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 Penutupan/Penggunaan Lahan terhadap Karakteristik Hidrologi Sub DAS Ciliwung Hulu
Abstrak: Watershed is an ecosystem consisting of upstream, middle and downstream. Upstream watershed ecosystem is play an important role, because its function to regulate hydrologic characteristics of the watershed. Ciliwung watershed is one of the superpriority watershed that must be taken high priority effort to rehabilitation. According to Suripin (2002), hydrological components affected by development activities in the watershed includes surface flow coefficient, coefficient of discharge regim river, the ratio between maximumminimum river discharge, mud content or sedimentary deposits in the river, the rate of frequency and period of floods, and also the state of groundwater. The aim of the research is to analyze land use/cover, changes of land use/cover in upstream ciliwung watershed and to analyze its influence on watershed hydrology (flood and maximum-minimum river discharge). In this research landsat image of 1990, 2001 and 2010 was used to analyze the land use/cover changes. After that the condition of land use changes and characteristics of watershed hydrology were compared and evaluated. Based on image interpretation of land cover in 1990 and 2001, the area dominated respectively by dense jungle, mixed farms and tea plantation. While land use in 2010 is dominated respectively by dense jungle, tea plantation and settlement. Patterns of land use/cover change at period 1990-2001 indicates substantially conversion of agriculture land such as the rice field, dryland farming and mixed farms into settlements. Area that converted respectively are 238.8 ha, 238,5 ha and 127,8 ha. Bush land is transformed into agriculture land as well, which are tea plantation (180,1 ha), mixed farms (140,7 ha) and other agricultural cultivation. Mixed farms is the most intensively converted land into dryland farming (411,3 ha). In the period 2001-2010, pattern of landuse/cover changes that occured is not too different but in a much larger scale. Large conversion of agriculture land occurred toward settlement (rice field 231,3 ha, mixed farms 176,2ha and dryland farming 128,9 ha). Mixed farms was converted into dryland v farming are 329,5 ha and rice field 212,8 ha. Amount of bush land converted to tea plantation, rice field and dryland farming were respectivally 107,1 ha, 144,9 ha and 108,4 ha. A decline in the quality of the upstream ciliwung watershed hydrology can be seen from characteristic of flood frequency, the quality of a flood, maximum-minimum river discharge and the ratio between maximumminimum river discharge. Increase of settlement and dryland farming area in the upstream ciliwung watershed contribute to declining of upstream ciliwung sub watershed hydrology characteristics.
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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