Judul: Identification of Changes in Food Consumer Behavior during the Covid-19 Pandemic in Jabodetabek
Abstrak: Adanya pandemi Covid-19, kemungkinan dapat mengakibatkan perubahan pola perilaku konsumen pangan. Penelitian ini bertujuan untuk mengetahui produk pangan yang dibeli selama pandemi Covid-19, mengidentifikasi cara pembelian produk pangan dan tempat pembeliannya, mengidentifikasi faktor yang memengaruhi konsumen dalam membeli produk pangan, serta membandingkan perilaku konsumen sebelum dan selama pandemi Covid-19 di wilayah Jabodetabek. Metode yang digunakan yaitu survei online dengan teknik purposive sampling. Data dianalisis menggunakan analisis deskriptif dan analisis korelasi. Hasil survei menunjukkan bahwa terdapat produk yang mengalami peningkatan pembelian yaitu sayur dan buah segar, telur, mi instan, air mineral, minuman herbal, serta jus buah. Produk yang mengalami penurunan pembelian yaitu minuman karbonasi, minuman energi, sirup, makanan siap saji, serta makanan kaleng. Produk yang tidak mengalami perubahan pembelian diantaranya beras, daging segar maupun olahan, ikan dan seafood, roti, biskuit dan kue kering, susu dan olahannya, makanan ringan, makanan beku, sereal sarapan, bumbu masakan instan, teh siap minum, minuman isotonik, serta konfeksioneri. Terjadi pula peningkatan cara pembelian melalui online store selama pandemi Covid-19. Hasil uji Chi-Square menunjukkan terdapat 13 faktor yang memengaruhi pembelian beberapa produk pangan selama pandemi Covid-19 diantaranya yaitu domisili, jenis kelamin, usia, pendidikan, pekerjaan, merek, sensori, manfaat, kemudahan diperoleh, kandungan gizi, keamanan pangan, harga, serta ketersediaan., The existence of Covid-19 pandemic is thought to have resulted in changes in food consumer behavior patterns. This study aims to determine the food products purchased during Covid-19 pandemic, identify how to purchase food products and where to buy them, identify factors that influence consumers to buy food products, and compare consumer behavior before and during the Covid-19 pandemic in Jabodetabek. The method used is an online survey with purposive sampling technique. Data were analyzed using descriptive analysis and correlation analysis. The survey results showed that there were products that experienced an increase in purchases, such as fresh vegetables and fruit, eggs, instant noodles, mineral water, herbal drinks, and fruit juices. Products that experienced a decline in purchases were carbonated drinks, energy drinks, syrups, ready-to-eat food and canned food. Products that are regularly purchased include rice, fresh and processed meat, fish and seafood, bread, biscuits and pastries, milk and processed foods, snacks, frozen foods, breakfast cereals, instant cooking spices, ready-to-drink tea, isotonic drinks, and confectionery. There has also been an increase in ways of purchasing via online stores during the Covid-19 pandemic. The results of Chi-Square test showed that there were 13 factors that influenced the purchase of several food products during the Covid-19 pandemic including domicile, gender, age, education, occupation, brand, sensory, benefits, accessibility, nutritional content, food safety, price, and product availability.
Keyword: Covid-19, Perilaku konsumen, Survei online, consumer behavior, covid-19, online survey

Judul: Changes in the Food Consumption of Adults in Java Related to the Covid-19 Pandemic
Abstrak: Penelitian ini bertujuan menganalisis perubahan konsumsi makanan pada orang dewasa di Jawa yang terjadi karena pandemi Covid-19. Desain penelitian yang digunakan adalah cross sectional survey secara online menggunakan google form melalui website Kudata dan media sosial. Jumlah total subjek akhir sebanyak 2040 orang dewasa yang terdiri atas 267 pria dan 1773 wanita. Uji Mann Whitney digunakan untuk menganalisis perubahan konsumsi makanan sedangkan uji korelasi Rank Spearman dan Chi-Square digunakan untuk menganalisis hubungan karakteristik individu dengan perubahan konsumsi makanan. Hasil penelitian menunjukkan baik pada pria maupun wanita terjadi peningkatan signifikan (p<0,01) pada konsumsi kelompok pangan nabati yaitu makanan pokok, kacang-kacangan, buah, dan sayur. Hal yang sama juga terjadi pada konsumsi pangan hewani yaitu daging, ikan, dan telur. Peningkatan signifikan (p<0,01) pada kelompok pangan lainnya terlihat pada konsumsi rempah, pangan organik, makanan ringan, dan makanan sepinggan. Pandemi juga menyebabkan terjadinya penurunan konsumsi gula, garam, dan lemak (GGL). Pada subjek wanita, penurunan konsumsi GGL terjadi secara signifikan (p<0,01) sedangkan pada subjek pria penurunan yang terjadi tidak signifikan. Hasil uji hubungan menunjukkan sebagian besar dari karakteristik sosial ekonomi, pangan, dan kesehatan berhubungan signifikan dengan perubahan konsumsi makanan tertentu pada orang dewasa (pria dan wanita) di Jawa., This aims of this study was to analyze the changes in food consumption among adults in Java related to the Covid-19 pandemic. A cross-sectional survey with online google forms was applied and then distributed through the Kudata and social media. The total subjects were 2040 adults consisting of 267 males and 1773 females. The Mann-Whitney test was applied to analyze changes in food consumption while spearman’s rank correlation and Chi-Square test were applied to analyze the correlation between the subject’s characteristics with changes in food consumption. The results shows a significant increase (p<0.01) in plant foods consumption including staple foods, legumes, vegetables, and fruits. The same result also applied with animal foods including meat, fish, and egg. A significant increase (p<0.01) in other food groups was seen in the consumption of spices, organic foods, snacks, and one-dish meals. However, the pandemic also cause decreases sugar, salt, and fat consumption in both subject groups. Moreover, a significant decrease (p<0.01) happens in the female group. The results of the correlation test show that most of the socio-economic, food, and health characteristics are significantly related to the changes of adults particular food consumption in Java.
Keyword: adults, changes in consumption, Covid-19 pandemic, eating habits, food consumption

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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