Judul: Diversification of Indonesian Export Markets to SICA: Competitiveness and Export Determinants of Main Commodities
Abstrak: Pandemi Covid-19 yang melanda seluruh negara membuat perekonomian negara Indonesia terkontaksi sebesar 2,07 % pada tahun 2020 kemudian tumbuh positif pada tahun 2021, pertumbuhan tertinggi disumbang dari sisi pengeluaran yang dicapai oleh komponen ekspor barang dan jasa. Central American Integration System (SICA) merupakan organisasi yang terdiri dari 8 negara di Kawasan Amerika Tengah yang memiliki populasi dan GDP per kapita yang cukup tinggi. Tingginya GDP per kapita menunjukkan daya beli yang tinggi sehingga dapat menjadi peluang bagi Indonesia untuk terus meningkatkan ekspor ke pasar SICA. Penelitian ini bertujuan untuk mengetahui daya saing dan determinan komoditas unggulan. Metode penelitian yang digunakan RCA, EPD, X-Model dan regresi data panel. Analisis regresi menunjukkan variabel yang berpengaruh positif dan signifikan yaitu GDP dan populasi negara importir pada komoditas HS 40, HS 48, dan HS 87, populasi Indonesia pada komoditas HS 48, FDI pada komoditas HS 87, RCA pada semua komoditas. Variabel yang berpengaruh negatif dan signifikan yaitu dummy Covid pada komoditas HS 48 dan 87. Adapun nilai tukar tidak berpengaruh signifikan., The Covid-19 pandemic that hit all countries caused the Indonesian economy to contract by 2,07% in 2020 and then expand in 2021. The highest growth was contributed by the expenditure side which was achieved by the component of exports of goods and services. The Central American Integration System (SICA) is an organization consisting of 8 countries in the region of Central America, which has a fairly high population and level of GDP per capita. The high level of GDP per capita shows high purchasing power, which indicates an opportunity for Indonesia to continue to increase exports to the SICA market. This study aims to determine the competitiveness and determinants of superior commodities. The research method used is RCA, EPD, X-Model and panel data regression. Regression analysis shows that the variables that have a positive and significant effect are GDP and the population of the destination country on HS 40, HS 48, and HS 87 commodities, the Indonesian population on HS 48 commodities, FDI on HS 87 commodities, and RCA on all commodities. The variable that has a negative and significant effect is the Covid dummy on HS 48 and 87 commodities. The exchange rate has no significant effect.
Keyword: dummy Covid, export, panel data regression, RCA, SICA

Judul: Analysis of the Efficiency and Determinants of Indonesia's Ten Largest Agricultural Commodities Exports to ASEAN+3 Countries
Abstrak: Ekspor Indonesia ke ASEAN+3 memiliki porsi yang sangat besar. Sektor pertanian menjadi salah satu sektor penting sebagai penyumbang surplus terhadap neraca perdagangan bahkan menjadi sektor yang berhasil bertahan ditengah pandemi Covid-19. Penelitian ini bertujuan untuk menganalisis determinan ekspor sepuluh komoditas pertanian terbesar Indonesia ke negara mitra dagangnya serta nilai efisiensi ekspornya. Metode yang digunakan adalah stochastic frontier gravity model dengan data panel berupa nilai ekspor sepuluh komoditas pertanian terbesar Indonesia ke 12 negara di kawasan ASEAN+3 periode 2000 – 2021. Hasil penelitian menunjukkan bahwa variabel GDP riil Indonesia dan GDP riil negara mitra dagang, trade openness dan nilai tukar riil negara mitra dagang berpengaruh positif terhadap nilai ekspor. Sedangkan, variabel jarak ekonomi berpengaruh negatif terhadap nilai ekspor. Rata-rata nilai efisiensi ekspor sepuluh komoditas pertanian terbesar Indonesia ke negara di ASEAN+3 yakni sebesar 0,37., Indonesia's exports to ASEAN+3 have a considerable portion. The agricultural sector has become one of the essential sectors as a surplus contributor to the trade balance. It has even become a sector that has managed to survive amid the Covid-19 pandemic. This study aims to analyze the determinants of exports of Indonesia's ten largest agricultural commodities to its trading partner countries and the value of their export efficiency. The method used is a stochastic frontier gravity model with panel data in the form of the export value of Indonesia's ten largest agricultural commodities to 12 countries in the ASEAN+3 region for the period of 2000 – 2021. The result showed that the average export efficiency value of Indonesia’s ten largest agricultural commodities to countries in ASEAN+3 is 0,37. Furthermore, the results showed that the variables of Indonesia's real GDP and the real GDP of trading partner countries, trade openness, and the real exchange rate of trading partner countries have positively affected on the export values. Meanwhile, the economic distance variable has a negative impact on export values.
Keyword: ASEAN+3, Efficiency Export, Stochastic Frontier Gravity Model, Ten Largest Agricultural Commodities

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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