Judul: Analisis Kelayakan Usaha Investasi Kopi Sistem Agroforestri melalui Koperasi Sari Buah Kopi Desa Mekarsari Kecamatan Cikajang Kabupaten Garut
Abstrak: Kabupaten Garut menjadi salah satu daerah penghasil kopi arabika terbaik di Jawa Barat dengan areal tanaman yang telah mencapai luas 5913 ha dan mampu memproduksi 3036 ton per musim. Koperasi Sari Buah Kopi Desa Mekarsari Kecamatan Cikajang Kabupaten Garut merupakan salah satu usaha lokal yang menjalankan bisnis kopi. Penelitian ini bertujuan untuk menganalisis dan mengetahui kelayakan usaha yang dijalankan oleh Koperasi Sari Buah Kopi di Desa Mekarsari Kecamatan Cikajang Kabupaten Garut. Penelitian ini menggunakan metode observasi dan wawancara langsung dengan pemilik usaha. Analisis data penelitian ini menggunakan Net Present Value (NPV), Internal Rate of Return (IRR), dan Benefit Cost Ratio (BCR). Hasil penelitian analisis kelayakan usaha Koperasi Sari Buah Kopi Desa Mekarsari Kecamatan Cikajang Kabupaten Garut dapat dikatakan layak untuk dijalankan. Kelayakan usaha tersebut dikarenakan hasil perhitungan NPV menunjukan angka positif sebesar Rp327.485.385,00 Benefit Cost Ratio (BCR) 3,80 dan Internal Rate Return (IRR) yang diperoleh sebesar 46%. Skenario usaha ini diharapkan dapat menjadi solusi dari peningkatan ekonomi masyarakat sekaligus perbaikan lingkungan dengan agroforestri kopi., Garut Regency is one of the best Arabica coffee producing regions in West Java with a plantation area of 5,913 ha and is capable of producing 3036 tonnes per season. Koperasi Sari Buah Kopi in Mekarsari Village, Cikajang District, Garut Regency is one of the local businesses that runs the coffee business. This study aims to analyze and determine the feasibility of the business run by the Koperasi Sari Buah Kopi in Mekarsari Village, Cikajang District, Garut Regency. This study uses the method of observation and direct interviews with business owners. Analysis of the research data uses Net Present Value (NPV), Internal Rate of Return (IRR), and Benefit Cost Ratio (BCR). The results of the business feasibility analysis of the Koperasi Sari Buah Kopi in Mekarsari Village, Cikajang District, Garut Regency can be said to be feasible to run. The feasibility of this business is because the NPV calculation results show a positive number of Rp327.485.385, the Benefit Cost Ratio (BCR) is 3,80 and the Internal Rate Return (IRR) is 46%. This business scenario is expected to be a solution for increasing the community's economy as well as improving the environment with coffee agroforestry
Keyword: agroforestry, arabica coffe, business feasibility analysis, Garut, koperasi

Judul: Kelayakan Usaha Perkebunan Kopi Arabika pada Anggota Koperasi Syariah Padamukti di Kabupaten Bandung Barat
Abstrak: In carrying out the arabica coffee business, the farmer cooperative members make a Memorandum of Understanding with Perum Perhutani through forest management with the community (PHBM) programme covering area of 356.84 hectare. The aim of this research is to analyze the feasibility of arabica coffee plantation Of Syari'ah Cooperation Padamukti members based on 3 business scales range < 0.5 ha, between 0.5-1 ha, and > 1 ha. Analysis method that has been used is non financial analysis method such as market aspects, technical aspects, management aspects, and legal aspects, social and environmental aspects. Financial analysis is based on the assessment criteria of investment such as NPV, IRR, Net B/C, and Payback Period. Sensitivity analysis calculates the changing price effect and declining production. The analysis results showed based arabica coffee plantation business of farmers Syari'ah Cooperation Padamukti members based on 3 business scales are feasible and worth to run. On business scale < 0.5 ha and business scale between 0.5 ha - 1 ha greater benefits than business scale > 1 ha. The result from sensitivity that the canging price effect and declining period still feasible to run.
Keyword: farmers cooperative members, arabica coffee plantation, feasibility

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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