Judul: Daily Activities and Food Selection Bornean Orangutan (Pongo pygmaeus) at Taru Jurug Animal Park, Surakarta City
Abstrak: Orangutan Kalimantan atau Bornean Orangutan (Pongo pygmaeus) merupakan satwa endemik yang hanya dapat dijumpai di Pulau Kalimantan dan tergolong ke dalam ordo Primata serta famili Hominidae. Pada umumnya, aktivitas harian yang biasa dilakukan orangutan diantaranya ialah makan, bergerak, istirahat, dan sosial. Orangutan sebagai satwa yang termasuk frugivor cenderung memiliki preferensi pakan pada buah. Penelitian ini bertujuan menganalisis aktivitas harian, preferensi pakan, serta palatabilitas pakan yang dikonsumsi orangutan kalimantan di Taman Satwa Taru Jurug, Kota Surakarta. Subjek yang diamati ialah dua individu orangutan berjenis kelamin betina dan jantan. Metode yang digunakan ialah focal animal sampling, penyajian pakan berupa cafetaria, penimbangan bobot konsumsi pakan. Hasil pengamatan menunjukkan bahwa lokomosi dan istirahat menjadi aktivitas yang dominan dilakukan oleh individu tori (♀) dan didi (♂). Apel, pear, pisang dan tempe rebus menjadi preferensi pakan dari kedua individu tersebut dengan bobot konsumsi pakan yang tidak berbeda signifikan berdasarkan perhitungan uji t terhadap jenis kelamin dengan jumlah bobot konsumsi pakan., Bornean Orangutan (Pongo pygmaeus) is an endemic animal that can only be found on the island of Borneo and belongs to the order Primate and family Hominidae. Orangutans' daily activities generally include eating, moving, resting, and social activity. Orangutans, as frugivores, tend to have a preference for food on fruit. This study aims to analyze the daily activities, feed preferences, and palatability of the feed consumed by the Bornean orangutan at Taru Jurug Animal Park, Surakarta City. The subjects observed were two male and female orangutans. The method used was focal animal sampling, serving food in the form of a cafeteria, and weighing feed consumption. The results showed that locomotion and resting were the dominant activities carried out by tori (♀) and didi (♂). Apples, pears, bananas, and boiled tempeh became the feed preferences of the two individuals with feed consumption weights that were not significantly different based on the calculation of the t-test for sex with the total weight of feed consumption.
Keyword: endemic, focal animal sampling, palatability, preference, Taru Jurug Animal Park

Judul: Behavior and Food of Reintroduced Bornean Orangutan (Pongo pygmaeus wurmbii) at Feeding Site and Forest Area in Lamandau Wildlife Sanctuary
Abstrak: Orangutan Kalimantan (Pongo pygameus wurmbii) adalah primata besar Asia berstatus ‘Dalam Bahaya Kritis’. Reintroduksi dilakukan untuk menekan penurunan populasi mereka di alam. Penelitian yang dilaksanakan pada bulan Februari-April 2021 di Suaka Margasatwa Lamandau bertujuan mengidentifikasi perbedaan perilaku di feeding site dan hutan alam, komposisi dan preferensi pakan tambahan dan alami orangutan kalimantan reintroduksi. Sebanyak empat kategori dari enam individu berbeda telah teramati selama 219 jam. Kedatangan orangutan ke feeding site secara nyata (P = 1 > α = 0,05) tidak dipengaruhi oleh pemberian pakan tambahan, sehingga aktivitas harian di hutan alamlebih besar. Aktvitas harian tertinggi yang dilakukan berturut-turut adalah makan, istirahat, dan berpindah. Komposisi pakan tambahan yang diberikan dalam bentuk buah berupa pisang (Musa spp.) dan pepaya (Carica papaya). Komposisi pakan alami tertinggi orangutan dari jenis-jenis tumbuhan adalah buah (51%), daun muda 25%, dan bagian tumbuhan lainnya (15%). Jenis pakan yang termasuk kategori sangat disukai adalah papung (Sandoricum emarginatum) sebesar 0,73, dan kumpang darah (Knema conferta) sebesar 0,66. Kategori lainnya yaitu sembilan jenis tumbuhan ‘Disukai’, tujuh jenis tumbuhan ‘Kurang Disukai’, 16 jenis tumbuhan ‘Tidak Disukai’, dan delapan jenis tumbuhan ‘Tidak Dikategorikan’., The Bornean orangutan (Pongo pygameus wurmbii) is a 'Critically Endangered' large Asian primate. Reintroduction had been implementing to suppress their population decline in the wild. The research was conducted in February-April 2021 at Lamandau Nature Sanctuary, aimed to identify differences in behaviour at the feeding site and natural forest, composition and preferences for additional and nature feed for Bornean orangutan reintroduced. A total of six different individuals with four categories had observed for 219 hours. The arrival of orangutans to the feeding site significantly (P = 1 > = 0,05) was not affected by additional feeding, so daily activities in natural forestswere longer. The highest daily activities performed consecutively were eating, resting, and moving. The composition of the supplementary feed had given in the form of fruit in the form of banana (Musa spp.) and papaya (Carica papaya). The highest composition of natural food for orangutans from plant species is fruit (51%), young leaves 25%, and other plant parts (15%). Types of feed which included in the category of 'Highly Favoured' were papung (Sandoricum ermarginatum) of 0,73 and kumpang darah (Knema conferta) of 0,66. Other categories are nine plant species 'Preferred', seven plant species 'Less Like', 16 plant species 'Disliked', and eight plant species 'Not Categorized'.
Keyword: Bornean orangutan, daily activities, feed preferences, feeding site, Lamandau nature sanctuary, reintroduction

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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