Judul: The effect of calcium carbonate concentration variation on the physical and mechanical properties of mineralized sengon wood (Paraserianthes falcataria (L.) Nielsen)
Abstrak: Kayu Sengon merupakan golongan kayu kelas awet IV-V dan kelas kuat IV-V maka mudah diserang organisme perusak seperti jamur dan serangga. Penelitian sebelumnya menyebutkan bahwa jenis kayu cepat tumbuh dapat menggantikan kayu hutan alam (rotasi panjang) dengan dilakukan pengawetan dan mineralisasi. Peningkatan sifat fisis dan mekanis kayu sengon akibat mineralisasi oleh larutan kalsium karbonat (CaCO3) dapat dilakukan sebagai alternatif untuk menambah nilai jual kayu sengon di pasaran. Hasil penelitian menunjukkan proses mineralisasi dengan menggunakan CaCO3 terbukti meningkatkan nilai sifat fisis dan mekanis pada kayu sengon. Penelitian ini bertujuan untuk mengetahui efektivitas dari penambahan CaCO3 kedalam kayu terhadap ketahanan sifat fisis, mekanis, dan anatomi serta mengetahui konsentrasi optimum dari kalsium karbonat. Kayu sengon di impregnasi dua kali menggunakan kalsium klorida (CaCl2) dan kalsium karbonat (K2CO3) dengan tiga variasi konsentrasi (0.5, 1 dan 2 mol/L). Konsentrasi optimum untuk meningkatkan sifat fisis dan mekanis pada penelitian ini ditunjukkan oleh larutan impregnasi 0.5 mol/L., Sengon wood falls into the durability class IV-V and strength class IV-V, making it susceptible to destructive organisms such as fungi and insects. Previous studies have indicated that fast-growing species of wood can replace long-rotation natural forest wood with proper preservation and mineralization. Enhancing the physical and mechanical properties of sengon wood through mineralization with calcium carbonate (CaCO3) solution can be an alternative to increase the market value of sengon wood. Research results show that the mineralization process using CaCO3 significantly improves the physical and mechanical properties of sengon wood. This study aims to determine the effectiveness of adding CaCO3 to the wood on the resistance of its physical, mechanical, and anatomical properties and to identify the optimum concentration of calcium carbonate. Sengon wood was impregnated twice using calcium chloride (CaCl2) and calcium carbonate (K2CO3) with three concentration variations (0.5, 1, and 2 mol). The optimum concentration for improving the physical and mechanical properties in this study was shown by the 0.5 mol impregnation solution.
Keyword: sengon, CaCO3, kayu mineralisasi, sifat fisis, mekanis kayu

Judul: The Effect of Calcium Carbonate (CaCO3) Impregnation Pressure Variation on the Physical and Mechanical Properties of Mineralized Sengon Wood.
Abstrak: Kayu sengon (Paraserianthes falcataria (L.) Nielsen) dikenal sebagai kayu cepat tumbuh dengan kerapatan, kekerasan, dan kekuatan rendah. Penelitian ini bertujuan meningkatkan kualitas kayu sengon melalui mineralisasi menggunakan kalsium karbonat (CaCO3) dengan variasi tekanan dan jenis kayu (gubal dan teras). Impregnasi dilakukan dalam dua tahap menggunakan larutan natrium hidroksida (NaOH), kalsium klorida (CaCl2), dan natrium karbonat (Na2CO3). Pengujian mencakup sifat fisis (kadar air, kerapatan, berat jenis, Anti-Swelling Efficiency) dan sifat mekanis (modulus elastisitas dinamis, modulus elastisitas statis, modulus patah, tekan sejajar serat, kekerasan, dan uji warna kayu). Hasil penelitian menunjukkan bahwa terjadi peningkatan signifikan pada sifat fisis dan mekanis kayu sengon setelah mineralisasi. Kerapatan kayu mencapai 0,51 g/cm
Keyword: sengon, mineralization wood, calcium carbonate

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