Judul: The Impact of Covid-19 on the agricultural sector  GRDP in Central Java  Province
Abstrak: Sektor pertanian memiliki peran penting dalam pembangunan ekonomi daerah khususnya di Provinsi Jawa Tengah. Provinsi Jawa Tengah mendapat julukan sebagai salah satu “daerah lumbung pangan nasional”. Sektor pertanian memiliki fungsi primer sebagai penyedia bahan pangan hingga persebaran distribusi pendapatan masyarakat melalui tingginya tingkat kesempatan kerja. Adanya pandemi Covid-19 menyebabkan perubahan struktur ekonomi dan berdampak pada penurunan laju pertumbuhan ekonomi daerah. Salah satu sektor yang berpeluang emas untuk membangkitkan pertumbuhan ekonomi adalah sektor pertanian. Penelitian ini bertujuan untuk menganalisis faktor-faktor yang memengaruhi PDRB sektor pertanian di Jawa Tengah, membandingkan PDRB sektor pertanian Jawa Tengah antara data aktual dengan hasil peramalan SARIMA selama masa pandemi Covid-19 serta memproyeksikan PDRB sektor pertanian selama empat tahun. Penelitian ini menggunakan metode regresi data panel dan model Seasonal Autoregressive Integrated Moving Average (SARIMA). Hasil penelitian menunjukan bahwa: 1) faktor-faktor yang memengaruhi PDRB sektor pertanian di Jawa Tengah secara positif dan signifikan adalah tenaga kerja sektor pertanian dan kredit pertanian sedangkan faktor negatifnya adalah Covid-19; dan 2) Pandemi Covid-19 berpengaruh terhadap menurunnya pertumbuhan sektor pertanian di Jawa Tengah dengan total prediksi penurunan PDRB sektor pertanian sebesar 5,67 triliun rupiah serta proyeksi pertumbuhan sektor pertanian sampai dengan tahun 2024 terus mengalami peningkatan dengan pertumbuhan yang lambat rata-rata 2,38%., The agricultural sector has an important role in regional economic development, especially in Central Java Province. Central Java Province has earned the nickname as one of the “national food storage areas”. The agricultural sector has a primary function as a provider of food and distribution of community income through high levels of employment opportunities. The Covid-19 pandemic has caused changes in the economic structure and had an impact on reducing the rate of regional economic growth. One sector that has a golden opportunity to generate economic growth is the agricultural sector. This research aims to analyze the factors that influence the GRDP of the agricultural sector in Central Java, compare the GRDP of the Central java agricultural sector between actual data and SARIMA forecasting results during the Covid-19 pandemic and project the GRDP of the agricultural sector for four years. This research uses the panel data regression method and the Seasonal Autoregressive Integrated Moving Average (SARIMA) model. The research results show that: 1) the factors that positively and significantly influence the GRDP of agricultural sector in Central Java Province are agricultural sector labor and agricultural credit, while the negative factor is Covid-19; and 2) the Covid-19 pandemic has resulted in a decline in the growth of the agricultural sector in Central Java with a total predicted GRDP loss in the agricultural sector of 5,67 trillion rupiah and the projected growth of the agricultural sector until 2024 continues to increase with slow growth averaging 2,38%.
Keyword: Data panel, PDRB sektor pertanian, RPJMD, Seasonal Autoregressive Integrated Moving Average

Judul: The Role of Leading Sectors in Supporting the  Economic Growth of East Java Province Before and During the Covid-19  Pandemic
Abstrak: Jawa Timur merupakan salah satu penggerak perekonomian Indonesia karena merupakan penyumbang PDRB terbesar kedua setelah DKI Jakarta. Namun, pada tahun 2020 perekonomian Jawa Timur menunjukkan kontraksi pertumbuhan hingga nilainya mencapai -2,33 persen. Hal tersebut tidak lepas dari adanya pandemi Covid-19 yang menyebabkan sebagian lapangan usaha juga menunjukkan pertumbuhan negatif. Dalam rangka mencapai tujuan dan sasaran pembangunan daerah terkhusus pertumbuhan ekonomi daerah secara optimal di Provinsi Jawa Timur, maka pembangunan daerah dapat disusun menurut tujuan antar sektor. Dengan menggunakan analisis deskriptif, pendekatan Location Quotient (LQ), pendekatan Shift Share, dan overlay melalui nilai PDRB Rill menurut lapangan usaha berdasarkan harga konstan 2010 didapatkan empat sektor unggulan diantaranya sektor industri pengolahan; perdagangan besar dan eceran, reparasi mobil dan sepeda motor; penyediaan akomodasi dan makan minum; informasi dan komunikasi. Keempat sektor unggulan tersebut memiliki peran penting dalam mendukung pertumbuhan ekonomi di Jawa Timur karena memiliki laju pertumbuhan yang cepat, kontribusi yang tinggi, dan pangsa pasar yang luas baik sebelum adanya pandemic maupun saat pandemi covid-19. Sehingga pemerintah perlu memprioritaskan sektor-sektor unggulan tersebut dalam mendukung pertumbuhan ekonomi di Provinsi Jawa Timur., East Java is one of the driving forces of Indonesia's economy as it is the second-largest contributor to the Gross Regional Domestic Product (PDRB) after DKI Jakarta. However, in 2020, the economy of East Java experienced a contraction with a growth rate reaching -2.33 percent. This was primarily due to the impact of the Covid-19 pandemic, which led to negative growth in several sectors. In order to achieve the objectives and targets of regional development, especially in terms of economic growth in East Java Province, regional development can be structured according to inter-sectoral goals. Through descriptive analysis, the Location Quotient (LQ) approach, the Shift Share approach, and overlay using the Real Gross Domestic Product (PDRB Rill) based on constant prices in 2010, four leading sectors were identified. These sectors are the manufacturing industry, wholesale and retail trade, motor vehicle and motorcycle repair, accommodation, and food services, as well as information and communication. These four leading sectors play a crucial role in supporting economic growth in East Java due to their rapid growth rate, high contribution, and broad market share, both before and during the Covid-19 pandemic.Hence, the government needs to prioritize these leading sectors to support economic growth in East Java Province.
Keyword: Covid-19, Economic Growth, Gross Domestic Regional Product, Overlay, Location Quotient, Shift Share

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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