Judul: The Effectiveness of Using Manure and  Urea in Post-Coal Mining Land Against Pakchong Grass Produktivity
Abstrak: Peningkatan ketersediaan produksi rumput pakchong berpotensi dilakukan pada lahan bekas tambang. Pemanfaatan pupuk kandang dan urea diperlukan sebagai upaya peningkatan unsur hara pada lahan bekas tambang. Penelitian ini bertujuan untuk mengevaluasi dosis pupuk kandang dan urea dalam meningkatkan produktivitas rumput pakchong di lahan bekas pertambangan batu bara. Penelitian ini terdiri dari 2 faktor yaitu dosis pupuk kandang (0, 5 ton ha-1 , 10 ton ha-1 ) dan dosis urea (0, 150 kg ha-1 , 300 kg ha-1 ). Data pertumbuhan dan produksi rumput pakchong dianalisis menggunakan analisis varian (ANOVA). Apabila parameter yang diukur menunjukkan perbedaan yang nyata akan dilanjutkan dengan uji Duncan. Hasil penelitian menunjukkan bahwa dosis pupuk kandang dan urea berpengaruh nyata (P<0,05) terhadap tinggi tanaman, jumlah daun, jumlah anakan, dan biomassa segar. Pemberian pupuk kandang dapat memperbaiki struktur tanah secara fisik, kimia, dan biologi tanah. Pemberian urea dapat merangsang pertumbuhan secara keseluruhan terutama cabang, batang, daun, dan berdampak penting pada pembentukan hijau daun. Pemberian pupuk kandang dengan dosis 5 ton ha-1 dan pupuk urea 300 kg ha-1 memiliki pertumbuhan dan produksi terbaik.
Keyword: manure, pakchong grass, post-coal mining land, urea

Judul: Increasing the Carrying Capacity of Post-Coal Mining Grazing Fields with Different Doses of Urea Fertilization
Abstrak: Penelitian ini bertujuan mengetahui pengaruh dosis pemupukan urea dan pemotongan yang berbeda terhadap pertumbuhan dan produktifitas rumput Brachiaria decumbens dalam meningkatkan kapasitas tampung di padang penggembalaan lahan pasca tambang batu bara. Penelitian menggunakan rancangan acak kelompok faktorial (RAKF) dengan dua faktor yaitu faktor A terdiri dari T1 = Pemotongan 5 cm dari permukaan tanah; T2 = Pemotongan 10 cm dari permukaan tanah. Faktor B terdiri dari P0 = Kontrol; P1 = Urea 100 kg ha-1; P2 = Urea 200 kg ha-1; P3 = Urea 300 kg ha-1. Parameter yang diuji adalah komposisi botani, kapasitas tampung existing dan peningkatannya, Proper Use Factor (PUF), produksi protein, tinggi, diameter, dan biomassa tanaman. Hasil penelitian kapasitas tampung existing sebesar 1,01 ST ha-1. Pemupukan urea berpengaruh terhadap diameter, biomassa tanaman, peningkatan kapasitas tampung dan produksi protein. Perlakuan T2 dan P2 efektif menghasilkan nilai PUF sebesar 66,30% dan meningkatkan kapasitas tampung menjadi 1,70 ST ha-1., This research aimed to determine the effect of different doses of urea fertilization and mowing on the growth and productivity of Brachiaria decumbens grass in increasing carrying capacity in pastures on post-coal mining land. The research used a randomized block factorial design (RBFD) with two factors, namely factor A consisting of T1 = Cutting 5 cm from the ground surface; and T2 = Cutting 10 cm from the ground surface. Factor B consists of P0 = Control; P1 = Urea 100 kg ha-1; P2 = Urea 200 kg ha-1; P3 = Urea 300 kg ha-1. The parameters tested were botanical composition, existing and increasing capacity, Proper Use Factor (PUF), protein production, height, diameter, and plant biomass. The research results showed that the existing carrying capacity is 1.01 AU ha-1. Urea fertilization affected diameter, plant biomass, increased carrying capacity, and protein production. Treatment of T2 and P2 was effective in produced a PUF value by 66.30% and increased the carrying capacity to 1.70 AU ha-1.
Keyword: botanical composition, carrying capacity, Proper Use Factor, urea fertilizer

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.
Keyword: