Judul: Penentuan Konsentrasi Ca(OH)2 dan Suhu untuk Proses Pengapuran (Liming) Kulit Ikan Tuna
Abstrak: Liming is one of the most important processes in beamhouse and has many functions relating to the nature and quality of leather. Concentration of calcium hydroxide and temperature are thought to be a factor affecting the liming process and the quality of leather produced. The objectives of this study were to determine the characteristics of tuna skin, to determine the effect of the concentration of calcium hydroxide and temperature on the liming, and to determine the best treatment of the concentration of calcium hydroxide and temperature on the quality of limed pelt. There were four responses observed, i.e. the protein content, fat content, swelling, and pH. Based on this research, tuna skin had higher level of protein that was high enough to be processed into leather. Treatment of calcium hydroxide concentration did not significantly effect to all responses. Level of 5% calcium hydroxide concentration was the best treatment, as it gave three responses that achieve the best conditions. Temperature treatment showed a significant effect on the responses of fat content and swelling. Specified temperature as the best level was 30 °C, because there were two responses that achieve the best conditions at that level.
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Judul: Penentuan Jenis Deliming Agent dan Kecepatan Pengadukan dalam Proses Penghilangan Kapur (Deliming) Kulit Liming Ikan Tuna
Abstrak: Deliming is a removal process of lime in a skin which can disrupt the process of tanning and lowering quality of leather produced. The type of deliming agent and stirring speed become the factors affecting the deliming process. The research intended to know the effects of the type of deliming agent, stirring speed, and whether these interactions affect the quality of the delimed pelt. Besides that, this research aimed to know the best interaction of these two factors to produce expected responses and the characteristics of the pelts. The types of deliming agents used in this study were NH4Cl, (NH4)2SO4, and H3PO4. Stirring speeds used were 150, 200, 250 rpm. There were four responses measured, i.e. decrease of pelt thickness, pH, calcium content, and organoleptic characterictics of the pelts. The decrease of thickness was measured by thickness gauge; the pH was measured by pH paper; calsium content was measured by atomic absorption spectrophotometer. Based on this research, the types of deliming agent, stirring speed, and interaction of both variables affected highly significantly on the responses of thickness decrease and calcium content. The type of deliming agent affected highly significantly on the response of pH. The best treatment in this study was deliming agent of NH4Cl with stirring speed of 150 rpm. The treatment resulted delimed pelt with characteristics: thickness decrease of 13.42%, pH of 8.28, calcium content of 139.31 ppm, and good elasticity and pressure strength.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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