Judul: Autecology of Begonia spp. (BEGONIACEAE) and their utilities by arfak tribe in Mokwam Manokwari)
Abstrak: Begonia merupakan anggota famili Begoniaceae yang memiliki penyebaran cukup luas di Indonesia, termasuk di Papua. Kerusakan alam sebagai akibat meningkatnya kebutuhan manusia akan ruang dan kebutuhan lainnya berdarnpak pada kerusakan ekosistem, termasuk habitat alami Begonia. Tujuan penelitian adalah mendokumentasikan jenis Begonia pada hutan pegunungan di daerah Mokwam, autekologi dan manfaat jenis tersebut bagi suku Arfak di daerah Mokwam sebagai upaya menuju pelestarian sumberdaya alam hayati secara umum dimasa akan datang.
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Judul: Diversity and Ecology of Begonia in the Nirmala Tea Plantation, Mount Halimun Salak National Park
Abstrak: Begonia merupakan salah satu dari enam marga tumbuhan berbunga terbesar yang tersebar dari daerah tropik hingga daerah sub tropik. Begonia mampu tumbuh dalam berbagai relung ekologi, dari dataran rendah sampai hutan pegunungan. Jenis tertentu dari marga Begonia dapat tumbuh di kebun teh sebagai tumbuhan bawah. Penelitian ini bertujuan mengidentifikasi keanekaragaman Begonia dan menganalisis hubungan faktor abiotik terhadap persebaran Begonia di Perkebunan Teh Nirmala. Pengambilan sampel dilakukan di Perkebunan Teh Nirmala, Taman Nasional Gunung Halimun Salak (TNGHS) dengan metode purposive sampling pada ketinggian 1070 dan 1500 m dpl. Sampel yang ditemukan di lapangan dibuat herbarium kering, kemudian diamati ciri morfologi dan diidentifikasi dengan mengacu pada hasil penelitian sebelumnya. Data ekologi yang diukur di lapangan dianalisis menggunakan Canonical Correspondence Analysis (CCA) untuk mengetahui pengaruh faktor-faktor lingkungan terhadap keberadaan Begonia. Begonia yang ditemukan pada penelitian ini hanya satu jenis, yaitu Begonia cucullata dengan tiga varian dan ditemukan dengan dua cara hidup yang berbeda, yaitu hidup terestrial dan epifit. Ketiga varian berbeda pada warna batang, warna daun permukaan adaksial dan abaksial, bulu pada tepi daun, ada tidaknya daun pelindung, dan tipe tepi daun. Sebaran Begonia cucullata dipengaruhi oleh suhu udara dan kecepatan angin. Begonia cucullata varian 1 terestrial memiliki indeks nilai penting dan dominasi tertinggi di dua ketinggian lokasi penelitian, Begonia is one of the six largest flowering plant genera that spread from the tropics to the sub-tropics. Begonia is able to grow in a variety of ecological niches, from lowlands to mountain forests. Some species of begonias can grow in tea gardens as an understorey. This study aims to identify Begonia diversity and analyze the relationship between abiotic factors and the distribution of Begonia in Nirmala Tea Plantation. Sampling was carried out at the Nirmala Tea Plantation, Gunung Halimun Salak National Park (TNGHS) with a purposive sampling method at altitudes of 1070 and 1500 m above sea level. The samples found in the field were made herbarium, then observed morphological characteristics and were identified by referring to the results of previous studies. Ecological data measured in the field were analyzed using Canonical Correspondence Analysis (CCA) to determine the effect of environmental factors to the existence of Begonia. Begonia found in this study is only one species, namely Begonia cucullata with three variants and found with two different habitats, namely terrestrials and epiphytes. The three variants differ in the color of the stem, the color of the adaxial and abaxial leaves, the indumenta on the leaf margin, the presence or absence of the stipula, and the type of leaf margin. The distribution of Begonia cucullata is influenced by air temperature and wind speed. Terrestrial Begonia cucullata variant 1 has the highest importance and dominance index at the two study sites.
Keyword: altitude, Begonia cucullata, environmental factors, three variants

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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