Judul: Pengaruh hutan pinus (p. Merkusii) terhadap karakteristik hidrologi di sub daerah aliran sungai Ciwulan Hulu KPH  Tasikmalaya, Perum Perhutani Unit III Jawa Barat
Abstrak: Kegiatan yang bersifat mengubah tata guna lahan, baik akibat kegiatan penebangan hutan, dan pengelolaan hutan akan sangat berpengaruh terhadap kualitas dan kuantitas air sungai. Hutan sudah sejak lama di yakini sebagai regulator air yang baik, yang mampu menyimpan air pada musim hujan dan mengeluarkannya di musim kering. Akan tetapi di Indonesia, hal ini belum banyak didukung oleh data ilmiah yang membuktikan peranan hutan tersebut, sehingga masih ada yang meragukan fungsinya.
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Judul: Pengaruh perubahan penggunaan lahan terhadap karakteristik hidrologi DAS Citarum Hulu
Abstrak: Land use change in a certain area will affect hydrologic characteristic there, so that it can be used as a reference whether the area is critical. This research objective is to study the effect of land use change to hydrologic characteristic of Upstream Citarum Watershed. There are 5 sites observed in Upstream Citarum watershed: Cikapundung, Citarik, Cirasea, Cisangkuy, and Ciwidey. This research was carred out by analyzing data of rainfall, discharge, and runoff, and by observing land use map. The result of analysis was then linked and matched to the data of land use descriptively. The result of this research showed that Cisangkuy sub-watershed was the worst due to its hydrologic characteristic. It can be seen from its increase in discharge and relatively high runoff coefficient in 2008, compared to ones of 2003. This condition was caused by land use changes happened there, which were decreasing primary land dry forests area, and increasing settlement area and wet rice field.
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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