Judul: Sifat Fisis, Mekanis dan Karakterisasi Magnetik Kayu Sengon (Falcataria moluccana Miq.) Terimpregnasi Nano Magnetit (Fe3O4) Sintesis dan Komersial
Abstrak: Sengon merupakan kayu cepat tumbuh yang memiliki beberapa kelemahan. Dalam rangka meningkatkan kualitas kayu sengon, terdapat beberapa perlakuan yang dapat meningkatkan kualitas kayu, salah satunya dengan cara metode impregnasi menggunakan nano magnetit (Fe3O4). Penelitian ini bertujuan menganalisis pengaruh perlakuan impregnasi menggunakan partikel nano magnetit komersial dan sintesis terhadap sifat fisis dan mekanis kayu sengon hasil impregnasi dan mengkarakterisasi kayu sengon magnetik. Hasil pengujian menunjukkan bahwa kerapatan, weight percent gain, dan kekerasan kayu sengon hasil impregnasi nano magnetit sintesis dan komersial tidak berbeda nyata. Sedangkan perubahan warna kayu hasil impregnasi nano magnetit sintesis dan komersial menunjukkan perbedaan yang nyata. Hasil pengujian vector network analyzer menunjukkan bahwa kayu sengon yang diberi perlakuan nano magnetit sintesis 2,5% memiliki daya serap yang lebih tinggi dalam menyerap gelombang elektromagnetik dibanding dengan nano magnetit komersial., Sengon is a fast-growing wood which has several drawbacks. In improving the qualities of sengon wood, there are several treatments that can improve the quality of wood, one of which is the impregnation method using nano magnetite (Fe3O4). This study aimed to analyze the effect of impregnation treatment using commercial and synthetic magnetite nanoparticles on the physical and mechanical properties of impregnated sengon wood and to characterize magnetic sengon wood. The test results showed that the density, weight percent gain and hardness of sengon wood from synthetic and commercial nano magnetite impregnation were not significantly different. Meanwhile, the color change of wood from synthetic and commercial nano magnetite impregnation showed a significant difference. The results of the vector network analyzer test showed that treated sengon wood with 2,5% synthetic nano magnetite had a higher absorption capacity in absorbing electromagnetic waves than commercial nano magnetite.
Keyword: commercial, impregnation, nanoparticle, sengon, synthesis

Judul: Dimensional Stability and Magnetic Characterization of Sengon Wood Impregnated by Synthesized Magnetite Nanoparticles (Fe3O4)
Abstrak: Sengon merupakan salah satu jenis kayu cepat tumbuh, namun memiliki karakteristik yang inferior sehingga diperlukan modifikasi kayu untuk meningkatkan kualitas dan memperluas penggunaan kayu. Penelitian ini bertujuan untuk menganalisis pengaruh impregnasi nano magnetit hasil sintesis eksitu terhadap stabilitas dimensi dan kemagnetan kayu sengon magnetik dan mengkarakterisasi kayu sengon hasil impregnasi partikel nano magnetit (Fe3O4) dengan dispersan furfuryl alcohol (FA) dan air demineralisasi, serta menentukan perlakuan yang terbaik untuk meningkatkan kualitas kayu sengon. Sintesis nano magnetit diawali dengan pencampuran FeCl2 dan FeCl3 menggunakan prekursor NH4OH. Kemudian nano magnetit dicampurkan menggunakan dispersan menjadi larutan impregnasi dengan 8 perlakuan konsentrasi yaitu tanpa perlakuan, KM 7,5%, KM 10%, dan KM 12,5%, KFA, KMFA 7,5%, KMFA 10%, dan KMFA 12,5%. Proses impregnasi dilakukan dengan pemberian vakum 0,5 bar selama 30 menit dan tekan 1 bar selama 120 menit. Hasil penelitian menunjukkan bahwa perlakuan memberikan pengaruh yang nyata terhadap stabilitas dimensi kayu sengon hasil impregnasi. Keberadaan Fe yang terdeposit di dalam rongga dan dinding sel kayu terlihat pada analisis Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDX). Hasil analisis Fourier Transform Infrared Spectrometry (FTIR), menunjukkan adanya gugus fungsi Fe-O (magnetit). Analisis X-ray Diffraction Analysis (XRD) memperlihatkan penurunan persentase derajat kristalinitas dan adanya puncak khas magnetit. Hasil analisis Vibrating Sample Magnetometry (VSM) menyimpulkan bahwa kayu sengon magnetik memiliki sifat superparamagnetik dan digolongkan dalam jenis soft magnetic materials. Berdasarkan hasil pengujian, FA lebih cocok digunakan sebagai dispersan dengan konsentrasi 10% sebagai hasil yang terbaik untuk memperoleh kayu sengon magnetik dengan stabilitas dimensi dan magnetik yang baik., Sengon is one of the fast-growing woods, however it has inferior characteristics, thus requiring wood modification to enhance its quality and expand its utilization. This research aims to analyze the effect ex-situ synthesized magnetite nanoparticles impregnation on the dimensional stability and magnetic properties of magnetic sengon wood and to characterize impregnated sengon wood with magnetite nanoparticles (Fe3O4) using furfuryl alcohol (FA) and demineralized water as dispersant. The research also aims to determine the best treatment for enhancing the quality of sengon wood. The synthesis of magnetite nanoparticles begins with the mixing of FeCl2 and FeCl3 using NH4OH as a precursor. The magnetite nanoparticles is then mixed with dispersants to create an impregnation solution with 8 treatments, consisting of untreated, KM 7.5%, KM 10%, dan KM 12.5%, KFA, KMFA 7.5%, KMFA 10%, and KMFA 12.5%. The impregnation process involves applying a vacuum of 0.5 bar for 30 minutes and a pressure of 1 bar for 120 minutes. The results showed impregnation treatment had a significant effect on dimensional stability of treated sengon wood. The presence of deposited Fe within the wood cell walls and cavities are observed by Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDX) analysis. Fourier Transform Infrared Spectrometry (FTIR) analysis indicates the presence of Fe-O functional groups (magnetite). X-ray Diffraction (XRD) analysis reveals a degree of crystallinity decrease and the presence of distinct magnetite peaks. Based on Vibrating Sample Magnetometry (VSM) analysis, sengon magnetic wood has superparamagnetic properties and soft magnetic materials category. Based on the results, FA is more suitable as a dispersant at a 10% concentration as the best result for obtaining
Keyword: dimensional stability, dispersant, impregnation, magnetite nanoparticles, sengon

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