Judul: Analysis of Online Purchase Decisions at Shopee and Tokopedia  According to Consumer Perceptions in Jabodetabek
Abstrak: Menurut Global Web Index (2019) Indonesia sebagai negara dengan persentase pengguna e-commerce tertinggi di dunia. Shopee dan Tokopedia adalah peringkat ke-1 dan ke-2 e-marketplace dengan jumlah kunjungan terbanyak pada kuartal IV tahun 2020 di Indonesia. Penelitian ini bertujuan untuk menganalisis pengaruh persepsi persepsi konsumen mengenai harga, kualitas layanan, dan citra merek terhadap keputusan pembelian online di Shopee dan Tokopedia yang berlokasi di Jabodetabek. Jumlah responden dalam penelitian ini sebanyak 179 responden. Teknik pengambilan sampel yang digunakan adalah non probability sampling dengan teknik purposive sampling. Analisis data dilakukan menggunakan analisis deskriptif dan analisis regresi linear berganda dengan melakukan uji asumsi klasik. Hasil penelitian ini menunjukkan bahwa setiap variabel independen, yaitu harga, kualitas layanan, dan citra merek berpengaruh positif terhadap keputusan pembelian online di Shopee dan Tokopedia. Selain itu, keseluruhan variabel independen tersebut juga berpengaruh positif terhadap keputusan pembelian online di Shopee dan Tokopedia. Nilai koefisien determinasi yang didapatkan pada penelitian ini sebesar 66% artinya sumbangan pengaruh variabel independen terhadap variabel dependen sebesar 66%., Global Web Index (2019) records Indonesia as the country with the highest percentage of e-commerce users in the world. Shopee and Tokopedia are ranked 1st and 2nd e-marketplace with the highest number of visits in the fourth quarter of 2020 in Indonesia. This study aims to analyze the influence of consumer perception perception regarding price, service quality, and brand image on online purchase decisions in Tokopedia and Shopee located in Jabodetabek. The number of respondents in this study was 179 respondents. Sampling techniques used are non probability sampling with purposive sampling techniques. Data analysis is performed using descriptive analysis and multiple linear regression analysis by performing classic assumption tests. The results of this study indicate that each independent variable, namely price, service quality, and brand image has a positive effect on online purchasing decisions at Shopee and Tokopedia. In addition, overall these independent variables also have a positive effect on online purchasing decisions at Shopee and Tokopedia. The value of the coefficient of determination obtained in this study is 66%, meaning that the influence of the independent variable on the dependent variable is 66%.
Keyword: consumer perceptions, e-marketplace, purchase decisions

Judul: Analisis Persepsi Konsumen terhadap Keputusan Pembelian Online di Tokopedia.
Abstrak: Pengguna internet di Indonesia semakin meningkat. Hal itu berpengaruh positif terhadap transaksi jual beli online. Pada saat ini persaingan e-commerce semakin ketat di Indonesia. Tokopedia harus meningkatkan keunggulan dalam bersaing dengan e-commerce lainnya untuk menarik banyak konsumen dengan memahami persepsi konsumen dalam pengambilan keputusan pembelian. Tujuan dari penelitian ini adalah mengidentifikasi karakteristik konsumen Tokopedia dan menganalisis pengaruh harga, kualitas layanan, dan merek terhadap keputusan pembelian online Tokopedia. Metode pemilihan sampel menggunakan metode non-probability sampling dengan teknik purposive sampling. Metode analisis yang digunakan adalah analisis regresi linier berganda. Hasil uji F menunjukkan bahwa pengaruh harga, kualitas layanan dan citra merek berpengaruh signifikan terhadap keputusan pembelian online tokopedia (sig. 0.000). Hasil uji t bahwa harga (sig. 0.044), kualitas layanan (sig. 0.040), dan citra merek (sig. 0.000) memiliki pengaruh signifikan terhadap keputusan pembelian online Tokopedia.
Keyword: keputusan pembelian, regresi linier berganda, Tokopedia

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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