Judul: Model pendugaan oksigen terlarut di tiga stasiun waduk Cirata
Abstrak: Keadaan kualitas air khususnya O₂ terlarut sangat menentukan kesuburan suatu perairan. bertujuan untuk mendapatkan deskripsi tentang keadaan kualitas air di 3 stasiun Waduk Cirata dan mengetahui model pendugaan O2 terlarut di tiap kedalaman pada waktu pagi dan siang hari. Hasil analisis menunjukkan bahwa kedalaman sangat berpengaruh pada kondisi O terlarut. Model persamaan regresinya sebagai berikut: y 2.53-0.138 X+ 0.00394 X2 -0.341 D; -0.22 D₂+0.259 D₁ dengan X adalah kedalaman, D,&D, peubah dummy untuk tempat (D, Maleber,D₂ = Maniis), D₁ = peubah dummy untuk waktu (D, siang hari). Semakin bertambahnya kedalaman, O₂ terlarut semakin rendah mengikuti fungsi kuartik. Konsentrasi O₂ terlarut lebih banyak pada siang hari dibandingkan pada pagi hari. Keadaan ini dikarenakan proses fotosintesis yang memproduksi O₂ terlarut berlangsung pada siang hari. Konsentrasi O, terlarut terbanyak ditemukan pada stasiun Jangari, keadaan ini dimungkinkan karena letak Jangari di inlet (tempat masuknya air) dimana O₂ terlarut belum banyak dimanfaatkan oleh organisme akuatik. Sedangkan letak Maleber yang berada di tengah, konsentrasi O₂ terlarutnya lebih sedikit dibandingkan Maniis yang letaknya dekat outlet (tempat keluarnya air). Hal ini dikarenakan jumlah KJA (Keramba Jaring Apung) antara Jangari dan Maleber lebih padat dibandingkan jumlah KJA di Maniis sehingga O2 terlarut pada Maniis lebih sedikit dimanfaatkan oleh organisme akuatik.
Keyword: forecasting

Judul: Analisis Sebaran Oksigen Terlarut di Sungai Ciapus, Bogor
Abstrak: Model matematika yang dikembangkan Streeter-Phelps dapat digunakan untuk memprediksi dan memudahkan pemantauan terhadap konsentrasi dissolved oxygen (DO) pada badan air. Penelitian ini bertujuan untuk menganalisis kondisi kualitas air, menerapkan pemodelan Streeter-Phelps dan menganalisis kemampuan self-purification Sungai Ciapus. Pengumpulan data primer berupa data kualitas air dan data hidrolik dilakukan di 10 titik pada musim hujan. Akurasi dari model dievaluasi dengan tes statistik, yaitu koefisien korelasi, koefisien determinasi, faktor bias, dan ANOVA. Kemampuan self-purification dianalisis dengan konstanta pemurnian. Hasil pengukuran kualitas air di bulan Maret dan bulan April menunjukkan bahwa nilai rata-rata untuk parameter suhu, pH, kekeruhan, dan DO masih sesuai dengan baku mutu kecuali untuk parameter BOD. Model dengan akurasi tertinggi diperoleh dari konstanta reaerasi yang dikembangkan Jha et al. Hasil penelitian juga menunjukkan bahwa Sungai Ciapus memiliki konstanta pemurnian sebesar 7.15 di bulan Maret dan 8.92 di bulan April. Berdasarkan hasil penelitian dapat disimpulkan bahwa Sungai Ciapus memiliki kemampuan self-purification yang tinggi namun pada rentang jarak tertentu terdapat interupsi proses tersebut akibat sumber pencemar tertentu.
Keyword: kualitas air, oksigen terlarut, self-purification, Streeter-Phelp, sungai

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