Judul: Analisis Pendapatan dan Efisiensi Usahatani Mangga Sebelum dan Selama Pandemi Covid-19 di Desa Kerep, Kabupaten Rembang
Abstrak: Musim panen mangga tahun 2020 yang bertepatan dengan adanya pandemi covid-19 menyebabkan petani mangga di Desa Kerep menghadapi kendala penurunan produksi dan harga jual mangga yang berpengaruh terhadap turunnya penerimaan petani. Penelitian ini bertujuan untuk menganalisis pendapatan, efisiensi usahatani, dan perbedaan pendapatan petani mangga di Desa Kerep sebelum dan selama pandemi covid-19. Penelitian ini menggunakan data primer dari 44 responden petani mangga di Desa Kerep. Usahatani mangga dianalisis menggunakan analisis pendapatan, R/C, dan uji beda pendapatan menggunakan uji Wilcoxon. Pengolahan data menggunakan software Microsoft Excel dan SPSS versi 26. Hasil analisis pendapatan dan R/C menunjukkan bahwa pendapatan dan R/C atas biaya tunai dan biaya total usahatani mangga sebelum pandemi covid-19 lebih besar daripada selama pandemi covid-19. Hasil uji beda menunjukkan bahwa terdapat perbedaan yang signifikan antara produktivitas, penerimaan, pendapatan, dan R/C atas biaya tunai dan biaya total usahatani mangga sebelum dan selama pandemi covid-19. Sedangkan biaya tunai dan biaya total usahatani mangga sebelum dan selama pandemi covid-19 tidak menunjukkan perbedaan yang signifikan. Berdasarkan hasil analisis usahatani dan uji beda dapat diketahui bahwa pandemi covid-19 berpengaruh terhadap pendapatan petani mangga di Desa Kerep.
Keyword: covid-19 pandemic, farmer's income, mango, price, production

Judul: Analysis of Catfish Farming Income Before and During the COVID-19 Pandemic,(Study Case in Catfish Farmer in Bekasi Regency West Java)
Abstrak: Tujuan penelitian ini sebagai berikut untuk mengetahui dampak dari COVID- 19 terhadap budidaya lele sehingga dapat diindikasikan akibat pandemi adanya perubahan harga input , output dan jumlah permintaan. Penulis melakukan studi kasus secara kolektif terhadap lima pokdakkan yang ada di Kabupaten Bekasi, melakukan wawancara mendalam tentang bagaimana hasil pendapatan usahatani sebelum dan semasa pandemi COVID-19 apakah masih menguntungkan atau tidak. Hasil dari penelitian ini sebagai berikut struktur biaya dan penerimaan selama pandemi mengalami perubahan,sedangkan untuk selama pandemi petani lele tetap mendapatkan imbalan karena efisien, dan menguntungkan , dan dapat disimpulkan petani selama pandemi COVID-19 permintaan akan lele meningkat hanya saja petani tidak dapat menjangkau konsumen secara langsung harus melewati tengkulak. Hasil output budidaya hanya di beli tengkulak karena mentahan, seharusnya petani dapat mengolahnya sehingga dapat sampai ke tangan konsumen secara langsung tanpa melalui tengkulak. Sehingga disarankan untuk petani kabupaten Bekasi dapat mendiversifikasikan usahataninya misalnya menjadi lele kuning frozen sehingga dapat dipasarkan secara online., The purpose of this study is as follows to determine the impact of COVID-19 on catfish cultivation so that it can be indicated that due to the pandemic changes in input, output prices,and number of demand. Writers conducted a collective case study of five pokdakkan in Bekasi Regency, conducted in-depth interviews about how the results of farming income before and during the COVID-19 pandemic were still profitable or not. The results of this study are as follows: the structure of costs and revenues during the pandemic has changed, while during the pandemic catfish farmers still get rewards because they are efficient, and profitable, and it can be concluded that during the COVID-19 pandemic the demand for catfish increases only that farmers cannot reach consumers. must go directly to middlemen. The output of cultivation is only bought by middlemen because it is raw, farmers should be able to process it so that it can reach consumers directly without going through middlemen. So it is recommended for Bekasi district farmers to diversify their farming, for example into frozen yellow catfish so that they can be marketed online
Keyword: Analytic, pandemic, demand, reward

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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