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: Factors That Affect The Export Value of Indonesia Natural Rubber in Destination Countries
Abstrak: Karet alam merupakan salah satu komoditas ekspor unggulan Indonesia yang menjadikan Indonesia sebagai produsen sekaligus eksportir terbesar kedua di dunia. Kelima negara tujuan ekspor karet alam Indonesia termasuk ke dalam negara-negara konsumen karet alam terbesar di dunia, seperti China, Jepang, Korea, India dan Amerika Serikat. Namun, pada beberapa tahun ini terjadi penurunan nilai ekspor karet alam yang cukup signifikan. Tujuan dari penelitian ini untuk menganalisis faktor-faktor yang memengaruhi nilai ekspor karet alam Indonesia di negara tujuan utama dengan menggunakan analisis regresi data panel dengan model fixed effect melalui pendekatan gravity model dalam periode tahun 1995 sampai 2019 dari lima negara pengimpor utama. Komoditas karet alam yang tercatat dalam penelitian ini dengan kode HS 4001 adalah kelompok karet alam, balata, getah perca, guayule, chicle dan getah alam semacamnya, dalam bentuk asal atau pelat, lembaran atau strip. Hasil estimasi menunjukkan bahwa faktor-faktor yang memengaruhi nilai ekspor karet alam Indonesia di negara tujuan utama secara signifikan dipengaruhi oleh produksi karet alam Indonesia, harga karet alam dunia, harga ekspor karet alam Indonesia dan harga minyak dunia., Natural rubber is one of the leading export commodities of Indonesia which makes Indonesia becomes the second largest producer and exporter in the world. Five destination countries for Indonesian natural rubber exports are among the largest natural rubber consumers countries in the world, such as China, Japan, Korea, India, and the United Stated of America. Unfortunately In recent years, there has been a significant decline in export value of Indonesian natural rubber. This study aims to analyze the factors affecting Indonesian natural rubber export value in Destination Countries. by using panel data regression analysis with fixed effect model through the gravity model approach in the period of 1995 to 2019 from five main importing countries. The commodity object of the research which HS code is 4001 is Natural rubber, balata, gutta-percha, guayule, chicle and similar natural gums, in primary forms or in plates, sheets or strip. The estimation result shows the factors that significantly affect the export value of Indonesia natural rubber in destination countries are production natural rubber of Indonesian, world natural rubber prices, export price of natural rubber Indonesia, and world crude oil prices.
Keyword: export value, fixed effect model, gravity model, natural rubber, panel data, export value, fixed effect model, gravity model, natural rubber, panel data

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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