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: . The effect of boiling treatment and veneer thickness on the characteristics of laminated veneer lumber (lvl) of jabon wood (anthocephalus cadamba miq)
Abstrak: Jabon (Anthocephalus cadamba Miq) merupakan jenis cepat tumbuh yang ketesediaannya menjanjikan sebagai bahan baku industri kayu. Namun kayu jabon memiliki sifat fisis dan mekanis yang buruk sebagai kayu solid, sehingga penggunaannya di industri kayu terbatas. Salah satu upaya untuk mengatasi permasalahan penggunaan kayu solid jabon yang terbatas adalah dengan mengolahnya sebagai vinir lamina. Penelitian ini bertujuan untuk menentukan pengaruh perlakuan perebusan log sebelum pengupasan yang dikombinasikan dengan variasi tebal vinir terhadap karakteristik vinir lamina dari kayu jabon. Karakteristik vinir lamina yang diuji berupa sifat fisis serta sifat mekanis. Pengujian pada penelitian ini mengacu pada JAS SE-11 2003 dan SNI 01-6240-2000. Hasil penelitian menunjukkan bahwa perlakuan perebusan yang dikombinasikan dengan variasi ketebalan vinir menggunakan perekat isosianat dapat memperbaiki sifat fisis maupun mekanis vinir lamina kayu jabon. Perlakuan perebusan kayu bulat sebelum pengupasan selama 8 jam pada air bersuhu 75°C dari vinir setebal 1 mm menghasilkan vinir lamina dengan kadar air, kerapatan, susut volume, keteguhan rekat, MOE, dan MOR yang lebih baik daripada vinir lamina dengan perlakuan lainnya., Jabon (Anthocephalus cadamba Miq) is a fast growing species which has promising availibility as raw material for wood industries. However, jabon has inferior mechanical and physical properties as solid wood, which makes limited utilization from it’s wood. In order to improve the utilization of jabon wood, this study made laminated veneer lumber from it.. The objective of this study is to determine physical and mechanical characteristics of LVL made of treated rotary cut jabon veneer. This research reffered to JAS SE-11 2003 and SNI 01-6240-2000. The results showed that treated jabon’s LVL made of logs heated by 75°C in 8 hours with 1 mm thickness compiler veneers has the best moisture content, density, volume shrinkage, glue bond, MOE, and MOR amongst the other treatments.
Keyword: kayu jabon, perebusan, tebal vinir, vinir lamina, LVL

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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