Search

Renewable energy sources such as solar, wind, hydroelectric and geothermal are considered sustainable and environmentally sound alternatives to fossil fuels. The aim of the study is to present a numerical simulation of water turbine for utilization of wave energy. Physical and mathematical is shown, also some numerical results with k − ε model are presented and discuss. It is given some result at different flow velocity 1m/s and 2m/s, different angle of the blades-50 and 60 0 and two ways of movement of water-top to down and bottom to up. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate cold water produced by chiller that will be distributed to the fan coil unit (FCU). The cold water distribution system from chiller requires good insulation, especially water pipes in and out of FCU to chiller so water temperature remains stable and chiller performance is not too heavy. Increasing temperature of cold water produced by chiller will affect the performance of the air conditioning system (AC) and the use of electrical energy. The object of this study is chiller unit with 18 FCU units located at the Bandung Electronic Center. Detailed measurements have been taken on the AC system. The results of thermodynamic analysis shows that there is a considerable comparison between the ideal heat loss and the actual heat loss, which is 131,972 kW for supply pipelines and 124,498 kW for return pipelines. Heat loss will also result in increased electricity consumption. The measurement and evaluation results showed the insulation of cold water distribution pipe is not effective enough because there are damaged parts of the insulation, the size or thickness of the insulation used does not match the size of the pipe causing unbalanced chilled water flow rate and heat loss. [ABSTRACT FROM AUTHOR]

Gas sensors are beneficial in a wide range of applications, including environment monitoring, industrial, and safety. Ideal characteristics of the desired gas sensor include low cost, and low power usage. The major advancement was, the role of alloy material as heating aliment was analyzed, and presented a gas sensor with nichrome as heating element. The ZnO semiconductor metal oxide was used as sensing material. The presented sensor was designed and simulated using FEM tool. The required micro heater bias voltage is reduced. And the ZnO sensing material resistance vs thermal conductivity was analyzed. [ABSTRACT FROM AUTHOR]

In this study, we implement a continuous-time linear time-invariant (LTI) system and validate its properties through system identification. We specifically explore two identification methods: one that relies on utilizing generalized Laguerre functions (GLF) and another that employs the least squares (LS) approach, all within a noisy environment. Our findings reveal a substantial reduction in Root Mean Square (RMS) error when employing the GLF identification method compared to the method utilizing least squares approximation. [ABSTRACT FROM AUTHOR]

The aim of this text is to show that when approximating a stable r-th order LTI system with one r-multiple pole and with a dead time (DT), the approximation using the generalized Laguerre Function (GLF) for large DT gives better results than using the simple Laguerre function (SLF). [ABSTRACT FROM AUTHOR]

Mumford-Shah models and piecewise-constant Mumford-Shah models are frequently used for reconstruction and segmentation in imaging and inverse problems. Higher-order models have the property that they better preserve polynomial trends while still preserving sharp edges in the underlying signals and avoiding the so-called gradient limit effect. We first introduce the respective models and point out relevant literature. Then we focus on recent solution strategies of the authors based on dynamic programming as well as the alternating direction of multipliers for the numerical solution of such models and illustrate their potential use. [ABSTRACT FROM AUTHOR]

This contribution presents a concept of a modification of derivative-free Nelder-Mead method to be used for the solution of optimization problems with polynomial equality constraint functions leading to generally non-convex feasible sets. Although the set of constraint functions is restricted to polynomials, the cost function itself does not even have to be continuous. A brief description of the modified algorithm is presented together with an example of its usage. [ABSTRACT FROM AUTHOR]

The paper is focused on the determination of mechanical fracture parameters of alkali-activated concrete (AAC) specimens of nominal dimensions 80 × 80 × 240 mm with central notches of the following types: straight-through notch, chevron notch with 90° notch angle and chevron notch with 120° notch angle. In accordance with the results of the experimental research, a numerical simulation of the fracture test of the specimens tested in three-point bending was carried out. The 3D FEM computational model is based on the configuration of the laboratory test and was developed in ATENA-GiD software. Artificial neural network (ANN)-based inverse analysis was used to identify the mechanical fracture parameters of studied composite. A neural network ensemble was created, with one robust network for each type of notch, covering the entire domain of identified parameters. The main goal of this paper is to present the results of the identification of the mechanical fracture parameters of the AAC and their comparison with the values obtained by direct evaluation of the experiments. Another objective is to investigate the influence of the notch type on the mechanical fracture parameters of the AAC. [ABSTRACT FROM AUTHOR]

This paper presents the evaluation of the fracture test of high-strength structural (HSS) steel grades S460 using a finite element (FEM) numerical model. Steels with better strength characteristics may exhibit different stress-strain diagram behavior and therefore material models need to be adequately prepared. The numerical model, which accurately simulates the experiments, was prepared using known information from tensile testing of high-strength steel. The aim is to determine the material parameters with high accuracy using inverse analysis so that complex numerical models of building structures such as steel halls and bridges can be prepared. The paper contains results from an experimental investigation compared with results from a numerical model of a tensile fracture test. Due to the good agreement, the derived material parameters can be applied in future research on high-strength structural steel in the construction industry. [ABSTRACT FROM AUTHOR]

This research work analyzed the shear strength of a bonded joint and the effect of basalt fibers added to a one- component polyurethane adhesive for load-bearing purposes. The shear strength was ascertained according to standard EN 302-1, and it was found that the addition of basalt fibers to the adhesive resulted in an increase in the shear strength of the bonded joint. The increase in strength was particularly evident when cold water was applied to the bonded joint, with the mean shear strength of the basalt fiber modified adhesive being 2.6 N/mm2 higher than the unmodified adhesive. However, in a standard climate without water exposure, the difference between the modified and unmodified adhesive was minimal. It was also confirmed that surface modification of basalt fibers by silanization resulted in very good adhesion of the polyurethane to the basalt fibers. [ABSTRACT FROM AUTHOR]

Particle surface treatment is often used for particleboard production to improve adhesive adhesion. Several types of surface treatment are used, e.g. water immersion, cold plasma, and alkaline treatment. A 10% sodium hydroxide (NaOH) solution was used in this research. Scanning electron microscopy was performed to better understand the microstructure of the treated rape straw surface and glued joints. The use of sodium hydroxide leads to surface damage and the formation of microcrystals on the surface of the straw. Treatment with a 10% NaOH solution proved to be ineffective based on the resulting mechanical properties of the manufactured particleboards. [ABSTRACT FROM AUTHOR]

Educational games are one of the significant elements that are used to innovate the educational process. The aim of the inclusion of these games is undoubtedly to motivate pupils and students to study, as well as significant attractiveness of the educational process. However, gamification (as this trend is generally referred to) is still a complement to other teaching methods. This paper explores the possibility of using the relatively open environment of LMS Moodle to implement gamification in teaching. [ABSTRACT FROM AUTHOR]

The rapid development of telecommunications technologies (ICT) and especially the internet has changed and continues to change the ways of teaching and learning. Educational organizations are becoming heavily dependent on ICT for the effective performance of daily tasks. Lately, the concept of "Bring your own device" (BYOD) has been implemented to support better education. In this paper the teachers' and students' opinions are analyzed and reasoned by generation characteristics. This paper adds to previous research on BYOD by highlighting key opinions of the users as well as providing a brief summary of research done between 2016–2021. [ABSTRACT FROM AUTHOR]

The presented paper is dealing with the UHPC specimens, which have been reinforced by basalt fibres. Primarily, the experimentally investigated specimens were subjected to three-point bending test, in order to evaluate fracture properties, such as Fracture energy Gf and Stress Intensity Factor (SIF) KI. The bending tensile strength fcf was evaluated as well. Measured mechanical parameters were observed and evaluated after one month of curing process. The results, presented in the paper, are part of the extensive material research supported by Czech Science Foundation. [ABSTRACT FROM AUTHOR]

In our research, we are focusing on the development of iterative algorithms for solving contact problems emerging in the analysis of steel structures bolt connections. Despite the project is focusing mainly on the development of efficient numerical algorithms, several supplementary problems have to be solved. In our research, we decided to utilize widely-used popular commercial software Ansys to provide the data for our algorithms implemented in Matlab as well as for the comparison of results. This paper presents experiences with our newly developed data interface. [ABSTRACT FROM AUTHOR]

In our research, we are interested in the automatized detection of corrosion on images of steel structures. The paper presents the influence of the roughness of image and the value of widely used measures, namely properties of grey-level co-occurrence matrix (GLCM) and grey level run length matrix (GLRLM). The results show the capability of these measures for the description of roughness in the image, which is typically considered significant evidence of corrosion. We suggest that image classification based on reviewed measures can be further utilized for standard classification methods. [ABSTRACT FROM AUTHOR]

Fractional calculus can be considered as rapidly developing research area widening limits of traditional computing. Current study is focused on development of numerical methods for solving fractional order differential equations using Haar wavelet methods. There are two Haar wavelet based approaches available in literature for solving fractional order differential equations. These two approaches are analyzed. Furthermore, the refined wavelet expansion is proposed in the case where the order of fractional derivative is less than one. The theoretical approach introduced is validated by numerical analysis. [ABSTRACT FROM AUTHOR]

For their advantageous properties and availability, basalt products have become an emerging green high-tech industrial material that is used in various building- and civil engineering applications as an alternative to widely used traditional types of reinforcement. Nevertheless, compared to the glass-, carbon- or steel-based fibers in cement composites, the literature focused on basalt reinforcing elements has been far less numerous. This paper is focused on a comparison of the impact of basalt (BF) and steel fibers (SF) on the mechanical properties of hardened concrete after 16 hours for the verification of early-age strength, which is essential in precast production, and at 28 days of hydration as a standard request. Several mixtures were prepared, containing different dosages of fibers: It was found that when a similar amount of both types of fibers was used, BF provided approximately 9% higher compressive strength of studied samples after 28 days. Moreover, when 0.48 vol.% and 0.90% of BF and SF, respectively, were added to the mixtures, the samples with BF showed more promising compressive strength by 15.3%. Nevertheless, in terms of the residual tensile strength, the same samples with BF exhibited almost five times worse performance than those prepared with SF, which should be addressed in future research. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the shear strength of the lap joints of beech wood. To achieve this objective, a one-component polyurethane adhesive filled with basalt fibers was used to create waterproof joints. The shear strength of the bonded joint was carried out according to EN 302-1. The results showed that the lap joints bonded with a one-component polyurethane adhesive containing 3% basalt fibers had significantly higher shear strength. While the average value of the shear strength of lap joints glued with one-component polyurethane without the filler in the hydrothermal stress was 8.8 N/mm2, the lap joints with basalt fibers achieved more than a 14% higher average shear strength of 10.1 N/mm2. In addition, the experimental data showed a higher occurrence of joint failure in the wood substrate when the modified adhesive was used, which contrasts with the behavior observed for reference joints bonded with an unmodified one-component polyurethane adhesive without basalt fibers. [ABSTRACT FROM AUTHOR]

The proposed application is designed to train Crystallised Intelligence according to the CHC Intelligence Model. This application is one of the modules of a research project entitled "Intelligent Neuro-Rehabilitation System for Patients with Acquired Brain Damage in Early Stages of Treatment" (Eddie for short). Project Eddie is focused on cognitive rehabilitation in the early stage of treatment (i.e. the first six months from the damage) to prevent chronification of the damage. All modules include a simple adaptation rule which moves the patient a level higher/lower based on completion/failure of the assigned tasks. With respect to the software side, the whole concept of the proposed neuro-rehabilitation information system is regarded as a portal. [ABSTRACT FROM AUTHOR]

RP games are increasingly becoming a phenomenon of contemporary education. Although a number of ready-made educational LARP games are offered, in connection with the covid-19 pandemic, the question arose of their transformation into a partially digital form with the preservation of live play at least in the form of partial game activities. The article is devoted to the description of our experience with the creation of a year-round role-playing game and its implementation in a digital environment. The game is focused on science education – chemistry, physics, biology and mathematics and is implemented in the LMS Moodle environment. Partial conclusions and feedback on the chosen computer environment after piloting the first part of the game will also be described. [ABSTRACT FROM AUTHOR]

Energy needs are currently still dominated by fossil fuels, so efforts are needed to increase the use of new and renewable energy. Coal fired power plants (CFPP) are one of the industries that use it, where the main fuel of the plant is coal and mixed fuel with biomass as co-firing. Empty oil palm fruit bunches (EOPFBs) are biomass that has geat potential to be used as a mixed fuel because of its very abundant availability, especially in Riau Province. However, empty oil palm fruit bunches (EOPFBs) has high content of potassium and chlorine, and a low combustion calorific value. It is necessary to treat the EOPFBs to have a good quality. This research aims to produce biocoal from biomass by reducing potassium and chlorine content by using peat water, as well as increasing the calorific value of oil palm empty fruit bunches by the torrefaction process. The washing process is carried out with variations in time and flow discharge, namely 5-60 minutes and 2-5 LPM. While the torrefaction process is carried out with variations in the time and temperature of torrefaction, namely 30-60 minutes and 200°C-300°C. The result of this research conducted produced potassium and chlorine levels of 3.7% and 1.53%. While the largest calorific value is 7470.59 kcal/kg at a processing time of 60 minutes and a torrefaction temperature of 300°C and an energy yield of 78% at a time and temperature of 30 minutes and 200°C. [ABSTRACT FROM AUTHOR]

Indonesia is an archipelagic country that has breathtaking panoramic views of beaches and mountains. One famous tourist destination in West Sumatra is the Harau Valley. In 2017, more than 400,000 tourists visited the Harau Valley, and the number continues to increase yearly. Herota Homestay is one of the lodging businesses that has been operating in the Harau Valley since 2018. Aware of the high tourist opportunities, Herota continues to strive to improve the quality of its services by providing dining services, therefore it is necessary to build restaurant facilities that were previously unavailable. The feasibility study of restaurant investment needs to be studied using engineering economy theory by calculating the Net Present Value (NPV), Interest Rate of Return (IRR), Benefit-Cost Ratio (B/C Ratio), and Payback Period (PBP). Previously, the customer satisfaction test was carried out using statistical analysis, and the t-test method with the help of SPSS software to analyze the relationship between service quality as the dependent variable and the accuracy of management services, additional services, and breakfast delivery as the independent variables. The results obtained from the t-test show that the accuracy of management service, breakfast delivery, and other services affect the Herota quality of service. Investment in restaurant construction is feasible with a projected profit and loss of IDR238,004,637; NPV of IDR17,834,617; IRR 11.48%; B/C ratio is 1.02, and PBP of 2 years and 11 months. [ABSTRACT FROM AUTHOR]

The new life adaptation protocol implemented in Institut Teknologi Sumaterea (ITERA) during the COVID-19 pandemic requires visitor identity check to restrict access to several buildings and reduce the massive spread of the corona virus. The inspection is carried out by manually collecting visitor information, which can result in a queues buildup of vehicles that want to enter the ITERA environment, and also, the identity of incoming visitors is not adequately monitored. In addition, the smart camera system for visit recording is built with the ability to identify visitors' faces, which triggers automatic gate access and records visitor information. Visitor information is stored in the form of identity number, name, visitor status, time/date of visiting, and information about the location of visitors. The visitor data is stored in a database and can be accessed by ITERA on the visitor website page. The system has an ability to trigger automatic gate to give an order to open or close the gate based on the face recognition results. The system development is divided into three stages: face recognition development, website-based data visualization creation, and hardware development. At each stage, the development produces a system with face recognition capabilities, a visitor recorder website, and a series of automatic gate hardware consecutively. The face recognition system connects directly to the website via the Firebase database. The development of the system capability for face recognition is carried out using a learning model of the K-Nearest Neighbor (K-NN) algorithm method, which obtains the training results have an accuracy of 99% using a confusion matrix method. [ABSTRACT FROM AUTHOR]

Defects in organic semiconductors can significantly affect the functionality of organic photonic devices. However, unlike inorganic materials, they are still little researched. This article investigates structural defect states in the bandgap of n-type small molecular semiconductor 2,2'-{[5,5'-(Naphthalene-2,6-diyl)bis(thiophene-5,2-diyl)]bis(2,2,2-trifluoroethan-1-yl-1-ylidene)}dimalononitrile (TNT-FEC). Using the energy-resolved electrochemical impedance spectroscopy (ER-EIS), we mapped the presence of defect states in this material, and by comparing measurements in the solution and the film, we identified the structural ones. Furthermore, we investigated the influence of the substrate on defect formation. Finally, using DFT and DFTB calculations, we analyzed the possibility of the conformers' presence, which can influence the structural properties of thin films. The combination of experimental and theoretical approaches in the analysis of defect states has been shown as suitable for studying structural defects' presence in the thin films of organic semiconductors. [ABSTRACT FROM AUTHOR]

The construction industry is currently struggling with a shortage of primary raw materials that are needed for buildings, road construction in particular. Taking into account the availability issues, dredging operations in river bands, dams, and lakes associated with a big volume of excavated sediments represent a very interesting precursor source for the alkali-activated materials (AAMs) production. However, despite the good availability and favorable chemical composition, the alkali activation of WS was studied only rarely. This study investigates the potential of dredged freshwater sediments as alkali-activation precursors through elevated temperature exposure. The reactive amorphous phase content is increased by treatment at 800 °C and changes in the mineralogical composition are evaluated. The suitability of freshwater sediments as construction materials is accessed by the determination of the mechanical strength. The obtained results reveal, that the utilization of thermogravimetry can be viewed as an effective tool for the determination of optimal temperature treatment. Achieved values of compressive and flexural strength point to the potential of this material as the construction material, notwithstanding, follow-up research is required to increase the mechanical performance through mixtures optimization. [ABSTRACT FROM AUTHOR]

Members of open double-symmetrical cross-sections are widely used in steel structures. In many cases their webs are subjected to transverse compression resulting from the effect of adjacent members or from the concentrated transverse loads. Resistance of the member web to transverse compression is affected by number of aspects, e.g. structural solution of the joint (welded or bolted with end plate), possible longitudinal normal stress in the member caused by axial load or bending moment, interaction with shear or effect of local buckling of the web. The paper focuses on specific problem of resistance of the web to transverse compression resulting from transverse load applied close to the unstiffened end of the member. The investigation of the resistance of the web to transverse compression is performed using advanced geometrically and materially nonlinear numerical analysis for various distances of the transverse load from the unstiffened end. The influence of this distance on transverse compression resistance is quantified. Rolled and welded cross-sections of various web slenderness are investigated. The results are, where possible, compared with results obtained from available design standards. [ABSTRACT FROM AUTHOR]

Nowadays, global problems such as environmental problems occur massively. Global problems cannot be solved quickly; a planned step is needed to solve them. One of the steps is through education. Education must be able to facilitate students to care about environmental problems. Education for Sustainable Development (ESD) is one way to solve this problem. We need to integrate ESD in learning, including in mathematics learning. The purpose of this study is to develop a student's worksheet integrated ESD in mathematics learning. The student's worksheet can be used widely if it has valid, practical and in effective criteria. The method used in this research is a Research and Development (R&D) which is carried out with a research design according to Plomp. Based on the results of the study, the validity score of the student's worksheet is 76.25% with valid category. The practicality score is 75,4% with practical category. The effectivity score is 75% with effective category. The scores mean that the student's worksheet is valid, practical, and in effective criteria. So that it can be concluded that the student's worksheet can already be used in learning mathematics. [ABSTRACT FROM AUTHOR]

This study aims to describe basic teaching skills of sixth Semester students enrolled at Micro Teaching Course in Mathematics Education study program. Basic teaching skills are the most pivotal aspect that should be possessed by students of Mathematics Education study program or pre-service teacher, thus they could conduct the learning process well. The basic teaching skills consist of questioning skill, reinforcement skill, variation skill, explanation skill, opening and closing skill. Furthermore, this research is a quantitative descriptive study with purposive sampling technique to determine 13 students as sample. The research instrument used was an assessment sheet. The study result showed that in the first practice, average students had good basic teaching skills scored 7.44, while in the second practice; there was an increase of the score to 7.92 with good category as well. The increase of the score occurred because of the reinforcement delivered by the lecturer during the course. [ABSTRACT FROM AUTHOR]

Basalt fibers and their products (fabrics, mesh, ropes etc.) are currently widely used as reinforcing elements in composites based on thermosetting plastics. Another possible application of basalt fibers lies in civil engineering where these fibers may be used in concrete as alternative to the conventional steel reinforcement. The basalt reinforcement can be realized in two ways: a) dispersed short basalt fibers (alternative to steel wires); b) basalt fiber reinforced plastic (BFRP) bars (alternative to steel rebars). As the "plastic" component, epoxy or vinyl ester resin is used. The primary driving force for replacement of steel reinforcing elements in concrete by another material (e.g. basalt fibers) is the steel sensitivity to electrochemical corrosion, which is frequently determining the lifetime of concrete structure. For the obvious reasons, basalt elements are not suffering from electrochemical corrosion, but it does not mean that they are completely corrosion-resistant. The present paper aims to contribute to the knowledge on corrosion behavior of BFRP bars in Simulated Sea Water (SSW). The experimental program consisted in exposing of BFRP bars to SSW and measurement of its tensile strength in time. It can be concluded that the strength controlling point is interlaminar shear of bars which is reduced by ongoing hydrolysis of epoxy resin during the bars exposure to Simulated Sea Water. [ABSTRACT FROM AUTHOR]

The main purpose of the research was to evaluate the abrasion resistance of a composite material made from a combination of flax fiber and bio-based epoxy resin. In the second group of samples, bio-epoxy was enriched with corundum additive. Composite material samples were produced using vacuum infusion technology. A Taber Abraser rotary abrasion machine was used to compare the abrasion resistance of the samples. It was found that the added filler has a significant effect on the abrasion properties. The addition of white corundum microcrystals in the amount of 2% by weight to the adhesive mixture led to a significant increase in abrasion resistance. Furthermore, it was found that despite the thorough control of the manufacturing process, the composite samples contain pores in the epoxy layer, which can affect the mechanical and physical properties. [ABSTRACT FROM AUTHOR]

In Indonesia, the use of monazite has been carried out for the rare earth processing industry by PT. Timah (Persero) Tbk with raw material in the form of tin mining waste. The pilot plant produces rare earth metal products in the form of hydroxides, such as lanthanum hydroxide La(OH)3, with a price range of US$ 230 per kg. Application of La(OH)3 includes water treatment, specialty glass, catalyst, optical coating, gas-exhaust convector, hydrogen storage material, superconductor, and dielectric material. This research was intended to specifically ball-mill lanthanum hydroxide (La(OH)3) with hydrogen gas followed by sintering and to characterize the product materials. The expected yield of this synthesis was material for the superconducting application. The sintering temperature was pre-determined based on a differential scanning calorimeter (DSC) test, which was 550°C for 1 hour. The product characterization included x-ray diffraction (XRD), particle size analysis (PSA), and scanning electron microscopy (SEM). Lanthanum di-hydride (LaH2) and lanthanum oxide (La2O3) were obtained as the products of this ball-milling, with the final compositions of 91.1 wt.% and 8.9 wt.%, respectively. The average particle size of the LaH2 and La2O3 powder mixture was 190.3 nm, downsized from 323.7 nm of La(OH)3 through the ball-milling process. SEM observation for the ball-milling product before sintering indicated the presence of particle aggregations. The increase in La2O3 content after sintering induced a higher crystallite strain of 2.0±0.1% compared to that after ball-milling. [ABSTRACT FROM AUTHOR]