Judul: The Relationship between Electronic Word of Mouth Communication and the Purchase Decision of Vegetable Products through Instagram Segari
Abstrak: Pandemi yang sebelumnya melanda Indonesia, mengakibatkan keterbatasan mobilititas masyarakat yang mengubah aktivitas masyarakat menjadi serba daring. Salah satu aktivitas yang mengalami perubahan tersebut yaitu aktivitas jual beli. Pertimbangan konsumen dalam belanja online dapat dilakukan salah satunya melalui ulasan yang ditulis melalui media internet atau yang dikenal dengan Electronic word of mouth. Electronic word of mouth dapat mendorong keputusan pembelian konsumen produk sayuran melalui e-commerce. Penelitian ini bertujuan untuk menganalisis hubungan penyebaran informasi melalui komunikasi electronic word of mouth dengan keputusan pembelian produk sayuran melalui media sosial instagram segari. Metode yang digunakan adalah metode penelitian survei dengan pendekatan kuantitatif menggunakan kuesioner yang didukung dengan data kualitatif berupa wawancara mendalam. Teknik pemilihan responden dilakukan dengan purposive sampling diambil dari pengikut instagram @Segari.id dan sudah pernah membeli produk sayuran Segari sebanyak 140 orang. Hasil penelitian menunjukkan bahwa dimensi electronic word of mouth yaitu, intensitas penggunaan media sosial instagram Segari dan isi informasi memiliki hubungan dengan keputusan pembelian., The pandemic that previously hit Indonesia resulted in limited community mobility which turned people's activities completely online. One of the activities that has experienced these changes is buying and selling activities. Consumer considerations in online shopping can be done one of them through reviews written through internet media or what is known as electronic word of mouth. Electronic word of mouth can encourage consumer purchasing decisions for vegetable products through e-commerce. This study aims to analyze the relationship between the dissemination of information through electronic word of mouth communication and the purchase decision of vegetable products through Instagram Segari social media. The method used is a survey research method with a quantitative approach using a questionnaire supported by qualitative data in the form of in-depth interviews. The respondent selection technique was carried out by purposive sampling taken from Instagram followers @Segari.id and 140 people who had bought Segari vegetable products. The results of the study show that the dimensions of electronic word of mouth, namely the intensity of social media instagram Segari use and information content, have a relationship with purchasing decisions.
Keyword: Electronic word of mouth, Instagram, Keputusan pembelian

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.
Keyword: