Judul: Pemodelan 8-Puzzle Menggunakan Integer Linear Programming
Abstrak: 8-puzzle adalah salah satu jenis permainan puzzle. Permainan ini menggunakan bidang persegi yang dibangun oleh sel 3 × 3 dengan delapan sel diisi oleh blok yang diberi label 1 sampai dengan 8 dan satu sel kosong. Tugas pemain adalah menyusun delapan blok persegi tersebut sampai membentuk susunan solusi. Dalam karya ilmiah ini akan dibahas bagaimana menentukan susunan awal yang dapat mencapai susunan solusi dan kemudian memformulasikan 8-puzzle menggunakan integer linear programming serta menyelesaikannya dengan software LINGO 11.0.
Keyword: 8-puzzle, Integer Linear Programming, Permainan puzzle, Aplikasi model, Pemrograman linear

Judul: Penyelesaian Permainan Sudoku, Challenger Puzzle, dan N-Queens Problem Menggunakan Integer Programming
Abstrak: Many people think that mathematics is complicated so they are not interested to learn it. Presenting mathematics in the form of a puzzle is one way to attract people to study mathematics. The puzzle will attract curiosity of someone to solve problems. When someone can solve the puzzle, then it implies that he in fact has studied mathematics. In this paper, some mathematical puzzles are formulated, such as Sudoku, Puzzle Challenger, and the N-Queens Problem using integer programming and are solved by using LINGO 11.0
Keyword: Sudoku, N-Queens Problem, Integer Programming, Challenger Puzzle

Judul: Bioelectricity Production from Citrobacter freundii GBH253 and Chlorella pyrenoidosa on Microbial Fuel Cell Anode with Different Carbon Sources
Abstrak: Microbial Fuel Cell (MFC) development has significantly increased from various aspects to get higher and more stable electricity. Developing MFC on microorganism aspect is very important because it plays a crucial role in the MFC system. C. freundii GBH253 is one of the potential exoelectrogen bacterium that could be developed for the MFC system. Integrating C. freundii GBH253 and electricity-producing microalgae, such as C. pyrenoidosa, in the anode of MFC could get more stable and higher electricity. In this study, C. freundii GBH253 and C. pyrenoidosa were coupled to produce electricity from different substrates. C. freundii GBH253 and C. pyrenoidosa were tested on three different media types before being tested on MFC. They were also examined for the co-cultivation test to determine the symbiotic relationship between the two microorganisms. The MFC test was conducted using the Randomized Block Design Factorial and the Tukey test to see significant differences from each treatment. The parameters observed in this study were voltage, power density, Chemical Oxygen Demand (COD), Coulombic Efficiency (CE), pH, and volatile fatty acid (VFA). C. freundii GBH253 cannot grow on microalgae medium, while C. pyrenoidosa could grow on bacterial medium and a mixture of bacterium and microalgae media. The bacterium gained benefit from co-culture with microalgae. In the MFC test, electricity was generated in all treatments, which bacterium + microalgae with acetate treatment could generate power density up to 211,97 mW/m2 and the most stable compared to others. Production of electricity in bacterium-microalgae combination dominated by the bacterium; hence, microalgae still help bacterium by producing electricity and raised the COD value. The pH value of all treatments was higher than the initial pH. Acetate and phenol were VFA produced in all treatments, whereas butyric acid and propionic acid were found in some treatments. Pearson correlation showed that some VFA highly correlated with power density.
Keyword: Chlorella pyrenoidosa, Substrate, Microbial Fuel Cell, Electricity Producing Microalgae, Volatile Fatty Acid, Citrobacter freundii