Judul: Covid-19 and Export Performance of the Agricultural Sector in Indonesia
Abstrak: Sektor pertanian merupakan sektor yang dapat dimanfaatkan untuk meningkatkan pembangunan ekonomi. Selama pandemi Covid-19, sektor pertanian menjadi salah satu sektor yang mampu tumbuh positif dengan kontribusi ekspor yang cukup tinggi. Penelitian ini bertujuan untuk menganalisis keterkaitan, pengganda output, pendapatan, dan tenaga kerja dari sektor pertanian, serta kinerja ekspor sektor pertanian pada masa pandemi Covid-19. Metode analisis yang digunakan adalah analisis input output dengan menggunakan Tabel Input Output Indonesia Tahun 2016, klasifikasi 185 sektor yang diagregasi menjadi 48 sektor. Hasil analisis menunjukkan bahwa komoditas sektor pertanian memiliki kemampuan yang lemah dalam meningkatkan sektor hulu dan hilirnya. Sektor pertanian yang memiliki pengganda output, pendapatan, dan tenaga kerja tertinggi didominasi oleh unggas dan hasil-hasilnya. Kinerja ekspor sektor pertanian berpengaruh terhadap peningkatan output, pendapatan, dan tenaga kerja paling besar pada sektor kelapa sawit, kelapa, serta unggas dan hasil-hasilnya. Hal ini disebabkan sektor tersebut mendapat dampak yang kecil akibat adanya Covid-19 dan permintaan impor dari luar negeri masih cukup tinggi., The agricultural sector is sector that can be used to increase economic development. During the Covid-19 pandemic, the agricultural sector became one of the sectors that were able to grow positively with a fairly high export contribution. This study aims to analyze the linkages, output multipliers, income, and labor from the agricultural sector, as well as the export performance of the agricultural sector during the Covid-19 pandemic. The analytical method used is input output analysis using the 2016 Indonesian Input Output Table, the classification of 185 sectors which are aggregated into 48 sectors. The results of the analysis show that agricultural sector commodities have a weak ability to improve their upstream and downstream sectors. The agricultural sector which has the highest multiplier of output, income, and labor, is dominated by poultry and their products. The export performance of the agricultural sector has the greatest effect on increasing output, income, and labor in the oil palm, coconut, poultry and their products. This is because the sector has had little impact due to Covid-19 and the demand for imports from abroad is still quite high.
Keyword: Covid-19, ekspor, input output, pertanian

Judul: The Impact of Covid-19 on the agricultural sector  GRDP in Central Java  Province
Abstrak: Sektor pertanian memiliki peran penting dalam pembangunan ekonomi daerah khususnya di Provinsi Jawa Tengah. Provinsi Jawa Tengah mendapat julukan sebagai salah satu “daerah lumbung pangan nasional”. Sektor pertanian memiliki fungsi primer sebagai penyedia bahan pangan hingga persebaran distribusi pendapatan masyarakat melalui tingginya tingkat kesempatan kerja. Adanya pandemi Covid-19 menyebabkan perubahan struktur ekonomi dan berdampak pada penurunan laju pertumbuhan ekonomi daerah. Salah satu sektor yang berpeluang emas untuk membangkitkan pertumbuhan ekonomi adalah sektor pertanian. Penelitian ini bertujuan untuk menganalisis faktor-faktor yang memengaruhi PDRB sektor pertanian di Jawa Tengah, membandingkan PDRB sektor pertanian Jawa Tengah antara data aktual dengan hasil peramalan SARIMA selama masa pandemi Covid-19 serta memproyeksikan PDRB sektor pertanian selama empat tahun. Penelitian ini menggunakan metode regresi data panel dan model Seasonal Autoregressive Integrated Moving Average (SARIMA). Hasil penelitian menunjukan bahwa: 1) faktor-faktor yang memengaruhi PDRB sektor pertanian di Jawa Tengah secara positif dan signifikan adalah tenaga kerja sektor pertanian dan kredit pertanian sedangkan faktor negatifnya adalah Covid-19; dan 2) Pandemi Covid-19 berpengaruh terhadap menurunnya pertumbuhan sektor pertanian di Jawa Tengah dengan total prediksi penurunan PDRB sektor pertanian sebesar 5,67 triliun rupiah serta proyeksi pertumbuhan sektor pertanian sampai dengan tahun 2024 terus mengalami peningkatan dengan pertumbuhan yang lambat rata-rata 2,38%., The agricultural sector has an important role in regional economic development, especially in Central Java Province. Central Java Province has earned the nickname as one of the “national food storage areas”. The agricultural sector has a primary function as a provider of food and distribution of community income through high levels of employment opportunities. The Covid-19 pandemic has caused changes in the economic structure and had an impact on reducing the rate of regional economic growth. One sector that has a golden opportunity to generate economic growth is the agricultural sector. This research aims to analyze the factors that influence the GRDP of the agricultural sector in Central Java, compare the GRDP of the Central java agricultural sector between actual data and SARIMA forecasting results during the Covid-19 pandemic and project the GRDP of the agricultural sector for four years. This research uses the panel data regression method and the Seasonal Autoregressive Integrated Moving Average (SARIMA) model. The research results show that: 1) the factors that positively and significantly influence the GRDP of agricultural sector in Central Java Province are agricultural sector labor and agricultural credit, while the negative factor is Covid-19; and 2) the Covid-19 pandemic has resulted in a decline in the growth of the agricultural sector in Central Java with a total predicted GRDP loss in the agricultural sector of 5,67 trillion rupiah and the projected growth of the agricultural sector until 2024 continues to increase with slow growth averaging 2,38%.
Keyword: Data panel, PDRB sektor pertanian, RPJMD, Seasonal Autoregressive Integrated Moving Average

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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