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A method for computing the autocovariance of renewal processes
Suyono,Ibnu Hadi 한국통계학회 2018 Journal of the Korean Statistical Society Vol.47 No.4
In this paper we derive formulae for the autocovariance functions of renewal and renewal reward processes. The derivation is based on a Poissonization technique of a renewal process. The formulae are expressed in the form of Laplace transforms. In some cases we may invert the Laplace transforms analytically, but in general we have to invert them numerically.
Adhiputra, Randy,Utami, Maisari,Suyono, Eko Agus,Budiman, Arief,Hariani, Poedji Loekitowati,Pratiwi, Ani Setyo,Wijaya, Karna Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.4
This research aims to study the simultaneous extraction and transesterification of Chlorella vulgaris (C. vulgaris) using microwave irradiation with methanol as solvent and potassium hydroxide (KOH) as catalyst. The microwave-assisted in-situ transesterification of C. vulgaris is assessed at various ratios of biomass-to-methanol, reaction times, and catalyst concentrations during the centrifugation and evaporation process. Gas chromatography-mass spectrometry (GC-MS) analysis is performed to confirm fatty acid methyl ester (FAME) composition. Biodiesel preparation is carried out by simultaneous extraction and transesterification of microalgae from C. vulgaris. The product is then characterized using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (<sup>1</sup>H-NMR); microalgae are observed using scanning electron microscopy (SEM). The highest amount of FAME is obtained at a biomass-to-methanol ratio of 1:12, reaction time of 40 min, and catalyst concentration of 2 wt%. Biodiesel shows conversion to about 77.64% of methyl ester (methyl myristate, methyl palmitoleate, methyl linoleate, methyl oleate, methyl arachidonate, and methyl 5,8,11,14,17-eicosapentanoate).
The Role of Facilitating Conditions and User Habits: A Case of Indonesian Online Learning Platform
AMBARWATI, Rita,HARJA, Yuda Dian,THAMRIN, Suyono Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10
The study examines the role of facilitating conditions and user habits in the use of technology in Online Learning Platform (OLP) in Indonesia. The adoption of online learning, persistence, and learning results in online platforms is essential for ensuring that education technology is implemented and gets as much value as possible. People who use technology and systems will embrace new technologies even more. This quantitative study is based on a survey of 254 respondents, who were active users of the technology, and considers the facilitating conditions and user habits variables. Two research hypotheses were tested using the Partial Least Square-Structural Equation Modeling method. Cronbach's Alpha, path coefficient, AVE, R-square, T-test were applied. The results showed that the factors significantly influence the Online Learning Platform technology behavioral intention. This impact is primarily associated with the availability of the resources required to use OLP technology. The availability of these resources includes supporting infrastructures such as widespread Internet access, easy access to mobile devices, and file sizes that affect access speed. The findings of this study suggest that it is necessary to introduce and increase the availability of resources for using OLP technology, and familiarize people with the technology features.
Anggelina Purnama,Karna Wijaya,Iqmal Tahir,Eko Agus Suyono,Arief Budiman 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.3
Optimizations of microwave-assisted extraction (MAE) and transesterification of bio-crude oil from spirulina (Arthrospira platensis) were conducted. The bio-crude oil from A. platensis was initially extracted using water as a solvent, centrifugation, dissolved with n-hexane, separation, and continued to evaporation. The optimization for the extraction was conducted with varieties of biomass-to-solvent ratio, extraction temperature, extraction time, and n-hexane contact time, yielding the optimum condition with biomass/solvent 1 : 7, extraction temperature 70 oC, extraction time 15 minutes, and contact time 25 minutes (D70/15-25) 5.56%. The average yield of the bio-crude oil obtained was 4.87%, variation 0.32, standard deviation 0.57, and standard error 0.14. The optimization for transesterification was carried out with variations of bio-crude oil-to-methanol ratio, reaction temperature, and reaction time, yielding the optimum condition with bio-crude oil/methanol 1 : 6, reaction temperature 65 oC, and reaction time 50 minutes (G65/50) 98%. The average yield of the biodiesel obtained was 88%, variation 50.29, standard deviation 7.09, and standard error 2.68. The cell damage before and after extraction and also conventional heating observed using SEM showed massive damage by this method.