Judul: Proses Peminyakan (Fatliquoring) pada Penyamakan Kulit Ikan Tuna (Thunnus sp) untuk Bahan Bagian Atas Sepatu
Abstrak: Fatliquoring is part of tanning process, which penetrate the fatliquoring agent into leather’s empty cells. This process can change the physical properties of leather, which make it softer, more elastic, flexible and give smooth grain surface. This research was conducted to observe the influence of fatliquor addition on physical characteristics of tuna’s skin for the shoe upper. Responses measured were thickness, shrinkage temperature, tear strength, tensile strength, elongation at break and organoleptic properties. The types of fatliquor agent used in this study were natural and synthetic, and the dosages were 3%, 6%, 9%, 12% and 15%. Based on this research, the types of fatliquoring agent significantly affected the tear strength and elongation at break. The dosages of fatliquor which was nested in the type of fatliquor agent significantly affected the shrinkage temperature, tear strength, tensile strength, and elongation at break. There was no factor that significantly affected the thickness increase. The best condition in this research was reached by synthetic fatliquoring agent with dosage of 3%. The best condition gave thickness increase of 32.4%, shrinkage temperature of 125oC, tear strength of 95.3 N/mm, tensile strength of 27.9 N/mm2, elongation at break of 45.3%, with a good natural brown colour, smooth of feel/handle and good elasticity.
Keyword: Bogor Agricultural University (IPB), tuna skin, physical properties, fatliquoring agent, fatliquoring

Judul: Penyamakan Kulit Ikan Tuna (Thunnus sp.) dengan Kombinasi Penyamak Krom dan Nabati
Abstrak: Tanning is a way to change unstable rawhide (easily damaged by physical, chemical and biological effects) into a stable leather against those effects. Combination tanning method was a tanning process using two or more tannages in order to complete each other advantages and disadvantages to obtain leather with desired characteristics. Tanning using chrome would increase the flexibility, resistency of high temperature and tensile strength of leather. While vegetable tannage used in tanning gave an effect on physical quality on leather, including tensile strength, tear strength and other characteristics. The main purpose of this study were determined the effect of type and concentration of vegetable tannage on physical and organoleptic characteristics of skin tannage in the tanning process, to decide the best type and concentration of tannage for tanning, and to decide the characteristic of the leather. Tannages used were chrome with a concentration of 8% and vegetable tannages (mimosa, gambier, quebracho) with concentrations of 10%, 15% and 20%. The observed reponses in this study were thickness, shrinkage temperature, tensile strength, tear strength, elongation at break, and organoleptic characteristics. Based on the study, gambier with 20% concentration combined with 8% chrome produced the best quality of leather, highest increase thickness, tear strength of 84.76 N/mm, tensile strength of 22.68 N/mm2 and elongation at break of 57.38%. Organoleptic test showed that the colours produced by gambier looked more attractive, natural, finer texture, so that can be applied for material in sofa or jacket manufacture.
Keyword: vegetable, chrome, combination tanning, tuna’s skin

Judul: igenvalues and Eigenvectors of Tridiagonal Matrix with Non Constant and Recurrent Diagonal Entries.
Abstrak: Matriks tridiagonal adalah suatu matriks yang mempunyai entri-entri bernilai nol kecuali pada diagonal utama, di bawah diagonal utama (subdiagonal) dan di atas diagonal utama (superdiagonal). Entri pada diagonal utama tidak konstan dan berulang. Setiap entri pada matriks tridiagonal ini adalah bilangan kompleks. Dalam karya ilmiah ini, akan dibuktikan 3 teorema untuk menentukan nilai eigen dengan 2 kasus dan 1 teorema untuk menentukan vektor eigen. Teorema pertama menentukan polinomial karakteristik dari matriks tridiagonal. Polinomial karakteristik dari matriks tridiagonal tersebut digunakan untuk menentukan nilai eigen pada teorema kedua dan ketiga serta menentukan vektor eigen pada teorema keempat
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