Judul: Identifikasi silika amorf dari sekam padi
Abstrak: Rice husk is an agriculture by product derived from rice milling, which is produced in a large quantity. Up to present time, rice husk is utilized for limited uses, such as for a fuel in brick production, processed to a charcoal planting medium, and burnt to ash for cleansing powder. With a certain technique, however, rice husk can be processed to produce amourphous silica. This research was aimed to find out characteristics of rice husk ash derived from incineration at different temperatures and oxidation by H2O2. This research consisted of two main steps, i.e. combustion of rice husk and identification of silica of the combustion product. Combustion of rice husk was done with both incineration and oxidation by H2O2. Incineration was run at 400°C, 500°C, 600°C, 700°C and 900°C for 5 hours. The oxidation of rice husk was run with added H2O2 30% until the entire organic compound disappeared (do not effervesce again). Identification of silica was carried out using polarization microscope, refractometer, DTA, FT-IR and XRD. In addition, identification of silica was also done for rice husk ash from common incineration, quartzsand from Pangkalanbun (Kalimantan) and for standard quartz. Chemical characteristics of rice husk, including SiO2, Al2O3, K2O, MnO, MgO, CaO, and total C was done as well. Identification with DTA showed that the silica derived from incineration of rice husk at 400°C, 500°C, 600°C, and from oxidation of rice husk with H2O2 have DTA curve that reflecting amourphous silica. In the contrary, the DTA curve of silica in the ash from incineration at 700 °C and 900°C are much more reflect DTA curve of crystallin silica. The results of identification using FT-IR and XRD showed that only silica in the ash from incineration at 900 °C showing characteristics of crystalline silica. The results revealed that incineration of rice husk at 400°C seem to be the optimum temperature to produce amourphous silica from rice husk for use as absorbent.
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Judul: Identifikasi silika amorf dari sekam padi
Abstrak: Sekam padi merupakan hasil sampingan dari produksi padi yang jumlahnya cukup melimpah. Selama ini pemanfaatan sekam padi masih terbatas, yaitu antara lain digunakan sebagai bahan bakar bata merah, media tanam berupa arang sekam, dan abu gosok. Sebenarnya melalui pendekatan teknologi, sekam padi ini dapat diolah lebih lanjut menjadi salah satu sumber silika amorf. Penelitian ini bertujuan untuk mengetahui karakteristik abu sekam padi yang dihasilkan dari dari berbagai tingkat suhu pembakaran dan dari proses oksidasi H2O2 Penelitian ini terdiri dua tahap yaitu tahap pengabuan dan tahap identifikasi. Tahap pengabuan dilakukan melalui dua cara, yaitu melalui pembakaran dan oksidasi H2O2. Pembakaran sekam padi dilakukan pada suhu 400°C, 500°C, 600°C, 700°C dan 900°C selama 5 jam. Pengoksidasian sekam padi dilakukan dengan menambahkan H2O2 30% pada sekam padi hingga bahan organik habis (tidak berbuih lagi). Identifikasi karakteristik abu sekam padi dilakukan dengan menggunakan mikroskop polarisasi, refraktometer, TD/DTA, FT-IR dan XRD. Selain itu juga dilakukan identifikasi karakteristik abu gosok, pasir kuarsa dari Pangkalanbun (Kalimantan) dan kuarsa standar serta analisis kimia sekam padi yang meliputi analisis SiO2, Al2O3, K2O, MnO, MgO, CaO, dan C total. Hasil analisis TD/DTA menunjukkan bahwa silika yang dihasilkan dari abu sekam padi hasil pembakaran 400°C, 500°C, 600°C, dan hasil oksidasi H₂O2 mempunyai kurva TD/DTA yang mencerminkan silika amorf, sedangkan silika yang dihasilkan dari abu sekam padi hasil pembakaran 700°C dan 900°C lebih mendekati kurva TD/DTA silika kristalin. Sementara itu hasil analisis FT-IR dan XRD menunjukkan bahwa semua silika yang dihasilkan dari abu sekam padi, baik hasil pembakaran maupun hasil oksidasi H2O2 mempunyai karakteristik yang mencerminkan silika amorf, dan hanya silika yang dihasilkan dari abu sekam padi hasil pembakaran 900°C yang lebih mendekati karakteristik silika kristalin. Pembakaran sekam padi pada suhu 400 °C merupakan suhu yang optimum untuk menghasilkan silika amorf sebagai bahan absorben.
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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