Judul: Implementation of the Random Forest and XGBoost Methods to predict the direction of closing prices on bitcoin cryptocurrencies
Abstrak: Kemampuan dalam memprediksi tren pergerakan harga cryptocurrency bitcoin dengan baik dan akurat sangat penting bagi investor karena akan mempengaruhi keputusan untuk membeli atau menjual aset yang dapat menghasilkan keuntungan yang signifikan. Namun, karena harga cryptocurrency bitcoin cukup fluktuatif maka ada ketidakpastian yang harus diperhitungkan. Dalam beberapa tahun terakhir, algoritma machine learning khususnya algoritma pembelajaran gabungan telah digunakan untuk memprediksi arah harga penutupan cryptocurrency bitcoin. Hasil penelitian menunjukkan model random forest memberikan akurasi sebesar 90.75% dengan AUC sebesar 90% dan model XGBoost memberikan akurasi sebesar 90.12% dengan AUC sebesar 89%. Variabel fitur yang paling berpengaruh dari masing-masing model yaitu Moving Average Convergence Divergence (MACD) dan William Percentage Range (William%R)., The ability to predict bitcoin cryptocurrency price movement trends well and accurately is very important for investors because it will influence decisions to buy or sell assets that can generate significant profits. However, because the price of the bitcoin cryptocurrency is quite volatile, there are exposures that must be taken into account. In recent years, machine learning algorithms especially federated learning algorithms have been used to predict the closing direction of the price of the cryptocurrency bitcoin. The research results show that the random forest model provides an accuracy of 90.75% with an AUC of 90% and the XGBoost model provides an accuracy of 90.12% with an AUC of 89% with the most influential feature variable from each model, namely Moving Average Convergence Divergence ( MACD) and William Percentage Range (William%R).
Keyword: machine learning, random forest, XGBoost, cryptocurrency, bitcoin

Judul: Prediction of The Closing Price of Stock using Backpropagation Neural Network Method
Abstrak: Saham adalah tanda penyertaan modal seseorang atau badan usaha dalam suatu perusahaan atau perseroan terbatas. Sebelum melakukan investasi, para investor perlu mempelajari prospek harga saham di masa mendatang. Oleh karena itu, peramalan harga saham sangat diperlukan. Pada karya ilmiah ini, dilakukan prediksi harga saham menggunakan metode jaringan saraf tiruan perambatan balik. Metode ini memperhitungkan input, jumlah neuron, dan fungsi pembelajaran yang harus ditentukan. Berdasarkan penghitungan Mean Absolute Error (MAE) dan Mean Absolute Percentage Error (MAPE), jaringan yang paling optimal adalah jaringan yang menggunakan input harga pembukaan saham dan tingkat suku bunga dengan satu neuron dan fungsi pembelajaran traincgb. MAE yang diperoleh sebesar 237.7063 rupiah dan MAPE sebesar 2.934777%., Stocks are sign of a person’s or business entity’s capital participation in a company or limited liability company. Before making an investment, an investor needs to study the prospect of future stock price. Therefore, making a forecast of future stock is indispensable. In this paper, backpropagation neural network method is used to forecast stock closing price. This method takes into accounts the input variables, the number of neurons, and it requires a learning function which must be defined. Based on Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE), the most optimal network is achieved by using stock opening price and interest rate as input variables with one neuron and traincgb learning function. The obtained MAE is IDR 237.7063 and MAPE is 2.934777% which is relatively small.
Keyword: stock closing price, backpropagation neural network, forecasting

Judul: Synthesis of Apatite - Chitosan Composite Using Duck Eggshell and Chitosan with Temperature and pH Control
Abstrak: Composite of apatite-chitosan was prepared by using chitosan as polymer matrix. Calcium phosphate was prepared from CaO and (NH4)2HPO4, which the ratio Ca : P had to be 1.67. Chitosan is produced by deacetilase from biopolymer chitin. Duck eggshell (95% CaCO3) as starting material was converted to be calcium oxide (CaO) through calcinations with temperature 1000oC for 5 hours. In-situ and ex-situ methods were prepared from apatite and chitosan (dissolved with acetate acid 2%). Calcium phosphate prepared for bone implantation, but it is too fragile and brittle to be implant into the body. So addition of chitosan can decrease crystalinity and increase mechanic characteristic (tougher). Composite apatite-chitosan was resulted by fast precipitation. Fast precipitation was held in a breaker glass with nitrogen atmosphere, under controlled temperature at 37oC and pH 7, in order to increase amount of hydroxyapatite. Precipitation with CaO which was dropped by (NH4)2HPO4. Hydroxyapatite and chitosan were appearing at samples with in-situ and ex-situ methods which indicating by peak matching of XRD (closed lattice parameter, crystal size), overlapping at FTIR spectra and supporting by SEM picture (homogenous and agglomerated particle). However, it still needs further research to examine biocompatibility osteoconductive degree of sample by in-vivo and in-vitro test.
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