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ISSN / EISSN : 1411-1047 / 2503-2364
Total articles ≅ 111
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, Muhamad Allan Serunting
JURNAL EKSAKTA, Volume 19, pp 26-34; https://doi.org/10.20885/10.20885/eksakta.vol19.iss1.art3

The Magnetic compound, Fe3O4, is one of the compounds that is easily hydrolyzed and oxidized. A coating method was presented in this study to prevent the process. The modifications of Fe3O4 were carried out by supporting alginate as natural polymers on the surface of Fe3O4. Preparation of magnetic alginate/Fe3O4 (Alg/Fe3O4) nanocomposite has been successfully synthesized. Alg/Fe3O4 material was synthesized using the coprecipitation method with Fe2+; Fe3+ (with molar ratio 1:2) and alginate 1% as precursors. Synthesized Alg/Fe3O4 nanoparticles were characterized by Fourier Transform Infrared Spectroscopy (FTIR), DelsaTM Nano C Particle Analyzer, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The Alg/Fe3O4 has an average diameter of 13.70 nm. Photodegradation test of synthetic methylene blue (MB) dye was found at pH 5.0 and irradiation time under UV245 for 60 minutes. The degradation results showed that the percentage of MB dye removal reached more than 90%.
Lina Fauziah, Miladiatul Wakidah
JURNAL EKSAKTA, Volume 19, pp 35-45; https://doi.org/10.20885/10.20885/eksakta.vol19.iss1.art4

Extraction of papaya leaves (Carica papaya L.) using Ultrasonic Cleaner has been performed. Papaya leaves were extracted for 6 hours in a methanol as solvent. The results of phytochemical screening showed that methanol extract contained secondary metabolites of flavonoids, alkaloids, tepenoid, saponin, and phenolic classes. Methanol extract was then partitioned liquid-liquid with n-hexane. Quantitative analysis of partitioning of n-hexane using papaya leaves using Gas Chromatography-Mass Spectrometry (GC-MS) showed the presence of neophytadiene (1.59%), palmitic acid (1.35%) and methyl linolenate (3.33%). The results showed that Ultrasonic Cleaner can be used to ultrasonic-assisted extraction of natural products especially for papaya leaves.
Uray Hety Humaira,
JURNAL EKSAKTA, Volume 18, pp 97-105; https://doi.org/10.20885/eksakta.vol18.iss2.art2

Development in the country is growing including in the West Borneo Province. However in 2015, the achievement of human development at the National level is quite low, while the District and City varied considerably. Human Development Index is one of the parameter for human development that are affected by many factors. In this paper, analysis for identify the factors for human development index in West Kalimantan Province by using Regression Analysis was conducted. Regression was based on time series data from 2012 until 2015. It is found that Fixed Effect Model is the best regression model with the R2 of 0.99853%. The influencing variables are Life Expectancy (AHH), Adjusted Per Capita (Expenditure), School Average (RLS), School Expectation (HLS), and Gross Regional Domestic Product at Constant Price (GRDP).
Kendri Wahyuningsih, Jumeri Jumeri, Wagiman Wagiman
JURNAL EKSAKTA, Volume 18, pp 121-136; https://doi.org/10.20885/eksakta.vol18.iss2.art4

Pinctada maxima shells from West Nusa Tenggara has natural minerals called calcite that can be decomposed into CaO compounds as a green catalyst that heterogeneous, base and environmentally friendly. CaO compounds in the nanometer scale is one option as an alternative substitute or replacement of the use of homogeneous catalysts. The purpose of this study was to test the catalytic activity of CaO compound from the pearl shells (P. maxima) based on particle size. The catalytic activity test has been measured against the percentage of yield of methyl ester produced by alcoholysis reaction. Characterization of nano-CaO compounds has been done using X-ray powder diffraction (XRD), Brunauer Emmett Teller (BET), scanning electron microscope energy-dispersive X-ray spectroscopy (SEM-EDX), transmittance electron microscopy (TEM), while methyl esters has been analyzed using the ASTM method. CaO catalyst on the nanometer-scale have more effective catalytic activity than micrometer scale with the yield percentage of methyl ester obtained are 81,61% and 30,71%, respectively. The results of methyl ester characterization by ASTM method has shown that methyl ester has specification that are close to diesel oil, so it can be used as an alternative or substitution on diesel engine.
A. Rindang Anggit Laksono, Yohanes Martono, Cucun Alep Riyanto
JURNAL EKSAKTA, Volume 18, pp 155-166; https://doi.org/10.20885/eksakta.vol18.iss2.art7

The aim of this research is to find the optimal condition for Zn(II) complexation with protoporphyrin IX which is a natural coloring pigment on quail eggshell. The concentration of protoporphyrin IX extract is 0.01% (w / w) of the dried extract. The results of the complex are analyzed using Response Surface Methodology (RSM). The design used was central composite design with 3 factor variables X1 = pH (2; 4; 6), X2 = ratios (1: 3,1: 4,1: 5) and X3 = time (30 ', 60', 90 '). The modeling used is linear and shows that the pH, ratio, and time factor have an influence on the complexation. This model gives the absorbance equation Y = 2.12506 - 0.049856X1 - 020316X2 - 0,00409857X3 and gives treatment in the most optimum complexation of pH 2; ratio of 1: 3; and time for 30 minutes with the absorbance of 1,293 and the desirability value of 0.825.
Ardi Nugroho, Fany Devita Ritonga
JURNAL EKSAKTA, Volume 18, pp 137-145; https://doi.org/10.20885/eksakta.vol18.iss2.art5

A rapid, non-destructive and reagent-free infrared spectroscopy combined with Partial Least Square (PLS) has been developed for the dexamethasone quantification in joint-pain killer traditional herbal medicine (THM). The main aim of this study is to select the best wavenumbers that are capable of providing the high coefficient of determination (R2), low values of Root Mean Square Error of Calibration (RMSEC), Root Mean Square Error of Cross Validation (RMSECV) and predictive residual error sum of squares (PRESS). Finally, wavenumbers 3646, 3642, 2461, 2453, 2432, 2406, 2229, 2209, 2197, 2097, 2092, 2064, 2059, 2047, 2026, 2009, 1969, and 1513 cm-1 were selected for the prediction of dexamethasone in the joint-pain killer traditional herbal medicine. The correlation between the actual values of dexamethasone determined in joint-pain killer traditional herbal medicine using infrared spectroscopy combined with PLS revealed the R2 values of 0.9988. The RMSEC values obtained 0,009455. The PRESS and RMSECV value obtained as the results of cross-validation model selection for dexamethasone in joint-pain killer traditional herbal medicine were 0,0022721.00 and 0,02902, respectively. The high value of R2 and low value of RMSEC, RMSECV and PRESS indicated that this method had high accuracy and precision in a validated condition for the dexamethasone quantification in the joint-pain killer traditional herbal medicine. These results indicated that infrared spectroscopy combined with PLS can be an alternative method for the dexamethasone determination in joint-pain killer traditional herbal medicine.his part contains English version of the The abstract presents background, method of the research/ literary study and discussion. The abstract consist of maximum 300 words. All sentence must represent the core of research presented in good structure of sentences.
JURNAL EKSAKTA, Volume 18, pp 145-154; https://doi.org/10.20885/eksakta.vol18.iss2.art6

Currency exchange rate of a country to the other countries is fluctuative. The movement of the exchange rate affects the country’s economy. The exchange rate can change any time according to the market mechanism, therefore currency exchange predictions is required to determine future economic policy. Based on the impact of exchange rate in economy fluctuations, an accurate model is needed to determine the exchange rate movements.In this case, the model is Locally Stationary Wavelet (LSW). This model combines stocastic process class based on wavelet non decimated. LSW model can catch most of the information in time series data. Based on the application of LSW mtehod on the data of the rupiah against the US dollar for the period April 2016 - March 2017, it can be concluded that model provides forecasting results approaching actual data therefore it can be used for forecasting exchange rates. The value of the mean absolute percentage error (MAPE) is 0,1201293%.
Umi Nurofi’Atin, Agus Maman Abadi
JURNAL EKSAKTA, Volume 18, pp 106-120; https://doi.org/10.20885/eksakta.vol18.iss2.art3

The suspension system is part of motorcycle that serves to absorb vibration and shocks of the road surface so as to improve the safety and comfort while driving. Motorcycle typically use double shockbreaker system which analogous to a two-spring system arranged in parallel. The aim of this researh is to analyze the model of the model of double shockbreaker motorcycle suspension system that working without outside force using passive suspension system. The data used are from damper tester experiment, then model analyzed using analytical method and the fourth order of numerical Runge-Kutta method. This research use shockbreaker observation datas that is the measurment data of spring constant and damping constant by performing damper tester using 4 different loads. The process model analysis using Matlab R2013a. Input variables are spring constant, damping constant, and the mass of the load. Methods of analysis using analytical method and the fourth order of Runge-Kutta method. While the resulting outputs are 2 spring constants, change the length of the spring, damping ratio, the optimal damping of the suspension, and the spring deflection chart against time. This model motorcycle suspension system uses solution of differential equations for the under damped suspension condition, that is the suspension system will be insulated a few moments before reaching the equilibrium position. Therefore, the resulting damping rate of the motorcycle is not optimal yet. This study found the optimal damping for each model of the suspension system. The level of accuracy of the fourth order of runge-kutta method for model analysis of the suspension system is quite high with error
Hikmah Fatmawati, Wellyana Puspitasari, Rohini Pujiarti, Sesy Ardyanti,
JURNAL EKSAKTA, Volume 18, pp 64-73; https://doi.org/10.20885/eksakta.vol18.iss1.art7

Research on utilization of snail (Pilla ampullacea) shell as CaO source for biodiesel conversion from rice bran oil has been investigated. CaO was derived by calcining the shell at pada 900oC for 2 h. The powder obtained from the process was characterized using x-ray diffraction (XRD), energy dispersive x-ray (EDX), Fourier-Transform Infra-red (FTIR) and surface basicity test. In order to test the activity of catalyst, effect of catalyst weight on the yield of conversion as studied. Results show that the derived material is composed from dominantly CaO and the material demonstrates activity in rice bran conversion into biodiesel. Compared to NaOH, the CaO catalyst exhibits more effectively active as shown by the higher yield. From varied catalyst weight, it is obtained that at the range of 2.5-10% catalyst weight does not affect significantly to the increasing yield.Â
Muhammad Muhajir, Yayi Diyah Palupi
JURNAL EKSAKTA, Volume 18, pp 74-84; https://doi.org/10.20885/eksakta.vol18.iss1.art8

Diarrhea being one of public health problems that important because it is third major contributor the pain children in various countries including indonesia. This research using data from islam hospital medical record jakarta in january 2017 shows that diarrhea cases were occupying the highest rank of various types of disease in patients children, using indicators long healed patients , the age of , andsex. Methods used to determine function survival who dominated in patients children are Kaplan Meier and Log Rank. The results of the analysis method kaplan meier got that patients male had the probability of healed longer than for patients female as well as patients age of 6- 11 years had the probability healed longer than the age of ≤ 5 years. To Log Rank test got that there is no significant difference between the survival function based on sex and age patients.
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