best range composition form the most suitable vegetable oil blends using two blending methods, physicochemical and stability oxidation analysis, and determination of the best composition and blending method. Methode one is blending Jatropha biodiesel with selected vegetable oil biodiesel, and methode two blending between Jatropha oil and selected vegetable oil before biodiesel processing. Blending was done with addition of 5% Jatropha in blends. The quality parameter that were tested includes acid value, fatty acid compotition (GC), cloud point, pour point, density, viscosity, iodine number, and oxidation stability ( Rancimat method). The preliminary research shows that the Coconut biodiesel is the best blending subtances, because it can give lowering of cloud point and pour point of Jatropha biodiesel at 3ºC and 6ºC, respectively. It happens in the range 50-70% Jatropha at method 1, and 35-55% Jatropha at method 2. The value of cloud point and pour point in that range was equal at 9ºC , -6ºC, respectively (method 1), and at 12ºC , -9ºC, respectively (method 2). In addition was done blends of Jatropha biodiesel with metil laurat to investigated the role of metil laurat to lowering cloud point and pour point of jatropha biodiesel. Metil laurat known as dominant fatty acid at Coconut biodiesel. Its blends has lowest cloud point and pour poit at -3ºC and -18ºC. Blends biodiesels shown decrease cloud point and pour point below the value of pure biodiesel that is Jatropha biodiesel (12oC - 0oC), coconut biodiesel (15oC - 6oC), and metil laurat ( 9ºC - 3ºC). Based on time to resistance at temperature 0ºC, 55% Jatropha in each blend methods had the longest time compare with others concentration. The result of cloud point show that blending method 1 is the best blending techniques compare with blending method 2. It shown by cloud point at methode 1 is lower than methode 2. Physicochemical analysis on each blends biodiesel showed the quality is in conformity with ASTM D 6751 and SNI 04-7182-2006, that are density in a range of 0.8565 - 0.8793 g/cm3, viscosity in a range of 3.85 - 5.7 mm2/second and iodine number in a range of 44,74 - 70, 98 g I2/100g. Analysis
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Judul: Quality Improvement of Biodiesel from Rubber Seed Oil by Blending with Biodiesel from Jatropha curcas Oil
Abstrak: This research aimed to utilize rubber seeds oil and Jatropha curcas oil as raw material for biodiesel, to increase cetane number from rubber seed biodiesel, and to decrease viscosity from Jatropha curcas biodiesel. The proximate analysis of raw materials result showed that rubber seeds and Jatropha curcas seeds contained 37.96% and 41.66% of oil, respectively. Both types of seeds oil were separated using hydraulic hot press machine and the separation of rubber seeds gave 12.35% of yield and 13.12 % of free fatty acid, while the separation of Jatropha curcas seeds gave 18.34% of yield and 2.10% of free fatty acid. Esterification-transesterification process for biodiesel production was applied for rubber seeds oil and transesterification process to produce biodiesel from Jatropha curcas oil. Rubber seeds oil was esterified by using methanol and sulfuric acid 5% as catalyst for 1 hour and 300-500 rpm. Subsequently, rubber seeds methyl ester and Jatropha curcas oil were transesterified by using methanol and 1% sodium hydroxide as catalyst for 1 hour and 300-500 rpm. The result shows that cetane number from rubber seeds biodiesel and Jatropha curcas biodiesel sequentially were 46.35 and 53.7 and the viscosity was respectively 4.86 cSt and 6.16 cSt. Blending 20% rubber seed oil with 80% of Jatropha curcas oil and 20% rubber seed biodiesel with 80% of Jatropha curcas biodiesel increased cetane number of rubber seed biodiesel to 52 and 51.8, respectively, and decreased the viscosity of Jatropha curcas biodiesel to 5.92 cSt and 5.75 cSt, respectively.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf