Judul: Karakteristik Minyak Kelapa sawit Mentah selama Kristalisasi sebagai Dasar Peningkatan Skala ppada Alat Kristalisasi
Abstrak: Pengolahan minyak sawit dilakukan dengan mesin-mesin dan peralatan pabrik yang tidak sederhana. Proses kristalisasi merupakan salah satu proses yang penting dalam pengolahan minyak kelapa sawit. Metode kristalisasi yang terdapat pada pabrik pengolahan minyak kelapa sawit ada dua yaitu dry crystallizatio~~da n solve~~r crystallizatioiz. Metode kristalisasi tanpa pelamt (dry crystallization) dipakai dalam penelitian ini. Dry crystallization mempunyai tujuan untuk memisahkan trigliserida minyak atau lemak menjadi dua atau lebih fraksi, yang merupakan akibat dari perbedaan karakteristik fisik dan bukan dengan penggunaan bahan kimia tambahan. Karakteristik fisik yang digunakan dalam penelitian ini adalah temperatur. Dengan berubahnya temperatur, sebagian minyak dari CPO akan mengkristal dan membentuk fraksi padat, sedangkan fraksi lelehnya adalah olein.
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Judul: Kajian Sifat Kristalisasi Lemak pada Minyak Sawit Kasar
Abstrak: Indonesia is the biggest crude palm oil (CPO) producer in the world. Study on fat crystallization of CPO is needed to improve the knowledge of CPO handling during storage and transportation. The aim of this study is to characterize fat crystallization properties of CPO related to storage and transportation. Solid fat content (SFC) of CPO were decreased in higher temperature. After four weeks storage, SFC of CPO were increased at 20 ºC and 25 ºC, but were decreased at 30-40 ºC. CPO crystallized in slow cooling rate (0.2 ºC/minute) had higher SFC, meanwhile CPO crystallized in faster cooling rate (0.5 ºC/minute and 1 ºC/minute) had lower SFC. CPO which crystallized under slow cooling resulted higher Avrami constant (k) and lower Avrami exponent (n) than CPO which crystallized under fast cooling. The Avrami constant on cooling rate 0.2 ºC/minute, 0.5ºC/minute, and 1 ºC/minute were 0.013, 0.003, and 0.002 respectively. CPO which crystallized under fast cooling had higher induction time and crystallization half time. The Avrami exponent on cooling rate 0.2 ºC/minute, 0.5 ºC/minute, and 1 ºC/minute was 1.614, 2.032, and 2.170 repectively. Faster crystallization occured on higher shear rate. CPO which crystallized under higher shear rate had longer induction time than lower shear rate.
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Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model