Judul: Utilization of Ficus benjamina and Ficus hispida by Birds at IPB Darmaga Campus
Abstrak: Tumbuhan Ficus dikenal sebagai keystone species bagi berbagai jenis satwa di ekosistem hutan tropis. Beberapa famili burung diketahui memiliki interaksi simbiosis mutualisme dengan tumbuhan Ficus. Berbagai penelitian mengenai komunitas burung telah dilakukan di Kampus IPB Darmaga sebagai kampus yang memiliki potensi kenekaragaman hayati tinggi namun belum ada penelitian yang mempelajari interaksi antara komunitas burung dan Ficus. Penelitian ini bertujuan untuk mengidentifikasi jenis, pemanfaatan ruang dan waktu, serta perilaku burung yang memanfaatkan Ficus benjamina dan Ficus hispida. Penelitian dilakukan pada bulan Maret-April 2021. Pengumpulan data dilakukan pada 3 pohon contoh F. benjamina dan 3 pohon contoh F. hispida dengan menggunakan metode instantaneous-scan sampling. Sebanyak 18 spesies burung teramati memanfaatkan kedua spesies Ficus. Secara umum, pemanfaatan F. benjamina oleh burung lebih tinggi daripada F. hispida. Pemanfaatan ruang dan waktu oleh burung bervariasi pada tiap spesies Ficus. Perilaku ingestif menjadi perilaku yang paling banyak tercatat dibandingkan perilaku diam, bersuara, berpindah, dan agonistik., Ficus plants are known as keystone species for various types of animals in tropical forest ecosystems. Several bird families are known to have mutualistic symbiotic interactions with Ficus plants. Various studies on bird communities have been carried out at the Darmaga Campus of IPB as a campus that has high biodiversity potential, but there has been no research that studies the interaction between bird communities and Ficus. This study aims to identify the species, use of space and time, and behavior of birds that utilize Ficus benjamina and Ficus hispida. The study was conducted in March-April 2021. Data were collected on 3 focal trees of F. benjamina and 3 focal trees of F. hispida using the instantaneous-scan sampling method. A total of 18 bird species were observed utilizing both Ficus species. In general, the utilization of F. benjamina by birds was higher than that of F. hispida. The use of space and time by birds varies in each Ficus species. Ingestive behavior is the most recorded behavior compared to vigilance, vocal, locomotion, and agonistic behavior.
Keyword: Ficus, Kampus IPB Darmaga, komunitas burung, perkotaan

Judul: The Utilization of Batai Tree (Paraserianthes falcataria) by Bird Communities at IPB Darmaga Campus
Abstrak: Pohon sengon (Paraserianthes falcataria) merupakan salah satu spesies pohon cepat tumbuh yang banyak ditanam masyarakat. Beberapa penelitian di Kampus IPB Darmaga menyebutkan adanya pemanfaatan pohon tersebut oleh komunitas burung, namun belum ada penelitian yang mengkaji peran pohon sengon dalam mendukung keanekaragaman burung. Penelitian ini bertujuan mengidentifikasi spesies burung yang memanfaatkan pohon sengon beserta penggunaan ruang dan waktu (pagi dan sore), serta perilaku burung dalam memanfaatkan pohon tersebut. Penelitian dilaksanakan antara bulan Januari – Mei 2023. Pengamatan perilaku burung dilakukan pada semua individu (scan sampling) dan dicatat pada akhir interval (5 menit) setelah waktu pengamatan dimulai (instantaneous sampling). Terdapat 33 spesies dari 21 famili yang memanfaatkan pohon sengon di Kampus IPB Darmaga dengan total perjumpaan sebanyak 1118 kali. Bagian atas tajuk merupakan ruang yang paling sering digunakan burung. Perjumpaan spesies dan individu burung yang memanfaatkan pohon sengon lebih banyak pada pagi hari. Burung sebagian besar memanfaatkan pohon sengon untuk diam baik mengamati sekitar ataupun beristirahat., The batai tree (Paraserianthes falcataria) is one of the fast-growing tree species commonly planted by communities. Several studies conducted at IPB Darmaga Campus have mentioned the utilization of this tree by bird communities, but there has been no research investigating the role of batai tree in supporting bird diversity. This study aims to identify bird species that utilize batai tree, as well as their spatial and temporal patterns of use (morning and evening), and the behaviors exhibited by birds while utilizing these trees. The study was conducted between January and May 2023. Observation of bird behavior was carried out for all individuals (scan sampling) and recorded at the end point of the interval (5 minutes) after the observation time began (instantaneous sampling). There were 33 species from 21 families observed utilizing batai tree at IPB Darmaga Campus, with a total of 1118 encounters. The upper canopy is the space that most often used by birds. Species and individual bird encounters were higher in the morning. Birds mostly utilized batai tree for perching, either for observing the surrounding or resting.
Keyword: batai, bird community, IPB Darmaga Campus

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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