Judul: Design of biogas carburetor for gasoline engine
Abstrak: Biogas is one of promising source of alternative energy nowadays. This gas contains methane at about 60% which is potential to be used as fuel. Biogas is also possible to replace gasoline as fuel on internal combustion engine. A new design of carburetor is needed to mixes air and biogas instead of air and gasoline. This carburetor consists of some main components, including venturi, venturi housing, choke, throttle, and flange. The design of carburetor may not disturb any other component of the engine and it should works with existing throttle and governor mechanism of the engine. This carburetor has many biogas ports inside its venturi. The number of ports during the test were varied, starts from 2, 4, 6, and 8 ports. The result of the test shows that carburetor with 2 ports has the best result and the performance of the engine decreases along with the addition of ports. However, application of biogas as fuel generally reduces the performance of the engine compared to normal gasoline–fueled engine. This reduction is caused by the low calorific value of biogas compared to gasoline. To makes the carburetor works better, some modifications have to be made and some materials have to be replaced with better one.
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Judul: Modifikasi Konverter Biogas untuk Motor Bensin
Abstrak: Biogas contains methane at about 60-65% which is potential to be used as fuel. Biogas is also possible to replace gasoline as fuel on internal combustion engine. A new design of biogas converter is needed to optimize biogas deployment as fuel on motor gasoline fuel. . The objectives of this research are modifying and testing biogas converter. This biogas converter consists of some main components, including venturi, venturi housing, choke, throttle, chamber tube and flange. The design of biogas converter could be worked with existing governor mechanism of the engine. Design of biogas converter are the gas cylinder 1 (Ø 50 × 80 mm), gas cylinder 2 (Ø 40 × 130 mm) and without gas cylinder. The experiment has been tested by measuring engine maximum motor rotation and pump discharge water. According to the experimental result the biogas converter with first gas cylinders show better perfome than the gas cylinder 2 or without gas cylinder, so it can optimize biogas deployment as alternative energy to drive the motor gasoline fuel. The pump discharge water 6.62 litres/min at 2390 rpm and maximum motor rotation use of biogas converter is 3390 rpm.
Keyword: Biogas converter, Internal combustion engine, Alternative energy, Biogas

Judul: Sebaran dan Populasi Siamang (Symphalangus syndactylus Raffles, 1821) di KHDTK Aek Nauli, Sumatera Utara
Abstrak: Siamang (Symphalangus syndactylus) merupakan salah satu satwa endemik Sumatera yang berasal dari keluarga Hylobatidae. Siamang dapat ditemui di daerah Sumatera Utara, selatan Danau Toba, hingga Bukit Barisan Selatan. Siamang memiliki morfologi yang unik berupa kantung suara (gular sac) sehingga ketika bersuara dapat mengeluarkan suara yang sangat keras. Tujuan penelitian ini adalah untuk mengidentifikasi sebaran, karakteristik populasi dan perilaku bersuara siamang di KHDTK Aek Nauli. Terdapat 15 titik sebaran siamang yang tersebar pada tiga tipe tutupan lahan, yaitu hutan primer, sekunder dan dominasi pinus. Berdasarkan uji Chi-square diperoleh bahwa pola sebaran spasial siamang berbentuk mengelompok, yang berarti��������²ℎ���������������� lebih dari atau sama dengan ��������²0,025. Jumlah kelompok siamang yang teridentifikasi 15 kelompok dengan jumlah 49 individu. Pendugaan populasi siamang yaitu 39±11 individu dengan ketelitian 71.8%. Kepadatan populasi 2.05±0.57 individu/km² dan 0.78±0.57 kelompok/km². Aktivitas bersuara pada kelompok siamang di KHDTK Aek Nauli paling sering dilakukan pada pukul 09.00–11.00 WIB.
Keyword: Aek Nauli, populasi, sebaran, siamang