Judul: Uji performansi down-draft gasifier (reaktor gasifikasi) biomass tipe imbert dengan gas cooler sebagai salah satu unit pemurniannya
Abstrak: Biomassa sebagai sumber energi di Indonesia umumnya diperoleh dari areal hutan (limbah tebangan, patahan cabang dan ranting), pertmian, perkebunan, dan areal pemukirnan. Energi yang tessimpan itu dapat dimanfaatkan dengan proses gasifikasi, dimana bahan biomassa yang berupa kayu (selulosa) dikonversi menjstdi gas oleh suatu reaktor gasifikasi (gasi$er). Bahan biomassa dapat diubah rnenjadi sumber energi listrik dengan cara memanfaatkan teknologi gasifikasi.
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Judul: Desain dan Uji Kinerja Sistem Pengumpanan Bahan Bakar Campuran Sekam Padi dan Arang Kayu Pada Reaktor Gasifikasi Tipe Downdraft.
Abstrak: Model reaktor gasifikasi untuk campuran bahan bakar sekam padi dan arang kayu yang telah dikembangkan dalam penelitian sebelumnya di IPB adalah reaktor tipe downdraft dengan sistem pengumpanan yang tidak kontinu. Penelitian ini bertujuan untuk melakukan pengembangan reaktor dengan membuat sistem pengumpanan kontinu menggunakan screw conveyor. Screw ini memiliki diameter pipa rumah screw 6.4 cm, diameter screw 5.8 cm, diameter poros 2.20 cm. Screw yang digunakan bertipe short pitch sehingga diperoleh jarak pitch sebesar 3.86 cm. Pengujian aliran bahan bakar, daya motor listrik, dan pengujian visualisasi api dilakukan untuk mengetahui kinerja sistem pengumpanan yang dirancang. Pengujian ini dilakukan dengan mengumpankan campuran bahan bakar antar sekam padi dan arang kayu dengan perbandingan berat 80:20 dan 60:40. Campuran bahan bakar terbaik untuk sistem pengumpanan reaktor tipe downdraft adalah campuran sekam dan arang kayu dengan perbandingan berat 60:40. Warna api yang didominasi oleh warna biru serta nyala api yang stabil menunjukan bahwa kualitas gas yang dihasilkan sudah cukup baik. Daya yang terukur ketika sistem pengumpanan kosong, pengumpanan campuran sekam dan arang kayu 80:20, dan pengumpanan campuran 60:40 secara berurutan adalah 242.00 ± 3.09 W, 243.73 ± 1.19 W, 245.91 ± 1.57 W.
Keyword: Gasification, feeding system, rice husk

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