Judul: Nilai Kalor Kayu yang Memiliki Kerapatan dan Kadar Lignin Berbeda
Abstrak: Wood is one of the biomass that can be used for alternative energy resources. However, calorific value of wood varies depending on its physical and chemicals properties. This research aims to analyze the effect of density and lignin content on calorific value of wood. Characterization of wood as an energy resource was examined by proximate analysis. Total lignin content of wood was measured by Klason lignin and acid soluble lignin content. The results showed that there was a high correlation between calorific value with wood density, total lignin content, and Klason lignin (r=0.96, r=0.71, and r=0.83, respectively). Based on the proximate analysis, the examined wood species have moisture content in range of 6.64 – 11.09%, volatile matter content 79.32 – 84.08%, ash content 0.31 – 1.18%, fixed carbon 15.27 – 20.37%, and calorific value of 4243– 4576 kcal/kg. Jati, ulin, merbau, and mahoni woods which have high density and lignin content were very good materials for biomass energy. However, jabon and balsa seemed that have very low density causing it has bulky characteristics.
Keyword: wood biomass energy, proximate analysis, lignin content, density, calorific value

Judul: Kadar Zat Ekstraktif dan Nilai Kalor Kayu yang Berbeda Kerapatan
Abstrak: Kayu merupakan salah satu biomassa yang dapat digunakan sebagai sumber energi alternatif terbarukan. Nilai kalor kayu dipengaruhi oleh banyak faktor antara lain kerapatan dan sifat kimia kayu. Penelitian ini menjelaskan pengaruh kadar zat ekstraktif terhadap nilai kalor enam jenis kayu yang berbeda kerapatan. Karakteristik kayu sebagai bahan energi diuji dengan analisis proksimat. Kadar zat ekstraktif kayu dinyatakan sebagai kelarutan dalam ekstraksi etanol/benzena diikuti dengan ekstraksi air panas. Hasil analisis proksimat menunjukkan keenam jenis kayu yang diuji memiliki nilai kadar air 6.64–11.09%, kadar zat terbang 79.91–84.45%, kadar abu 0.32–1.18%, kadar karbon terikat 15.10–19.74%, dan nilai kalor 4243–4576 kkal/kg. Kadar zat ekstraktif berpengaruh terhadap nilai kalor kayu dengan korelasi positif yang tinggi (R² = 0.81). Hal tersebut diduga berkaitan dengan pengaruh positif zat ekstraktif terhadap kerapatan dan kadar karbon terikat. Zat ekstraktif terlarut etanol/benzena pada enam jenis kayu berkontribusi antara 4.34–12.47% terhadap nilai kalor kayu.
Keyword: ekstraktif, nilai kalor, kerapatan kayu, analisis proksimat

Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
Keyword: