Judul: Perkembangan regenerasi anakan alam pada rumpang hutan dengan sistem silvikultur TPTJ di IUPHHK-HA PT. Sarpatim, Kalimantan Tengah
Abstrak: Gaps formed by the loss of one or several trees. Gap phase is the initial phase of forest natural regeneration. The purpose of this research is to analyze the pattern of natural regeneration development in forest gaps and forest stand composition at IUPHHK-HA PT. Sarpatim. Analysis of gap natural seedlings composition used single plot and analysis of forest stands used nested line plot at TPTJ and conservation forest area. Results showed that the number of plants species much more on large gaps with species composer is dominated by pioneer species such as Macaranga hypoleuca, M. gigantea, and Breynia oblongifolia otherwise small gaps is dominated by climax species such as Hopea dryobalanoides, Syzygium borneense, Shorea laevis, etc. Dominance values overall is low (C near to 0), richness value is high (R > 5), and diversity value is medium (2 < H’ < 3) up to high (H’ > 3). Result of Pearson correlation test showed that gap size positively correlated with the dominance, richness, and diversity values with the strength of correlation is weak. Forest stand species composition at research sites dominated by the dipterocarp groups such as Shorea smithiana, S. parvifolia, S. leprosula, S. laevis, and Dipterocarpus caudiferus. Dendogram clusters of species similarity do not follow the trend that closeness of felling age has high similarity values due to the high variation of forest sites, microclimate, and forest management activities.
Keyword: Bogor Agricultural University (IPB), species compositions, pioneer species, natural seedlings, forest gaps, climax species

Judul: Pemulihan Vegetasi di Areal Hutan yang Dikelola dengan Sistem TPTJ (Studi Kasus di Areal IUPHHK-HA PT. Suka Jaya Makmur, Kalimantan Barat)
Abstrak: Massive utilization of forest resources became one factor which caused degradation on natural forest. Forest degradation which occurred continuously could cause a change in forest composition. This could happen because seedling from invasive species dominated the area of natural forest. This research aimed to determine the composition and structure recovery of forest stands managed by TPTJ system on area of IUPHHK-HA PT. Suka Jaya Makmur, West Kalimantan. The results showed that non-commercial Dipterocarp species group had the biggest value of density and proportion among all levels Dipterocarp. Curve diameter distribution showed a balanced logged forest. The diversity in all plotarea was high. Kelampai and meranti were dominated in canopy level. Jambu monyet and kelampai were the species that dominated in seedling level. Tree and seedling had a different composition, it was shown by the ID value at >50%. This was shown by cluster analysis which divided into four groups. Commercial species proportion was generally larger than other non-commercial species.
Keyword: selective cutting and line planting, vegetation recovery, forest utilization

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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