Judul: Klasifikasi dan perkembangan tanah berasal dari tufa masam toba daerah Sumatera Utara
Abstrak: Tufa masam Toba (tufa liparit) yang terdapat di daerah Sumatera Utara menyebar cukup luas, sekitar 2 juta hektar, mulai dari ketinggian SO meter hingga mendekati 2000 meter dari atas oermukaan laut. Perbedaan ketinggjan ini menyebabkan oerbedaan tingkat perkembanoan tanannya. Tingkat pe rkembangan tanah ditentukan berdasarkan sifat morfoloqis dan genesis t anah. Secara morfologis, ditetapkan berdasarkan pada kelengkapan horizon-horizon genetik dan kedalaman solumnya. Sedangkan secara genesis ditetapkan berdasarkan tingkat pelapukannya baik secara kuantitatif maupun kualitatif sebagai hasil evaluasi analisis fisika, kimia dan mineralo gi tanahnya. Penelitian tanah daerah Sumatera Utara tahun 1988, menggunakan klasifikasi tanah sistem Taksonomi Tanah 1987. Sementara sistem klasifikasi tanah terus berkembang dengan terbitnya "Keys to Soil Taxonomy 11 tahun 1990 dan tahun 1992. Pada penelitian ini disesuaikan dan be£ pedoman oada sistem Keys to Soil raxonomy 1992. Untuk mengarahkan penelitian ini, maka diajukan hi potesis yaitu : (1) Tanah berasal dari tufa masam Toba yang berada di dataran rendah lebih berkembang dibandingkan dengan yang berada di dataran pegu nungan; (2) Perkembangan horizon bawah penciri tanah dari daerah pegunungan ke dataran rendah berturut-turut adalah : andik - kambik - argilik - kandik. Metoda penelitian rlilakukan dengan memilih enam pedon pewakil berbeda ketinggian dari atas permukaan laut yaitu : pedon P1 di Desa 8aniara (18D5 m dpl), P2 di desa Simangunsong (136D m dpl), P3 di desa Sitinjo (1090 m dpl), P4 di desa Tiga Oolok (720 m dpl), P5 di desa Marihat Ulu (41D m dpl) dan P6 di desa Sei Alim Ulu (80 m dpl). Analisis contoh tanah dari keenam pedon tersebut, meliputi sifat-sifat fisis, kimia dan mineralogi tanah. Analisis mineral liat dan liat amorf dengan metoda Differential Thermal Analysis (OTA) . ...
Keyword: Tufa Masam Toba;

Judul: Reklasifikasi andosol menurut taksonomi tanah di daerah aliran sungai Wampu Sumatera Utara
Abstrak: Tujuan penelitian untuk pengkajian secara lapangan dan laboratorium terhadap sifat-sifat dari masing-masing pedon dan mengklasifikasikan kembali Andosol di daerah penelitian. Empat pedon Andosol di daerah aliran sungai Wampu Sumatera Utara yang terbentuk dari bahan Andesito-Dasit yang berasal dari bahan volkanik gunung Sinabung dan Sibayak telah diteliti secara fisiko-kimia, kimia dan mineralogi. Hasiln'ya menunjukkan bahwa Andosol di daerah penelitian, tergolong tanah-tanah yang masih muda perkembangannya. Tanah bersolum sedang sampai dalam, berwarna hitam gelap, dan tebal, batas horison kabur dan berlempung halus (fine loamy) dengan komposisi mineral liat alofan. Tanah agak masam dengan kejenuhan basa rendah sampai sedang dan kapasitas tukar kation yang tinggi. Andosol di daerah penelitian menurut Taksonomi Tanah 1975-/19B7, keempat pedon termasuk Inceptisol, sub ordo Andept, great group Dystrandept, dan sub group Typic Dystrandept. Pada kategori famili pedon TP dan RK (yang berada di daerah atasan) dikategorikan sebagai Typic Oystrandept, berlempung halus, alofanik, isotermik; pedon NT dan BM di daerah bawahan (dataran rendah) sebagai Typic Dystrandept, berlempung halus, alofanik isohypertermik. ...
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Judul: Algorithm construction of HLI hash function
Abstrak: Cryptography is a study of mathematical techniques related to aspects of information security regarding on confidentiality, data integrity, entity authentication, and data origin authentication. Data integrity is a service, which is associated with the conversion of data carried out by unauthorized parties. To maintain data integrity, one can use hash functions. An hash function is a computationally efficient function to map an arbitrary length bitstring to a fixed length bitstring called as hash value. The use of hash function in maintaining the information integrity and authentication is in digital signatures, virus protection, and software distribution. Illustration of the hash function in the integrity and authentication of information that is emailed as follow. The sender sends the information and hash value to the recipient. If the hash value of the information is equal to the hash value that is sent by the sender, then information has not been changed. Otherwise the information has been changed. An hash function has two properties, one way and collision resistance. An hash function is called one way if it is computationally infeasible to find any input such that when given any hash value . Meanwhile an hash function is called collision resistant if it is computationally infeasible to find any two inputs where such that . The purpose of this study is to construct a HLI hash function algorithm, to analyze the speed and security of the hash functions as a results of construction. Furthermore, it is to compare it with SWIFFT. Hash function is constructed based on the result of algebraic operations on modular polynomial ringwith . Modular polynomial ring noted as is a set of all polynomials of degree at most with coefficients in . can be represented as a set of integer vector of modulo in dimension . So, it is simple to implement in a computer. In vector operations, is lattice . Furthermore, alattice that is defined from certain polynomial ring is called ideal lattice. HLI hash function is consists of addition and multiplication algorithm in the ring. Addition algorithm consists of sumation operations of modulo and multiplication consists of multiplication operations of modulo . Generally, algorithm of HLI hash function consists of multiplication operations of modulo and addition operations of modulo . However, if the input is binary number then multiplication algorithm only consists of multiplication operation of modulo , so algorithm of HLI hash function consists of multiplication operations of modulo and addtion operations of modulo . An hash function is secured if it has two properties, i.e., one way and collision resistance. HLI hash function hash is one way, it is following the proof of Micciancio. It is has collision resistant because of polynomial is irreducible over and monic. Moreover, it is proved that for every unit vector , the vector is small vector. If the input of hash function is a binary number then HLI hash function only involves addition operations of modulo . So the time that used almost same with SWIFFT. The excellence of HLI hash function is the key size smaller than SWIFFT. This effect on
Keyword: hash function, modular polynomial ring, lattice