Judul: Study on plant oil capillarity in wick cook stove
Abstrak: Rural households consume about 20% of total national consumption of fossil fuel and over 68% of these are in the form of kerosene for household cooking and lighting. Since several years ago Indonesia became net importer of oil including kerosene which have caused a big burden to government budget. Therefore, to overcome this problem, the government has enacted President Regulation No.5, 2006 on National Energy Policy and the Department of Energy and Mineral Resources Regulation No. 32, 2008 on Energy Self-Supporting Village Program. The objective of this study was to investigate the possibility of using several plant oils an alternative cooking fuel and to determine their respective thermal efficiency. Due to their high viscosity, the velocity of these plant oils in stove wicks is very slow causing inperfect burning condition. There were two methods of improvement to solve the problem, namely, by determining fuel characteristics to meet kerosene cook stove or modifying cooking stove design based on biofuel characteristics. The focus of this study was on the latter method. The first attempt was to reduce the viscosity of plant oil by providing metal bar connecting the flame and oil tank. By determining the capilary height of each plant oil within the wick bundles, it was possible determine the optimum height of the wicks which consequently can shorten the height of the cooking stove. During the test, Coconut oil, jatropha oil, bintaro oil, peanut oil, and used cooking oil had been selected and was used kerosene as control. There were four parameters measured during a series of test runs, namely, the flaming ability, the capillaryy height, fuel consumption, and combustion efficiency. Capillaryy height and oil rising velocity within the wicks of the tested plant oil could be reduced due to heating efect of heat conduction by the installed steel bar. From the experimental studies using modified cook stove with shortened wick length it was found that the thermal efficiency for kerosene, coconut oil, peanut oil, bintaro oil, used palm oil, and jatropha oil were 44.5%, 25.6%, 17.3%, 19.7%, 18.4%, and 24.5% respectively. The overall fuel consumption rate was in the range of 0.56 g/s for kerosene and 0.32–0.37g/s for plant oil and 1.30-2.90 g/s for plant oil-kerosene mixture. The provision of heat conductor had improved the efficiency of the modified stove to 41.2% using pure kerosene, 37.8% with coconut oil-kerosene mixture 19.5%, for peanut oil-kerosene mixture, 34.4%, for bintaro oil-kerosene mixture 22.7%, used plant oil, and 35.7% using physic nut (Jatropha Curcas), respectively. The overall fuel consumption rate was in the range of 2.02 g/s for kerosene, 1.15–1.33 g/s for plant oil and 4.68-10.44 g/s for plant oil-kerosene mixtures. In order to optimize the capillary effect further, a mathematical model was developed. The model relates the capillary height and the rising velocity of plant oil within the stove wicks with the wicks physical properties and transport properties of the tested plant oils.
Keyword: Combustion Efficiency, Wick Stove, Capillary Effect

Judul: Modification and  Performance Test of The Wick Stove Fueled by Waste Cooking Oil
Abstrak: Penggunaan minyak jelantah sebagai bahan bakar kompor sumbu merupakan salah satu solusi pemanfaatan limbah minyak jelantah. Minyak jelantah memiliki viskositas tinggi sehingga minyak sulit naik pada sumbu kompor. Hasil uji pendahuluan menunjukkan kinerja awal kompor rendah dengan efisiensi 16%. Penelitian ini bertujuan meningkatkan efisiensi energi dari kompor sumbu minyak jelantah dengan cara memodifikasi bahan sumbu dan sistem inlet udara serta melakukan uji kinerja kompor yang telah dimodifikasi tersebut. Metode yang digunakan adalah uji kapilaritas sumbu, penyesuaian luas inlet udara berdasarkan perhitungan kebutuhan udara pembakaran, dan water boiling test. Bahan sumbu yang sesuai karakteristik minyak jelantah adalah benang katun dengan nilai kapilaritas 1.06 g/menit. Diameter lubang inlet udara diperbesar dari 1 mm menjadi 3 mm dan 5 mm. Kinerja kompor terbaik ditunjukkan oleh kompor dengan modifikasi sumbu saja, dimana efisiensi sistem meningkat dari 16% menjadi 26%, laju pembakaran meningkat dari 0.35 kg/jam menjadi 0.42 kg/jam, dan efisiensi kompor meningkat dari 24% menjadi 40%. Kinerja kompor dengan penerapan modifikasi sumbu dan inlet udara berhasil meningkatkan efisiensi sistem menjadi 22% dibandingkan sebelum modifikasi, dengan laju pembakaran 0.40 kg/jam, dan efisiensi kompor 38%. Tetapi kinerja ini lebih rendah dibanding penerapan modifikasi sumbu saja, karena penambahan luas inlet udara tidak diiringi peningkatan kontak udara dengan bahan bakar.
Keyword: modify, waste cooking oil, wick stove

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular