Showing papers by "Sebelas Maret University published in 2019"

Preparation of nitrogen and sulphur Co-doped reduced graphene oxide (rGO-NS) using N and S heteroatom of thiourea

Abstract: Graphene oxide (GO) has been synthesized via modified Hummer's method with graphite powder as a starting material. The synthesized reduced graphene oxide (rGO) was prepared by GO as a precursor. Synthesis of rGO-NS was performed by hydrothermal method using a dopant thiourea as nitrogen (N) and sulphur (S) donors with the ratio of GO: thiourea = 1:10, 1:15, and 1:20 (w/w), respectively. Characterization using Fourier Transform Infra-Red (FTIR) spectroscopy shows several peaks that have an agreement with −OH, C=O, C=C, C-OH, and C-O functional groups for GO and absorption peaks of −OH, C=C, and CO functional groups for rGO with different intensity, while modified materials of variation rGO-NS emerged typical absorptions of −OH, C=C, C=N, C-N, and C-S functional groups. GO and rGO material that have been analysed using X-Ray Diffraction (XRD) shows a dominant peak at 2θ 10.77° (001) and 24.97° (002), respectively. While the distance between layers (dSpacing) on rGO (3,56 A) was lower than GO (8,22 A). Compared to rGO, XRD analysis also shows that the addition of N and S on GO structure caused shifting of 2θ in 23,73°-24,06° (002) and calculated d spacing of rGO-NS is found to be 3,70 A−3,74 A. Morphological observation of rGO-NS using Scanning Electron Microscopy (SEM) shows that rGO-NS is a thin transparent sheets formed because the exfoliation process of GO material.

Affective variables and informal digital learning of English: Keys to willingness to communicate in a second language

Abstract: This study examined the under-researched relationship between informal digital learning of English (IDLE) activities (receptive IDLE activities and productive IDLE activities), affective variables (grit, motivation, self-confidence and second language speaking anxiety) and willingness to communicate in a second language. Data ( N = 183) were collected through a questionnaire from one state university in an English-as-a-foreign-language Indonesian context. The results showed that students’ willingness to communicate correlated significantly with all of the IDLE activities and affective variables. However, only productive IDLE activities, grit, self-confidence, and motivation were identified as the significant predictors of students’ willingness to communicate. Findings suggest that students’ IDLE engagement and affective states play a significant role in a second language communication. In particular, pedagogical benefits of affective variables (e.g., grit, self-confidence, and motivation) and productive IDLE activities should be emphasised to facilitate students’ willingness to communicate in a second language. These results will broaden current knowledge of IDLE and second language communication behaviour, which can contribute to bridging the interdisciplinary gap between computer assisted language learning, second language acquisition, and psychology.

Development Frameworks of the Indonesian Partnership 21st-Century Skills Standards for Prospective Science Teachers: A Delphi Study

Abstract: In the 21st century, students from all levels of education face extreme global competition, technology that is driven by information, and rapid media-saturation. These dramatic accelerational challenges are the reason why the educational system must prepare students with the skills needed in the era of globalization. Based on a document published by The Board of National Education Standards in 2010 on the importance of establishing a framework for 21st-century education in Indonesia, the necessity of appropriate standards has become very important to the current educational system. This paper aims to discuss conceptual frameworks for prospective science teachers in Indonesia. Using an extensive literature review of three document (P21, enGauge-21CS, and ATC21S) and group discussion with a two-round Delphi study, we have constructed the Indonesian Partnership for 21st-Century Skills Standards (IP-21CSS) based on an agreement between 15 panelists. From the results of this study, we have established four IP-21CSS that were perceived by panelists as appropriate standards for prospective science teachers in Indonesia ranging from 4.5 to 5 or in the high level. These standards include: (1) 4Cs (critical thinking, creative thinking, collaboration, and communication); (2) ICTs (technology, media, and information literacy); (3) spiritual values (religious beliefs and spiritual awareness); and (4) character building (teachers’ attitudes and scientific attitudes). Therefore, it concludes that the implementation of 21st-century education learning that emphasizes each IP-21CSS indicator needs to be considered as an essential component in the courses process for prospective science teachers in Indonesia.

Minimizing waste using lean manufacturing and ECRS principle in Indonesian furniture industry

Abstract: The manufacturing industry is considered as one important sector, which has a significant influence on the economic growth of a country. The increase of fierce competition among products requires t...

Environmental risk of maritime territory subjected to accidental phenomena: Correlation of oil spill and ship grounding in the Exxon Valdez's case

Abstract: Ship has become inseparable part of international trading scheme which involves large scale commodities in export-import. During its operation to reach the designated destination, vessel traffic and geographical condition are possibly causing the accidents on the ship. As chain of reaction, commodities/cargoes can be spilled which influence surroundings. Emergency situation is certainly taking place if the cargo is classified as dangerous item, such as chemical compound and crude/product oil. Effect to environment can be immense, which includes living ecosystems and species. This work presents a series of discussions related to environmental casualties due to accidents which take place in maritime territory. Statistical data of accidental phenomena in the recent century is summarized. Infamous accident of the Exxon Valdez is considered as the prime case, and the environmental casualties are discussed which can be further references for maritime countries in regulation planning for prevention and mitigation accounting for oil spill.

Material Characterizations of Gr-Based Magnetorheological Elastomer for Possible Sensor Applications: Rheological and Resistivity Properties.

Abstract: Considering persistent years, many researchers continuously seek an optimum way to utilize the idea of magnetorheology (MR) materials to be practically used for everyday life, particularly concerning resistivity sensing application. The rheology and resistivity of a graphite (Gr)-based magnetorheological elastomer (Gr-MRE) were experimentally evaluated in the present research. Magnetorheological elastomer (MRE) samples were prepared by adding Gr as a new additive during MRE fabrication. The effect of additional Gr on the rheological and resistivity properties were investigated and compared with those of typical MREs without a Gr additive. Morphological aspects of Gr-MRE were characterized using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Rheological properties under different magnetic fields were evaluated using a parallel-plate rheometer. Subsequently, the resistivity of all samples was measured under different applied forces and magnetic fields. From the resistivity evaluation, two relationship curves resistance (R) under different applied forces (F) and different magnetic fields (B) were established and plotted by using an empirical model. It was observed from the FESEM images that the presence of Gr fractions arrangement contributes to the conductivity of MRE. It was also observed that, with the addition of Gr, rheological properties such as the field-dependent modulus can be improved, particularly at low strain amplitudes. It is also demonstrated that the addition of Gr in MRE can contribute to the likely use of force detection in tactile sensing devices.

Improvement of Antioxidant Activity and Physical Stability of Chocolate Beverage Using Colloidal Cinnamon Nanoparticles

Abstract: In this study, the functionality of colloidal cinnamon nanoparticles in improving the antioxidant activity and suspension stability of a chocolate beverage formulated with two types of cocoa powder (natural and alkalised) was investigated. Cinnamon-loaded nanoparticles based on shellac and xanthan gum prepared using anti-solvent precipitation were incorporated in the chocolate beverage in multilevel proportions. The results showed that the addition of the nanoparticles improved the total phenolic content up to 40% and antioxidant activity up to 60% depending on the level of the nanoparticles added. Improvement of the physical stability of the chocolate beverage was observed regardless of the cocoa powder type. As the sedimentation index of the beverages made with alkalised and natural cocoa powders after 96 h was 5.7 and 85.7, respectively, the stabilisation effect of the nanoparticles seemed to be significantly influenced by the characteristics of the beverage raw material. The prevention of cocoa particle sedimentation was attributed to the colloidal network that originated from xanthan gum as shown by Cryo-SEM imaging or the increased viscosity of the mixture (i.e. from 2.4 to 27.7 mPa s at a shear rate of 50 s−1). Incorporation of the colloidal cinnamon nanoparticles had no significant effect on pH and a slight effect on the colour of the chocolate beverages. The formulated nanoparticles could be a promising complement to “ready-to-drink” products to enrich the bioactive content and prolong suspension stability.

Nanoparticles as components of electrochemical sensing platforms for the detection of petroleum pollutants: A review

Abstract: Accurate monitoring of environmental pollutants has become a primary concern due to rapid progress in the oil industry during recent years. Nanoparticles (NPs) for electrochemical sensing are emerging as crucial tools for pollutant monitoring such as aromatics hydrocarbon, polyphenols, and toxic gases produced by the oil industry. NPs provided increasing the sensitivity and selectivity of the sensor through increasing the surface area, owing to the high surface-to-volume ratios, and a highly active site area so that the molecules could be easily adsorbed on the surface electrode to undergo a redox reaction. This paper presents a comprehensive overview of the latest nanoparticles used for electrochemical sensing. Moreover, some parameters such as sensitivity, selectivity, the limit of detection, including a specific mechanism detection of analyte targets, and response time have been discussed to determine optimum condition for polyphenols, aromatic compounds, and toxic gases detection. Some recent results have been presented and discussed.

Elementary school teacher’s obstacles in the implementation of problem-based learning model in mathematics learning

Abstract: This study aims to describe the teachers' obstacles in applying problem-based learning model in Mathematics learning of elementary schools. This method of this study was a qualitative descriptive. The data sources were three third-grade teachers of the elementary schools. The data analysis consisted of stages of data collection, data reduction, data presentation, and data verification. The results of the study show: in the planning stage, obstacles occur when teachers need careful preparation in making learning plans and determining problems at the beginning of learning. In the implementation phase, the obstacle that occurs is a lack of time in maximizing activities in all phases. The teacher finds it difficult to direct students to problems that require solutions. Teachers need enough time to organize students in group activities. Also, they have difficulty dividing time when guiding groups because students are still waiting for the teacher to explain to the group without doing it themselves first. Another difficulty faced is making students actively ask questions or respond to learning activities, and feedback from problem-solving is less profound.

A highly sensitive safrole sensor based on polyvinyl acetate (PVAc) nanofiber-coated QCM

Abstract: A novel, highly sensitive and selective safrole sensor has been developed using quartz crystal microbalance (QCM) coated with polyvinyl acetate (PVAc) nanofibers. The nanofibers were collected on the QCM sensing surface using an electrospinning method with an average diameter ranging from 612 nm to 698 nm and relatively high Q–factors (rigid coating). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the PVAc nanofiber surface morphology, confirming its high surface area and roughness, which are beneficial in improving the sensor sensitivity compared to its thin-film counterpart. The as-spun PVAc nanofiber sensor could demonstrate a safrole limit of detection (LOD) of down to 0.7 ppm with a response time of 171 s and a sensitivity of 1.866 Hz/ppm. It also showed good reproducibility, rapid response time, and excellent recovery. Moreover, cross-interference of the QCM sensor response to non-target gases was investigated, yielding very low cross-sensitivity and high selectivity of the safrole sensor. Owing to its high robustness and low fabrication cost, this proposed sensing device is expected to be a promising alternative to classical instrumental analytical methods for monitoring safrole-based drug precursors.

The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents

Abstract: Abstract C60 fullerene exhibits unique optical properties that have high potential for wide photo-optical applications. To analyze the optical properties of C60, its excitation and emission properties were studied using UV-Vis absorption and photoluminescence (PL) spectroscopy, which were performed in various, non-polar organic solvents such as toluene, xylene, and trichloroethylene (TCE). The C60 solutions in toluene, xylene, and TCE displayed similar excitation bands at 625, 591, 570, 535, and 404 nm corresponding to Ag → T1u and Ag → T1g transitions. However, these bands differed from the solid C60 observed by UV-Vis diffuse reflectance spectroscopy. The two emission band energies of C 60 solution in toluene and xylene were nearly the same (1.78 and 1.69 eV), whereas the C60 solution in TCE was shifted to 1.72 and 1.65 eV. Because the polarity of TCE is higher than that of toluene and xylene, the PL spectrum of the C 60 solution in TCE was red-shifted. The PL spectroscopy had a better capability than UV-Vis absorbance spectroscopy to distinguish the different interactions between C60 and the organic solvents due to their different solvent polarities.

High energy density of all-screen-printable solid-state microsupercapacitors integrated by graphene/CNTs as hierarchical electrodes

Abstract: Microsupercapacitors (MSCs) are alternative power sources that have the potential to fulfill the increasing demand for wearable and on-chip electronics as they are small and lightweight, and show extremely high charge–discharge rates and power densities, and have high flexibility. However, the critical challenge of recent MSCs is the limitation of low energy density and complicated fabrication processes that are high cost and time-consuming. Here, we reported an all-screen-printable method for fabricating all-solid (including electrolytes) and flexible MSCs by rationally designed composite electrodes with electrochemically exfoliated graphene (ECG) and long single-walled carbon nanotubes (CNTs). This method demonstrated to be a facile and scalable route to fabricate and assemble MSCs in a cost-effective manner and with high throughput. As a result, the resulting MSC devices exhibit an areal capacitance of 7.7 mF cm−2 and volumetric capacitance of 77.3 F cm−3, with an excellent cyclic stability of >99% after 15 000 cycles; this can be attributed to the creation of a high diffusion path and the promotion of ion transport capability. The cell exhibits energy and power densities of 10.7 mW h cm−3 and 3.17 W cm−3, respectively. Moreover, there was negligible degradation in capacitance when subjected to bending deformation with radius reduced to 0.5 mm, indicating excellent mechanical flexibility and operation stability. Further, the output voltage and current can be rationally designed by multiple connections of MSC devices in series and parallel to fulfill the demands of various applications. This study provides a scalable and cost-effective method to produce solid-state MSCs with high energy density, which paves the way for their applications in potential wearable devices.

Whatsapp sebagai Media Literasi Digital Siswa

Abstract: Whatsapp is as one of the most influential social media and widely used by people in Indonesia. Students in Indonesia in the digital era are now using gadgets in their daily activities both at school and outside of school. However, most of these students use social media applications, especially Whatsapp, only for social media, whereas in the application, there are benefits that can improve digital literacy skills. The purpose of this research is to find out: 1) the use of whatsapp as the digital literacy media of students and 2) the digital literacy skills of students in terms of language skills. The method used in this study is to refer, note, and study the literature. This research is a qualitative descriptive study. The results of this study are, 1) the level of digital literacy of students with whatsapp social media is still lacking and 2) improvement of students’ digital literacy ability in terms of aspects of language ability, namely, listening, speaking, reading, watching, writing, and writing.

Thermal Stability and Rheological Properties of Epoxidized Natural Rubber-Based Magnetorheological Elastomer.

Abstract: Determination of the thermal characteristics and temperature-dependent rheological properties of the magnetorheological elastomers (MREs) is of paramount importance particularly with regards to MRE applications. Hitherto, a paucity of temperature dependent analysis has been conducted by MRE researchers. In this study, an investigation on the thermal and rheological properties of epoxidized natural rubber (ENR)-based MREs was performed. Various percentages of carbonyl iron particles (CIPs) were blended with the ENR compound using a two roll-mill for the preparation of the ENR-based MRE samples. The morphological, elemental, and thermal analyses were performed before the rheological test. Several characterizations, as well as the effects of the strain amplitude, temperature, and magnetic field on the rheological properties of ENR-based MRE samples, were evaluated. The micrographs and elemental results were well-correlated regarding the CIP and Fe contents, and a uniform distribution of CIPs was achieved. The results of the thermal test indicated that the incorporation of CIPs enhanced the thermal stability of the ENR-based MREs. Based on the rheological analysis, the storage modulus and loss factor were dependent on the CIP content and strain amplitude. The effect of temperature on the rheological properties revealed that the stiffness of the ENR-based MREs was considered stable, and they were appropriate to be employed in the MRE devices exposed to high temperatures above 45 °C.

Tren Penelitian Anggaran di Indonesia

Abstract: This study aims to provide an overview development of budgeting research in Indonesia. The study was taken from 19 accredited journals in Indonesia. Research samples were obtained from 2008 to 2018 and 74 articles were discussed on budgeting. This study classified the articles based on the sectors of reasearch, research methods and research variables used by the researchers. The most researched sector of the budgeing is in the public sector, while the most widely used method is the quantitative method. Whereas the most reasearch in independent variable is participation in budgeting, the dependent variable that is mostly studied is Performance because it is possible for a person's performance to depend on how the budget management is carried out.

The influence of problem based learning towards social science learning outcomes viewed from learning interest

Abstract: The aim of this study is to determine the influences of Problem Based Learning and learning interest at improving the cognitive learning outcomes in social science of fourth-grade elementary school students. This study is a quasi-experiment study with pre-test and post-test control group design. The sample collection is taken with stratified cluster random sampling technique. The sample of this study is 109 fourth-grade elementary school students, consisted of 50 students from experiment group and 59 students from control group. The students from experiment group are given the application of Problem Based Learning, while the students in control group are given the application of Direct Instruction. The data collection is carried by using the instruments of social science learning outcomes test and social science learning interest questionnaire. The validity of test and questionnaire instruments is carried by expert judgement. The difficulty level, distinguishing power, and reliability of test instrument is tested by using ITEMAN application. The internal consistency and reliability of questionnaire instrument is tested by using SPSS application. The data is analysed by using two-way anova. The outcomes of the study show that PBL and learning interest contribute significant impact towards social science learning outcomes of elementary school students.

Preservice English teachers’ perceptions of English as an international language in Indonesia and Korea

Abstract: Preservice English teachers’ perceptions about English as an international language (EIL) have not been adequately examined in different cross-cultural contexts. To fill that void, a total of 590 p...

Hydrodynamic characteristics of the microbubble dissolution in liquid using orifice type microbubble generator

Abstract: The aim of this work was to investigate the characteristics of oxygen dissolution into water in aeration using an orifice type microbubble generator (MBG). The analysis was conducted using dimensional analysis by taking into account bubble diameter distribution and oxygen mass transfer rate. The characteristics of microbubbles produced by MBG were affected by the combination of air and water flow rates through the MBG. In this study, the ranges of air and water flow rates were set at 0.1–1.0 l/min and 30.0–80.0 l/min, respectively. The microbubbles were captured by a high-speed camera using shadow photographic technique to obtain the bubbles size distribution as well as the average diameter of the bubbles. The volumetric mass transfer coefficient of oxygen was measured using dynamic physical absorption model. The results verified that the size of microbubble depend on air and water flow rates. The increase of the gas flow rate increased the average bubble diameter. On the other hand, the increase of the water flow rate decreased the average bubble diameter. Furthermore, the increase of water flow rate increased the oxygen volumetric mass transfer coefficient. Finally, by using dimensional analysis, the empirical correlation of volumetric mass transfer coefficient, average bubble diameter, and bubble diameter distribution, was proposed. The correlation showed that liquid Reynolds number played most important role in average bubble diameter and oxygen mass transfer rate obtained in MBG aeration.

The field-dependent rheological properties of plate-like carbonyl iron particle-based magnetorheological elastomers

Abstract: This paper investigated the rheological properties of a novel magnetorheological elastomer (MRE) with plate-like carbonyl iron particles (CIPs) as magnetic particles. MRE samples with different shape of CIPs; plate-like (MRE-P) and spherical-like (MRE-S), were prepared. The current work further highlights the effects of varying curing magnetic field towards the rheological properties. X-ray diffraction and magnetic properties analysis were carried out to observe not only the surface morphology of the CIPs but also the cross-section of CIPs in the MRE samples. Rheological properties such as strain amplitude, frequency, and magnetic field sweep test were measured using a rotational rheometer. The MRE-P samples demonstrated higher storage modulus and the loss factor lower than MRE-S. Besides that, the MR effect of MRE-P samples is slightly lower than that of MRE-S correspond to 114% and 137%, respectively.

Enhancing Elementary School Students’ Abstract Reasoning in Science Learning through Augmented Reality-Based Interactive Multimedia

Abstract: Elementary school students’ rational skill is terminated on concrete situations; therefore, enhancing abstract reasoning becomes a prompt for students to be more critical in solving science problems. The objective of the study was to improve abstract reasoning in science learning using interactive multimedia based on augmented reality (AR) for fifth-grade students. This study used a Classroom Action Research conducted in two cycles consisting of Plan, Act & Observe, and Reflect stage each. Data collection techniques used tests and observations involving 28 students. The credibility of the research data was examined based on technical triangulation and source triangulation while the collected data were analyzed descriptively. The results of the study on process aspect showed that the use of interactive multimedia based on augmented reality gave positive changes to the learning processes on earth and rock structure topic in the fifth grade of elementary school. The students’ enthusiasm during the learning processes thus strengthened student-teacher interaction as they enjoyed the learning processes actively, independently, and collaboratively. The interactive multimedia based on augmented reality facilitates the students to reason by exploring more realistic visual objects to eases student understanding of science concept, associating inter-concepts and implementation of information analysis, and problem-solving. The success of the product showed that students’ abstract reasoning in science learning enhanced by 24.20% (in the first cycle) and 23.08% (in the second cycle). The results of this study concluded that the use of interactive multimedia based on augmented reality could enhance abstract reasoning skill of the fifth-grade elementary school students.

The Effectiveness of Accounting E-module Integrated with Character Value to Improve Students' Learning Outcomes and Honesty

Abstract: This study was aimed to examine the effectiveness of e-accounting module integrated character values to improve students’ learning outcomes and honesty. This was motivated by lack of students' understanding of accounting materials so that students tended to take dishonest actions like cheating while doing assignments or examinations. Honesty is one of the characters developed in many curriculla, so that honest character needs to be integrated in learning activities. The data collected in this study were the data on students’ learning outcomes collected through multiple choice tests and the data on students’ honesty collected through questionnaires. Students’ learning outcomes data were analyzed through independent sample t test and the data on students' honesty were analyzed descriptively by narrative. The t test results obtained sig values 0.014 < 0.05 so that there were significant differences between the learning outcomes of the experimental class and the control class. The results of the questionnaire analysis showed that the students’ honesty level of the experimental class was in a very good category and the control class was in the good category.

A Note on Multiple Secret Sharing Using Chinese Remainder Theorem and Exclusive-OR

Abstract: This paper reviews the former existing scheme on (n,n) -multiple secret sharing (MSS) for color images along with its slight limitation. This scheme generates a set of n shared images from a set of n secret images using the Chinese remainder theorem (CRT) and Boolean exclusive-OR (XOR) operation. This scheme works well if the number of secret images n is even number. However, the former scheme has a slight problem while the number of secret images n is an odd number. This paper proposes a new technique to overcome this problem by introducing symmetric and transferred masking coefficients to generate a set of shared images. To further improve the security level of the proposed method, a set of secret images is first transformed with hyperchaotic scrambling method before generating shared images. The security of the proposed (n,n)-MSS can also be increased by merging a shared color image into 2-D matrix representation. As documented in the experimental results, the proposed method offers a promising result on (n,n) -MSS scheme regardless of the number of secret images n is odd or even number. In addition, the proposed method outperforms the former existing (n,n)-MSS schemes in terms of quantitative measurements.

Fermentation Inhibitors in Ethanol and Biogas Processes and Strategies to Counteract Their Effects

Abstract: Bioethanol and biogas production are the most common fermentation process to convert organic waste into energy. The presence of inhibitory compounds affects the performance of fermentation, leading ...