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: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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