Judul: Feeding Behavior and Feed Nutritional Content of Javan Langur (Trachypithecus auratus) at Leuweung Sancang Nature Reserve
Abstrak: Keberadaan pakan alami lutung budeng sangat bergantung pada ketersediaan habitatnya di alam yang nantinya akan berpengaruh terhadap keberadaan populasi lutung budeng di habitat aslinya. Tujuan penelitian ini adalah mengidentifikasi jenis tumbuhan pakan lutung budeng, menganalisis kandungan nutrisi pakan lutung budeng, dan mengidentifikasi perilaku makan lutung budeng di CA Leuweung Sancang. Metode yang digunakan yaitu Ad-libitum sampling dan Scan sampling untuk mencatat jenis tumbuhan pakan dan perilaku makan, serta analisis proksimat, kalsium, fosfor, dan gross energy untuk mengetahui kandungan nutrisi tumbuhan pakan lutung budeng. Jenis tumbuhan pakan lutung budeng di CA Leuweung Sancang yaitu sebanyak 47 jenis dari 30 famili. Persentase perilaku makan yaitu sebesar 40,70% dari keseluruhan aktivitas hariannya. Kadar air dan kandungan bahan ekstrak tanpa nitrogen (BETN) tertinggi terdapat pada jenis Terminalia catappa. Kadar abu, kandungan fosfor, dan kandungan energi tertinggi terdapat pada jenis Averrhoa bilimbi. Kandungan protein kasar tertinggi pada jenis Pongamia pinnata. Kandungan serat kasar dan lemak kasar tertinggi pada jenis Ardisia humilis. Kandungan kalsium tertinggi pada jenis Cananga odorata., The availability of natural feed for Javan langur (Trachypithecus auratus E. Geoffroy Saint-Hilaire, 1812) is very dependent on the existence of its habitat in nature which will later affect the persistence of the Javan langur population in its natural habitat. This study aims to identify the feed plants, analyse the nutritional content of feed plants, and identify the feeding behaviour of Javan langur at Leuweung Sancang Nature Reserve. The methods used were Ad-libitum and Scan sampling which recorded the feed plant species and feeding behaviour, and then proximate analysis also calcium, phosphorus, and gross energy to determine the nutritional content of feed plants. There are 47 type of feed plants in Leuweung Sancang Nature Reserve from 30 families. Feeding behaviour composed 40.70% of all daily activities. The results of the nutrient analysis showed that the highest water and extract material without nitrogen was attributed to Terminalia catappa. The highest ash, phosphorus, and gross energy content values was obtained in Averrhoa bilimbi. The highest crude protein content value was obtained in Pongamia pinnata. The highest crude fibre and crude fat content value was obtained in Ardisia humilis. The highest calcium content value was obtained in Cananga odorata.
Keyword: feeding behavior, feed plants, Javan langur, nutritional content

Judul: Studi Habitat Lutung Jawa (Trachypithecus auratus E. Geoffroy 1812) di Resort PTN Cimande, Taman Nasional Gunung Gede Pangrango
Abstrak: Lutung jawa (Trachyppithecus auratus) adalah primata endemik Indonesia yang termasuk kategori rentan dalam IUCN. Keberadaan lutung akan tetap berlanjut dengan tersedianya habitat yang baik, sehingga informasi mengenai kondisi habitat lutung jawa diperlukan untuk pengelolaan habitat yang lebih baik. Penelitian mengenai habitat lutung jawa bertujuan mengidentifikasi komponen-komponen habitat, mengidentifikasi jenis tumbuhan pakan dan bagian yang dimakan, serta mengukur ketersediaan tumbuhan pakan. Penelitian dilakukan pada bulan Maret 2024 di RPTN Cimande, Taman Nasional Gunung Gede Pangrango. Data penelitian didapatkan dengan melakukan observasi lapang dan pengukuran di lapangan. Hasil penelitian menunjukkan bahwa lutung dapat dijumpai pada ketinggian 684-884 mdpl dengan kelerengan 0%-45%. Jenis tumbuhan yang sering dikonsumsi lutung ialah teureup, ki bolong, dan kayu afrika, dengan perbandingan bagian tumbuhan yang dimakan yakni 58,82% daun dan 41,18% buah. Keberadaan tumbuhan pakan mendominasi pada habitat lutung jawa, sehingga ketersediaannya dapat dikatakan melimpah. Selama penelitian dijumpai primata selain lutung jawa yakni monyet ekor panjang, surili, dan owa jawa, namun tidak teramati terjadinya konflik antar primata., Javan langur (Trachypithecus auratus) is an endemic primate in Indonesia that is categorized as vulnerable by IUCN. The existence of langurs will continue with the availability of suitable habitat, so information regarding the habitat conditions of javan langurs is needed for better habitat management. Research on javan langur habitat aims to identify habitat components, types of food plants and the parts they eat, and measure the availability of food plants. The research was conducted in March 2024 at RPTN Cimande, Gunung Gede Pangrango National Park. Research data were obtained by conducting field observations and measurements in the field. The research results show that langurs can be found at an altitude of 684-884 meters above sea level with a slope of 0%-45%. The plants often consumed by langurs are teureup, ki bolong, and kayu afrika, with the ratio of plant parts eaten being 58,82% leaves and 41,18% fruit. Food plants dominate the javan langur habitat, so their availability is abundant. During the research, primates other than javan langurs were found, namely long-tailed monkey, surili, and javan gibbon, but no conflict between primates were observed.
Keyword: food plants, habitat, javan langur

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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