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: The Effect of Impregnation Time and Polymerization Temperature of Calcium Carbonate (CaCO3) on the Physical Mechanical Properties of Mineralized Sengon Wood
Abstrak: Sengon merupakan salah satu jenis kayu yang ditanam di hutan tanaman dan termasuk ke dalam jenis kayu cepat tumbuh (fast growing). Penelitian bertujuan mengidentifikasi keefektifan mineralisasi menggunakan metode impregnasi kalsium karbonat terhadap sifat fisis dan mekanis kayu sengon. Variasi perlakuan yang diberikan yaitu waktu impregnasi dan suhu polimerisasi. Penelitian dilakukan dengan metode impregnasi CaCl2 dan Na2CO3 yang diimpregnasi dengan tekanan 0,5 MPa. Hasil penelitian menunjukkan bahwa peningkatan waktu impregnasi dan suhu dapat meningkatkan nilai sifat fisis, mekanis, dan uji warna. WPG meningkat sebesar 27,78% pada suhu 100 °C. Nilai kerapatan tertinggi sebesar 0,51 g/cm3. MOEd dan MOEs menunjukan tren yang meningkat seiring dengan bertambahnya waktu impregnasi. Kuat tekan sejajar serat meningkat hingga 67,03% pada suhu 100 °C. Nilai perubahan warna (?E) menunjukkan peningkatan signifikan dengan intensitas pemanasan yang lebih tinggi, menunjukkan warna kayu menjadi lebih gelap. Hasil penelitian menunjukkan bahwa impregnasi dengan CaCO3 dan pemanasan dapat meningkatkan sifat mekanis dan fisik kayu sengon, menjadikannya lebih stabil dan kuat., Sengon is one of the types of wood planted in plantation forests and is classified as a fast-growing wood. This study aims to identify the effectiveness of mineralization using the calcium carbonate impregnation method on the physical and mechanical properties of sengon wood. The treatment variations given include impregnation time and polymerization temperature. The study was conducted using CaCl2 and Na2CO3 impregnation methods under a pressure of 0,5 MPa. The results showed that increasing impregnation time and temperature could enhance the physical, mechanical properties, and color test values. Weight Percent Gain (WPG) increased by 27,78% at a temperature of 100 °C. The highest density value was 0,52 g/cm³. Both modulus of elasticity in dynamic (MOEd) and static (MOEs) showed an increasing trend with longer impregnation times. Compressive strength parallel to the grain increased by up to 67,03% at 100 °C. The color change value (?E) showed a significant increase with higher heating intensity, indicating the wood became darker. The study results indicate that impregnation with CaCO3 and heating can improve the mechanical and physical properties of sengon wood, making it more stable and stronger.
Keyword: MOEd, WPG, compressive strength, mineralization, vacuum-press

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