Judul: Peramalan Harga Batu Bara Acuan Mengunakan Metode Autoregressive Integrated Moving Average dan Fungsi Transfer
Abstrak: Indonesia sebagai salah satu negara penghasil komoditas batu bara terbesar di dunia memiliki peranan yang penting dalam memenuhi permintaan batu bara di dunia global. Dewasa ini, sebagian besar negara-negara di Eropa kembali beralih kepada batu bara sebagai sumber tenaga pembangkit listriknya. Hal ini disebabkan adanya pandemi Covid-19 serta adanya konflik antara Rusia dan Ukraina yang membuat sumber energi menjadi terancam. Oleh sebab itu, peramalan harga batu bara diperlukan untuk menentukan kebijakan yang tepat dalam menghadapi banyaknya permintaan kebutuhan batu bara di masa mendatang. Pergerakan harga batu bara dipengaruhi oleh harga gas alam. Faktor harga gas alam tersebut akan dimodelkan dalam peramalan harga batu bara acuan menggunakan metode fungsi transfer sebagai deret inputnya. Penelitian ini membandingkan metode ARIMA dan fungsi transfer dalam peramalan harga batu bara acuan. Hasil penelitian ini menunjukkan bahwa model ARIMA dan model fungsi transfer secara berturut-turut menghasilkan nilai MAPE sebesar 23,14% dan 17,66%. Berdasarkan nilai MAPE yang dihasilkan metode fungsi transfer memiliki kemampuan peramalan yang lebih baik dibandingkan dengan metode ARIMA., Indonesia as one of the largest coal producing countries in the world has an important role in coal global demand. Currently, most countries in Europe are turning to coal as a source of electricity. This is due to Covid-19 pandemic and the conflict between Russia and Ukraine which endangers energy sources. Therefore, forecasting coal prices in the future is needed to determine the right policy in dealing with the large demand for coal. Coal price fluctuation are influenced by several factors such as the prices of the other commodities instance natural gas price. The natural gas price factor will be modeled in coal price forecasting using the transfer function method as the input series. This study compares the ARIMA and Transfer Function in coal price forecasting. The results showed that MAPE values of ARIMA and transfer function method are 23,14% and 17,66%. Based on MAPE values that forecasting using the transfer function method has a better ability than ARIMA method in forecasting coal prices.
Keyword: ARIMA, coal, transfer function

Judul: Penerapan Metode Generalized AutoRegressive Conditional Heteroskedasticity untuk Peramalan Harga Minyak Mentah Dunia.
Abstrak: Minyak mentah merupakan salah satu komoditas yang sangat dibutuhkan di berbagai bidang. Harga minyak mentah dunia yang terus mengalami fluktuasi tentunya mengambil pengaruh yang besar terhadap perekonomian negara. Data harga minyak mentah yang dikumpulkan bersifat time series atau proses pengumpulannya dilakukan dari waktu ke waktu dengan periode bulanan. Oleh karena itu, diperlukan suatu sistem yang dapat membuat peramalan harga minyak mentah dunia kedepannya yang diharapkan dapat menjadi bahan pertimbangan pemerintah untuk pengambilan keputusan. Salah satu metode yang dapat digunakan untuk meramalkan harga minyak mentah dunia adalah ARIMA (Auto-Regressive Integrated Moving Average) dan model GARCH (Generalized Auto-Regressive Conditional Heteroskedasticity). Pemodelan yang dilakukan terbukti bahwa data harga minyak mentah dunia periode Januari tahun 2002 hingga Juni 2022 memiliki efek heteroskedastisitas yang tidak dapat diatasi jika hanya menggunakan model ARIMA. Hasil dari pengolahan data diperoleh bahwa model ARIMA (0,1,2) yang dilanjutkan model ARCH (2) merupakan model terbaik dengan nilai MAPE sebesar 5,32%. Nilai akurasi yang diperoleh tergolong sangat baik untuk peramalan harga minyak mentah dunia., Crude oil is one of the commodities that are needed in various fields. World crude oil prices that continue to fluctuate, of course, have a big influence on the country's economy. Crude oil price data collected is time series or the collection process is carried out from time to time with monthly periods. Therefore, we need a system that can forecast future world crude oil prices which are expected to be taken into consideration by the government for decision making. One method that can be used to predict world crude oil prices is ARIMA (Auto-Regressive Integrated Moving Average) and GARCH (Generalized Auto-Regressive Conditional Heteroskedasticity) model. After modeling, it is proven that the world crude oil price data for the period January 2002 to June 2022 has a heteroscedasticity effect that cannot be overcome if only using the ARIMA model. The results of data processing show that the ARIMA (0,1,2) followed by the ARCH model(2) is the best model with a MAPE value of 5,32%. The accuracy values obtained are classifield as very good for forecasting world crude oil prices.
Keyword: ARIMA, ARCH, GARCH, harga minyak mentah, peramalan

Judul: Efektivitas Gugus Pelindung ‒OH Fenolik pada Floroasetofenon dan 3,4- Dihidroksibenzaldehida dalam Upaya Menyintesis Kuersetin
Abstrak: Quercetin is a of flavonol compound with hydroxylated A and B rings. Synthesis of this group of compounds is commonly through condensation reaction between hydroxylated acetophenoneand benzaldehyde derivatives and needs introduction of phenolic-OH protecting groups. In this study, tetrahydropyranylether (OTHP) and benzylether (OBn) were compared for their effectiveness in protecting the 2 phenolic‒OH groups in phloroactophenone and 3.4-dihydroxybenzaldehyde as the first step in quercetin synthesis. OTHP gave a huge steric hindrance so it could not protect the phenolic-OH of phloroacetophenone. On the contrary, OBn protected phloroacetophenone and 3,4-dihydroxybenzaldehyde more effectively. Two equivalent of BnBr in dimethylformamide after 24 hours, produced 2’,4’-di-Obenzylphloroacetophenone and 3,4-bis-(benzyloxy)benzaldehyde with 48% and 55% of yield, respectively. The condensation reaction between the two protected precursors produce mixture of products predicted to contain eriodictiol chalcone Bn-protected. Oxidative cyclization of the chalcone was yet to be succeeded to failed to form tetra-O-benzylquercetin. However, the effectiveness of OBn as a phenolic-OH protective group has been successfully demonstrated in this study
Keyword: phloroacetophenone tetrahydropyranil, 3.4-dihydroxybenzaldehyde, chalchone, benzyl