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: Peramalan Nilai Tukar Rupiah Terhadap Dolar Amerika dengan Pendekatan Analisis Regresi dan ARIMA
Abstrak: Nilai tukar merupakan harga mata uang satu negara yang dinyatakan dalam mata uang negara lain. Nilai tukar berfluktuatif sehingga perlu dilakukan peramalan agar dapat membantu pelaku ekonomi dalam membuat keputusan yang tepat. Fluktuasi nilai tukar dipengaruhi oleh faktor-faktor makroekonomi, seperti inflasi dan jumlah uang beredar. Pengaruh faktor-faktor makroekonomi terhadap nilai tukar dapat dimodelkan dengan regresi linear berganda. Parameter model regresi diestimasi menggunakan metode Ordinary Least Square (OLS). Pada model regresi linear berganda terdapat asumsi-asumsi klasik yang harus dipenuhi. Apabila terjadi korelasi antara residual ke-t dengan residual ke-(t-1), dikatakan residual model mengalami autokorelasi. Dalam karya ilmiah ini, digunakan metode Cochrane-Orcutt untuk mengatasi pelanggaran asumsi tidak adanya autokorelasi pada residual model. Selain faktor makroekonomi, fluktuasi nilai tukar juga dipengaruhi oleh nilai tukar pada periode sebelumnya. Pada karya ilmiah ini dilakukan peramalan nilai tukar rupiah terhadap dolar AS menggunakan metode regresi linear dan ARIMA. Setelah itu, akan dilakukan perbandingan hasil ramalan menggunakan Mean Absolute Percentage Error (MAPE). Hasil peramalan menunjukkan bahwa metode regresi linear memiliki tingkat keakuratan yang lebih baik dibandingkan dengan model ARIMA karena memiliki nilai MAPE yang lebih kecil., Exchange rate is the price of one country’s currency which is expressed in other country’s currency. The exchange rate is volatile so it is necessary to forecast in order to assist economic actors in making the right decisions. Exchange rate fluctuations are influenced by macroeconomic factors such as inflation and money supply. The effect of macroeconomic factors on the exchange rate can be estimated using multiple linear regression. The regression parameters are estimated using the Ordinary Least Square (OLS) method. There are classical assumptions that must be satisfied in multiple linear regression. If there is correlation between the (t)-th residual and the (t-1)-th residual then the residual model has autocorrelation. In this study, the Cochrane-Orcutt method is used to overcome the violation of assumption that there is no autocorrelation in the residual model. The exchange rate fluctuations are also influenced by exchange rate in previous period. In this study, the exchange rate is forecasted using linear regression and ARIMA. Then, their accuracy are compared by evaluating Mean Absolute Percentage Error (MAPE). The forecasting results showed that linear regression has a better accuracy rate than ARIMA model because it has a smaller MAPE value.
Keyword: ARIMA, Cochrane-Orcutt, exchange rate, linear regression

Judul: Hybrid solar cells of ZnO nanoparticles/chlorophyll was modified metal ions (Zn2+ and Cu2+ )
Abstrak: Zinc Oxide (ZnO) is a n-type semiconductor with a wide the energy band (Band Gap) is 3.37 eV at room temperature and 3.34 eV at low temperature with a large exiton binding energy is 60 meV. ZnO has been synthesized by hydrothermal method, resulting in a decrease in particle size over the duration of the hydrothermal changes. Crystallographic structure of ZnO were characterized using XRD, has shown the characteristic pattern of a hexagonal wurtzite structure, the crystallite size increases to changes in particle size. Changes in particle size has also led to a change in the absorption peak of ZnO as has been demonstrated posted under test using the optical properties of UV-Vis spectrophotometer. Changes of this uptake has also led to changes in the energy band gap, which increases its band gap energy of the particle size. In electronic applications, especially in solar cells. Chlorophyll is considered less effective, because of their very nature are easily degraded as a result of several reactions which are acid, lighting and temperature. The results of the stability test using a halogen lamp 34 W/m2 for 5 hours, that the substitution of chlorophyll with metal ions Zn2+ and Cu2+ has been shown to form more stable than natural chlorophyll. The characterization of the optical properties, the combination of ZnO / chlorophyll in the form of hybrid films has led to a shift in the absorption region of ZnO becomes more widely from the UV to Visible. ZnO/chlorophyll has absorption range of 350-515 nm, ZnO / Zn-feofitin 332-401 nm and 332-632 nm for Cu-feofitin. The combination of ZnO/chlorophyll and CuSCN as a solid electrolite in hybrid solar cell, a modified chlorophyll with metal ions Zn2+ and Cu2+ has been shown to form a more stable I-V curve. It is characterized by its fill factor value greater than natural chlorophyll. Nevertheless, solar cells with natural chlorophyll has been able to produce higher efficiency values of chlorophyll were substituted.
Keyword: Hydrothermal, ZnO/Chlorophyll modified, Hybrid Solar Cell