Judul: Addition of Coconut Coir Fiber Bio-admixture on the Physical and Mechanical Properties of Concrete
Abstrak: Admixture merupakan bahan yang ditambahkan kedalam campuran beton untuk mengubah sifat-sifat beton sesuai dengan tujuan yang diinginkan. Selama ini admixture yang digunakan dalam pembuatan beton terbuat dari bahan kimia yang memiliki dampak negatif bagi lingkungan. Salah satu serat alam yang ketersediaannya melimpah di Indonesia yaitu sabut kelapa. Pemanfaatan serat sabut kelapa sebagai admixture merupakan salah satu cara untuk mengurangi dampak negatif admixture berbahan kimia terhadap lingkungan serta meningkatkan nilai tambah dari sabut kelapa. Pemanfaatan serat karbon sabut kelapa sebagai bio-admixture merupakan salah satu inovasi pemanfaat serat alam. Penambahan bio-admixture serat karbon sabut kelapa pada beton dinilai dapat mengubah sifat fisis dan mekanis beton. Penelitian ini bertujuan untuk melihat pengaruh penambahan bio-admixture serat karbon sabut kelapa terhadap sifat fisis dan mekanis beton. Hasil penelitian menunjukkan karakteristik serat karbon sabut kelapa seperti kadar air dan kadar abu telah memenuhi standar SNI 06-3730-1995. Penambahan serat karbon sabut kelapa secara keseluruhan menurunkan nilai kerapatan dan kuat tekan beton. Namun penambahan serat dengan persentase 1,5%, suhu hydrothermal 150 oC, dan ukuran serat 60-100 mesh dapat meningkatkan kuat tekan beton sebesar 3,22%., Admixture is a material added to concrete mixture to change the properties of the concrete according to the desired purpose. Most admixtures are chemical based which have a negative impact on the environment. Utilization of coconut coir fiber as an admixture is one way to reduce the negative impact of chemical admixtures on the environment and increase the added value of coconut coir. Utilization of coconut coir carbon fiber as a bio-admixture is one of the innovations to utilize natural fiber. This study aims to examine the effect of the addition of coconut coir carbon fiber bio-admixture on the physical and mechanical properties of concrete. The results showed that the characteristics of coconut coir fiber carbon fiber such as water content and ash content met the SNI 06-3730-1995 standard. In general the addition of the coconut coir carbon fiber lowered the density and compressive strength of concrete. However the addition of fiber with a percentage of 1.5%, hydrothermal temperature of 150oC, and fiber size of 60-100 mesh increase the compressive strength of the concrete by 3.22%.
Keyword: bio-admixture, concrete, natural fiber, coconut coir

Judul: Coconut Coir Polymer Composites at Various Catalyst Content and Alkalisaton Time
Abstrak: Material komposit berpenguat serat alam mulai dikembangkan sebagai alternatif komposit fiberglass. Sabut kelapa berpontensi dijadikan sebagai penguat komposit polimer. Sifat hidrofilik menjadi kelemahan komposit berpenguat serat alam. Alkalisasi dan penambahan katalis dilakukan untuk meningkatkan kekuatan mekanis dan stabilitas dimensi komposit berpenguat serat alam. Penelitian ini bertujuan menganalisis pengaruh waktu alkalisasi dan kadar methyl ethyl ketone peroxide sebagai katalis terhadap sifat fisis dan mekanis papan. Papan komposit dibuat dengan target kerapatan 1 g/cm3 menggunakan serat yang diberi perlakuan alkalisasi 2, 4, 6, dan 8 jam dengan NaOH 5% serta penambahan katalis 2,4, dan 6%. Hasil penelitian menunjukkan kerapatan papan, nilai keteguhan lentur dan keteguhan patah meningkat dengan adanya peningkatan waktu alkalisasi dan penambahan kadar katalis. Waktu alkalisasi lebih dari 4 jam dan penambahan kadar katalis lebih dari 4% dapat menurunkan kekuatan mekanis papan komposit. Secara umum papan komposit polimer sabut kelapa memenuhi SNI 8154-2015. Papan komposit terbaik diperoleh dari perendaman alkalisasi 4 jam dan kadar katalis 2%., Natural fiber reinforced composite materials began to be developed as an alternative to fiberglass composites. Coconut fiber has the potential to be used as a polymer composite reinforcement. Hydrophilic nature is the weakness of natural fiber reinforced composites. Alkalization and catalyst addition were carried out to improve the mechanical strength and dimensional stability of natural fiber reinforced composites. This study aims to analyze the effect of alkalization time and methyl ethyl ketone peroxide content as catalys on the physical and mechanical properties of the board. Composite boards were made with a target density of 1 g/cm3 using fibers treated with 2, 4, 6, and 8 hours of alkalization with NaOH 5% and 2, 4, and 6% catalyst addition. The results showed that the board density, flexural and fracture strength values increased with an increase in alkalization time and the addition of catalyst content. Alkalization time of more than 4 hours and the addition of catalyst content of more than 4% can reduce the mechanical strength of the composite board. In general, the coconut fiber polymer composite board meets SNI 8154-2015. The best composite board was obtained from 4 hours alkalization soaking and 2% catalyst content.
Keyword: sifat fisis, sifat mekanis, Alkalisasi, Katalis

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