Judul: Characteristics and Distribution of Nesting Trees for the Tapanuli Orangutan (Pongo tapanuliensis) in the Bulu Mario Corridor, Batang Toru Landscape
Abstrak: Orangutan tapanuli (Pongo tapanuliensis) pada tahun 2017 ditetapkan sebagai spesies yang berbeda dari orangutan sumatera (Pongo abelii). Sarang bagi orangutan memiliki fungsi yang penting bagi keberlangsungan hidup orangutan. Penelitian ini bertujuan menganalisis karakteristik pohon sarang, komposisi vegetasi dan kelimpahan tumbuhan pakan, serta sebaran pohon sarang orangutan tapanuli di Koridor Bulu Mario. Metode yang digunakan untuk pengambilan data karakteristik dan sebaran pohon sarang orangutan adalah eksplorasi sedangkan data komposisi vegetasi dan kelimpahan pakan menggunakan analisis vegetasi. Pohon sarang didominasi oleh hoteng batu (Lithocarpus maingayi Bakh) dengan karakteristik antara lain diameter 22,6 – 32,0 cm, luas tutupan tajuk 3,8 – 7,8 m2, tinggi total 16,1 – 19,0 m, tinggi bebas cabang 9,1 – 11,4 m, tinggi tajuk 3,6 – 5,0 m, jarak antar tajuk kurang dari 1 m, lokasi bersarang pada posisi 2, dan tinggi sarang 17,0 – 19,9 m. Vegetasi dan kelimpahan pada hutan primer didominasi oleh andarasi dan torop, hutan sekunder didominasi oleh hoteng batu, dan kebun didominasi oleh durian serta karet., The tapanuli orangutan (Pongo tapanuliensis) was designated a different species in 2017 from the Sumatran orangutan (Pongo abelii). Nests for orangutans have an important function for the survival of orangutans. This study aims to analyze the characteristics of nesting trees, vegetation composition and abundance of forage plants, as well as the distribution of the nest trees of the Tapanuli orangutan in the Bulu Mario Corridor. The method used to collect data on the characteristics and distribution of orangutan nest trees was exploration, while data on vegetation composition and feed abundance used vegetation analysis. The nest tree is dominated by hoteng batu (Lithocarpus maingayi Bakh) with characteristics such as diameter 22.6 – 32.0 cm, canopy area 3.8 – 7.8 m2, total height 16.1 – 19.0 m, free height branch 9.1 – 11.4 m, canopy height 3.6 – 5.0 m, distance between crowns less than 1 m, nesting location at position 2, and nest height 17.0 – 19.9 m. Vegetation and abundance in primary forest is dominated by andrasi and torop, secondary forest is dominated by hoteng batu, and gardens are dominated by durian and rubber.
Keyword: Nest tree characteristics, orangutan tapanuli, vegetation composition

Judul: Karakteristik Pohon Tempat Bersarang Orangutan Sumatera (Pongo abelii Lesson, 1827) di Kawasan Hutan Batang Toru, Kabupaten Tapanuli Utara – Sumatera Utara
Abstrak: The decline of natural habitat of Sumatran Orangutan (Pongo abelii Lesson, 1827) and persecution causing it's population decline. Batang Toru Forest has an important value as a habitat of Sumatran Orangutan which is separated from it's main habitat in Leuser Ecosystem (Aceh). Orangutan is rare species and it has preferention of choosing the nest location and the species of nesting tree with spesific characteristics. The objective of this research is to discover the characteristics of Sumatran Orangutan's nesting tree in Batang Toru Forest. The research conducted at October 23th until December 22th 2008 in Research Station Yayasan Ekosistem Lestari – Sumatran Orangutan Conservation Program (YELSOCP) in the 12,75 km2 area of West Block of Batang Toru Forest, in North Tapanuli of North Sumatera. Equipment that used are girth measuring tape, 30 m measuring tape, 20 m rope, machete, compas, flagging tape, digital camera, camera trap, thermo-hygrometer, watch, and stationary. Primary data are vegetation structure and composition, temperature and humidity, water availability, and profil of nesting tree (species of tree, total height, diameter, crown width, and crown shape), nest height, nest position, and the existence of other animals. This primary data are colected by nest survey method and vegetation analysis. Secondary data are general condition of research site and bio-ecology of Sumatran Orangutan. During the research found 154 nesting trees, it’s content 20 tree species. 33,74% (52 trees) of it is Hoting (Lithocarpus spp.). The tree height of nesting tree is about 16-20 m (34%) with average tree height from all trees is 20,35 m and average nest height in 17,24 m. In such as low nest and tree height the Orangutan's nest is covered by the taller crown of other trees from rain and wind. Orangutan tend to build their nest at tree with diameter 10-19 cm and average diameter from all the trees is 23,71 cm. The crown width less than 11 m2 with average from all the trees 15,64 m2. Orangutan's nest near the river indicated that nest location preferention caused by the location near the river is lower (the slope area). In the research location, potential competitor animal are Siamang (Symphalangus syndactilus), Gibbon (Hylobates agilis ungko), Pig-tailed monkey (Macaca nemestrina), Binturong (Arctictis binturong), squirrel (Callosciurus notatus) and Hornbill. The concultion of nesting tree characteristics are total height 16-20 m, diameter 10- 19 cm, crown width less then 11 m2, and ball shape crown. Hoting (Lithocarpus spp.) is tree species that qualify with that tree characteristics, for that reason Orangutan in Batang Toru Forest prefer to use this tree species than other tree. The location preferention is location which is covered from rain and wind.
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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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