Judul: Penerapan Algoritma C4.5 dan Random Forest pada Tingkat Penjualan Serum Somethinc di Shopee
Abstrak: Kegiatan jual beli online di Indonesia semakin meningkat. Shopee merupakan platform jual beli online dengan kunjungan tertinggi di Indonesia pada kuartal IV tahun 2022. Kategori barang yang memiliki transaksi tertinggi di Shopee adalah produk kecantikan. Brand Somethinc merupakan produk kecantikan lokal yang sangat sukses di Shopee dengan menempati peringkat pertama dalam penjualan produk serum di Indonesia. Penelitian ini menerapkan metode klasifikasi C4.5 dan Random Forest untuk melihat peubah penting dalam penjualan serum Somethinc di Shopee. Peubah yang digunakan berasal dari profil toko yang meliputi: jumlah pengikut, jumlah produk, performa pesan, rating toko, dan waktu bergabung. Data penjualan yang kontinyu didiskritisasi menggunakan k-means menjadi data ordinal dengan tingkat rendah, sedang, tinggi, dan sangat tinggi. Terdapat ketidakseimbangan pada kelas penjualan sehingga dilakukan teknik SMOTE. Penerapan teknik SMOTE meningkatkan nilai akurasi dan F1-score. Algoritma C4.5 menghasilkan pohon keputusan yang berisikan aturan dalam klasifikasi. Random Forest menghasilkan urutan kepentingan peubah berdasarkan nilai MDG berturut-turut dari tinggi ke rendah yaitu: jumlah pengikut, jumlah produk, performa pesan, waktu bergabung, dan rating toko., Online buying and selling activities in Indonesia are increasing. Shopee is an online buying and selling platform with the highest visits in Indonesia in the fourth quarter of 2022. The category with the highest transactions at Shopee is beauty products. Somethinc is a very successful local beauty product at Shopee which have highest sales of serum products in Indonesia. This study applies the classification method C4.5 and Random Forest to see important variables in the sales of Somethinc serum at Shopee. The variables used come from store profiles which include: number of followers, number of products, chat performance, store rating, and length of stay. Continuous sales data is discretized using k-means into ordinal data with low, medium, and high levels. There is an imbalance of data in the sales class so that the SMOTE technique is used. The C4.5 algorithm produces a decision tree that contains rules for classification. Random Forest generates the order of variable importance based on the Mean Decrease Gini (MDG) values in descending order, which are as follows: number of followers, number of products, message performance, joining time, and store rating.
Keyword: Algoritma C4.5, Random Forest, k-means, serum Somethinc, Shopee

Judul: Pengaruh Rating dan Online Customer Review Terhadap Keputusan Pembelian di E-commerce Shopee
Abstrak: Kemajuan teknologi informasi menimbulkan adanya E-commerce yang membuat aktivitas belanja menjadi semakin mudah. Berdasarkan jumlah pengunjung bulanan situs E-commerce pada kuartal IV 2020, Shopee merupakan E-commerce yang paling banyak dikunjungi oleh pengguna internet. Penelitian ini bertujuan menganalisis pengaruh rating dan online customer review terhadap keputusan pembelian di E-commerce Shopee. Sumber data menggunakan data primer yang diperoleh berdasarkan hasil pengisian kuesioner oleh responden dan data sekunder yang diperoleh melalui literasi jurnal ilmiah, buku, dan sumber bacaan lainnya. Penelitian ini dilaksanakan pada bulan juni 2022. Responden pada penelitian ini adalah mahasiswa Institut Pertanian Bogor. Teknik data yang digunakan yaitu uji validitas dan uji reliabilitas dengan metode pengolahan data yang digunakan yaitu analisis deskriptif dan SEM-PLS. Hasil penelitian menjelaskan bahwa Variabel rating berpengaruh secara positif dan signifikan terhadap variabel keputusan pembelian dan variabel customer online review berpengaruh secara positif dan signifikan terhadap keputusan pembelian., Advances in information technology have given rise to E-commerce which makes shopping activities easier. Based on the number of monthly visitors to E-commerce sites in the fourth quarter of 2020, Shopee is the most visited E-commerce by internet users. This study aims to analyze the effect of ratings and online customer reviews on purchasing decisions at E-commerce Shopee. Data sources use primary data obtained based on the results of filling out questionnaires by respondents and secondary data obtained through literacy in scientific journals, books and other reading sources. This research was conducted in June 2022. Respondents in this study were students of the Bogor Agricultural University. The data technique used is the validity test and reliability test with the data processing method used is descriptive analysis and SEM-PLS. The results of the study explain that the rating variable has a positive and significant effect on the purchasing decision variable and the online customer review variable has a positive and significant effect on the purchasing decision. Keywords: E-commerce, Online Customer Review, Rating, Purchase Decision, SEM-PLS
Keyword: E-commerce, Online Customer Review, Rating, Purchase 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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