Judul: Resistance of Mangium Wood Glulam (Acacia  mangium Willd.) Impregnated with Polystyrene against Subterranean Termites through  Graveyard Test
Abstrak: Glulam merupakan produk rekayasa alternatif yang ditujukan untuk memaksimalkan penggunaan kayu berdiameter kecil. Glulam berbahan baku kayu cepat tumbuh seperti mangium (Acacia mangium Willd.) perlu dimodifikasi untuk meningkatkan ketahanannya terhadap organisme perusak kayu. Impregnasi menggunakan polistirena dapat meningkatkan ketahanan kayu. Penelitian ini bertujuan menganalisis ketahanan glulam kayu mangium terimpregnasi polistirena terhadap rayap tanah melalui uji kubur selama 4 bulan. Impregnasi dilakukan dengan metode vakum tekan. Uji kubur dilaksanakan berdasarkan SNI 7207: 2014 dan ASTM D 1758-06.Glulam terimpregnasi polistirena memiliki nilai rata-rata polymer loading sebesar 5,25%, kadar air 13,83%, dan kerapatan 0,71 g/cm3. Setelah dilakukan uji kubur, nilai rata-rata kehilangan berat solid mangium, glulam kontrol, dan glulam polistirena berturut-turut sebesar 9,31%, 0,99%, dan 0,31%. Sementara itu, tingkat ketahanan berturut-turut sebesar 7,33; 7,33; dan 8,67. Secara keseluruhan, glulam polistirena memiliki ketahanan terhadap rayap tanah yang lebih baik dari kayu solid dan glulam kontrol., Glulam is an alternative engineering product aimed at maximizing the use of small-diameter wood. Glulam made from fast-growing wood such as mangium (Acacia mangium Willd.) needs to be modified to increase its biodeterioration resistance. The impregnation method using polystyrene can increase wood resistance. This study purposes to analyze the resistance of glulam mangium impregnated with polystyrene through the graveyard test for 4 months. The impregnation used the vacuum-pressed method. The graveyard test referred to SNI 7207:2014 and ASTM D 1758-06. Polystyrene glulam had average polymer loading of 5.25%, moisture content of 13.83%, and density of 0.71 g/cm3. After the graveyard test, the average weight loss of solid wood, glulam (untreated), and polystyrene glulam were 9,31%, 0,99%, and 0.31%. Meanwhile, the protection level were 7,33; 7,33; and 8.67. Overall polystyrene glulam had higher resistance against subterranean termites than solid wood and glulam (untreated).
Keyword: glulam, impregnation, mangium, polystyrene, wood resistance

Judul: Resistance of Rubberwood Glulam (Hevea brasiliensis Muell. Arg) Impregnated with Polystyrene to Subterranean Termites in Field Test
Abstrak: Kayu karet (Hevea brasiliensis Muell. Arg) ini termasuk ke dalam kelas awet V dimana rentan terhadap serangan organisme perusak kayu, sehingga ketahanannya perlu untuk ditingkatkan. Penelitian ini bertujuan untuk menganalisis pengaruh perlakuan impregnasi polistirena pada ketahanan glulam karet terhadap serangan rayap tanah setelah pengujian lapangan (field test) selama 4 bulan. Karakteristik glulam polistiren memiliki nilai rata-rata polymer loading sebesar 6,89%, kerapatan 0,71 g cm-3 dan kadar air 14,07%. Setelah dilakukan uji lapang, solid karet, glulam kontrol dan glulam polistiren masing-masing memiliki rata-rata nilai kehilangan berat sebesar 20,14%; 24,38%; dan 24,02% dengan rata-rata nilai ketahanannya terhadap rayap tanah sebesar 7,33; 7,33; dan 7,00. Hasil tersebut menunjukkan bahwa teknik glulam dan impregnasi polistirena yang diterapkan kurang efektif untuk meningkatkan ketahanan kayu awal (solid) terhadap serangan rayap tanah. Hal ini disebabkan karena nilai polymer loading yang kecil, sehingga perlu ditingkatkan agar ketahanannya juga dapat meningkat., Rubberwood (Hevea brasiliensis Muell. Arg) resistance is categorized as class V, susceptible to be attacked by destructive organisms. However, this resistance property can be improved through several actions. This study aims to analyze the effect of polystyrene impregnation on rubberwood glulam resistance to subterranean termites attack after field tests for 4 months. The polystyrene glulam had an average polymer loading of 6,89%, density of 0,71 g cm-3 and moisture content of 14,07%. After field testing, solid rubber, control glulam and polystyrene glulam each had an average weight loss value of 20,14%, 24,38% and 24,02% with an average of resistance to subterranean termites value of 7,33, 7,33 and 7,00. These results indicate that the polystyrene glulam technique has a less effective effect on increasing the resistance of solid wood to subterranean termites. This was due to the low polymer loading, which was important to be optimized in order to increase the wood resistance.
Keyword: glulam, impregnation, polystyrene, rubberwood, wood resistance

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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