Judul: Analisis Metadata terhadap Struktur Populasi Orangutan Sumatra dan Ketersediaan Buah di Stasiun Penelitian Suaq Balimbing, Aceh Selatan, Indonesia
Abstrak: One factor that affects the distribution of orangutans in an area is fruit availability. When fruit availability is high, the energetic daily cost will be low because of the limited competition between individuals. This study aimed to observe how fruit availability affected the population structure of Sumatran Orangutans (Pongo abelii) in Suaq Balimbing. The observation was done with nest-to-nest and focal animal sampling observation methods, which analyzed using the Kruskal-Wallis test. Results show that many orangutans were spotted in the area during the years (2007-2019), with the highest number of 32 in 2010. The population structure dominancy spotted were unflanged males, mothers, juveniles, and flanged males, respectively. Adult males tend to move out from their birth area and have a comprehensive home range compared to mothers and/or females, which tend to have a small home range and stay in their birth area. Fruit availability has no significant effect on the presence of the individual of Sumatran orangutans in Suaq Balimbing. It might because Suaq Balimbing are known to have a very high fruit availability every year so that aggreration is common to happen with the orangutans.
Keyword: energetic cost, fruit availability, habitat productivity, Pongo abelii, population number

Judul: Habitat analysis and population estimation of sumatran orangutan (Pongo abeii Lesson 1827 at the Forest of Batang Toru, North Sumatra
Abstrak: The Batang TofU forest located in North, Center and South of Tapanuli, North Sumatra was recently found as one of Sumatran orangutan population habitat. A survey of trees species, nesting behavior and population of Sumatran orangutan was carried out during October 2007 up to January 2008 and aimed to analyze: (1) the forest structure, composition and trees distribution (including feeding and nesting trees); (2) estimated density and popUlation; and (3) the threat factors influenced the survival of Sumatran orangutan in Batang TofU forest. The results of the inventory of trees with diameter at breast height (DBH) 2: 10 cm in 3.84 ha areal sampling showed that 274 species in 56 families, represented by 1,896 individuals with total basal area of 148.9 m2lha and density of 498 treeslha. This forest was richer in tree species than other lowland forests in North Sumatra, Borneo and the Malay Peninsula and was dominated by Sapotaceae trees. The most prominent species were Tristania maingayi, Casuarina sumatrana, Quercus sumatrana and Ganua motleyana in every types of forest and differenced with Batang Gadis National Park which dominated by Dipterocarps. There were 96 feeding trees species in 25 families, represented by 536 individuals with total basal area of 46.7 m2lha. The prominent heights of feeding trees were below 30 m and distributed abundantly in the old moist secondary forests. The most important feeding trees for orangutans (Diospyros sp., Eugenia sp., Nephelium sp., Lithocarpus sp., Ficus sp., Artocarpus sp., Durio sp., and Garcinia sp.) were abundantly found in the old moist secondary forests, too. Orangutans commonly prefer to nest on the top of tree bar and the main branch of trees (DBH 20-30 cm; heights 15-20 m), especially in the middle canopy (20-30 m). Considering that there were enough feeding trees in this canopy. The most preferred nesting trees genus/species were Quercus sp., Syzygium sp., Shorea sp., Diospyros sp. and Lithocarpus sp. It was also invented 267 orangutan nests along 40.125 km cumulative lengths of line transects or equal with 0.54 percent of study area conducted at 11 sites. Densities were found higher in the old moist secondary forest while it was conversely lower density in the mixed forest. The distributions of nests were tended to clumped, related to the distribution of feeding trees. Orangutan population in 748.86 km2 ha potential habitat was approximately 337-421 individuals. Their distribution was limited by elevation and food availability. Human activities such as land conversion for agriculture purposes had become important factors affecting orangutan distribution. Field fact finding showed that many orangutan direct sightings and nests were located much closer to area human activities and logging concessions. This eventually has become real and concreted threat to their remaining population. It's needed to conduct further research in long-term monitoring and develop a strategic planning which promotes community involvement for the conservation of orangutan.
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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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