Judul: Sistem Pemasaran dan Nilai Tambah Produk Olahan Ubi Jalar (Ipomoea batatas, L.) di Desa Cikarawang dan Desa Petir, Kecamatan Dramaga, Kabupaten Bogor
Abstrak: Sweet potato is a source of carbohydrat and protein, relatively inexpensive for consumption. The farmers had high dependency to the middleman, the lack of market access and price information in farmer’s level lead the bargaining position of the farmers low, and the activity of sweet potatoes processing. Therefore, the research is conducted to determine the marketing systems and value-added of processed sweet potato product. The objective of this research is to analyze the agency and functions of marketing, marketing channel, market structure and market behavior; to analyze marketing margin, farmer’s share, and the ratio of benefits to costs; to calculate value-added of dumpling, flour, and cracker. Data collection was held by observation and interviews to the farmers and entrepreneurs of processed sweet potato products in the Cikarawang village and Petir village by purposive sampling method, whereas for the marketing agency data collection was held by following the flow of information from the previous marketing agency and purposive sampling. The results are shown that the third channel was relatively efficient to distribute grade A and B sweet potato, while the first channel was relatively efficient to distribute grade C sweet potato. The results of value added analysis of processed sweet potato products have shown that the value added ratio and profit level of dumpling was the highest than other processed sweet potato products.
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Judul: Profitabilitas Usaha Pengolahan serta Nilai Tambah Produk Ubi Jalar pada Kelompok Tani Hurip di Desa Cikarawang, Bogor
Abstrak: Sweet potato has potentialy to be developed in an effort to diversify food. Sweet potato production in Indonesia is high, one of production centre in West Java. Sweet potato as food has not been used optimally. Post-harvest processing can increase the shelf life as well as the added value of sweet potatoes. Farmers Hurip (KTH) is a producer of sweet potato flour in the Bogor area. The aim of this research is to analyze the profitability and value added processing sweet potato to flour at KTH. The research was conducted at KTH is located in the village of Cikarawang, Dramaga District, Bogor Regency. This research was conducted from February 2013 to April 2013. The results showed that the sweet potato process business run by KTH has not been able to turn a profit. That is because quite a high variable costs, especially in raw material costs. Current efforts KTH sweet potato flour has not been able to break even, which means that the company has not been able to cover the cost factor and still experiencing losses. Value added generated by the use of dry shredded material is greater than the fresh sweet potatoes.
Keyword: value-added, sweet potato flour, profitability, cost analysis

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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