Hendrik Setiawan, Hendrik
Jurusan Teknik Elektro Universitas Surabaya, Surabaya

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PERBANDINGAN MODEL ARIMA PADA DATA SPASIAL TRAFIK INTERNET AGREGAT Soesetijo, Sis; Budimulyono, Febrianto; Purnama, Lukas Hadi; Santoso, Welly Wellandow; Setiawan, Hendrik
Seminar Nasional Informatika (SEMNASIF) Vol 1, No 3 (2011): Network And Security
Publisher : Jurusan Teknik Informatika

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Abstract

Pengukuran data spasial trafik internet dilakukan secara agregat selama 46 hari dengan mengambil 4 lokasi pengukuran trafik internet di kampus Universitas Surabaya yaitu Fakultas Bisnis dan Ekonomika, Fakultas Teknik, Perpustakaan dan Kampus Ubaya Ngagel. Pemodelan trafik ini merupakan model trafik internet harian menggunakan model ARIMA (Auto Regressive Integrated Moving Average) dengan validasi model menggunakan qqplot dan uji distribusi normal pada residu model. Oleh karena trafiknya merupakan trafik harian, maka terdapat 184 model ARIMA pada ke-empat lokasi pengukuran trafik tersebut. Hasil pertama yang diperoleh bahwa model ARIMA(1,1,2) merupakan model ARIMA yang umum (sering muncul) pada pemodelan di empat lokasi traf
Lanthanum and Nickel Recovery from Spent Catalyst using Citric Acid: Quantitative Performance Assessment using Response Surface Method Petrus, Himawan Tri Bayu Murti; Wijaya, Ardyanto; Iskandar, Yusuf; Bratakusuma, Danu; Setiawan, Hendrik; Wiratni, Wiratni; Astuti, Widi
Metalurgi Vol 33, No 2 (2018): Metalurgi Vol. 33 No. 2 Agustus 2018
Publisher : Pusat Penelitian Metalurgi dan Material - LIPI

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (523.642 KB) | DOI: 10.14203/metalurgi.v33i2.437

Abstract

Heavy metals and Rare earth elements (REEs) are nowadays being used widely in many industries from electronics to petroleum industries as catalysts. However, their disposal caused serious problems to the environment. With the sharp growth in its usage, there is a better way to use and utilize valuable metals from secondary sources such as their disposal rather than using new raw materials. The aim of this work is to study the potential of citric acid as a leaching agent to extract lanthanum and nickel in various acid concentration and leaching temperature. The raw material used in this work is spent catalyst from Pertamina Refinery Unit VI, Balongan, Indonesia. The spent catalyst is decarbonized with a heat treatment at 725°C for 10 minutes before the leaching process. The leaching process used 0.1; 1; and 2 M of citric acid with a varied temperature of 30, 60, and 80°C. The lanthanum recovery was calculated by comparing the mass percentage of lanthanum before leaching process and after leaching process using Energy Dispersive X-Ray Spectroscopy (EDX). The results were analyzed by response surface methodology (RSM) and are proved to be a reliable method to depict and analyze the leaching characteristics. The molarity of the citric acid is the most significant independent variables used in the research for lanthanum recovery response. However, based on the Pareto analysis result there are no significant variables that affect the recovery of nickel. The second order polynomial fitting model is also proved to be compatible with the response of lanthanum recovery but is less compatible with nickel recovery.