Judul: Analysis of the agricultural revenue and household welfare of mangosteen cultivators in Bojongkembar village, Cikembar district, Sukabumi regency
Abstrak: Kombinasi antara pendapatan yang rendah dan tingginya pengeluaran berpotensi menyebabkan tingkat kesejahteraan rumah tangga petani manggis di Desa Bojongkembar tidak tercapai. Tujuan penelitian ini adalah: (1) Menganalisis pendapatan usahatani manggis di Desa Bojongkembar, (2) Menganalisis pengeluaran rumah tangga petani manggis, (3) Mengidentifikasi tingkat kemiskinan rumah tangga petani manggis. Metode analisis yang digunakan dalam penelitian ini adalah analisis R/C ratio, analisis pengeluaran, serta tingkat kemiskinan rumah tangga dengan kriteria Garis Kemiskinan BPS Kabupaten Sukabumi. Hasil penelitian ini menunjukkan bahwa: (1) Analisis pendapatan usahatani manggis di Desa Bojongkembar menghasilkan nilai R/C ratio yang menunjukkan bahwa usahatani menguntungkan, (2) Pendapatan dari usahatani manggis belum memenuhi pengeluaran rumah tangga petani baik untuk konsumsi pangan maupun non pangan serta pendapatan manggis masih rendah dibawah Upah Minimum Kabupaten Sukabumi, dan (3) Merujuk pada Indeks Garis Kemiskinan Kabupaten Sukabumi 2021 masih terdapat rumah tangga petani yang pengeluaran per kapita per bulan di bawah Garis Kemiskinan. Luas lahan minimal tanaman manggis yang dapat memenuhi pengeluaran rata-rata rumah tangga petani adalah sebesar 4,65 hektar., The combination of low income and high expenditure has the potential to cause the welfare level of mangosteen farming households in Bojongkembar Village not to be achieved. The objectives of this study are: (1) Analyzing mangosteen farming income in Bojongkembar Village, (2) Analyzing mangosteen farmer household expenses, (3) Identifying the poverty level of mangosteen farmer households. The analytical methods used in this study are R/C ratio analysis, expenditure analysis, and household poverty level with BPS Poverty Line criteria of Sukabumi District. The results of this study indicate that: (1) Analysis of mangosteen farming income in Bojongkembar Village resulted in an R/C ratio value indicating that farming is profitable, (2) Income from mangosteen farming has not fulfilled farmer household expenditures for both food and non food consumption and mangosteen income is still below the Sukabumi District Minimum Wage, and (3) Referring to the Sukabumi District Poverty Line Index 2021 there are still farmer households whose per capita expenditure per month is below the Poverty Line. The minimum land area for mangosteen crops that can meet the average expenditure of farmer households is 4,65 hectares.
Keyword: poverty line index, farm income, R/C ratio, minimum wage

Judul: Factors Affecting Production and Income of Mangosteen  Farming in Kaligesing District, Purworejo Regency
Abstrak: Produksi manggis di Kabupaten Purworejo mengalami perubahan jumlah produksi akibat dari pengaruh penggunaan input yang kurang optimal serta umur pohon yang tua khususnya di Kecamatan Kaligesing sebagai sentra produsen buah manggis. Selain itu, harga jual yang rendah diikuti dengan jumlah produksi yang sedikit serta biaya produksi yang tinggi menyebabkan pendapatan menjadi rendah. Tujuan dari penelitian ini adalah untuk menganalisis faktor – faktor yang memengaruhi produksi dan pendapatan usahatani manggis di Kecamatan Kaligesing. Penelitian ini dilaksanakan di Desa Somongari dan Kaligono. Jenis data yang digunakan dalam penelitian ini berupa data kuantitatif dan kualitatif yang bersumber dari data primer dan sekunder. Jumlah sampel sebanyak 60 responden dengan teknik simple random sampling. Metode analisis data menggunakan analisis deskriptif dan analisis regresi linear berganda. Usahatani manggis di Kecamatan Kaligesing menguntungkan untuk dijalankan berdasarkan nilai R/C yang dihasilkan. Hasil regresi menunjukkan variabel luas lahan berpengaruh signifikan terhadap produksi manggis serta variabel harga jual, biaya pupuk kendang, dan biaya pupuk NPK berpengaruh signifikan terhadap pendapatan petani manggis., Mangosteen production in Purworejo Regency experienced changes in the amount of production as a result of the influence of the use of inputs that were less than optimal and the age of old trees, especially in Kaligesing District as a center for mangosteen fruit producers. In addition, the low selling price followed by the small amount of production and high production costs causes low income. The purpose of this research is to analyze the factors that influence the production and income of mangosteen farming in Kaligesing District. This research was carried out in the Villages of Somongari and Kaligono. The type of data used in this study is in the form of quantitative and qualitative data originating from primary and secondary data. The number of samples is 60 respondents with simple random sampling technique. Methods of data analysis using descriptive analysis and multiple linear regression analysis. Mangosteen farming in Kaligesing District is profitable to run based on the resulting R/C value. The regression results show that the variable land area has a significant effect on mangosteen production and the variable selling price, the cost of manure, and the cost of NPK fertilizer have a significant effect on the income of mangosteen farmers.
Keyword: farming, income, mangosteen, production

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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