Judul: Fruits and Vegetable Purchase Intentions and Decisions through E-Commerce: Development of Theory of Planned Behavior
Abstrak: Tren pemanfaatan akses internet di Indonesia mengalami peningkatan yang signifikan, termasuk dalam perdagangan elektronik. Pandemi COVID-19 di Indonesia berdampak pada perubahan perilaku konsumen dalam berbelanja dari konvensional menjadi online yang terus meningkat. Perubahan perilaku tersebut untuk mengurangi aktivitas fisik di luar rumah dan memudahkan konsumen dalam belanja. Penelitian ini bertujuan untuk menganalisis pengaruh sikap, norma subjektif, kontrol perilaku, kepercayaan, dan situasi pandemi COVID-19 terhadap keputusan pembelian buah dan sayur melalui e-commerce. Penelitian ini menggunakan data primer yang diperoleh dari 190 responden dengan metode purposive sampling. Data dianalisis menggunakan metode analisis deskriptif dan Structural Equation Model-Partial Least Square (SEM-PLS). Hasil penelitian menunjukkan bahwa variabel kontrol perilaku dan situasi pandemi COVID-19 memiliki pengaruh yang positif dan signifikan terhadap niat dan keputusan pembelian buah dan sayur melalui e-commerce saat pandemi COVID-19., The trend of internet access in Indonesia has experienced a significant increase, including in electronic commerce. The COVID-19 pandemic in Indonesia has an impact on changing consumer behavior in shopping from conventional to online which continues to increase. These behavioral changes can reduce physical activity outside the home and make it easier for consumers to shop. This study aims to analyze the effect of attitudes, subjective norms, behavioral control, beliefs, and the COVID-19 pandemic situation on fruit and vegetable purchasing decisions trough e-commerce. This study uses primary data obtained from 190 respondents with a purposive sampling method. Data were analyzed using descriptive analysis methods and Structural Equation Model-Partial Least Square (SEM-PLS). The results showed that behavioral control variable and the COVID-19 pandemic situation had a positive and significant influence on intentions and decisions to purchase fruit and vegetables through e-commerce during the COVID-19 pandemic.
Keyword: COVID-19, e-commerce, purchasing decision, SEM-PLS

Judul: The Influence of Psychological Factors on the Decision to Purchase Organic Vegetables and Fruits through E-commerce during the Covid-19 Pandemic
Abstrak: Perkembangan internet yang semakin pesat dimanfaatkan masyarakat untuk melakukan transaksi bisnis secara daring sehingga muncul adanya e-commerce. Situasi Pandemi Covid-19 menyebabkan peningkatan pengguna e-commerce sebagai alat untuk berbelanja. Sayur dan buah organik sebagai alternatif piihan pangan sehat mulai dicari di masa pandemi Covid-19. Kebutuhan ini dapat dipenuhi melalui pemanfaatan e-commerce sebagai media transaksi jual beli saat pandemi Covid-19. Penelitian ini bertujuan untuk menganalisis pengaruh faktor psikologis kepercayaan, keamanan, dan kemudahan terhadap keputusan pembelian sayur dan buah organik melalui e-commerce. Penelitian ini menggunakan data primer dari 200 responden di wilayah Jabodetabek melalui kuesioner secara daring. Metode yang digunakan dalam penelitian ini adalah analisis deskriptif dan analisis SEM-PLS. Hasil penelitian menunjukkan bahwa variabel kepercayaan, keamanan, kemudahan berpengaruh positif dan signifikan terhadap keputusan pembelian online. Perusahaan e-commerce perlu memperhatikan variabel yang berpengaruh signifikan sebagai bahan pertimbangan dalam memasarkan produknya., The community is using the rapid development of the internet to conduct online business transactions, resulting in the emergence of e-commerce. The Covid19 pandemic situation has led to an increase in e commerce users as a means of shopping. Organic vegetables and fruits began to be sought as an alternative to healthy food choices during the Covid-19 pandemic. This demand can be fulfilled using e commerce as media for buying and selling transactions during the Covid19 pandemic. This study analyses the influence of psychological factors of trust, safety, and convenience on purchasing decisions for organic vegetables and fruits through e-commerce. This study used primary data from 200 respondents in the Jabodetabek area through an online questionnaire. The method used in this research is descriptive analysis and SEM-PLS analysis. The results showed that the variables of trust, security, convenience have a positive and significant effect on online purchasing decisions. E-commerce companies need to put emphasize on variables that have a significant effect on marketing their products.
Keyword: Covid-19, E-commerce, Online Purchasing Decision, SEM-PLS

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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