Judul: Covid-19 and Export Performance of  the Indonesia Agroindusty Sector
Abstrak: Sektor agroindustri merupakan leading sector yang berperan dalam menciptakan nilai tambah pertanian dan menghasilkan devisa melalui ekspornya. Tahun 2020 kinerja ekspor agroindustri mengalami pertumbuhan negatif akibat Covid-19 yang memengaruhi perekonomian Indonesia maupun global. Tujuan dari penelitian ini adalah menganalisis peranan sektor agroindustri bagi sektor perekonomian melalui dampak penyebaran dan efek multiplier serta mengkaji kinerja ekspor agroindustri Indonesia di masa pandemi Covid-19. Penelitian ini menggunakan data sekunder dari Tabel Input-Output Indonesia tahun 2016 dan perubahan ekspor masing-masing subsektor agroindustri tahun 2020. Hasil analisis menunjukkan subsektor industri karet dan barangnya memiliki koefisien penyebaran yang tertinggi, sementara nilai kepekaan penyebaran tertinggi diperoleh industri kimia dan barangnya. Nilai multiplier output tertinggi dihasilkan subsektor industri karet dan barangnya. Nilai multiplier pendapatan dan tenaga kerja didominasi oleh subsektor industri makanan. Kinerja ekspor sektor agroindustri terhadap output, pendapatan, dan tenaga kerja berdampak paling besar bagi padi, kelapa sawit, peternakan, dan industri makanan di masa pandemi Covid-19., The agro-industrial sector is a leading sector that plays a role in creating added value for agriculture and generating foreign exchange through its exports. In 2020, the export performance of agro-industry experienced negative growth due to Covid-19 which affected the Indonesian and global economy. This study aims to analyze the role of the agro-industrial sector for the economic sector through the impact of the spread and the multiplier effect and examine the export performance of Indonesian agroindustry during the Covid-19 pandemic. This study uses secondary data from the Indonesian Input-Output Table in 2016 and changes in exports of each agro-industry sub-sector in 2020. The results of the analysis show that the rubber and goods industry sub-sector has the highest distribution coefficient, while the highest dispersion sensitivity value is obtained by the chemical industry and its goods. The highest output multiplier is produced by the rubber and goods industry subsector. The value of the income and labor multiplier is dominated by the food industry sub-sector. The export performance of the agro-industry sector on output, income and labor has the biggest impact on rice, palm oil, livestock, and the food industry during the Covid-19 pandemic.
Keyword: covid-19, export, input-output, agricultural

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: 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.
Keyword: