Judul: Kajian Klasifikasi Usahatani Ubi Jalar pada Petani Kecil Berdasarkan UU No.20 Tahun 2008, (Studi Kasus di Desa Cikarawang, Kecamatan Dramaga, Kabupaten Bogar, Provinsi Jawa Barat)
Abstrak: Sweet potato has potential as a diversified source of high carbohydrate food, can be used as a food chart, pakanm and industrial raw materials. Reviewing the size of the business in commodity sweet potatoes in pespektif SMEs considered important, sweet potato farming in the perspective of SMEs is measured by net worth and the value of revenues per year, but in the measurement of economic studies of a business can be calculated based on the performance of its business. By using the performance measures the government is much easier to classify a business in specific groups according essence helps policies potentially weak. So to know the circumstances of this research attempts to review the actual conditions experienced sweet potato farming on small farmers as one economic agent in Indonesia. Selection of study sites and respondents were purposively. The required data are the primary data and secondary data, and then analyzed quantitatively using microsoft office exel and the results were analyzed qualitatively. analysis shows the performance of farms in the "small farmers" with an average land area of 0:21 ha penelitain location, shows that farming is done "small farmers" is a productive business with the R / C 1.34 against cash cost or value of R / C 1:10 of the total costs and benefits with cash receipts amounted to USD 2 384 578.34 per year or total revenues of Rp 769 262.95 per year. And in the perspective of SMEs klasifiaksi net sales and net assets for the year in the small farmers of the research included in the scale "micro-enterprises". Microenterprises have a great amount of effort, but it has a weak economic structure in which a low value product, which is not a legal form of business, and education level were rendah.Maka businesses to achieve the essence of policies that help those who are structurally weak, the government needs to review back perspective of classification MSMEs (Micro, Small, and Medium Enterprises) in Article 6 of Law No. 20 of 2008 in order to adapt to the actual conditions, or existing definitions can be added into UGMKM (landless Enterprises, Micro, Small and medium enterprises).
Keyword: Bogor Agricultural University (IPB), business performance., policy, the size of SMEs, Small farmers

Judul: Economic Efficiency Analysis of Sweet Potato Farming in Cikarawang Village, Dramaga District, Bogor Regency
Abstrak: Desa Cikarawang merupakan salah satu daerah sentra produksi ubi jalar di Kecamatan Dramaga. Produktivitas ubi jalar di Desa Cikarawang cenderung menurun tiap tahunnya. Produksi dan produktivitas ubi jalar yang menurun diduga disebabkan oleh alokasi input produksi yang tidak optimal. Produksi ubi jalar yang rendah akan berpengaruh terhadap pendapatan yang diterima oleh petani. Penelitian ini dilakukan untuk menganalisis pendapatan usahatani ubi jalar, menganalisis faktor-faktor yang memengaruhi produktivitas ubi jalar, dan menganalisis efisiensi penggunaan input produksi yang optimal. Metode analisis data yang digunakan yaitu analisis pendapatan usahatani, analisis regresi linear berganda, dan metode Nilai Produk Marginal. Hasil penelitian ini menunjukkan bahwa usahatani menguntungkan karena pendapatan bernilai positif dan R/C ratio lebih besar dari satu. Faktor-faktor yang berpengaruh secara positif dan signifikan terhadap produktivitas ubi jalar adalah pupuk kandang dan pestisida cair. Faktor produksi yang belum efisien pada usahatani ubi jalar yaitu pupuk kandang dan pestisida cair sehingga perlu untuk ditambah. Kata kunci: analisis pendapatan, efisiensi ekonomi, NPM, produktivitas, R/C ratio, Cikarawang Village in Dramaga District is one of the main sweet potato production areas. The productivity of sweet potatoes in Desa Cikarawang tends to decrease each year. The decreasing production and productivity of sweet potatoes are suspected to be caused by suboptimal allocation of production inputs. The low production of sweet potatoes will affect the income received by farmers. This research was conducted to analyze the income from sweet potato farming, analyze the factors affecting sweet potato productivity, and analyze the efficiency of optimal production input usage. The data analysis methods used were farm income analysis, multiple linear regression analysis, and the Marginal Product Value method. The results of this study indicate that farming is profitable because the income is positive and the R/C ratio is greater than one. Factors that positively and significantly affect sweet potato productivity are manure and liquid pesticides. The production inputs that are not yet efficient in sweet potato farming are manure and liquid pesticides, which therefore need to be increased.
Keyword: produktivitas, R/C ratio, analisis pendapatan, efisiensi ekonomi, NPM

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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