Judul: Karakteristik cross laminated timber kayu kecapi (Sandoricum koetjape Merr) berdasarkan orientasi sudut lamina
Abstrak: Cross Laminated Timber (CLT) is a multi-layer wooden panel made from lumber. Each layer of boards are placed cross-wise to the adjacent layers for increased rigidity and stability. The objectives of this research is used to determine the magnitude of the influence of orientation angle of the lamina of the mechanical and physical properties of cross laminated timber panels from kecapi wood (Sandoricum koetjape Merr) by using isosianat adhesive. The CLT panel was made from kecapi wood with 15 cm in thickness (five layers) from the board with 3 cm x 18 cm x 150 cm in size and orientation angle 450 and 900. The adhesive was used isosianat with surface weight 280 g/m³. Testing of the physical properties of CLT consist of moisture content, density, shrink/swelling and delamination test. Otherwise testing of mechanical properties of CLT include bonding strength and racking test. Result of racking test show that CLT’s stiffness at 450 angle larger than 900 angle; likewise, the strength of CLT show that at 450 angle stronger than 900 angle.
Keyword: Bogor Agricultural University (IPB), angle orientation., isosianat, kecapi wood, cross laminated timber

Judul: Karakteristik Cross Laminated Timber Kayu Jabon berdasarkan Ketebalan dan Orientasi Sudut Lamina
Abstrak: Along with the technological developments, a new method of laminated timber has been found, called by cross laminated timber (CLT). CLT is an engineered product of wood composed of some lamina or layers bonded in an arrangement of layers crossing one another. The purpose of this research was to design a panel of CLT by modifying the combined patterns of different thickness and orientation angles of lamina in order to have the highest strength values and determine the characteristics of CLT panels as structural timber. The study results are expected to provide alternative benefits or uses of wood from the community forests as a product of CLT, give information to the people about the quality of CLT panel from the community forest and increase the chance of timber development from the community forests for structural wood products. The thickness of lamina applied in the manufacture of CLT panels were 1.0, 1.67, 2.0 and 3.0 cm with the width of 15 cm and the length of 120 cm. CLT panel was formed of three layers or lamina with the cross-sectional size of 5 cm x 15 cm x 120 cm based on the value of its MOE with three types of combination in lamina thickness, namely type A1 (1 cm, 3 cm, and 1 cm), type A2 (1 cm, 2 cm, and 1 cm), and type A3 (1.67 cm, 1.67 cm, and 1.67 cm). The middle layer was based on the orientation angles of lamina: 0°, 30°, 45°, 60°, and 90°. The adhesive used was water based polymer isocyanate (WBPI) with the glue spreading of 280 g/m2 for both surfaces. Testing was based on ASTM D 143 (2005) and JAS 234:2003 standard. The result showed that the combined thickness of lamina had a significant effect on the mechanical properties of MOE, MOR and compressive strength parallel to fibers on CLT panels. The lamina orientation angles had a significant effect on the physical properties of volume shrinkage and expansion on CLT panels. On the other hand, as for the mechanical properties, the angle orientation of lamina showed a significant effect on MOE, MOR, compressive strength parallel to fibers, and the bonding strength of CLT panels. The interaction between a combined thickness of lamina and angle orientation only significantly influenced the compressive strength parallel to fibers of CLT panels. Meanwhile, based on the scoring of CLT panel, the combined thickness of lamina type A3 and the angle orientation of 30o had the best properties. This is because the number of connections on the angle orientation of 30o Key words: Cross laminated timber, jabon wood, physical and mechanical properties, less than those of other angle orientations. The resulted analysis of the whole or intact timber (control) showed that in general CLT panels have better properties of volume shrinkage and expansion than the intact original timber.
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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