Judul: Rosot metana (CH4) pada berbagai penggunaan lahan
Abstrak: Metana (CH4) merupakan salah satu gas rumah kaca yang penting peranannya dalam mempengaruhi radiasi bumi, selain karbondioksida (CO₂). Konsentrasi metana secara global rata-rata adalah sebesar 1700 ppbv (Khalil, 1992). Laju peningkatan konsentrasi metana di atmosfer rata-rata sebesar 1 2% per tahun atau 16,6 ppbv per tahun (Blake et al., 1982; Keller et al., 1983; Khalil dan Rasmussen, 1990). Besarnya laju peningkatan ini disebabkan karena bertambahnya sumber-sumber pengemisi metana yang melebihi rosotnya. Total rosot metana d atmosfer adalah sebesar 460 ± 100 Tg/tahun, sedangkan sumber-sumber pengemisi metana mengemisikan 505 ± 105 Tg/tahun (1 Tg= 1 Terragram = 1 Juta Ton) (Crutzen, 1991). Tanah di daerah tropis telah lama diketahui dapat berperan sebagai sumber dan pengoksidasi metana tergantung kondisi kandungan oksigennya (Delmas et al., 1992). Dari hasil penelitian ini didapat bahwa dari berbagai jenis penggunaan lahan di Propinsi Sumatera Barat, Jambi dan Lampung, yaitu hutan primer, hutan sekunder, HTI sengon, perkebunan karet, kebun kulit manis, perkebunan tebu, tanah. pertanian, semak belukar dan padang alang-alang semua menunjukkan fungsinya sebagai rosot metana.
Keyword: 

Judul: Studi rosot metana (CH4) oleh tanah hutan di bawah tegakan pinus merkusii di hutan pendidikan Gunung Walat Sukabumi
Abstrak: Dewasa ini, gejala pemanasan global (global warming) menjadi salah satu masalah lingkungan yang selalu dibicarakan. Pemanasan global terjadi akibat adanya peningkatan konsentrasi gas-gas rumah kaca di atmosfer. Metana (CH) merupakan salah satu gas rumah kaca yang penting dalam mempengaruhi terjadinya pemanasan global. Dengan kadar metana 1,3 ppmv di atmosfer dapat menaikkan temperatur secara global sebesar 1,3°C jika dibandingkan dengan tidak adanya metana di atmosfer (Donner dan Ramanathan, 1980). Tanah di hutan tropis diketahui sebagai faktor yang penting dalam menentukan kadar metana di atmosfer. Hutan tropis yang mempunyai lahan kering memberikan kondisi yang baik bagi pertumbuhan bakteri methanotroph. Dalam kondisi seperti ini tanah hutan berfungsi sebagai rosot (sink) bagi metana. Tujuan dari penelitian ini adalah untuk mengetahui konsentrasi ambien metana, laju penyerapan (rosot) metana, fluktuasi harian rosot metana dan untuk mengetahui faktor- faktor yang mempengaruhi laju penyerapan (rosot) metana oleh tanah hutan di bawah tegakan Pinus merkusii di Hutan Pendidikan Gunung Walat, Sukabumi.
Keyword: 

Judul: The Construction of Greedy SVP LLL Algorithm
Abstrak: A lattice is a set of all integer linear combination of a set of linearly independent vectors in ℝ𝑛���. The independent vectors are called bases of lattice. Any lattice can be generated from many bases, and these bases have the same cardinality. In the lattice, the most fundamental and renowned problem is the Shortest Vector Problem (SVP). SVP is a tracking problem of the shortest nonzero vector in a lattice with equivalent bases. In two dimensions, SVP problem has resolved exactly by Gauss’ algorithm. When the lattice dimension is higher than two, A.K. Lenstra, H.W. Lenstra and L. Lovasz gave a LLL algorithm to compute approximation of nonzero shortest vector in the lattice. Reduced bases solution obtained from LLL algorithm still be an approximation and has polynomial running time of arbitrary dimension which large enough. In 1994, Schnoor and Euchner modified this LLL algorithm as a new variant which later was named deep insertion LLL algorithm. This algorithm is a modified version of the LLL algorithm to the terms of the exchange step to improve the accuracy of output of LLL reduced bases and applying it to the subset sum problem. The purpose of this research are: (1) Reconstruct the LLL algorithm and deep insertion LLL algorithm using a geometric approach. (2) Construct a greedy SVP LLL algorithm. (3) Implement the three algorithms in a symbolic programming language, and evaluate them experimentally. A bases ℬ=[𝐛���1,𝐛���2,…,𝐛���𝑛���] in ℝ𝑚��� is called reduced LLL with parameter 𝛿��� if satisfies: (a) |𝜇���𝑗���𝑖���|≤12, for every integer 𝑖���,𝑗��� with 1≤𝑖���<𝑗���<𝑛���. (b)𝛿���‖𝜋���𝑗���(𝐛���𝑗���)‖2≤‖𝜋���𝑗���(𝐛���𝑗���+1)‖2, for 𝑗���=1,2,…,𝑛���−1,where 𝛿��� is a reduced parameter of real numbers with 14<𝛿���<1. The first requirement is the reduced basis 𝛿��� must “nearly orthogonal” and in its computation case, this requirement can be reached out by using the Gram-Schmidt’s orthogonalization. While the second requirement is called exchange step, or used to called as Lovasz condition. By using both of these requirements, then they establish the LLL algorithm. Then, Schnoor and Euchner modify the LLL algorithm based on the requirements of the exchange step called the deep insertion LLL algorithm, where the exchange step is based on the comparison of the projected vector in orthogonal complement [𝐛���1,𝐛���2,…,𝐛���𝑘���−1]⊥ after j-th reduction. To construct greedy SVP LLL algorithm, the requirements of the exchange step is based on purely by comparing norm of lattice 𝐛���𝑗��� with norm lattice 𝐛���𝑖��� for 𝑖���=1,2,3…,𝑗���−1. The process of insertion reduced vector after the exchange step also has done greedily. Then, we calculate the number of arithmetic operation in greedy SVP LLL algorithm for further analysis. The result of our exprimentation for three algorithms on the certain matrix size shows that the running time of the three algorithms increases propotional to the size of the matrix. The result also shows that by using 𝛿���=34 for the LLL algorithm and the deep insertion LLL algorithm, and the greedy SVP LLL algorithm which is a new variant made by using no parameter of 𝛿���, outperform of the other of two previous algorithm in terms of speed with the same output.
Keyword: LLL algorithm, LLL deep insertion algorithm, greedy SVP LLL algorithm