Judul: Studi Kelayakan Pendirian Pabrik Pengolahan Ulang Kopi Rakyat di Daerah Produsen Kabupaten Dairi Sumatera Utara
Abstrak: Kopi merupakan salah satu komoditi perkebunan yang penting artinya dalam perekonomian Indonesia. Produksi kopi Indonesia sebagian besar merupakan hasil perkebunan rakyat. Pada umumnya mutu kopi rakyat jauh lebih rendah bila dibandingkan dengan mutu kopi hasil perkebunan besar, sehingga belum siap untuk diekspor.
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Judul: Pendekatan pasca panen dalam rangka perbaikan mutu kopi rakyat : studi kasus di Kecamatan Talang Padang Kabupaten Lampung Selatan
Abstrak: Bagi perekonomian Indonesia kopi mempunyai arti penting karena menyangkut kehidupan sebagian besar petani di beberapa daerah, masyarakat pengusaha kopi, industri-industri kopi dan para eksportir. Peranan Indonesia di pasaran Internasional relatif masih kecil walaupun Indonesia tergolong eksportir kedua kopi robusta setelah Ivory Coast. Kopi Indonesia digolongkan ko- pi termurah dan lebih murah jika dibandingkan dengan kopi se jenis dari Afrika (BPP AEKI, 1981). Hal yang ikut menekan harga kopi Indonesia di pasaran Internasional adalah kurangnya jaminan kelangsungan suplai dan mutu yang berasal dari Indonesia. Kopi Indonesia diusahakan oleh perusahaan negara perkebunan/PT perkebunan, perkebunan swasta besar dan perkebunan rakyat. Perkebunan kopi rakyat merupakan penghasil produksi kopi yang terbesar di Indonesia, dimana 92.5 persen dari produksi nasional berasal dari perkebunan rakyat. Se- dangkan luas pertanaman kopi rakyat meliputi 93.20 persen dari total tanaman kopi yang ada..
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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