Judul: Karakterisasi Komposit Karbon Berbahan Lignin dari Kayu Akasia (Acacia mangium Willd.) dan PET (Polietilena Tereftalat)
Abstrak: Serat Karbon merupakan jenis serat yang mempunyai konduktivitas termal tertinggi dengan bahan baku Polyacrylonitrile (PAN) yang bersifat non-renewable, mahal, tidak ramah lingkungan serta belum dapat di produksi di Indonesia. Lignin dari kayu akasia dan Polietilena Tereftalat (PET) menjadi alternatif pengganti PAN sebagai bahan baku serat karbon yang dapat menurunkan biaya pembuatan dan ramah lingkungan. Penelitian ini bertujuan untuk menghasilkan karbon komposit berbahan lignin kayu akasia dan PET yang murah, ramah lingkungan serta mudah didapatkan hingga mendapatkan rekomendasi produk karbon komposit yang tepat. Karakterisasi dilakukan dengan menggunakan perlakuan kadar lignin dan PET yang berbeda yaitu (Lignin 20% : PET 80%), (Lignin 30% : PET 70%), dan (Lignin 40% : PET 60%) dengan melaui tiga tahapan karakterisasi yaitu pencetakan (L), Stabilisasi (S), dan Karbonisasi (A). Penelitian karbon komposit campuran antara lignin dari kayu akasia dan PET memperoleh hasil yang optimal di setiap pengujian karakterisasi TGA, FE-SEM, XRD, dan FTIR. Namun, pengujian sifat mekanis perlu dilakukan agar dapat menentukan produk yang tepat dari komposit karbon., Carbon fiber has the highest thermal conductivity with raw materials Polyacrylonitrile (PAN), which is non-renewable, expensive, not environmentally friendly, and cannot be produced in Indonesia. Lignin from acacia wood and polyethylene terephthalate (PET) are alternatives to PAN as raw materials for carbon fibers that can reduce manufacturing costs and are environmentally friendly. This study aims to produce carbon composites made from acacia wood lignin and PET that are cheap, environmentally friendly, and readily available to get recommendations for the right carbon composite products. Characterization was carried out using different lignin and PET content treatments, namely (Lignin 20%: PET 80%), (Lignin 30%: PET 70%), and (Lignin 40%: PET 60%), by going through three characterization stages, namely Printing (L), Stabilization (S), and Carbonization (A). The research on carbon composite mixture between lignin from acacia wood and PET obtained optimal results in each TGA, FE-SEM, XRD, and FTIR characterization test. However, mechanical properties testing must be done to determine the right product from the composite carbon.
Keyword: blends, carbon, characterization, lignin, PET

Judul: Surface Modification and Orientation Effects toward Flexibility Increase and Inertia OPEFB Fibers on Sandwich Biocomposite
Abstrak: Ketersediaan serat TKKS di alam cukup melimpah, dimana sifat TKKS dapat dimanfaatkan sebagai pembuatan biokomposit. Biokomposit adalah jenis komposit terdiri dari bahan matriks polimer dan penguat serat alam. Penggabungan material komposit secara berlapis dengan ditambahkan core diantara lapisan dapat menahan beban lentur, impak dan meredam getaran. Tujuan penelitian ini adalah mengetahui pengaruh modifikasi permukaan dan orientasi terhadap kuantitas termal serta fleksibilitas serat, dimana pra-perlakuan delignifikasi dan asetilasi dilakukan untuk menghilangkan kadar lignin serta hemiselulosa, sehingga terjadi modifikasi terhadap permukaan agar memiliki kualitas yang baik dalam penerapannya. TKKS yang diberi perlakuan flame retardant dengan dilapisi CaCO3 atau ATH mampu menahan nyala api hingga mencapai 22.51 ± 9.49 detik. Uji sudut kontak yang dilakukan dengan air menunjukkan serat bersifat hidrofobik pada proses asetilasi dengan nilai sudut 104.08°. Pembuatan biokomposit menggunakan metode hot press dan orientasi berbeda, kemudian dilakukan dengan pengujian sifat mekanik yaitu uji kekerasan, uji impak dan uji tarik., The availability of OPEFB fiber in nature is quite abundant which it can be utilized as a biocomposite. Biocomposite is a type of composite that consist of a polymer matrix material and natural fiber reinforcement. The incorporation of composite materials in layers with the addition of cores between layers can withstand flexural loads, impact and dampen vibrations. This study aims to determine the effect of surface modification and orientation on thermal quantity and fiber flexibility. Delignification and acetylation pre-treatment is necessary to remove lignin and hemicellulose content until becomes modification on the surface to have good quality in its application. OPEFB treated with flame retardant coated with CaCO3 or ATH able to maintain flames up to 22.51 ± 9.49 seconds. The contact angle test carried out with water showed that the fiber was hydrophobic in the acetylation process with an angle value of 104.08°. The manufacture of biocomposites employs the hot press method and different orientations. Afterward, it through the mechanical testing such the hardness test, impact test and tensile test.
Keyword: biocomposite, orientation, OPEFB

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