Judul: Characteristics of Rotary-cut Veneer of Boiled Jabon and Sengon Logs.
Abstrak: Fast growing Jabon and Sengon are largely rotary-cut to produce veneer for plywood, com-ply and LVL. In order to provide better information on veneer production and utilization, the effects of wood juvenility and veneer thickness on lathe checks of Jabon and Sengon rotary-cut veneer were evaluated. Before peeling, jabon and sengon log were boiled at 50 and 75 oC for 4 and 8 hours, respectively. The boiled logs were peeled to produce veneer of 1.0, 1.5 and 2.0 mm in thickness. Lathe checks of veneers were measured under an optical video microscope. The rotary-cut veneer was grouped and evaluated separately at every segmented of 1.0 cm width from bark to pith. Results showed that wood juvenility and veneer thickness had an important effect on lathe checks for the rotary-cut veneer. In general, the number of lathe check of the veneer increases with increasing veneer thickness and decrease from pith to bark. Boiling of logs before rotary-cutting could decrease the value of lathe check. The results indicated that boiling of logs at 75 oC for 4 and 8 hours could minimize the number of lathe checks in manufacturing of 1.0, 1.5 and 2.0 mm rotary-cut veneer from juvenile jabon and sengon woods.
Keyword: Boiling, jabon, juvenility, lathe check, sengon, thickness variation

Judul: Pengaruh Perlakuan Perebusan dan Variasi Ketebalan Vinir terhadap Karakteristik Vinir Lamina Kayu Sengon (Falcataria moluccana (Miq.) B. Grimes)
Abstrak: Sengon is a wood species mostly planted in a community forest. Sengon-wood is a fast-growing species with small-diameter. The whole part of sengon-wood consisted a juvenile wood at the age up to five years. At present, sengon-wood utilization is limited for packaging so that it needs to be further developed into other products such as LVL (Laminated Veneer Lumber). This study was conducted to analyze the effect of boiling treatments on sengon-wood and veneer thickness on the characteristics of LVL. The LVL characteristics tested were moisture content, density, specific gravity, volume shrinkage, bonding strength, and bending strength of LVL (Laminated Veneer Lumber). This study used the modified JAS SE-11 2003 and SNI 01-6240-2000. LVL moisture content of less than 14 % was obtained. Value of physical properties (density, specific gravity, and volume shrinkage) were 0.30 – 0.44 g/cm2, 0.24 – 0.37, dan 4.34 – 6.29 %, respectively. Value of mechanical properties (bonding strength, MOE, and MOR) were 18.04 – 45.77 kg/cm2, 27755.47 – 5.9487.62 kg/cm2 dan 100.24 – 423.59 kg/cm2, respectively. Generally, the LVL made of veneers sengon with boiling treatment on 75 oC for 8 hours and 1 mm veneer thickness had better physical and mechanical characteristics than the other treatments
Keyword: veneer thickness., sengon wood, LVL, isocyanate, boiling treatments

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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