Judul: Wavelet and ARIMA Analysis in Forecasting Gold Price of PT Antam Tbk Indonesia
Abstrak: Peramalan adalah suatu proses memperkirakan secara sistematis tentang kemungkinan yang akan terjadi di masa depan berdasarkan informasi masa lalu. Data deret waktu adalah urutan pengamatan berdasarkan waktu. Analisis data deret waktu dapat menggunakan beberapa metode, yaitu metode analisis domain waktu seperti ARIMA, atau analisis domain frekuensi seperti wavelet. Dalam analisis ARIMA, stasioneritas data merupakan salah satu faktor yang harus dipenuhi. Wavelet adalah fungsi matematis yang memotong data ke dalam beberapa komponen yang berbeda dan mempelajari setiap komponen berdasarkan resolusi yang sesuai dengan beberapa skala. Data asli didekomposisi untuk menghasilkan koefisien wavelet dan koefisien skala yang kemudian digunakan untuk memprediksi data pada periode berikutnya., Forecasting is an estimation of a systematic process which is most likely to occur in the future based on past informations. Time series data are sequence of observations, which are ordered in time. Analysis of time series data can use several methods, namely a time domain analysis method such as ARIMA, or frequency domain analysis such as wavelet. In ARIMA analysis, stationarity of data is one factor that must be met. Wavelet is a mathematical function that cut the data into different components and study each component with a resolution corresponding to some scales. The original data are decomposed to produce wavelet coefficients and scale coefficients, which are then used to predict the time series in the next period.
Keyword: forecasting, wavelet, time series, ARIMA

Judul: Peramalan Harga Saham PT Garuda Indonesia Saat Covid-19   dengan Menggunakan Model ARIMA
Abstrak: Avlation is one of the industries that has an impact on the restriction system to prevent the spread of the Covid-19 virus. Therefore, investors find it difficult to assume whether making an investment at the time of restriction will bring future profits or losses. To overcome this, forecasting is needed. One method that is often used is the ARIMA model. The data used is the daily stock price of PT Garuda Indonesia from January 1, 2020 to April 26, 2021. The most suitable model is ARIMA(2,1,2) with a MAPE around 4.3%. After forecasting for the next 10 periods, the MAPE is obtained at around 0.78%, this means that the error rate is quite low., Penerbangan merupakan salah satu industri yang berdampak pada saat sistem pembatasan untuk mencegah penyebaran virus Covid-19. Oleh karena itu, investor merasa kesulitan untuk mengasumsikan apakah melakukan investasi pada saat pembatasan akan mendatangkan keuntungan atau kerugian di masa yang akan datang. Untuk mengatasi hal tersebut perlu dilakukan peramalan. Salah satu metode yang sering digunakan adalah Model ARIMA. Data yang digunakan adalah data saham harian PT Garuda Indonesia dari 1 Januari 2020 sampai dengan 26 April 2021. Model yang paling sesuai adalah ARIMA(2,1,2) dengan MAPE sebesar 4.3%. Setelah dilakukan peralaman untuk 10 periode yang akan datang diperoleh MAPE sebesar 0.78%, artinya tingkat kesalahan yang dihasilkan cukup rendah.
Keyword: ARIMA, Covid-19, forecasting, avlation.

Judul: Heterologous Expression Of Endo-Β-Xylanase From Bacillus Pumilus Strain Bcrs-01 In Escherichia Coli.
Abstrak: Xylanases are glycoside hydrolase family 11 which depolymerise xylan in the plant cell wall, the most excessive form of hemicellulose. Endo-β-xylanases (EC 3.2.1.8) are most important to breakdown β-1,4-glicoside bond of xylan to produce disaccaride xyloolygosaccaride (XOs) and xylose (monomer). Bovine rumen fluids have potential to obtain endo-β-xylanase produced of bacteria. The objectives of this study were to obtain xylanase producing bacteria and to express xynA gene encoding endo-β-xylanase from bacterium in Escherichia coli. Twenty nine isolate bacteria have been succesfully isolated from bovine rumen fluid in agar medium containing birchwood xylan. Isolate BCRS-01 bacterium was previously screened for the high production of xylanase. Based on 16S rRNA gene sequence analysis, BCRS-01 showed high similarity (99%) to Bacillus pumilus (accession number NR043241). The crude xylanase had optimal activity at 55oC, pH 7.0. Furthermore, the crude xylanase exhibited broad pH stability from 4.0 to 10.0 and remained more than 60% and 40% of its activity after incubation at pH 4.0 until 10.0, respectively for 60 min. It also showed a stability at temperature 25-50oC since it retained 80% and 50% of its activity when incubated at 50oC or 30 and 60 min, respectively. The xylanase activity was strongly inhibited by Ca2+ and Cu2+ at concentration 10 mM, and as little as 1 mM for Mn2+. Therefore, this xylanase has potentially used as additive feeds in animal feed industry. The DNA sequence xynA gene encoded endo-β-xylanase was amplified and cloned into the expression vector pET-15by under the control of T7 promoter. The recombinant protein had succesfully expressed in Escherichia coli BL21 (DE3) pLysS. A protein recombinant of approximately, 26.7 kDa was observed on the SDS-PAGE analysis. Crude extract of recombinant endo-β-xylanase demonstrated activity of enzyme at 56 U mL-1 using birchwood xylan as a substrate at 55oC for 10 min.
Keyword: Bacillus pumilus, bovine rumen fluid, endo-β-xylanase, heterologous expression.