Judul: Karakteristik Minyak Sawit Kasar Selama Penyimpanan dan Pengaliran
Abstrak: Crude palm oil (CPO) is one of Indonesia's main commodity. Nowadays, Indonesia is the largest CPO producer in the world. To increase the competitiveness of CPO in Indonesia, handling, storage, and transportation of CPO should be managed efficiently. The objective of this research was to obtain the basic data about the quality characteristics and rheological properties of CPO during storage and pipe flow transportation. The quality parameters of CPO that observed in this study were free fatty acids (FFA), iodine value, carotenoid content, and the deterioration of bleachability index (DOBI). The observed parameters of the rheological properties were flow behavior index (n) and consistency index (K). CPO that used in this research had 3.44% of FFA, 52.64 of iodine value, 816 ppm of carotenoid content, and 3.21 of DOBI. CPO was stored at the storage temperature of 20, 25, 30, 35, and 40 oC over 4 weeks. The results showed that during storage, FFA levels increased, while the carotenoid content and DOBI decreased. The higher storage temperature resulted in higher rate of decline in CPO quality. At each storage temperature, the longer storage resulted in decreased quality of CPO. Based on this research, the best storage temperature to maintain the quality of CPO was at 20 oC. At the room temperature, CPO was pseudoplastic (0<n<1 and K>0), but at the higher storage temperature, CPO had rheological properties that closer to Newtonian (n=1 and K>0). The analysis of rheological properties during storage showed that storage time had no effect on the rheological properties of CPO. Study on CPO flow by using circulated pipeline in isothermal conditions showed that melting temperature was the critical temperature for maintaining low viscosity to assure the flow of CPO. Flow of CPO in high temperature caused decreasing in quality of CPO significantly.
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Judul: Kajian Pengaruh Suhu terhadap Densitas dan Sifat Reologi Minyak Sawit Kasar (Crude Palm Oil)
Abstrak: Indonesia is the largest CPO producer in the world. Production of CPO in Indonesia increases in each year. Increasing of CPO production must be balanced with the development of its transportation systems. One of the efficient transportation system of CPO is pipeline transportation. On this pipeline transportation, density and rheology is a crucial parameter for pipeline design calculation and simulation of its momentum transfer process and system. The aim of this research was to get data of the density and rheological properties of CPO on different temperature. The samples used in this research were obtained from four different factories of palm oil in Indonesia. The density was measured by AOCS 1997 method and the rheological properties of CPO was measured by Haake Rotoviscometer RV20 (Karlsruhe, Germany).The results showed that the temperature influenced on density and rheological properties of CPO. Density decreased with increasing of temperature. The flow behavior index (n) increased with increasing temperature but the consistency index (K) and apparent viscosity of CPO decreased with increasing of temperature. Generally, CPO exhibited a pseudoplastic behavior at temperature of 25-40oC and a Newtonian behavior at temperature of 45-55oC.
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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