Judul: Studi Perilaku Simakobu (Simias concolor Miller, 1903) dan Pola Penggunaan Habitat di Area Siberut Conservation Programme, Sumatera Barat
Abstrak: Simakobu was one of endemic primates in Siberut island that become attention of Siberut Conservation Programme. This species was threatened mainly by heavy hunting and commercial logging by local people. This study aims to determine the behavior of simakobu and habitat use. This research was conducted from July 2011 until January 2012 in SCP. Pattern of behavior data collected via Scan Sampling. The results found that simakobu in exploiting their food used more sitting posture than hanging posture. Actively grooming often existed between female and juvenile and passively grooming existed on male. The highest percentage calls of simakobu was occurred at 07.00-08.00 am with loud call duration in 20-30 second. Simakobu often used space between the first branch of the tree to the canopy at 21-25 meter in height.
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Judul: Ketersediaan Pakan antar Kelompok Simakobu (Simias concolor) di Hutan Peleonan, Siberut Utara, Kepulauan Mentawai
Abstrak: The endemic primate Simakobu (Simias concolor) in Mentawai is endangered due to habitat decreases. The purpose of this study was to discover the availability of food trees in the home ranges of two groups of Simakobu, Aldran group and Aldo group. Each of them consists of a different number of group members. Although Aldran group has more group members, Aldo group’s home ranges is 0,4 Ha wider than Aldran’s. However, the variety of food trees in Aldran’s home range is 11.8 % higher than Aldo’s. There are 113 species of trees inventoried in Peleonan forest and 53 types of which are food sources of Simakobu. Coccoseras borneensis is the most dominant food tree available in the both regions. Simakobu’s preferences are the young leaves and fruits. In general, the food abundance and variety in both home ranges are still adequate. The less varied food trees available in Aldo’s area and the group composition are expected to be the driving factors that made Aldo group explores more and eventually has a wider home range.
Keyword: the availability of food tree, Simias, simakobu, Siberut, Mentawai Islands

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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