Judul: Karakterisasi Limbah Abu Batubara (Fly Ash dan Bottom Ash) untuk Pemanfaatan dalam Bidang Pertanian
Abstrak: The use of coal as a fuel would produce solid waste such as fly ash and bottom ash which haven’t been widely used especially in agricultural sector. This is because government regulation No. 85th (1999), coal ash waste classified as hazardous waste. The objective of this research was to study the characteristic of coal ash waste from two different sources, as the basis for the utilization for agricultural sector development. The characteristic test of coal ash waste done through with several chemical analysis namely total chemical analysis, analysis of heavy metals content by TCLP (Toxicity Characteristic Leaching Prosedure) which refers to the USEPA (1992), pH (H20 1:5), and solubility of macro and micro nutrients. The total chemical showed that fly ash and bottom ash contain several nutrients so that it could be used as an amelioran. In addition fly ash and bottom ash also contain Pb, Cd, Cu, Zn, Cr, and Hg. However, TCLP test showed that the heavy metal content of fly ash from PLTU Nagan Raya and PT. Pupuk Kaltim were lower than the standard of TCLP according to USEPA (1992) and government regulation No. 85th (1999). The result of the pH measurement showed that the coal ash from the PLTU Nagan Raya, Aceh was alkaline in that pH value of fly ash and bottom ash were 8.9 and 8.0 respectively. While the pH value of fly ash from PT. Kaltim was 5.1. The results of the solubility test generally showed that the Ca and Mg elements were higher than that of K, Na, Fe and Mn. Moreover, there were other elements including Cu, Zn, Pb and Cd found in low concentration.
Keyword: TCLP test, fly ash, bottom ash

Judul: Unsur-unsur yang dibebaskan dari proses pencucian abu terbang (fly ash) dari PLTU Suralaya
Abstrak: Coal combustion produce solid waste known as fly ash. A number of fly ash cause serious problem almost in every coal power plant. However fly ash consist of potential nutrient that could be used in agriculture. This research studied the chemical characteristics of fly ash and the nutrients released under leaching during 3 months. Three kind of fly ash are used fresh, 6 months deposited fly ash out-door, and 5 years out-door deported fly ash. The analyses conducted were pH, EC (Electrical Conductivity), macro elements (K, Na, Ca, Mg), micro elements (Fe, Mn, Zn, Cu), and metals (Cr, Ni). The result showed that the three fly ash samples in this research were alkali. The pH value of fresh fly ash is 11,1. The six months fly ash was 9,4 in pH value and five years fly ash was 8.4 in pH value. Electrical conductivity of fresh fly ash was 3,12 dSm-1. It was higher than electrical conductivity of landfiil’s fly ash. Electrical conductivity of six months fly ash and five years fly ash were0,76dSm-1 and 0,39 dSm-1. According to this research, fresh fly ash also contained more elements than landfiil’s fly ash. This research also used percolation method. Result of percolation method show that pH value of percolate were between 7,3 to 7,8. Percolate pH value of fresh fly ash was higher than percolate pH value landfiil’s fly ash. Percolate electrical conductivity were between 0,20 dSm-1 to 0,35 dSm-1. Percolation method also showed that percolate contained variety number of macro elements (K, Na, Ca, Mg). This percolate also has small number of micro elements (Fe, Mn, Zn, Cu) and metals (Cr, Ni). Percolate elements in the first month was higher than it were in the third month.
Keyword: 

Judul: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
Keyword: