Judul: Diversity and Use of Plants in Kelekak in Namang Village, Central Bangka
Abstrak: Kelekak merupakan kearifan lokal yang telah lama dikembangkan oleh masyarakat di Kepulauan Bangka Belitung. Kelekak merupakan suatu kebun campuran (agroforestri) yang terdiri atas beragam pohon penghasil buah dan kayu. Pengetahuan masyarakat Desa Namang dalam pemanfaatan tumbuhan penting dikaji dan didokumentasikan agar pemanfaatan tersebut dapat berkelanjutan serta meningkatkan kesejahteraan masyarakat. Penelitian bertujuan untuk menginventarisasi keanekaragaman spesies tumbuhan, mengindentifikasi pemanfaatan, bioprospeksi potensi tumbuhan, dan sistem kepemilikan lahan kelekak oleh masyarakat, serta mengidentifikasi upaya konservasi kelekak di Desa Namang. Metode penelitian dilakukan dengan wawancara, analisis vegetasi, observasi lapang, dan studi pustaka. Jumlah spesies tumbuhan di seluruh kelekak diperoleh sebanyak 101 spesies yang berasal dari 45 famili. Pemanfaatan tumbuhan oleh masyarakat Desa Namang dikategorikan menjadi beberapa kategori pemanfaatan dengan pemanfaatan terbanyak yaitu pemanfaatan untuk pangan. Sistem kepemilikan lahan oleh masyarakat sebagian besar merupakan lahan milik pribadi dengan rata-rata luas lahan sebesar 2 hektar., Kelekak is local wisdom that has long been developed by the people of the Bangka Belitung Islands. Kelekak is a mixed garden (agroforestry) consisting of a variety of fruit and wood producing trees. The knowledge of the Namang Village community in the use of plants is important to study and document so that this use can be sustainable and improve community welfare. The research aims to inventory the diversity of plant species, identify utilization, bioprospection of plant potential, and the kelekak land ownership system by the community, as well as identify kelekak conservation efforts in Namang Village. The research method was carried out using interviews, vegetation analysis, field observation, and literature study. The diversity of plant species in each kelekak was found to be 101 species from 45 families. The use of plants by the people of Namang Village is categorized into several categories of use with the largest use being use for food. The community's land ownership system is mostly private land with an average land area of 2 hectares.
Keyword: agroforestry, plants diversity, plants utilization

Judul: Diversity and Use of Plants in Kelekak in Air Mesu Village, Central Bangka
Abstrak: Kelekak merupakan kebun tradisional masyarakat Kabupaten Bangka Tengah yang termasuk dalam sistem agroforestri. Terdapat beberapa spesies tumbuhan yang dibudidayakan di kelekak. Penelitian bertujuan untuk mengidentifikasi komposisi spesies tumbuhan, potensi pemanfaatan dan bioprospeksi, sistem kepemilikan lahan kelekak, dan upaya konservasi kelekak. Penelitian dilakukan dengan menggunakan metode analisis vegetasi, wawancara, dan studi literatur di tiga tipe kelekak yaitu, kelekak belakang rumah, pinggir desa, dan hutan. Spesies tumbuhan yang ditemukan terdiri atas berbagai macam famili dan habitus. Spesies tumbuhan yang mendominasi di kelekak yaitu durian (Durio zibethinus L.). Flavonoid dan saponin menjadi kandungan bioaktif yang paling sering ditemukan pada spesies tumbuhan di kelekak. Vitamin B dan C menjadi kandungan nutrisi yang paling sering ditemukan pada spesies tumbuhan di kelekak. Hasil panen dan harga jual spesies tumbuhan di kelekak dibedakan atas satuan butir dan kilogram (kg). Pendistribusian hasil panen masih dilakukan secara sederhana melalui tengkulak dan pasar. Upaya konservasi yang dilakukan di kelekak yaitu dengan membuat kebun bibit khusus spesies-spesies yang terdapat di kelekak., Kelekak is a traditional garden of the Central Bangka Regency community that is included in the agroforestry system. There are several plant species cultivated in kelekak. The study aimed to identify plant species composition, potential utilization and bioprospection, kelekak land ownership system, and kelekak conservation efforts. The research was conducted using vegetation analysis, interviews, and literature studies in three types of kelekak, namely backyard kelekak, village edge and forest. The plant species found consisted of various families and habitus. The dominant plant species in kelekak is durian (Durio zibethinus L.). Flavonoids and saponins are the most common bioactive ingredients found in plant species in kelekak. Vitamins B and C are the most common nutrients found in plant species in kelekak. The harvest and selling price of plant species in kelekak are differentiated by pieces and kilogram (kg). The distribution of crops is still done simply through middlemen and markets. Conservation efforts carried out in kelekak include creating a special nursery for the species found in kelekak.
Keyword: agroforestry, Composition, potential, kelekak, plants

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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