Judul: Keanekaragaman Jenis Tumbuhan Bawah di Gunung Papandayan Bagian Timur, Garut, Jawa Barat.
Abstrak: Gunung Papandayan has the potential of various types of fauna and flora that has become the unity in its natural environment. The objectives of this research was to determine the composition, diversity and potential of undergrowth that are found in the eastern part of Gunung Papandayan. The total of undergrowth species on Gunung Papandayan approximately 101 species of 34 families. The level of undergrowth diversity on five sites varies with a value of highest H’ at Supabeureum (3.36), while Tegal Mariuk has the smallest value of H’ (2.40). The low level of vegetation dominance indicated that undergrowth in five sites spread on a lot of species. Undergrowth vegetation communities in five sites are differs with IS score was < 75 %. Undergrowth species which are found on Gunung Papandayan has potential as food, medicinal plants, ornamental plants, and livestock feed.
Keyword: undergrowth, Gunung Papandayan, diversity, analysis of vegetation

Judul: Komposisi Jenis dan Struktur Tegakan Hutan Terganggu di Gunung Papandayan, Garut, Jawa Barat
Abstrak: Growth process of forest community to reach balanced condition often undergoes disturbances which create destruction. Papandayan mountain has been known since Dutch colonial government as an area with very rich floristic composition. Research on species composition and stand structure of disturbed forest has never been conducted in this area. The objective of this study is to learn the species composition and stand structure of disturbed forest in Papandayan mountain, whose forests are disturbed both by human and by natural process. Research results show that biodiversity and species richness in sites disturbed by human are higher than those disturbed by nature. Besides that, forest crown stratification pattern in disturbed forest shows that there is no any forest crown which reaches stratum A (>30 meter). They only reach stratum B (20–30 meter) and stratum C (4–20 meter). Crown stratification in disturbed forest never reached stratum A because stratum A constitutes the character of stable forest condition.
Keyword: stand structure, species composition, Papandayan Mountain, disturbed forest

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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