Judul: Analisis Daya Saing dan Faktor-Faktor yang  Memengaruhi Ekspor Karet Remah di  Asia Timur dan  Amerika Utara
Abstrak: Karet remah merupakan salah satu komoditas unggulan ekspor Indonesia. Penelitian ini bertujuan antara lain untuk menganalisis daya saing ekspor karet remah Indonesia, menganalisis faktor-faktor yang memengaruhi ekspor karet remah Indonesia, dan memproyeksikan volume ekspor karet remah Indonesia di kawasan Asia Timur dan Amerika Utara pada tahun 2021-2025. Hasil analisis Revealed Comparative Advantage (RCA), Export Product Dynamic (EPD), dan Accelaration Ratio (AR) menunjukkan karet remah Indonesia berdaya saing secara komparatif dan kompetitif serta mampu menguasai pasar ekspor karet remah di Asia Timur dan Amerika Utara meskipun bersaing ketat dengan karet remah Thailand dan Vietnam. Hasil analisis Gravity Model menunjukkan variabel PDB perkapita negara tujuan, nilai tukar riil negara tujuan terhadap Dolar Amerika Serikat, dan jarak ekonomi berpengaruh signifikan terhadap volume ekspor karet remah Indonesia di Asia Timur dan Amerika Utara. Hasil analisis Autoregressive Integrated Moving Average (ARIMA) memproyeksikan volume ekspor tahunan karet remah Indonesia pada periode tahun 2021-2025 ke Asia Timur mengalami kenaikan, sedangkan volume ekspor ke Amerika Utara pada periode yang sama mengalami penurunan., Crumb rubber is one of Indonesia's leading export commodities. This study aims such as, to analyze the competitiveness of Indonesia's crumb rubber exports, analyze the factors that influence Indonesia's crumb rubber exports, and predict Indonesian crumb rubber exports volume in East Asia and North America in 2021-2025. The Revealed Comparative Advantage (RCA), Export Product Dynamic (EPD), and Acceleration Ratio (AR) results show that Indonesian crumb rubber comparatively and competitively excels and could seize export market in East Asia and North America despite competing with Thai and Vietnamese. The result of Gravity Model shows that the GDP percapita of importer country, the real exchange rate of the importer country against the US Dollar, and economic distance have a significant effect on the volume of Indonesian crumb rubber exports in East Asia and North America. The result of Autoregressive Integrated Moving Average (ARIMA) predicts that the annual export volume of Indonesian crumb rubber in 2021-2025 to East Asia will increase, while export volume to North America in the same period will decrease.
Keyword: AR, ARIMA, EPD, Gravity Model, RCA

Judul: Analysis of Indonesian Natural Rubber Export Performance to Destination Country
Abstrak: Indonesia merupakan salah satu negara eksportir terbesar karet di dunia, namun demikian nilai ekspor cenderung berfluktuatif. Tujuan penelitian ini adalah untuk menganalisis kinerja nilai karet alam Indonesia ke negara tujuan utama dengan kode HS 4001 pada periode 2012-2021. Metode yang digunakan dalam penelitian ini dalam menganalisis daya saing adalah Revealed Comparative Advantage (RCA), Export Dynamic (EPD), dan X model. Penelitian ini juga menggunakan gravity model dalam mengestimasi determinan permintaan ekspor karet alam Indonesia ke negara tujuan utama. Berdasarkan hasil RCA menunjukkan karet alam Indonesia berdaya saing tinggi. Analisis EPD menunjukkan pangsa pasar lost opportunity di USA, Kanada, dan China, falling star di Jepang, India, dan Korea Selatan, dan retreat di Brazil dan Turki. Analisis X-Model menunjukkan pengembangan pangsa pasar potensial hampir di seluruh negara kecuali Brazil dan Turki. Hasil analisis gravity model menunjukkan, GDP negara tujuan utama dan harga komoditas berpengaruh positif dan signifikan terhadap nilai ekspor karet alam Indonesia. Nilai GDP riil Indonesia dan jarak ekonomi memiliki pengaruh negatif terhadap nilai ekspor karet alam Indonesia. Sementara nilai tukar tidak berpengaruh signifikan., Indonesia is one of the largest rubber exporters in the world, however, the export value tends to fluctuate. The purpose of this study was to analyze the value performance of Indonesian natural rubber to the main destination countries with the HS code 4001 in the 2012-2021 period. The method used in this study in analyzing competitiveness is Revealed Comparative Advantage (RCA), Export Dynamic (EPD), then X model. This research also uses gravity model in estimating the determinants of demand for Indonesia's natural rubber exports to the main destination countries. Based on RCA results, Indonesia's natural rubber is highly competitive. EPD analysis shows market share lost opportunity in the USA, Canada, and China, falling star in Japan, India, and South Korea, and retreat in Brazil and Turkey. X-Model analysis shows the potential market share development in almost all countries except Brazil and Turkey. Analysis results gravity model shows, the GDP of the main destination countries and commodity prices have a positive and significant effect on the export value of Indonesia's natural rubber. Indonesia's real GDP value and economic distance have a negative effect on the value of Indonesia's natural rubber exports. While the exchange rate has no significant effect.
Keyword: EPD, Gravity Model, Natural rubber, RCA, X-Model

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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