# State University of Malang

• Malang, Jawa Timur, Indonesia
Recent publications
3D printing is one of the manufacturing technologies that can be used for making a prototype part. Fused deposition modeling (FDM) is one 3D printing technology that has economic advantages in the use of materials and a variety of machine choices. Currently, the working capacity of 3D printing machines has many kinds but 235 × 235 × 250 mm of the working area is seldom seen on the market. Its working area becomes a problem if it is used to print a big model that has oversize than the working area of the machine. Therefore, the big model can be segmented and printed separately to solve the current problem. Furthermore, all segmented part is assembled to get the desired 3D printed part. The 3D assembled part is connected by a joint structure. So, the purpose of this study is to investigate the characteristic of the dovetail joint on a 3D model assembled to tensile load on polylactic acid (PLA) material using computer simulation. The ASTM D3039 standard is applied to get the mechanical properties of PLA material that is printed by a 3D printer machine. Furthermore, the data obtained is made as an input in simulation software. The maximum shear stress and factor safety are two output parameter that is evaluated to define the best parameter combination. The results showed that the shear stress minimum is 18.805 MPa and the factor safety of the model is 0.56983. It occurred on variation models w1 25 mm, w3 6 mm, and t 30 mm. The significant result is due to the increase in joint area, angle of joint, and bending moment.
The increasing demand for energy from fossil fuels and depleting reserves has made researchers look for efficient energy and guaranteed its availability. This paper intends to understand the effect of TiO2 nanoparticles on Tetraselmis chuii (T. chuii) microalgae combustion using a thermogravimetric (TG) analyzer. The kinetic parameters were analyzed using the Coats-Redfern method on the ten models of reaction. The results showed that the combustion of T. chuii occurred in three stages, with the main combustion present at a range of 186.43–589.75 °C. The presence of TiO2 plays as an accelerator which promoted the decomposition of lipids to the lower temperature and shortened the combustion time. However, the presence of TiO2 increases the final residue. The adding of TiO2 reduced the activation energy up to 11.82% (from 72.99 to 64.36 kJ.mol−1) in the model of Chemical Reaction Order F1.5. This phenomenon confirmed that the presence of TiO2 affects thermal decomposition and activation energy.Keywords T. chuii Titanium dioxideNanoparticleCombustionCoats-Redfern
Defects in injection molding machine products are analyzed through simulation. The simulation aims to analyze the effect of cooling temperature and injection time on the quality of the injection molded toothbrush head product. Product quality includes quality prediction, weld line, and short shot. The simulation method begins with product design, then determines the simulation parameters including coolant temperature (16, 17, and 18 °C) and injection time (2.0, 2.2, and 2.4 s). ANSYS was run to obtain mold temperature and simulate product quality using AutoDesk Moldflow Advise. Simulation results at a cooling temperature of 16 °C and an injection time of 2.0 s produce a mold temperature of 41.98 °C which has a percentage of product quality reaching 99.6%. Product defects are found in the form of bubbles and shrinkage caused by the temperature of the molten plastic being too high and the cooling temperature too low.KeywordsCooling temperatureInjection moldingInjection timeProduct qualitySimulationToothbrush head
Plasma cutting is an unconventional machining that is widely used in industry because of its productive efficiency. The desired cutting quality is kerf width and material removal rate (MRR). Those cutting qualities on plasma cutting are influenced by the parameters of electrical current (I), cutting speed (Cs), stand of distance (SoD), and gas pressure (P). In this research, material SS 316 was used on plasma cutting using several different parameter combinations. Taguchi robust parameter design is adopted as an optimization strategy, and fractional orthogonal array L18 is chosen as the experimental design. Signal-to-noise ratio (S/N) robustness index is adopted as the quality measure of the cutting. The optimization strategy found that I = 60A, Cs = 1500 mm/min, SoD = 2 mm, and P = 5.5 bar give the optimum in MRR with 13.60498 in S/N or improve 0.1955 compared from initial design, while I = 50A, Cs = 1500 mm/min, SoD = 3 mm, and P = 5 bar give the optimum in kerf width with −8.0701 in S/N or improve 1,46,595 compared from initial design.KeywordsRobust Parameter DesignPlasma CuttingKerf WidthMRRTaguchi Method
The current study explored relations between principal self-efficacy for instructional leadership, work engagement, job satisfaction, and motivation to leave the work as a principal from the principal strengthening training perspective. Participants in the study were 125 principals in the junior school selected using a saturated sampling procedure. This study uses qualitative methods with structural equation modeling (SEM). SEM analysis revealed that principal self-efficacy for instructional leadership was positively related to work engagement and job satisfaction. The relationship between principal self-efficacy for instructional leadership and motivation to leave was not significant. Work engagement and job satisfaction are positively related to motivation to leave. This study showed that Indonesian government policies related to the training of strengthening principals improve principal self-efficacy for instructional leadership. Based on the results of this study, the successful implementation of principal strengthening training in Indonesia can be adopted by policymakers from other countries because it can increase self-efficacy for instructional leadership, work engagement, job satisfaction, and prevent motivation to leave from the principal. In particular, this principal strengthening training program uses the ORPAER intervention model (observe, reflect, plan, act, evaluation, and reflect) combined from the syntax of Theory U and the ILEAD (Introduction, Link, Enforcement, Awareness, and Development) approach. This intervention model can improve the competence of principals, the principals’ problem-solving skills, creative thinking, and emotional engagements.
The protective ability of an organic inhibitor varies and is affected by the pH of the solution. Related with this fact, this work investigated corrosion inhibition performance of Bee Wax Propolis (BWP) extract on 304 SS in various environment (0–14 pH). The BWP extract inhibitor had formed a passive layer on the surface, indicated by the increase of the passive region. The inhibition efficiency changed randomly at all pH. The optimum inhibition efficiency for the acid and alkaline condition happened at pH 2 (96.60%) and 12 (97.75%). BWP was found to control corrosion better at pH 2 and 12.
Ascidians accumulate extremely high levels of vanadium (V) in their blood cells. Several V-related proteins, including V-binding proteins (vanabins), have been isolated from V-accumulating ascidians. In this study, to obtain a deeper understanding of vanabins, we performed de novo transcriptome analysis of blood cells from a V-rich ascidian, Ascidia sydneiensis samea, and constructed a database containing 8532 predicted proteins. We found a novel vanabin with a unique acidic amino acid–rich C-terminal domain, designated VanabinX, in the database and studied it in detail. Reverse-transcription polymerase chain reaction analysis revealed that VanabinX was detected in all adult tissues examined, and was most prominent in blood cells and muscle tissue. We prepared recombinant proteins and performed immobilized metal ion affinity chromatography and a NADPH-coupled V(V)-reductase assay. VanabinX bound to metal ions, with increasing affinity for Cu(II) > Zn(II) > Co(II), but not to V(IV). VanabinX reduced V(V) to V(IV) at a rate of 0.170 μM per micoromolar protein within 30 min. The C-terminal acidic domain enhanced the reduction of V(V) by Vanabin2 to 1.3-fold and of VanabinX itself to 1.7-fold in trans mode. In summary, we constructed a protein database containing 8532 predicted proteins expressed in blood cells; among them, we discovered a novel vanabin, VanabinX, which enhances V reduction by vanabins.
Nickel Phosphate Trisulfide (NiPS3) prepared using the LPE technique was used as a saturable absorber (SA) in a thulium-doped fluoride fiber laser for the generation of mode-locked pulses. The polishing method was used to prepare the arc-shaped fiber before the NiPS3 solution was drop-casted onto it to form the SA device. The SA exhibited nonlinear optical properties, with modulation depth and saturation intensity of 29.44 % and 0.547 kW/cm² respectively. Insertion of the SA in the TDFF cavity produced mode-locked pulses with central wavelength and 3-dB bandwidth of 1505 nm and 0.68 nm respectively, with a pulse width of 3.56 ps. The mode-locking operation also has a repetition rate of 582 kHz and an SNR of about 58 dB at a pump power of 280 mW. The maximum average output power measured was 2.4 mW at maximum pump power, with maximum pulse energy and peak power at 4.12 nJ and 1.16 kW respectively. Due to the optical interaction between NiPS3 and the evanescent wave in this arrangement, a larger damage threshold can be achieved, enabling the laser performance to operate at higher output power. Tunability was achieved by simultaneous adjustment of extinction and wavelength knob on the tunable Mach-Zehnder Filter (TMZF). The shape of spectra remained unchanged and continued exhibiting Kelly’s sidebands throughout the tunability range of about 2 nm. These results provide the first demonstration of tunable mode-locked pulses in the S-band region.
The high prevalence of Autism Spectrum Disorder (ASD) necessitates acquiring early detection tools that can lead to appropriate interventions for children and assist children in performing as many life functions as possible. In addition, early detection tools for ASD can realize quality early childhood development. This study aims to review various types of assessments for early detection of ASD in children using the literature review method. The following articles are from the website https://eric.ed.gov/ as search engine for scientific articles. Using the keywords “autism spectrum disorder assessment tools” and “early detection for autism,” then peer-reviewed only and year filters since 2018, 2,829 articles were found. Then from the identified articles, they are re-elected based on title, abstract, and time of publication to produce 16 articles whose early detection tool was tested on more than 50 participants and began at the earliest possible age. The results show that various screening and diagnostic tools for ASD prioritize areas such as social communication, behavioral problems, emotional problems, sensory regulatory issues, and engagement issues. The instrument’s limitations, which include an expensive price, a lengthy process, the need for expert involvement, and cultural differences, create a growing gap that must be bridged immediately.
The honey pineapple fruit (Ananas comous(L) Merr) is a fruit that is produced by Indonesian farmers. The sweet flavour of the honey pineapple depends on the water content level in the honey pineapple. The honey pineapple is a fruit that spoils easily. The storage period of the pineapple is between 1-7 days with a temperature of under 220C. The objective of this research is to identify the characteristics of probiotic fermented drinks made from the honey pineapple fruit, with the addition of spices such as ginger, cinnamon, and a percentage of palm sugar. There are two treatments in processing, based on the ratio of added ingredients, P1 = 60%pineapple fruit; 20% cane sugar; 10% ginger; 10% cinnamon, P2 = 60%pineapple fruit; 25% cane sugar; 10% ginger; 5% cinnamon. The observed variables are the pH of the drink and the temperature during the hour of observation. The measured test standard was adjusted to the SNI (Indonesian National Standard) 3719-2014 of produced fruit juice on the quality of fruit juice drinks, with the provision of having a distinct smell, flavour, and colour in normal conditions. The results organoleptically obtained result was that the percentage of palm sugar during the third and fifth measurement hour had a high score from 10 panellists, which was a level (4) strong smell with the duration of the ripening day. The pH level test did not differ much in P1(20% palm sugar) and P2(25% palm sugar) substituted in the pineapple fruit juice, which was 3.3 – 5.0.
Fun and pervasive education into students’ daily lives is an important part of children’s development. Learning methods and cognitive styles are one of the important aspects of the dynamics of learning. This research was a quasi-experimental study using the pretest-posttest of a nonequivalent control group design. Therefore, research based on these is expected to impact students’ early reading ability. There are 20 students in the experimental and 20 students in the control classes. The age range is 5–6 years, with heterogeneous gender. The experimental group used the gamification method, while the control group used the Beyond Center and Circle Times (BCCT) method. The gamification method and students with field independence cognitive style are proven to have superiority in improving early reading ability.
Learning activities become teaching and learning activities that are quite complicated and challenging. As for a learning model that can be applied, namely the collaborative learning (CL) model with problem-based learning (PBL). This model is like providing space in developing students' social skills. Thus, with the initiative of the researcher to conduct a literature study to be able to examine how the influence in learning with the application of the CL and PBL methods. The research carried out applies a systematic meta-analysis approach with various reference articles that are still relevant according to the research topic in the last 10 years. In addition to this, the implementation in the form of collaborative groups is expected to create an exchange process between the ideas possessed by students. Referring to the results of the study through various references, the conclusion obtained is that the learning model with CL combined with PBL allows the teacher and students to share information efficiently and effectively. The implementation of Collaborative Problem Based Learning can optimize the ability to think critically and creatively for students.
Unlabelled: Although e-Portfolio is acknowledged as one of the powerful pedagogical practices that enhance learning in higher education (HE), not much is known about the types of social media (SM) utilized as e-Portfolios and the benefits for students. This literature analysis, using directed content analysis, aims to explore the above vacuum. The research questions in this study are: (1) In what ways do the SM as e-Portfolios benefit students in HE? (2) To what extent are the benefits of SM as e-Portfolios comparable to those of conventional e-Portfolios? and (3) What are the drawbacks that practitioners and researchers need to be concerned with? Findings indicate that blogs are the most popular SM used as e-Portfolios to support learning, followed by social networking sites and collaborative projects. The study yields 13 advantages and 12 drawbacks when SM is manipulated as e-Portfolios. These findings conclude that the use of SM as e-Portfolios has a great potential in supporting students' learning and development by providing an environment for them to learn meaningfully from their experiences and engage in critical reflections and dialogues that allow them to gain new knowledge and valuable insights and thus, improve their skills. A pedagogical framework for the planning and implementation of SM as e-Portfolios is suggested based on the findings and aims of the papers that were reviewed. Supplementary information: The online version contains supplementary material available at 10.1007/s12528-022-09344-z.
Electrospinning is the most common and most widely used method of making nanofiber. The simple process of electrospinning is widely used for nanofibers manufacturing with various polymeric materials. In this research, an electrospinning device has been made using a flyback as a high voltage power supply, and synthesis of nanofiber by using electrospinning from polymer materials: polyvinyl alcohol (PVA) has been carried out. Optimization of nanofibers synthesis was performed by investigating the effect of the input voltage on the morphology of nanofibers. Increasing the input voltage can affect the morphology of the PVA fiber formed. This increase is thought to be caused by the speed of the electric field at the output voltage of the electrospinning which can affect the flow rate of the PVA coating on the substrate. In addition, the applied output voltage electric field can affect the surface morphology of PVA nanofibers due to its relationship with viscosity conditions.
We develop an unconventional Monte Carlo simulation within the phase-space formulation of quantum mechanics taking into account a global-nonseparable random variable whose strength is epistemically restricted on the order of Planck’s constant. Compared to the ordinary variational Monte simulation, we find that energy expectation values of simple quantum systems such like harmonic oscillators can be calculated by our method with a reasonable accuracy and competitive calculation time at a large sampling N of random numbers (e.g., at N > 10⁵ samples). We also discuss the comparison of simulations performed in different computing resources.
Four-wave mixing (FWM) was demonstrated using polymer-coated Iron phosphorus trisulfide (FePS3) arc-shaped fiber as a device for nonlinear application. The FWM-based system had a maximum FWM conversion efficiency and wavelength tuning range of −37.5 dB and 6 nm, respectively. The FWM-based laser output was highly stable, with a maximum fluctuation in FWM conversion efficiency of only 0.1 dB. The overlaying of low refractive index (RI) polymer on the FePS3 arc-shaped fiber enhanced the device’s performance, with an effective nonlinear coefficient, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}, of the device was calculated to be 666.7 W− 1 km− 1. The proposed nonlinear device is an exciting device for integration in optical network applications.
This study investigated the effect of corporate governance on corporate risk management. By using the regression analysis method, different results on the effects of the variables independent commissioners, female commissioners, meeting frequency, and audit committee members’ expertise background on corporate risk management were obtained. In addition, companies in Singapore that had high levels of risk management activities were found to experience faster recovery after the crisis caused by the COVID-19 pandemic compared to other countries (Malaysia, Indonesia, and the Philippines). Overall, this study concludes that corporate governance has an important role in improving the risk management activities of a firm. This study may serve as a consideration for corporate governance implementation to improve corporate risk management.
The growth of inhabitants and vehicles on one side and limited infrastructure often make traffic congested. Intelligent Traffic System (ITS) is one of the applications in machine learning to manage traffic intelligently. One field in ITS is traffic prediction, where machine learning learns from historical data to forecast future traffic conditions. Natively, the traffic network is in the graph structure where a place is connected to other places through a roadway. The typical machine learning architecture learns from Euclidean data, whereas the characteristic of the graph is non-Euclidean; hence the graph was manipulated to fit on the architecture. Graph Neural Network (GNN) is a recent machine learning architecture designed to learn from graph structure directly. Each node can learn the embedding of the nodes and predict other node information through a message passing mechanism. GNN has some variants, and they are combined with other existing architectures due to the complexity of the problem and the requirement to learn the spatial and temporal features of the traffic network. This article reviews GNN variants and various techniques in traffic forecasting problems.
The Capacitated Vehicle Routing Problem with Time Windows (CVRPTW) is one of the variants of the Vehicle Routing Problem (VRP), which is the problem of determining the optimal route from the depot to the customer which is located spread out with different requests. In CVRPTW problem solving considers capacity and time constraints. Determining the optimal route can reduce costs and energy spent during the distribution process. The General Variable Neighborhood Search (GVNS) algorithm can be applied to the CVRPTW problem. GVNS is a VNS algorithm whose solution is improved using RVND. The GVNS algorithm begins with finding the initial solution, followed by randomization of the solution using perturbation, and then the repair procedure is carried out using RVND. Perturbation and improvements to the GVNS algorithm are performed repeatedly according to a predetermined maximum iteration. The GVNS algorithm has never been applied to CVRPTW. Therefore, in this research, the GVNS algorithm will be implemented on CVRPTW which then the results will be compared with the VNS algorithm. The GVNS algorithm for CVRPTW is implemented using the Borland Delphi 7.0 programming language. The program has been tested using 3 datasets, each consisting of 50 points. The experiment was carried out 10 times which then resulted in the optimal solution and compared with the solution from the VNS algorithm. Based on the solution obtained, the GVNS algorithm is better than the VNS algorithm on the three datasets that have been tested. The product in the form of this application can be used more practically to solve CVRPTW problems using the GVNS algorithm.
An element x in a ring R with unity is called almost clean if there exists some idempotent element e in R and a regular element u in R such that x = e + u. This article aims to show the existence of almost clean elements in a certain matrix ring over an integral domain R with unity and provide its characterizations.
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• Department of Electrical Engineering
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