Judul: The Effect Number of internodes and Time of Shoots Cutting and Number of Shoots Cut on The Productivity of Sweet Potatoes (Ipomea batatas L.) Clone Ase Kapas.
Abstrak: Ubi jalar (Ipomea babatas L.) merupakan salah satu tanaman sumber karbohidrat yang ada di Indonesia. Sistem budidaya tanaman yang kurang baik menyebabkan tidak maksimalnya produktivitas dari tanaman ubi jalar. Penelitian ini bertujuan mengetahui pengaruh jumlah buku dan waktu pemotongan pucuk pucuk dan jumlah pucuk yang di potong terhadap produktivitas ubi jalar (Ipomea batatas L.) klon Ase Kapas. Perlakuan buku dengan tiga taraf yaitu lima, enam dan tujuh buku sedangkan perlakuan pemotongan pucuk dengan lima taraf yaitu pemotongan dua pada bulan kedua, pemotongan dua pada bulan ketiga, pemotongan enam pada bulan kedua, pemotongan enam pada bulan ketiga dan tidak dipotong. Hasil penelitian menunjukkan perlakuan pemotongan pucuk dan jumlah buku tidak berpengaruh terhadap bobot, diameter, panjang dan jumlah umbi. Perlakuan tujuh buku berpengaruh terhadap parameter vegetatif tanaman., Sweet potato (Ipomea babatas L.) is one of carbohydrate sources in Indonesia. The poor crop cultivation system causes the productivity of the sweet potato crop is not maximal. This research aim to determine the effect number of internode and time of shoots cutting and number of shoots cut on the productivity of sweet potato (Ipomea batatas L.) clone Ase Kapas. The treatment of the internodes was three levels, namely five, six and seven segments, while the treatment of the shoot cutting was five levels, namely cutting two in the second month, cutting two in the third month, cutting six in the second month, cutting six in the third month and no cutting. The results showed that shoot cutting and internodes treatments had no effect on weight, length diameter and number of tubers. The treatment of seven segments had an effect on the vegetative parameters of the plant.
Keyword: Cutting, internodes, productivity, shoot, vegetative

Judul: The Growth and Tuber Yield of Sweetpotato (Ipomoea batatas L.) Ase Kapas at Various Rates of Nitrogen Fertilizer
Abstrak: Ubijalar merupakan tanaman pangan penting di Indonesia. Produktivitas ubijalar dapat dipengaruhi oleh pemupukan. Tujuan penelitian ini yaitu menentukan dosis nitrogen bagi pertumbuhan dan produksi ubijalar Ase Kapas. Penelitian dilakukan pada bulan Januari sampai Juli 2020 di Kebun Percobaan Cikabayan IPB dengan rancangan kelompok lengkap teracak dengan 3 ulangan. Dosis N yang diaplikasikan yaitu 0; 22,5; 45; 67,5; dan 90 kg ha-1 . Bahan tanam yang digunakan yaitu bagian stek pucuk. Curah hujan selama penelitian cenderung tidak sesuai dengan kondisi optimal pertumbuhan ubijalar. Pada tanah dengan kandungan nitrogen berstatus sedang (0,29% setara dengan 174 kg ha-1 ), dosis N tidak berpengaruh signifikan terhadap perubahan panjang dan diameter sulur, jumlah daun dan cabang, panjang dan diameter umbi, serta bobot basah dan kering umbi dan brangkasan. Pada tanah dengan kandungan N total sedang, dosis 0 kg N ha-1 dapat diaplikasikan untuk mendukung pertumbuhan dan produksi yang baik bagi ubijalar klon Ase Kapas., Sweetpotato is an essential crop plant in Indonesia. The productivity of the sweetpotato could be affected by fertilization. The objective of this research is to assess optimal nitrogen rate for growth and root yield of sweetpotato Ase Kapas. The experiment was conducted at IPB University experimental field Cikabayan from January to July 2020 used randomized complete block design with 3 replications. The level of nitrogen fertilizer consists of 0; 22,5; 45; 67,5; and 90 kg ha-1 . The planting material is the vine cuttings. The rainfall during this experiment tends to be insufficient as climate requirements. In the soil with moderate N content (0.29% equal to 174 kg ha-1 ), nitrogen had no significant effect on the growth of length and diameter of main stem, the amount of leaves and secondary stems, length and diameter of storage roots, wet- and dry-weight biomass of storage roots and aboveground part. In the soil with a moderate N total, dose of 0 kg N ha-1 could be applied to support good growth and yield of sweetpotato clone Ase Kapas.
Keyword: produktivitas, suplai nitrogen, umbi, Urea, nitrogen supply, storage root, productivity

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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