Judul: Spatial Distribution of Sumatran Orangutan Activities (Pongo abelii Lesson, 1827) in Rawa Singkil Wildlife Reserve Area, Aceh Province
Abstrak: Populasi orangutan sumatera terus mengalami penurunan salah satunya disebabkan oleh permasalahan habitat. Upaya pembinaan habitat penting dilakukan untuk mendukung penaikan populasi orangutan. Mengingat orangutan merupakan satwa yang sulit dijumpai secara langsung, maka penelitian terkait jejak aktivitas orangutan sumatera penting untuk dilakukan. Penelitian ini bertujuan mengidentifikasi jenis-jenis jejak aktivitas orangutan sumatera, mengetahui bentuk sebaran spasial jejak aktivitas orangutan sumatera, dan menganalisis hubungan antara jejak aktivitas dengan karakteristik habitat orangutan sumatera di kawasan Suaka Margasatwa Rawa Singkil. Pengambilan data dilakukan pada petak pengamatan berukuran 1.000 x 1.000 meter, pada petak tersebut dibuat 4 jalur dengan menggunakan metode line transect. Jenis jejak aktivitas orangutan sumatera yang dijumpai yaitu sarang dan bekas pakan. Jenis jejak berupa sarang lebih banyak ditemukan. Bentuk sebaran spasial jejak aktivitas orangutan sumatera adalah mengelompok dengan nilai Ip sebesar 0,55. Jejak aktivitas orangutan sumatera banyak ditemukan pada hutan rawa primer dengan topografi datar (0 – 8%), jauh dari pemukiman (>8000 m), dan dekat dengan sumber air (<1000 m)., The population of Sumatran orangutans continues to decline, one of which is caused by habitat problems. Efforts to foster habitat are important to support the increase in the orangutan population. Given that orangutans are animals that are difficult to find in person, it is important to conduct research on the traces of Sumatran orangutan activity. This study aims to identify the types of Sumatran orangutan activity tracks, determine the spatial distribution of Sumatran orangutan activity tracks, and analyze the relationship between activity tracks and Sumatran orangutan habitat characteristics in the Rawa Singkil Wildlife Reserve area. Data collection was carried out on an observation plot measuring 1,000 x 1,000 meters, in that plot 4 lines were made using the line transect method. The types of traces of Sumatran orangutan activity found were nests and former feed. Types of traces in the form of nests are more commonly found. The form of the spatial distribution of Sumatran orangutan activity traces is clustered with an Ip value of 0.55. The traces of Sumatran orangutan activity are mostly found in primary swamp forest with flat topography (0 – 8%), far from settlements (>8000 m), and close to water sources (<1000 m).
Keyword: Orangutan sumatera, Suaka margasatwa rawa singkil, Sebaran spasial

Judul: Spatial Distribution of Activity Trace of Sumatran Elephant in the Bambangan Restoration Area, Way Kambas National Park.
Abstrak: Konflik gajah sumatera dengan manusia yang masih banyak terjadi saat ini dapat menyebabkan penurunan populasi gajah sumatera, sehingga kajian terkait sebaran spasial sebagai upaya mitigasi konflik gajah dengan manusia penting untuk dilakukan. Penelitian ini bertujuan untuk mengidentifikasi jenis jejak aktivitas, menduga bentuk sebaran spasial jejak aktivitas, dan menganalisis hubungan jejak aktivitas dengan karakteristik habitat gajah sumatera di areal Restorasi Bambangan. Pengambilan data dilakukan menggunakan metode line transect secara simultan pada 4 jalur transek sepanjang 1 km. Jenis jejak aktivitas gajah sumatera yang ditemukan yaitu, bekas pakan, feses, gesekan, lintasan, dan tapak. Jenis jejak aktivitas yang paling banyak ditemukan adalah feses. Bentuk sebaran spasial jejak aktivitas gajah sumatra adalah mengelompok dengan nilai Ip yaitu 0,62. Jejak aktivitas gajah sumatera banyak ditemukan pada tipe tutupan lahan belukar rawa dengan kelas kelerengan datar (0-8%) dan berjarak dekat dari sumber air (0-250 m) serta jauh dari permukiman (>5000 m)., Conflicts between sumatran elephants and humans that still occur a lot today can cause a decline in the sumatran elephant population, so studies related to spatial distribution as an effort to mitigate elephant-human conflicts are important. This study aims to identify the types of traces of activity, estimate the form of spatial distribution of traces of activity, and analyze the relationship of traces of activity with the characteristics of the habitat of sumatran elephants in the Bambangan Restoration area. Data retrieval was carried out using the line transect method simultaneously on 4 transect lines along 1 km. The types of traces of sumatran elephant activity found were food trace, feces, friction, track, and footprint. The most common type of activity trace found was feces. The form of the spatial distribution of the sumatran elephant's activity traces is clumped with an Ip value of 0,62. The traces of sumatran elephant activity are mostly found in swamp scrub land cover types with a flat slope class (0-8%) and are close to water sources (0- 250 m) and far from settlements (> 5000 m).
Keyword: Activity trace, Bambangan Restoration area, Spatial distribution, 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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