Judul: Optimization of sugar cane (Saccharum officinarum L.) ratoon cropping pattern and plant cane at PT. Madubaru PG. Madukismo, Yogyakarta
Abstrak: Gula merupakan salah satu komoditi perdagangan utama yang digunakan untuk mengubah cita rasa makanan atau minuman menjadi manis. Konsumsi gula di Indonesia terus meningkat mengikuti pertambahan jumlah penduduk, peningkatan taraf hidup, dan pertumbuhan juml ah industri yang memerlukan gula sebagai bahan bakunya. Namun peningkatan konsumsi gula belum bisa diimbangi oleh produksi gula dalam negeri. Tujuan penelitian ini adalah melakukan optimisasi pada pola ratoon tanaman tebu di perkebunan tebu, dengan fungsi tujuan meminimalisasi biaya dan atau memaksimalkan hasil. Data yang diambil adalah data sekunder pada lahan tebu PG. Madukismo di kabupaten Sleman dan Bantul dalam kurun waktu lima tahun terhitung mulai tahun 2008 sampai tahun 2012. Kebun yang digunakan sebagai penelitian berjumlah enam kebun, tiga dari Sleman da n tiga dari Bantul. Masing-masing dihitung jumlah produksi tebu dan gulanya, kemudian dihitung biaya produksi yang dikeluarkan secara keseluruhan, sehingga didapatkan hasil akhir laba dari perusahaan. Berdasarkan penelitian yang dilakukan, jumlah keprasan yang sebaiknya dilakukan untuk mendapatkan keuntungan yang terus meningkat adalah sebanyak tiga kali keprasan.
Keyword: sugar cane, ratoon, production costs

Judul: Pengelolaan Tanaman Tebu (Saccharum officinarum L.) di Pabrik Gula Madukismo, PT. Madubaru, Yogyakarta: dengan Aspek Khusus Mempelajari Produktivitas Tiap Kategori Tanaman
Abstrak: The study of the productivity of the various categories of sugarcane held in the Madukismo Millsworking area, Madubaru Company, Yogyakarta. This activity began in February 13 to May 14, 2012. The sample is taken at Sleman and Bantul district. The method used is the direct field observation, data from the division of plant productivity, as well as interviews with farmers. The results obtained on the productivity of down land is higher than up land. Differences in land characteristics influence the productivity of sugarcane. In addition, the downland productivity tended to decrease from the plant cane (PC) to ratoon crop (RC) in each subsequent season. For up land, there is higher productivity at ratoon cane I (RC 1) increase from low productivity in the plant cane (PC) and then back on every ratoon crop the following season. To overcome the low productivity of ratoon sugarcane needed to do the loading or replanting, or ratoon intensif nurse.
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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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