Judul: Peningkatan Nilai Tambah Limbah Produksi Minyak Kelapa Sawit Sebagai Bahan Baku Beton
Abstrak: Peningkatan luas perkebunan kelapa sawit di Indonesia diikuti dengan peningkatan produksi dan jumlah limbah kelapa sawit. Salah satu limbah produksi minyak kelapa sawit dihasilkan dari proses pemurnian crude palm oil (CPO) yaitu spent bleaching earth (SBE). Penelitian ini akan memanfaatkan limbah spent bleaching earth (SBE) sebagai bahan substitusi pasir pada pembuatan beton. Penambahan serat alam dari limbah tandan kosong kelapa sawit (TKKS) pada pembuatan beton diharapkan dapat menambah kekuatan mekanik beton berbahan dasar spent bleaching earth yang memenuhi syarat SNI. Proses pembuatan beton dimulai dengan mencampurkan semua bahan, pengadukan, pencetakan, pemadatan secara maual dan perawatan selama 28 hari. Pembuatan beton dilakukan dengan mensubstitusi SBE sebesar 10%, 30% dan 50% dan serat sebanyak 2%, 4% dan 6%. Substitusi SBE dapat menurunkan kekuatan beton sedangkan substitusi serat TKKS dapat meningkatkan kekuatan beton.
Keyword: Spent bleaching earth, beton, tandan kosong kelapa sawit

Judul: Formulasi Paving block dari Berbagai Bahan Berbasis Limbah Padat Spent bleaching earth
Abstrak: Spent bleaching earth (SBE) is a solid waste produced by refinery of crude palm oil industry. Utilization of SBE as a substitution material of paving sand is one alternative that can be applied SBE utilization. The research was expected to outcome formulation and determines the best type of material in paving blocks manufacture. The process began by mixing all ingredients, forming and compaction. Compaction method used in this research was conducted manually. The best mixing formulation was obtained by performing some variation of materials usages, such as sand and SBE 0, SBE1 and RSBE. Comparisons of percentage concentration between SBE 0/SBE 1/RSBE and sand were (0% : 100%), (20% : 80%), (40% : 60%), (60% : 40%), (80% : 20%) and (100% : 0%). Paving blocks formulation of A1B1 (20% SBE 0 : 80% sand) was the best formulation obtained in this study. It was proven by the value of compressive strength of 15:34 MPa, water absorption of 2.66 % and there was no defect in the testing of its resistance to sodium sulfate and thermal conductivity value of 0.5882 (W/mK).
Keyword: Formulation, Paving block, Spent bleaching earth

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