Judul: Mapping the Habitat Suitability of the Sumatran Elephant (Elephas maximus sumatranus Temminck 1847) within Bukit Barisan Selatan National Park
Abstrak: Gajah adalah spesies kunci di Taman Nasional Bukit Barisan Selatan (TNBBS). Sebagai salah satu upaya konservasi spesies ini perlu dilakukan studi kesesuaian habitat. Tujuan penelitian ini adalah untuk memodelkan kesesuaian habitat dan mengidentifikasi faktor yang memengaruhi sebaran populasi gajah sumatera. Pemodelan habitat dilakukan menggunakan software Maxent, sedangkan variabel bebas yang digunakan adalah ketinggian, kelerengan, suhu, jarak dari jalan, jarak dari sungai, jarak dari perkebunan, jarak dari semak, jarak dari area terbuka, jarak dari pemukiman, serta tutupan lahan hutan yang diolah menggunakan software RStudio yang menghasilkan nilai class area, mean shape index, mean patch size, men patch fractal dimensional, dan number of patch. Titik kehadiran gajah diperoleh dari data sekunder GPS collar dari pihak BBTNBBS. Hasil pemodelan menunjukkan habitat yang sangat sesuai bagi gajah Sumatera di TNBBS yaitu seluas 16.901,61 ha dan 51.185,74 ha sebagai habitat yang sesuai. Beberapa faktor yang mempengaruhi kesesuaian habitat dan sebaran populasi gajah sumatera di TNBBS yaitu ketinggian, tutupan lahan hutan, dan jarak dari sungai., The Sumatran elephant (Elephas maximus sumatranus) plays a pivotal role as a keystone species within the Bukit Barisan Selatan National Park (BBSNP). Conservation efforts necessitate a thorough examination of its habitat suitability. This study aims to model the habitat suitability for the Sumatran elephant and identify factors that influence the distribution of Sumatran elephant. Habitat modeling was carried out using Maxent software, while the independent variables used were height, slope, temperature, distance from roads, distance from rivers, distance from plantations, distance from bushes, distance from open areas, distance from settlements, and cultivated forest land cover using RStudio software which produces class area, mean shape index, mean patch size, mean patch fractal dimension, and number of patches. Elephant presence data were derived from secondary GPS collar data within BBSNP. The modeling results reveal extensive areas of highly suitable habitat totaling 16,901.61 ha, with an additional 51,185.74 ha identified as suitable habitat. Factors influencing habitat suitability and the distribution of the Sumatran elephant population in BBSNP include elevation, forest cover, and distance from rivers.
Keyword: Habitat suitability, modeling, sumatran elephant, BBSNP

Judul: Spatial Distribution of Traces of Sumatran Elephant (Elephas maximus sumatranus Temminck, 1847) Activity in Pemerihan Resort Bukit Barisan Selatan National Park
Abstrak: Penurunan populasi gajah Sumatra mengindikasikan pentingnya kajian penelitian terkait jejak aktivitas gajah Sumatra. Penelitian ini bertujuan untuk mengidentifikasi jenis jejak aktivitas, menduga bentuk sebaran spasial jejak aktivitas, dan menganalisis hubungan jejak aktivitas dengan karakteristik habitat gajah Sumatra di Resort Pemerihan. Metode yang digunakan adalah pengamatan langsung pada jalur transek sepanjang 1 km dan studi literatur. Hasil penelitian menunjukkan bahwa jenis jejak aktivitas gajah Sumatra terdiri dari feses dan tapak. Jejak aktivitas yang paling banyak ditemukan adalah feses di hutan sekunder. Bentuk sebaran spasial jejak aktivitas gajah Sumatra adalah mengelompok dengan nilai IM=2,61. Sebaran spasial jejak aktivitas gajah Sumatra hubungan dengan karakteristik habitat yaitu tipe tutupan lahan (hutan sekunder), kelas topografi (datar), jarak dari sumber air (<1000 m), dan jarak dari permukiman (1000-2000 m). Pengelolaan habitat dan populasi gajah Sumatra melalui pengayaan pakan dan kegiatan penangkaran diperlukan sebagai bentuk upaya konservasi gajah Sumatra., The decline in the sumatran elephant population indicates the importance of research studies related to the traces of Sumatran elephant activities. This study aims to identify the types of activity traces, estimate the shape of the spatial distribution of activity traces, and analyze the relationship between activity traces and the characteristics of the Sumatran elephant habitat at Pemerihan Resort. The method used is direct observation on a 1 km transect line and literature study. The results showed that the types of traces of Sumatran elephant activity consisted of feces and footprints. The most traces of activity found were feces in secondary forest. The form of the spatial distribution of the Sumatran elephant's activity traces is clustered with a value of IM=2,61. The spatial distribution of Sumatran elephant activity traces is related to habitat characteristics, namely land cover type (secondary forest), topographic class (flat), distance from water sources (<1000 m), and distance from settlements (1000-2000 m). Management of the habitat and population of Sumatran elephants through enrichment of feed and captive activities is needed as a form of Sumatran elephant conservation efforts.
Keyword: activity traces, Pemerihan Resort, spatial distribution shape, Sumatran elephant

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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