Judul: Economic Valuation of the Great Yellow-crested White Cockatoo (Cacatua galerita)
Abstrak: Kakatua putih besar jambul kuning (Cacatua galerita) merupakan primadona dalam perdagangan satwa liar. Penelitian ini bertujuan untuk menghitung valuasi ekonomi Cacatua galerita dengan pendekatan harga pasar, willingness to pay (kesediaan membayar), dan biaya pemeliharaan, serta membandingkan ketiga metode tersebut. Penelitian dilakukan dengan studi literatur dan pemantauan sosial media dalam pendekatan harga pasar, pendekatan kesediaan membayar dilakukan wawancara kepada 100 pengunjung Taman Margasatwa Ragunan (TMR) secara accidental sampling, dan pendekatan biaya pemeliharaan dilakukan wawancara kepada pengelola TMR dan penangkaran Mega Bird and Orchid Farm (MBOF). Hasil penelitian menunjukkan valuasi ekonomi Cacatua galerita dengan pendekatan harga pasar, kesediaan membayar, dan biaya pemeliharaan berturut-turut sebesar Rp35.547.204/ekor, Rp3.656.900/ekor, dan Rp7.119.001/ekor. Metode pendekatan terbaik untuk menghitung valuasi ekonomi Cacatua galerita yaitu pendekatan harga pasar yang ditinjau dari valuasi ekonomi yang dihasilkan, efektivitas, serta efisiensi biaya yang relatif murah dalam pengambilan dan analisis data., The great yellow-crested white cockatoo (Cacatua galerita) is a favorite in the wildlife trade. This research aims to calculate the economic value of Cacatua galerita using the market price approach, willingness to pay, and maintenance costs, as well as comparing the three methods. The research was carried out using literature studies and social media monitoring using the market price approach, the willingness to pay approach carried out interviews with 100 visitors to the Ragunan Wildlife Park (TMR) using accidental sampling, and the maintenance cost approach carried out interviews with TMR managers and the Mega Bird and Orchid Farm (MBOF). The research results show that the economic valuation of Cacatua galerita using the market price approach, willingness to pay, and maintenance costs is Rp. 35,547,204/head, Rp. 3,656,900/head, and Rp. 7,119,001/head. The best approach method for calculating the economic valuation of Cacatua galerita is the market price approach in terms of the resulting economic value, effectiveness and relatively lowcost efficiency in data collection and analysis.
Keyword: biaya pemeliharaan, harga pasar, kakatua putih besar jambul kuning, kesediaan membayar, valuasi ekonomi

Judul: Tata Niaga dan Pendugaan Volume Perdagangan Ilegal Satwa Kakatua Kecil Jambul Kuning (Cacatua sulphurea) dan Kakatua Koki (Cacatua galerita)
Abstrak: Perburuan dan perdagangan ilegal satwaliar di Indonesia selain menyebabkan penurunan populasi di alam juga menyebabkan negara mengalami kerugian. Penelitian ini bertujuan untuk mengetahui alur tata niaga perdagangan kakatua kecil jambul kuning dan kakatua koki ilegal, karakteristik pelaku dan menduga volume juga nilai perdagangannya. Metode pengambilan data melalui wawancara dengan kriteria narasumber bergerak dibidang hukum, perdagangan, satwaliar seperti GAKKUM, BKSDA Jakarta, BEA Cukai dan putusan Mahkamah Agung. Data yang dipergunakan yaitu dari tahun 2015-2020, menggunakan analisis deskpritif kualitatif dan kuantitatif. Tiga jenis alur ditemukan dalam tataniaga ilegal burung kakatua kecil jambul kuning dan kakatua koki. Alur tata niaga yang paling sering terjadi adalah Redundant channels. Perdagangan dilakukan secara langsung, hybrid dan daring. Penelitian ini menemukan 20 transaksi dan dugaan volume perdagangan total 38 satwa yang diperdagangkan pada rentang 2015-2020. Pendugaan nilai perdagangan 2015-2020 burung kakatua kecil jambul kuning sebanyak Rp 28.450.000 dan burung kakatua koki sebanyak Rp 34.250.000 total keduanya adalah Rp 62.700.000., Poaching and illegal wildlife trade in Indonesia, apart from causing a decline in the population in the wild, is also detrimental to the state. This study aims to determine trade system, perperator characteristics and estimate the volume and value of Yellow-crested Cockatoo and Sulphur-crested illegal trade. The data collection method through interviews with the criteria of sources engaged in law, trade, wildlife such as GAKKUM, BKSDA Jakarta, BEA Cukai and Supreme Court decision. Data used are from 2015-2020, using qualitative and quantitative descriptive analysis. Three type are found in the illegal trade in yellow-crested cockatoos and chef's cockatoos. The most common trade system flow is redundant funnels. Trading is done in person, hybrid and online. The study found 20 transactions and estimated trading volume total is 38 animals traded between 2015-2020. The estimated trading value for the yellow-crested cockatoo in 2015-2020 is IDR 28,450,000 and Sulphur-crested cockatoo is IDR 34,250,000, both amounting to IDR 62,700,000.
Keyword: bird, cockatoo, illegaly, trade, wildlife

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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