Judul: Feeding activity of orangutan (Pongo pygmaeus) in Schmutzer Primate Centre, Jakarta.
Abstrak: The study of feeding activity and feeding preference of eight orangutans has been conducted at Schmutzer Primate Centre, Jakarta, from March to September 2008. Feeding activity data collection was performed using focal animal sampling, while feeding preference of each object was collected by direct observation on the single cage. Based on 336 hours observation within 6 months, orangutan spent 53,18% of the time on feeding, 17,27% on resting, and 14,79% on traveling. The daily activity pattern was distributed bimodally with peaks at about 08.00 and 14.00. Feeding activity was greater in the morning (08.00–10.30) and in the afternoon (13.30– 16.00), while resting was greater at the midday. The percentage of fruits / vegetables consumed provided by the Schmutzer Primate Centre was greater (96,90%) than foods available in the exhibition cages (3,10%). Three species of plants were consumed frequently; fig (Ficus benjamina) (0,48%), rumput gajah (Pannisetum purpureum) (0,24%) and velvet tamarind (Dialium indicum) (0,21%), respectively. In addition, orangutan sometimes eat soil, feces, and insect. Based on feeding preference observed on the single cage, there were 3 kinds of foods highly preferred by orangutan, such as, egg, mango, and banana.
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Judul: Aktivitas Makan dan Preferensi Pakan Orangutan Sumatera (Pongo abelii Lesson, 1827) di Resort Bukit Lawang, Taman Nasional Gunung Leuser
Abstrak: Orangutans are one of the primates which known as great apes and it is endemic in the island of Sumatera. This research was done at Sumatran Orangutan Viewing Center in Bukit Lawang. The aim of this study is to know the feed preferences and feeding activities of sumatran orangutan. The methods used in this study are Focal Animal Sampling which is done by following one individual orangutans during a certain period and single swath method in three different plots. The observations showed that orangutan’s feeding activity are smaller than resting and moving activity. There are 47 kinds of food that was eaten by orangutans. This food consisting of 5 habitus that is a tree, liana, herbaceous, clumps, and epiphyte. The part of plants that mostly consumed are leaves as much as 48,61%, fruit 27,49%, others (termites, ants, insects, soil) 12,75%, bark 7,17%, and flower 3,98%. Based on the feed preferences, the preferred type of feed are sibolangit (Garcinia lateriflora), rattan (Calamus sp.), and rambung (Vernonia arborea).
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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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