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: Analysis of Technical Production and Income from Sweet Potato Farming in Bandorasa Wetan Village, Cilimus Sub-district, Kuningan Regency
Abstrak: Desa Bandorasa Wetan merupakan salah satu produsen ubi jalar terbesar di Kabupaten Kuningan yang juga menjadi sentra pengolahan ubi jalar. Persoalan yang dihadapi petani ubi jalar dalam mengelola usahatani adalah bagaimana mengalokasikan faktor-faktor produksi secara tepat agar dapat memaksimumkan produksi sehingga akan meningkatkan pendapatan. Oleh karena itu, tujuan dari penelitian ini yaitu untuk menganalisis usahatani ubi jalar di Desa Bandorasa Wetan yang berkaitan dengan (1) faktor-faktor yang memengaruhi produktivitas (2) efisiensi produksi (3) pendapatan petani (4) hubungan efisiensi teknis dan pendapatan petani. Metode yang digunakan dalam penelitian ini adalah regresi linear berganda dengan metode Maximum Likelihood Estimation (MLE), analisis efisiensi teknis dengan metode Stochastic Frontier Analysis (SFA), analisis pendapatan dengan menggunakan R/C ratio, serta analisis hubungan efisiensi teknis dan pendapatan dengan uji Rank Spearman. Hasil penelitian menunjukkan bahwa pupuk urea, pupuk phonska, dan pupuk TSP berpengaruh positif dan signifikan terhadap produksi ubi jalar. Nilai rata-rata efisiensi teknis adalah sebesar 0,91. Pendapatan usahatani ubi jalar lebih besar dari nol dan nilai R/C ratio lebih besar dari satu. Terdapat hubungan positif dan signifikan antara nilai efisiensi teknis dan pendapatan usahatani., Bandorasa Wetan Village is one of the largest sweet potato producers in Kuningan Regency and is also a sweet potato processing center. The problem faced by sweet potato farmers in managing their farming business is how to allocate production factors appropriately in order to maximize production so that it will increase income. Therefore, the aim of this research is to analyze sweet potato farming in Bandorasa Wetan Village in relation to (1) factors that influence productivity (2) production efficiency (3) farmer income (4) the relationship between technical efficiency and farmer income. The method used in this research is multiple linear regression using the Maximum Likelihood Estimation (MLE) method, technical efficiency analysis using the Stochastic Frontier Analysis (SFA) method, income analysis using the R/C ratio, and analysis of the correlation between technical efficiency and income using Rank Spearman test. The research results showed that urea fertilizer, TSP fertilizer, and labor had a positive and significant effect on sweet potato production. The average value of technical efficiency is 0,91. Sweet potato farming income is greater than zero and the R/C ratio value is greater than one. There is a positive and significant relationship between technical efficiency values and farming income.
Keyword: correlation, production factors, productitivy, profit, stochastic frontier

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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