Judul: Analisis Integrasi Pasar Saham ASEAN-3 dan Guncangan Indikator Makroekonomi Sebelum dan Saat Covid-19
Abstrak: Pandemi Covid-19 meningkatkan ketidakpastian dan perilaku risk aversion pada pasar saham. Selain itu, di saat pandemi kebijakan makroekonomi tiap negara berbeda-beda untuk melindungi kestabilan pasar saham. Penelitian ini fokus meneliti pengaruh dari pandemi Covid-19 dan guncangan indikator makroekonomi terhadap integrasi pasar saham negara ASEAN-3 yang terdiri atas Indonesia, Malaysia, dan Singapura periode Januari 2019 - Desember 2021. Metode analisis yang digunakan yaitu Vector Error Correction Model with Exogenous (VECMX). Hasil penelitian menunjukkan bahwa integrasi pasar saham ASEAN-3 lebih tinggi saat terjadi pandemi Covid-19. Namun tidak terdapat pengaruh signifikan dari pandemi Covid-19 terhadap ketiga indeks saham ASEAN-3. Selain itu, pengaruh guncangan indikator makroekonomi Indonesia terhadap indeks saham negara ASEAN-3 lainnya cenderung kecil.
Keyword: ASEAN-3, Covid-19, Macroeconomic, Integration, VECMX

Judul: The Relationship between stock price index and  interest rates in ASEAN-5 countries before and during the Covid-19 pandemic
Abstrak: Pandemi Covid-19 adalah fenomena yang terjadi pada akhir tahun 2019, Covid-19 memiliki dampak tidak hanya bagi kesehatan juga berdampak pada keadaan ekonomi suatu negara. Hal tersebut juga berpengaruh terhadap tingkat suku bunga dan indeks harga saham pada negara ASEAN-5. Tujuan dari penelitian ini adalah untuk menganalisis hubungan tingkat suku bunga dan ineks harga saham di negara ASEAN-5 pada masa sebelum dan saat pandemi Covid-19. Penelitian ini menggunakan metode deskriptif dan kuantitatif dengan menggunakan analisis VARX (Vector Autoregressive with Exogenous). Hasil dari penelitian ini yaitu pada masa sebelum pandemi Covid-19 indeks harga saham negara ASEAN-5 cenderung stabil dikarenakan kebijakan moneter yang eketif melalui suku bunga, namun pada masa pandemi Covid-19 suku bunga tidak berpengaruh secara signifika terhadap indeks harga saham, hal tersebut dikarenakan tingginya sentimen negatif investor terhadap indeks harga saham saat pandemi Covid-19. Berdasarkan interpretasi IRF exogenous, indeks harga saham dan suku bunga negara ASEAN-5 masih berfluktuatif dengan adanya guncangan penambahan kasus Covid-19. Hal tersebut menunjukkan bahwa ekonomi negara ASEAN-5 masih rentan terhadap guncangan pandemi Covid-19., The Covid-19 pandemic is a phenomenon that occurred at the end of 2019. Covid-19 has an impact not only on health but also on the economic state of a country. This also affects interest rates and stock price indexes in ASEAN-5 countries. The purpose of this study was to analyze the relationship between interest rates and stock price indexes in ASEAN-5 countries before and during the Covid-19 pandemic. This study used descriptive and quantitative methods using VARX (Vector Autoregressive with Exogenous) analysis. The results of this study in the period before the Covid-19 pandemic the stock price index of ASEAN-5 countries tended to be stable due to effective monetary policy through interest rates, but during the Covid-19 pandemic interest rates did not significantly affect the stock price index, it was due to high negative investor sentiment towards the stock price index during the Covid-19 pandemic. Based on the IRF exogenous interpretation, the stock price index and interst rate of ASEAN-5 are still fluctuating whit their shock of Covid-19 cases. This shows that the ASEAN-5 economies are still vulnerable to the shocks of the Covid-19 pandemic.
Keyword: ASEAN-5, Covid-19, interest rate, stock price index, VARX, ASEAN-5, Covid-19, interest rate, stock price index, VARX

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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