Judul: Peramalan Kurs Rupiah terhadap Dolar dengan Metode Berbasis Rata-rata Fuzzy Time Series Markov Chain.
Abstrak: Kurs atau nilai tukar mata uang sangat penting dalam perekonomian. Oleh karena itu, perlu dilakukan upaya untuk memprediksi besarnya nilai kurs di periode berikutnya. Pada karya ilmiah ini, metode peramalan yang yang digunakan adalah metode fuzzy time series Markov chain yang dikombinasikan dengan metode berbasis rata-rata untuk penentuan jumlah interval yang efektif. Tujuan dari karya ilmiah ini adalah meramalkan nilai kurs rupiah terhadap dolar Amerika menggunakan metode berbasis rata-rata fuzzy time series Markov chain, serta menghitung tingkat kesalahan peramalan menggunakan ukuran kesalahan mean absolute percentage error. Dalam metode ini data kurs rupiah terhadap dolar Amerika diubah menjadi himpunan fuzzy sehingga diperoleh fuzzy logical relationship group. Hasil prediksi menunjukkan bahwa nilai mean absolute percentage error yang diperoleh dalam peramalan kurs periode Maret 2014-Maret 2016 hanya sebesar 0.71%, yang berarti hasil prediksi dianggap cukup baik.
Keyword: fuzzy time series Markov chain, nilai kurs, mean absolute percentage error

Judul: Peramalan Nilai Tukar Rupiah terhadap Dolar Menggunakan Model ARIMA dan Metode Fuzzy Time Series
Abstrak: Peramalan merupakan sesuatu yang belum pasti dan sulit untuk diduga. Setiap negara memiliki mata uang sebagai alat tukar, pergerakan nilai tukarnya dapat mempengaruhi perekonomian suatu negara. Tujuan penelitian ini adalah meramalkan nilai tukar rupiah terhadap dolar menggunakan metode peramalan konvensional ARIMA dan metode peramalan fuzzy time series serta membandingkan kedua metode tersebut dengan melihat ukuran kesalahan peramalan menggunakan Mean Absolute Percentage Error (MAPE). Model ARIMA yang menggunakan metode Box Jenkins adalah metode konvesional yang menggunakan himpunan tegas dalam proses peramalannya sementara metode fuzzy time series adalah metode peramalan menggunakan himpunan fuzzy dalam prose peramalannya. Kedua metode ini menggunakan sejumlah data untuk meramalkan nilai tukar rupiah terhadap US dolar di masa yang akan datang. Nilai MAPE yang diperoleh untuk validasi peramalan menggunakan ARIMA adalah 2.47%, metode fuzzy time series 25 periode sebesar 1.42% dan metode fuzzy time series 60 periode sebesar 1.80%, sehingga dapat disimpulkan bahwa metode fuzzy time series menghasilkan peramalan yang lebih baik dibandingkan ARIMA.
Keyword: ARIMA, fuzzy time series, nilai tukar, peramalan.

Judul: Application of phycocyanin from microalgae Spirulina platensis as light harvesting in anatase TiO2 nanoparticle solar cell.
Abstrak: The dye sensitized solar cell (DSSC) has been assemblied used hybrid titanium oxide (TiO2) film/phycocyanin. The TiO2 film was synthesized by sol gel method with titanium chlorida (TiCl4) as precursor by hydrolysis used sulfuric acid (H2SO4). Furthermore, it calcinated for 2,5 hours in variation of annealing temperature (400oC, 600oC, 800oC, dan 1000oC). In XRD patterns exhibited which annealing temperature at 400oC to 800oC were anatase phase all. When annealed at temperature 1000oC, it caused phase transformation from anatase to rutile. The crystals size according to XRD patterns were 13,75 nm, 20,79 nm, 25,25 nm, 48,88 nm and particle size from SEM images were 43,06 nm, 44,91 nm dan 64,99 nm, 80,40 nm, respectively. The crystals and particle size increased with annealing temperature. The film thickness influenced material absorption. The optical measurement of TiO2 film and TiO2/phycocyanin hybrid film used UV-Vis spectrophotometer. Additional phycocyanin caused peak width of absorbed region from ultraviolet to visible region. The band gap energy of TiO2 can be calculated using the cut off wavelength obtained from the absorbance spectrum of a nanoparticles TiO2 films. Based on intersection between linear and energy (hv) axis. In this study just limited for anatase phase. It was caused anatase band gap is wider than rutile phase. That’s meaningful for solar cell application such as dye sensitized solar cell (DSSC). The absorption coefficient average at difference annealing temperature such as at 400oC, 600oC, 800oC were 8,1600x102, 1,7535x103 and 4,0154x102, where α < 104 include to direct transition. Band gap energy 400oC, 600oC, 800oC were 3,79 eV, 3,59 eV, and 3,35 eV, respectively. Based on this result, exhibition that band gap energy of TiO2 semiconductor film decreased with increasing annealing temperature. Spirulina platensis was cultivated in technical modification (Hastuti) with aeration under light intensity about 3000 lux. The cell density (stationer phase) for eighth day which OD value was more than 0,5. It means, the culture can be harvested. In 80 liters Spirulina platensis culture have been produced biomass dry about 10,46 gram and extracted phycocyanin in dry powders was 5,50 gram. The phycocyanin absorption spectrum at the wavelength of 619,36 nm (visible region) which had relaxation energy was 2,945 eV. The emission peak at the wavelength of 708,55 nm with relaxation energy about 2,793 eV. The Stokes shift based on difference energy absorption and emission calculated about 0,152 eV. Both of this showed phycocyanin can absorbed and radiated the sun light which received. This choice characteristic pigment was a good one related to sensitizer in solar cell application. Integration between light harvesting protein and TiO2 semiconductor surface had important role in improving of output as solar cell materials. The presence of carboxylate group (-COOH) made pigment be more efficient was due to anchored to the surface of TiO2 ampoter. The phycocyanin pigment had carboxylate group which reacted with TiO2 surface formed ester. The carboxylate group increased of dye electronics couple from excited state (p anti bonding orbital) to semiconductor acceptor state (TiO2 conduction band). The samples which made based on annealing temperature variation formed be solar cell respectively. Furthermore, cells be assembled for
Keyword: anatase, dye sensitized solar cell, efficiency, gap energy, phycocyanin