Judul: Indonesian Natural Rubber Export to Japan and Its Determinants
Abstrak: Karet alam merupakan salah satu komoditas perkebunan unggulan Indonesia yang sebagian besar ditujukan untuk kegiatan ekspor. Kinerja ekspor karet alam Indonesia ke beberapa negara tujuan utama mengalami tren penurunan selama periode 2011-2019. Jepang merupakan salah satu negara tujuan utama ekspor karet alam Indonesia yang mengalami tren penurunan nilai ekspor. Penelitian ini bertujuan untuk menganalisis ekspor karet alam Indonesia ke Jepang dan faktor-faktor yang memengaruhinya selama periode 2011-2019 dengan menggunakan metode deskriptif kualitatif dan Error Correction Model (ECM). Hasil penelitian menunjukkan harga karet alam dunia dan penerapan kebijakan AETS berpengaruh signifikan terhadap nilai ekspor karet alam Indonesia ke Jepang dalam jangka panjang. Hasil penelitian juga menunjukkan bahwa nilai tukar rupiah terhadap dollar Amerika Serikat berpengaruh signifikan terhadap nilai ekspor karet alam Indonesia ke Jepang dalam jangka pendek. Indonesia perlu meningkatkan kualitas produksi dan produktivitas lahan karet alam serta memperbaiki kinerja industri hilir karet agar dapat meningkatkan kinerja ekspor karet alam Indonesia ke Jepang., Natural rubber is one of Indonesia's leading plantation commodities, which is mainly intended for export activities. The export performance of Indonesian natural rubber to several destination countries experienced a downward trend during the 2011-2019 period. Japan is one of the leading export destinations for Indonesian natural rubber, which experienced a downward trend in export value. This study aims to analyze Indonesian natural rubber exports to Japan and its determinant factors during the 2011-2019 period using descriptive qualitative and the Error Correction Model (ECM) method. The results show that the natural rubber price and the implementation of AETS policy had significant effect on the export value of Indonesian natural rubber to Japan, in the long term. The results also show that the rupiah exchange rate against the US dollar had significant effect in the short term. Indonesia needs to improve the quality of natural rubber production and productivity as well as improve the rubber industry performance to increase the performance of Indonesian natural rubber export to Japan.
Keyword: ECM, Export Value, Natural Rubber

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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