Judul: Peningkatan Keawetan Kayu Kecapi (Sandoricum koetjape Merr) dan Kayu Rambutan (Nephelium spp.L) dengan Pemanasan dalam Minyak serta Pengaruhnya Terhadap Sifat Fisis dan Mekanis Kayu.
Abstrak: INTRODUCTION: Community forest is the alternative of wood resource beside natural forest to fulfill wood demand which tend to increase every year. However, the use of low quality woods from community forest should be improved with proper technology, especially to increase the durability from biodeterioration such as preservation. The process of wood durability improvement is expected to be environmentally safe and affordable for public. In that regard, this study aimed to determine the durability of woods after oil heat treatment, and its effect on the physical properties (weight and density) and mechanical properties (MOE and MOR) of the woods. METHOD: Kecapi wood (Sandoricum koetjape Merr) and rambutan wood (Nepheliumspp) were used in this study and were heated in cooking oil waste at temperatures of 100 oC, 150 oC, and 180 oC for an hour and two hours. After heat treatment, the durability of woods were tested in the field to be exposed to subterranean termites based on graveyard test method (ASTM D 1758-96). The test of wood physical properties (weight and density) and mechanical properties (MOR and MOE) were conducted based on ASTM D 143. RESULT: The results showed that the durability of woods against subterranean termites increased after heat treatment. The durability value of kecapi increased from 4 to 8 by heating at 180 °C for an hour, while the durability value of rambutan increased from 7 to 10 by heating at 100 °C for an hour. Wood heating in oil also significantly increased the weight and density of the two wood species. Generally, the mechanical properties of wood were not significantly influenced by this oil heat treatment, except the MOE of kecapi wood that slightly decreased after the treatment.
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Judul: Sifat Fisis dan Pengeringan Kayu Rambutan, Nangka, dan Kecapi serta Penggunaan Larutan Urea dalam Pengendalian Cacat Pengeringannya.
Abstrak: The use of woods from community forest should be supported by proper technology to produce good products quality and in accordance with their intended uses. One of the factors that influences and being a requirement in wood products is the suitable moisture content to the environmental condition that stabilize the products dimension in the use. Therefore the objectives of this study was to determine the physical properties, drying properties, as well as developing the defects control technique in the drying of rambutan (Nephelium spp), kecapi (Sandoricum koetjapi) and nangka (Artocarpus heterophyllus) woods. The procedures performed in this study consisted of the physical properties testing of woods (BS: 373-1957), the test for basic drying properties based on Terazawa (1965), and drying defects control using saturated urea solution.The results showed that wood with higher density (rambutan) dried more slowly and more prone to defects compared to nangka and kecapi woods, wich had medium and low densities. Rambutan wood had a poor drying properties that was prone to surface cracking. While nangka and kecapi woods had a rather good drying properties. The soaking treatment in saturated urea solution, significantly reduced checking defect in the three tested wood species.
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Judul: Invers Drazin dari Matriks Toeplitz Singular
Abstrak: Matriks Toeplitz adalah matriks yang setiap unsur pada diagonal utama bernilai sama dan setiap unsur pada subdiagonal yang bersesuaian dengan diagonal utama juga bernilai sama. Matriks singular adalah matriks yang tidak bisa ditentukan inversnya. Akan tetapi, dapat diupayakan untuk ditentukan inversnya menggunakan invers matriks yang diperumum. Invers Drazin merupakan salah satu jenis invers matriks yang diperumum. Pada karya ilmiah ini ditentukan invers Drazin dari matriks Toeplitz singular dengan menggunakan metode Leverrier Faddeev. Kemudian, ditentukan invers Drazin dari matriks Toeplitz singular yang direpresentasikan sebagai penjumlahan segitiga bawah dan segitiga atas matriks Toeplitz berdasar pada teorema Gohberg dan Semencul., Toeplitz matrix is a matrix in with element on the main diagonal has the same value and on the subdiagonal corresponding to the main diagonal also has the same value. Singular matrix is a matrix that has no inverse. However, it can be attempted to determine the inverse using a generalized inverse matrix. Inverse Drazin is a type of generalized matrix inverse. This paper discussed the inverse Drazin for a singular Toeplitz matrix using the Leverrier Faddeev method. Then, the Drazin inverse of the singular Toeplitz matrix which is represented as a sum of products of lower and upper triangular Toeplitz matrix based on Gohberg and Semencul theorem.
Keyword: inverse Drazine, singular Toeplitz matrix