Judul: Hubungan Persepsi Calo Beras Terhadap Peranannya Dengan Fungsinya Dalam Tataniaga Beras Di Pasar Induk Cipinang
Abstrak: Pasar Induk Cipinang (PIC) merupakan pusat pemasaran tataniaga beras Jabotabek dan nasional. Pelaku pasar di PIC terdiri dari pelaku formal dan Informal, salah satu pelaku informal adalah calo beras. Peran mereka pada dasarnya adalah positif yaitu sebagai negosiator atau penghubung antara pedagang pemasok dan pedagang grosir sehingga diharapkan menjadi katalisator tataniaga beras di PIC, namun sering disalahgunakan sehingga kadang merugikan pedagang pemasok dan pedagang grosir. Kedudukannya sebagai pelaku informal kadang-kadang tidak disadari oleh para calo beras, sering mereka mengambil fungsi pelaku pasar lain dan tidak menjalankan fungsinya sebagai perantara pedagang pemasok dan pedagang grosir.
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Judul: Struktur, Tingkah Laku, dan Keragaan Pasar pada Tataniaga Pisang
Abstrak: Penelitian bertujuan untuk mempelajari mekanisme pasar pada tataniaga pisang, terutama ditinjau dari segi struktur, tingkah laku, dan keragaan pasamya. Dalam studi ini, struktur pasar didekati dengan mendiskripsikan (1) jumlah dan ukuran lembaga tataniaganya serta konsentrasi pasarnya, dan (2) hambatan bagi pesaing baru untuk masuk pasar (barriers t o entry). Tingkah laku pasar didekati dengan diskripsi (1) praktek penentuan harga, (2) stabilisasi pasar, (3) standarisasi, dan (4) praktek tidak jujur yang dilakukan oleh lembaga tataniaga. Keragaan pasar didekati dengan melihat (1) perkembangan harga dan (2) penyebaran marjin tataiiaga, yang terdiri atas biaya tataniaga dan keuntungan lembaga tataniaga.
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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