bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implementation of an optimal control for reducing individuals infected by hepatitis B virus
Authors: Aminatun Z , Widowati  , Solikhin  
Published: July 2021

Abstract
Hepatitis B is an inflammatory liver disease caused by hepatitis B virus, whose spread can be contagious and becomes a serious world health problem. The spread of hepatitis B can be modeled using the Susceptible, Infected, and Recovered (SIR) model. This paper aims is to reduce individuals infected with hepatitis B virus by applyingoptimal control strategies. The SIR model is given optimal control with three control variables, namely health promotion, treatment, and vaccination. Optimal control form is determined by the Pontryagin Maximum Principle (PMP) method to minimize the number of infected individuals and the associated costs. The step of PMP method i.e. Identify the Lagrange multipliers, and then minimizea Hamiltonian function, further obtaine stationary conditions, and finally find an optimal control. The results of numerical simulations completed by the Runge-Kutta Order 4 show effectiveness in minimizing infected individuals. In addition, it can also maximize individual recovery by giving the proposed three control variables.
The determinant of hours of work (the empirical case for Indonesian old–age)
Authors: Subanti S , Riani A L , Lestari E P , Hakim A R , Susiyanti S 
Published: July 2021

Abstract
The increase in the population of old - age or elderly had become an inevitable thing for both developed and developing countries, Indonesia is one of them. With increasing life expectancy, getting healthier, and the desire to stay active; this encourages old – age individuals to carry out economic activities, one of them by working. This activity is not only to fulfill basic needs but also not all individuals of old – age receive pension social security. This paper aims to examine the determinants of the hours of work for old – age or elderly individuals in Indonesia. The paper findings, for old – age individuals who are under 75 years old, the factors influence the hours of work are economic factors (such as wages and non-labor income), the head of household status, marital status, education, urban rural, and industrial origin. However, the old – age individuals who are above 75 years old, these factors have no real influence. Activities carried out by this elderly group, both economic and non-economic, are more about efforts to maintain their routines so that they still feel healthy, they can meet many people, they do not depend on others, and become independent individuals. The suggestion, the government needs to pay attention to working hours and determine the proper industrial origin for elderly who still want to work; they should encourage the care programs for the elderly who come from their families, this is more beneficial for the elderly because it is expected to minimize the risk of illness and death. Furthermore, for old – age individuals who previously worked in the informal sector, the government needs to improve retirement security.
Height wave modelling using spatial extreme value with max stable process (MSP) brown-resnick model
Authors: Hakim A R , Warsito B , Yasin H 
Published: July 2021

Abstract
Analysis of extreme data containing spatial elements can be used the Spatial Extreme Value method, which is applied with a max-stable process approach. The data preprocessing process begins by identifying the extreme data of each location for each time period or block. This method is also called Block maxima. The data obtained from the Block Maxima process will follow the Generalized Extreme Value (GEV) distribution. GEV has three forms of distribution, namely Gumbel, Frechet and Weibull. In this study, the data will be transformed into the frechet distribution margin because the frechet has a heavy tail shape, this is required in MSP modeling. Smith model, Schlater model, and Brown Resnik model are the three main models in MSP. Brown technical model is used in this research because Brown Resnick form is a flexible ta of stationary max stable processes in Gaussian random fields. The best model is selecting based on the smallest TIC value from all combinations of Trend surface models. The selected model is then used to determine the prediction of the extreme wave height for each location with a certain time period. The location used in this study is a point where fishermen are widely used to find fish, namely Semarang, Pekalongan, and Rembang which are in Central Java Province.
Measuring risk based on skewed t distribution approach
Authors: Sulistianingsih E , Rosadi D , Abdurakhman  
Published: July 2021

Abstract
This paper analyses a Skewed t Distribution approach to estimate Value at Risk (VaR) as a tool that can measure a risk investment. The method can estimate an investment risk that can overcome the shortcoming of classical VaR, which cannot capture the existence of fat tail and skewness. The application of the method was utilized to evaluate the individual risk of four stocks taken from the NYSE Index, namely Advance Micro Devices Inc (AMD), The Coca-Cola Company (KO), Pfizer Inc. (PFE), and Walmart Inc (WMT). It can be summarized from the result of the analysis that VaR (in several confidence levels) based on the distribution approach is powerful in risk measurement and can give an alternative to the investor for estimating the risk.
Numerical approach nonminimaly supported design for two parameters generalized exponential model and its efficiency
Authors: Widiharih T , Mustafid  , Sudarno  , Prahutama A 
Published: July 2021

Abstract
Nonminimally supported designs is a design that the number of supported design is greater than the number of parameters of the model. We construct nonminimally supported design with the number of the supported designs is the number of parameters plus one and it has uniform weight. We use two methods to construct nonminimally supported design, first we create the formula of determinant information matrix then miximized it, second by adding one supported design from minimally supported design. The formula to determine the supported design is a complicated nonlinear function, so we use numerically approach. Furthermore we conclude the best of nonminimally supported design based on the highest value of determinant information matrix. Efficiency of nonminimally supported design to minimally supported design is ratio of determinant information matrix nonminimally supported design and determinant information matrix minimally supported design.
Sentiment analysis of e-commerce application in Traveloka data review on Google Play site using Naïve Bayes classifier and association method
Authors: Oktaviani V , Warsito B , Yasin H , Santoso R , Suparti  
Published: July 2021

Abstract
E-commerce is a business operation model which rapidly growing today. Many business actors and the customer take advantage of E-commerce itself. Thus, it influences people’s socially and economically. Traveloka is one of the best e-commerce applications that is often visited in Indonesia. Each application allows users to post an application review. The review aims to evaluate and improve the quality of the future product. For that purpose, analysis sentiment can be used to classify the review into positive or negative sentiment. Sentiment analysis can provide information that can be extracted. From the observed data, it can provide useful information for those who need it. Some sentiment analysis stages contain sentiment data collection, data preprocessing, term weighting using TF-IDF, sentiment labeling using sentiment scoring, review data classification using the Naïve Bayes Classifier method, and text association. The model was evaluated using 10 Fold Cross-Validation. Measurements were made with the Confusion Matrix. The results obtained from the reviews given by Traveloka users on Google Play using the Multinomial Naïve Bayes was obtained overall accuracy in 91.20% and kappa accuracy in 59,56 %. The higher overall accuracy value and kappa accuracy obtained, the better performance of the classification model.
Analysis of bayesian method in queuing system customer service locket Semarang Tawang railway station
Authors: Sugito  , Mustafid  , Prahutama A , Warsito B , Salsabela A A 
Published: July 2021

Abstract
Jamming is one of the serious problems in Indonesia caused by the increase of vehicles. The government has been made solution for this situation for example was public transportation. The train is one of the suitable public transportation because of the ticket price was cheap. Tawang Railway Station Semarang was the biggest railway station in Semarang. In the specific day such long holiday or celebration day, many people have chosen train to take them. This make a queuing situation on the counter of station especially on customer service locket which provide information about the station and more. Queue theory models provide the random of arrival and service time. The Bayesian theory suits to handle the problem of queuing that has been working for several times to repair the prior information with new information of sample and also can make a combination of the distribution after assumption steady state. Based on the analysis of the queue models for customer service are (G/G/c):(GD/∞/∞) from the posterior distribution with combination from prior distribution and likelihood sample. The prior distribution used in this research is Poisson. The likelihood sample used Uniform Discrete and Negative Binomial distribution. The posterior distribution is a combination of Uniform Discrete and Beta distribution. Queue models can be used to count the size of the system performance. Based on the calculations and analysis with RGui, it can be concluded that the queuing system of customer service locket have been good because its steady state and busy probability is higher than jobless probability.
Application of Clayton Copula to identify dependency structure of Covid-19 outbreak and average temperature in Jakarta Indonesia
Authors: Novianti P , Kartiko S H , Rosadi D 
Published: July 2021

Abstract
Today Indonesia is experiencing health problems that are also being faced by all countries in the world, namely Covid-19. Jakarta, the capital of the state of Indonesia, is one of the provinces that has been the epicenter of the Covid-19 cases. Aim of study is to determine dependency between Covid-19 and maximum temperature in Jakarta, Indonesia. Data of Covid-19 cases used are daily cumulative cases, new cases, and deaths. The correlations used are Pearson, Spearman, and Kendall. The correlation coefficient only provides information on the measure of the two variable relationship and does not show the structure of dependency between these variables. One of the methods used to see the dependency structure between variables is copula. One of the copula that is widely used is the clayton copula because of its flexible characteristics. Meanwhile, to see the dependency structure between variables will be used the Copula method from Clayton Copula. The results show that maximum temperature is significantly associated with the Covid-19 pandemic. Based on clayton copula model, the small parameters indicate small dependencies between Covid-19 and maximum temperature.
Modification of activated carbon of rice husk using HDTMA-Br (SMAC) surfactant as nitrite ion (NO2
−) adsorbent
Authors: Arnelli  , Santoso B , Astuti Y 
Published: July 2021

Abstract
Surfactant modified activated carbon (SMAC) is a product resulting from the modification of activated carbon with surfactants to increase the adsorption ability of activated carbon against ions in water. Carbonization using pyrolysis at 300°C, 350°C, and 400°C. Activation of carbon was carried out in two ways, the first activation using H3PO4 activator, followed by heating at 410°C for 1 hour. Second, activation using H3PO4 followed by radiation with microwaves. The resulting activated carbon was modified with HDTMA-Br to form SMAC, then SMAC was applied for adsorption of nitrite (NO2
−) ions. This study aimed to determine the optimum conditions for carbonization temperature, radiation time, radiation power, adsorption time of HDTMA-Br. The adsorption capacity of SMAC on nitrite ions and the adsorption process of HDTMA-Br were studied (thermodynamic data). Characterization was carried out using FTIR, SEM, and GSA. The optimum carbonization temperature was 300°C; the optimum activation was 5 minutes and 400 watts, the optimum time for HDTMA-Br adsorption was 4 hours with the adsorption capacity was 7.304 mg/g. SMAC is effective in adsorbing nitrite ions where the adsorption capacity was 0.741 mg/g, and the adsorption efficiency is 98.833%. The adsorption of HDTMA-Br on activated carbon was physical adsorption, SMAC has an N-(CH3)3 group from HDTMA-Br with a SMAC surface area of 24.173 m2/g.
Sorption of waste lubricant oil spills from seawater using natural hollow fibres
Authors: Sukmawati A , Septiani W , Surkardan M D 
Published: July 2021

AbstractWaste lubricant oil is mostly produced by its replacement on engines machine, which is frequently discarded into the environment to seawater in particular. Calotropis gigantea and Ceiba pentandra fibres had the potential to be used as a natural oil absorbent material. This study was conducted on these fibres’ oil sorption capacity in artificial seawater, using different variations in the thickness of the oil layer, contact time, mass absorbent, and temperature. The highest sorption capacity was obtained by 65,70 g/g for Calotropis gigantea, 79,71 g/g for Ceiba pentandra on fibre weight of 0.3 g, 9 mm oil film thickness, contact time 60 minutes, at room temperature. This report represents that both fibres are highly effective sorption on waste lubricant oil.
Antimicrobial activity of secondary metabolites of endophytic bacteria F4 of papaya leaf (Carica papaya L)
Authors: Sarjono P R , Silvia D , Mulyani N S , Ismiyarto  , Ngadiwiyana  , Prasetya N B A , Andriani Yosie 
Published: July 2021

Abstract
Papaya leaves have been known to contain secondary metabolite compounds as antimicrobial, so that endophytic bacteria is also suspected of having secondary metabolite compounds as antimicrobial. In previous research, endophytic bacteria have been isolated from papaya leaf and obtained 5 endophytic bacteria which were F1, F2, F3, F4 and F5. Three bacterias that have been known for their antibacterial activity were F1, F3, and F5. This research aims to determine the antimicrobial activity of F4 endophytic bacteria. The results showed that single isolates of endophytic bacteria F4 is a type of Gram-positive bacteria with a basil cell shape (stem). F4 endophytic bacteria has 3 growth phases; they are logarithmic phase occurs at 0-8 hours, stationary phase at 8-34 hours, and phase of death at 34-46 hours. Phytochemical results showed that MS18 contained saponin group compounds, while MS36 contained alkaloids and saponin group compounds. The highest antimicrobial activity was in the death phase, MS36 with minimum inhibitory concentration (KHM) to Escherichia coli, Candida albicans, and Bacillus subtillis were 15.5 mg/mL, respectively; 16.5 mg/mL and 16.5 mg/mL by disc diffusion method, whereas to Aspergillus niger of 0.5 mg/mL by dry weight method.
Effect of chitosan as adsorben to bacto agar quality from Gelidium sp.
Authors: Darmawan M , Siswanti H W , Nurhasni  , Fransiska D 
Published: July 2021

Abstract
Gelidium sp. is a seaweed that produces agar with a high gel strength. Bacto agar must have a high purity, so it needs a right purification method. One of the ways by adsorption process using chitosan. The aim of this research was to determine the influence of chitosan as an adsorbent and the optimum condition of its adsorption process. Bacto agar was extracted with water at 90°C. An alkali and acid pretreatment were added in the extraction process in order to increase thephysico-chemical properties of the agar gels. The agar extract was adsorbed by chitosan with various concentration of chitosan (0.5; 0.75; and 1%) and adsorption time (0, 30, and 60 minutes). The characteristic of bacto agar include moisture content, ash content, acid-insoluble ash content, sulphate content, gel strength, viscosity, syneresis, gelling and melting points, analysis of its molecular structure by FTIR and SEM. Bacto agar resulted in this research were tested as a bacterial culture medium using Total Plate Count (TPC) method. The best chitosan treatment process was obtained in bacto agar at 0,75% and 0 minute of adsorption which is had the physico-chemical properties that met the criteria of commercial bacto agar with 3.50% of bacto agar yield, 14.61% moisture content, 4.02% ash content, 0.93% acid-insoluble ash content, 1.34% sulphate content, 1054.96 g/cm2 gel strength, 60 Cp viscosity, 4.62% syneresis, 65 °C and 20.75 °C of melting and gelling points respectively. The microbial analysis shows that bacto agar can be used as a bacterial culture medium.
Synthesize of self-electrostatic interaction chitosan-carrageenan membrane and its properties
Authors: Ismillayli N , Hadi S , Andayani I G A S , Honiar R , Mariana B , Sanjaya R K , Hermanto D 
Published: July 2021

Abstract
The preparation of polyelectrolyte complex (PEC) based on bio-composite materials often requires crosslinking agents to achieve the desired stability and properties of the material formed. PEC with opposite charges has the advantage in self-crosslinking through electrostatic interactions. Chitosan is a positively charged polysaccharide with -NH3
+ group while κappa-carrageenan is a negatively charged polysaccharide with -OSO3
− group. This work focused on synthesizing chitosan-carrageenan membrane and determining its characteristics. The membrane was prepared by interacting chitosan and carrageenan hydrosols at a pH of 5. The obtained chitosan-carrageenan membrane had better physical-mechanical properties, including tensile strength (load), elongation (strain), and elasticity (modulus young), adsorption, and resistance of water, than the constituent polymers. The FTIR spectra indicated the presence of self interaction in membrane between protonated amine groups of chitosan and sulfate groups of carrageenan. The difference in surface morphology among chitosan-carrageenan membrane and its constituent membranes was confirmed by SEM analysis.
Utilization of bamboo leaf silica as a superhydrophobic coating using trimethylchlorosilane as a surface modification agent
Authors: Silviana S , Dalanta F , Sanyoto G J 
Published: July 2021

Abstract
In recent years, there has been an increasing research interest regarding the development of superhydrophobic coating for various purposes with tetraethyl orthosilicate (TEOS) as the source of silica. Unfortunately, TEOS is hazardous as an alkoxide and need long step as well as time consuming to synthesize it. Typically, previous researches using fluoroalkylsilane (FOK) as the surface modification agent is containing fluoro compound which is not safety to use. This paper is aimed to develop a cost-effective and environmental-friendly superhydrophobic coating by utilizing bamboo leaf silica. This work was particularly conducted to develop the method of purification of bamboo leaf ash as the source of silica to produce superhydrophobic coating material. This method could be an effective and efficient way of preparing a superhydrophobic coating using silica bamboo leaf with eco-friendly solvent exchange agents. This observation used n-hexane, cyclohexane, isooctane as a solvent exchange, and trimethylchlorosilane (TMCS) as a surface modification agent which is not containing fluoro component. The initial bamboo leaf silica and purified silica were examined using XRD, BET, XRF, and SEM EDX Mapping to obtain essential information such as structure, porosity, purity, and surface topography. Also, the coated zinc plat with different solvents was assessed hydrophobicity by contact angle measurement and surface morphology by SEM. The efficient and effective formulation of the superhydrophobic coating was attained by applying n-hexane solvent, 13 %-v/v TMCS, 1.75 %-w/v of bamboo leaf silica was the highest of contact angle.
Synthesis of ferrate using NaOCl and Fe(OH)3 from electrolysis of used iron, and its application for metanil yellow degradation
Authors: Gunawan  , Prasetya N B A , Haris A , Febriliani F 
Published: July 2021

Abstract
Synthesis of ferrate using NaOCl and Fe(OH)3 from electrolysis of used iron, and its application for metanil yellow degradation had been done. The electrolysis was conducted using used iron and zink plates at anode and cathode electrodes, respectively, Na2SO4 electrolyte. The dissolved iron ion from the electrolysis then was made alkaline using NaOH pellet and NaOCl was soaked to the solution to form ferrate (FeO4
2-). The ferrate was used for metanil yellow degradation and it was compared with other oxidators such as permananate, hydrogen peroxide and dichromate. The ferrate solution formed was indicated by a change from brown to dark purple which was indicated the oxidation of Fe(III) to Fe(VI) with a maximum wavelength of 510 nm. The optimum degradation of metanil yellow by ferrate was obtained at pH 8, molar ratio of 2:1, and for 25 min. Ferrate was the most effective oxidator compared with permananate, hydrogen peroxide and dichromate.
Investigation of mango (Mangifera odorate) sap and starch as organic adhesive of bio-briquette
Authors: Rodiah S , Al Jabbar J L , Ramadhan A , Hastati E 
Published: July 2021

Abstract
Rice husk and coconut shell waste is potential biomass found in Palembang that has not been utilized properly. Besides being used for primary purposes, biomass can be used for energy sources like renewable energy. Biomass residues can be obtained from the pyrolysis process with thermal cracking units (UTC) and used as bio-briquettes. Bio-briquette is prepared from a mixture of pyrolysis residues of coconut shell and rice husk with a mass ratio of 2:1 using a combination of adhesive mucilage (mango sap) and paste (starch). The adhesive is prepared by dissolving the starch in water, then mixing it into melted mango sap. The mass ratio of the sap and starch is 1:1 (w/w), while the ratio of the mixture of adhesive and water is 1:10. Based on the ATR-FTIR characterization, it showed that the C = C strain group and the C-H bending group appeared at 2800 cm−1, which was confirmed by its appearance at 800 cm−1 in the fingerprint area. Then, appears peak in the area of 1300 cm−1, indicating the presence of a nitro group, which is assumed to have come from mango sap. Measurements of the briquette physicochemical properties such as moisture content, ash content volatile matter, and fixed carbon were measured using the proximate analysis method. Furthermore, the addition of coconut shells in producing bio briquettes from rice husks increased the calorific value by 7.305 MJ kg−1. So that, bio-briquette is an effective as an alternative energy source to replace fossil fuel for household purposes.