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: Identifikasi Gangguan Ekosistem Hutan Gunung Papandayan di Garut, Jawa Barat
Abstrak: Gunung Papandayan is one of the active volcanoes in West Java and it is a conservation area consisting Nature Reserve and Nature Tourism Park. Therefore, the protection of Gunung Papandayan’s forest ecosystem is needed to be done so that the area can be well maintained. This study was conducted on the forest area which was disturbed by the eruption and also by human activities. The level of disturbance was determined by measuring the tree basal area with line plot method. The socio-economic data was collected from 5 villages which borders Gunung Papandayan. The result showed that the presence of disturbance in Gunung Papandayan. The disturbance was occurred by three factors, consisting natural such as eruption, human factor such as forest fires, illegal logging, and forest encroachment, and also accessibility. The level of forest disturbance on the area of eruption, forest fires and forest encroachment was categorized as high level; while at the illegal logging area was categorized as medium level.
Keyword: cause of disturbance, disturbance level, forest disturbance, Gunung Papandayan

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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