Judul: Karakteristik Kulit Ceker Ayam dengan Penyamakan Kombinasi Krom dan Penyamak Nabati
Abstrak: Penyamakan kulit merupakan proses yang bertujuan untuk mengubah kulit mentah yang mempunyai sifat tidak stabil menjadi lebih stabil. Tujuan penelitian ini adalah untuk mengetahui kombinasi optimal antara penyamak krom dan nabati, sehingga dampak negatif penyamak krom terhadap lingkungan dapat dihindari. Penelitian ini menggunakan kulit ceker ayam. Perlakuan proses penyamakan kulit terdiri atas 4 taraf konsentrasi yang dimodifikasi dari konsentrasi bahan penyamak awal (8%) yang kemudian dianggap sebagai perlakuan P0 yaitu 100% krom ; P1 75% krom + 12.5% ekstrak daun jambu biji + 12.5% ekstrak daun teh; P2 50% krom + 25% ekstrak daun jambu biji + 25% ekstrak daun teh; dan P3 25% krom + 37.5% ekstrak daun jambu biji + 37.5% ekstrak daun teh, masing-masing dengan 3 ulangan. Hasil penelitian menunjukkan bahwa perlakuan P0 memberikan pengaruh yang sama dengan perlakuan P1 serta perlakuan P1 sama dengan perlakuan P2 dan P3 pada kekuatan tarik. Perlakuan P0, P1, P2 dan P3 memberikan pengaruh yang sama pada kekuatan regang dan kekuatan sobek. Penggunaan ekstrak daun jambu biji dan ekstrak daun teh sebanyak 25% yang dikombinasikan dengan 75% krom memberikan kekuatan tarik yang sama dengan penggunaan 100% krom.
Keyword: daun jambu biji, daun teh, kulit ceker ayam, penyamak krom

Judul: Karakteristik Kulit Ceker Ayam yang Disamak dengan Kombinasi Krom dan Mimosa serta Ekstrak Daun Teh (Camelia sinensis).
Abstrak: Skin tanning is process of converting rawhide skin protein into skin tanned by tanning materials, that result a change in the physical properties of unstable to stable and resistant to environmental influences such as physical pressure, weather, and microorganisms. Waste from tanning process is solid waste, gas, and liquid. For not polluting the environment, liquid waste containing chromium (0.7%) should be processed in the mix with natural tanning materials, like tea. This research used the skin of chicken claw that used combination of tanning (chemical tanning and tea extract) with different concentrations of chrome and nature tanning materials (mimosa and tea extracts) (70:20:10), (60:20:20) and (50:20:30), respectively. Parameters in this reseacrh was the quality of the skin tensile test, elongation test and skin rips test. The best concentration of tea extract for physical characteristics of the tanned chicken claw leather is addition of tea extract 10% intensile test, 20% tea extract in elongation test and 30% tea extract in skin rips test.
Keyword: Bogor Agricultural University (IPB), tea, tanning, eather

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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