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: The Influence of Online Consumer Reviews on Purchasing  Decisions on High Involvement Products with Shopee and Tokopedia marketplace  mediation in Bogor City
Abstrak: Tahun 2019-2020 (Q2) diketahui penetrasi internet di Indonesia mencapai 73,7% dengan jumlah pengguna internet 196.71 juta jiwa, angka tersebut meningkat 8,9% dari tahun 2018 dengan pertumbuhan pengguna 25.53 juta jiwa menurut APJII 2020. Data tersebut menunjukan toko offline mulai berubah menjadi toko online. Hal ini didukung oleh survei SIRCLO pada tahun 2020, platform belanja online yang paling banyak digunakan masyarakat Indonesia adalah marketplace (97% responden). Tujuan penelitian yang dilakukan adalah: mengidentifikasi karakteristik pelanggan Shopee dan Tokopedia, serta menganalisis pengaruh online consumer reviews terhadap keputusan pembelian pada high involvement products dengan mediasi lokapasar Shopee dan Tokopedia di Kota Bogor. Pada penelitian yang dilakukan digunakan teknik sampling non-probability, yaitu teknik purposive sampling dengan jumlah 100 responden yang memiliki karakteristik yang pernah berbelanja online melalui Shopee dan Tokopedia. Teknik analisis data yang digunakan adalah analisis deskriptif dan analisis Structural Equation Modeling-Partial Least Score (SEM-PLS). Hasil penelitian menunjukan terdapat dua variabel yang berpengaruh signifikan terhadap keputusan pembelian dengan mediasi Shopee dan Tokopedia yaitu, Review Valence dan Source Credibility.
Keyword: High Involvement Products, Purchase Decisions, Shopee and Tokopedia Marketplace, Online Consumer Reviews, 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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