Judul: Analisis Risiko Produksi Talas (Colocasia giganteum (L.) Schott) di Kelurahan Situ Gede Kota Bogor
Abstrak: Produktivitas talas di Kelurahan Situ Gede dipengaruhi oleh bibit, pupuk organik, pupuk N, pupuk P, pupuk K, lamda sihalotrin dan tenaga kerja. Bibit, pupuk organik, pupuk K, lamda sihalotrin dan tenaga kerja berpengaruh positif terhadap produktivitias talas di Situ Gede. Risiko produktivitas talas di Kelurahan Situ Gede dipengaruhi oleh bibit, pupuk organik, pupuk N, pupuk P, pupuk K, lamda sihalotrin dan tenaga kerja. Pengaruh yang paling nyata berasal dari penggunaan pupuk P. Bibit, pupuk N, pupuk P, pupuk K dan lamda sihalotrin termasuk risk reducing factor. Pupuk organik dan tenaga kerja tergolong risk inducing factor yakni faktor yang menyebabkan risiko produktivitas talas di Situ Gede. Hubungan antara risiko produktivitas dan pendapatan tunai usahatani talas ialah negatif. Hubungan antara risiko produktivitas dan pendapatan total usahatani talas juga negatif. Prinsip High Risk High Return tidak sesuai dengan usahatani talas di Situ Gede.
Keyword: produktivitas, risiko, talas, hubungan, Situ Gede

Judul: Analisis preferensi risiko dan efisiensi teknis usahatani talas di Kota Bogor
Abstrak: Risk preferences play an important role in farmer’s decisions on input allocation and hence in output supply. Talas productivity in Bogor City was low that it was influenced by risk preferences of farmer. The objectives of this study were to analyze: (1) technical efficiency of talas farming in Bogor City, (2) talas farming technical inefficiency sources in Bogor City, (3) risk preferences of farmer in the face of talas farming production risk in Bogor City, and (4) the effect of risk preferences of farmer to talas farming technical efficiency in Bogor City. Frontier production function model with heteroskedastic error structure estimated by Maximum Likelihood estimation developed by Kumbhakar was adopted to analyze risk preferences of farmer and technical efficiency of talas farming in Bogor City. Sixty five samples were drawn by simple random sampling method. The results show talas farming are technically efficient, and farmer socio-economic characteristics such as land holding and age influence talas farming technical inefficiency sources in Bogor City. All farmers are risk taker that influences input allocation and technical efficiency. Result shows risk taker farmers used input higher that yield high technical efficiency and high productivity.
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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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