bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical assessment of a gas-fired condensing boiler model for residential buildings application
Authors: Simic K , T’Jollyn I , Faes W , Borrajo Bastero J , Laverge J , De Paepe M
Published: December 2021

According to the official statistical reports, gas-fired boiler units still remain to be one of the main equipment types for meeting the space heating and daily hot water demand of the residential dwellings across the European Union. Due to the prevalence of the natural gas grid and performance stability, gas-fired boilers are considered to remain as one of the standard energy sources. On the other hand, even though gas-fired water heating technology is a well-known concept, existing numerical models found in the literature are often case-specific with poor reusability mostly reflected in fitted efficiencies. Algorithms behind these models usually require the input of large amount of hardly attainable design characteristics of the units. In this paper, a modelling method for acquiring the performance of a heating gas-fired condensing boiler unit will be shown. The model is based on the limited input data available in the official characteristics of the units issued by the relevant manufacturers. The simulations are programmed by using the programming language Modelica and the software tool Dymola. The model is based on the fixed natural gas intake which combusts into a stable mixture of the combustion gases that further heat the circulating water. During the heat transfer process inside the condensing boilers there is a possibility for condensate formation out of the water vapour of the combustion gases which increases the efficiency of the unit. The formation of condensate, however, is depending on the return water temperature of the unit which has to be lower than the dew point temperature of the combustion gasses. The goal of this research is to determine how accurate can performance indicators of gas-fired boilers be attained with the use of a limited amount of available input data together with clearly defined assumptions that follow the modelling methodology.
Node generation in complex 3D domains for heat conduction problems solved by RBF-FD meshless method
Authors: Zamolo Riccardo , Nobile Enrico
Published: December 2021

A novel algorithm is presented and employed for the fast generation of meshless node distributions over arbitrary 3D domains defined by using the stereolithography (STL) file format. The algorithm is based on the node-repel approach where nodes move according to the mutual repulsion of the neighboring nodes. The iterative node-repel approach is coupled with an octree-based technique for the efficient projection of the nodes on the external surface in order to constrain the node distribution inside the domain. Several tests are carried out on three different mechanical components of practical engineering interest and characterized by complexity of their geometry. The generated node distributions are then employed to solve a steady-state heat conduction test problem by using the Radial Basis Function-generated Finite Differences (RBF-FD) meshless method. Excellent results are obtained in terms of both quality of the generated node distributions and accuracy of the numerical solutions.
Modelling turbulent heat transfer in rough channels using phenomenological theory
Authors: Peeters J W R
Published: December 2021

Rough walls are often encountered in industrial heat transfer equipment. Even though it is well known that a rough wall affects velocity fields and thermal fields differently (and therefore also skin friction factors and Stanton or Nusselt numbers), predicting the effect of rough walls on turbulent heat transfer remains difficult. A relation between the scalar spectrum and the Stanton number is derived for channels with both smooth and rough walls. It is shown that the new relation agrees reasonably well with recent DNS experiments for wall roughness sizes of k
+
< 150 and when Pr = 0.7 − 1.0. Under these conditions, a thermal analogue of Moody’s diagram can be created using the newly developed relation.
Heat transfer in shallow caves: influence of turbulent convection
Authors: Qaddah B , Soucasse L , Doumenc F , Mergui S , Rivière P , Soufiani A
Published: December 2021

The enhancement of the conservation conditions of cave paintings requires a detailed understanding of heat transfer in such cavities. This article presents a numerical investigation of turbulent free convection in a parallelepipedic cavity. Non-homogeneous wall temperatures are prescribed from a large-scale model taking into account external temperature fluctuations damped by heat diffusion in the rock massif above the cavity. Large Eddy Simulation is performed to solve the turbulent flow fields for a given wall temperature field corresponding to a Rayleigh number of 8.5 x 109. The outcomes of the model are analysed in terms of statistical mean. Results show complex large scale flow patterns with regions of high turbulent intensity. The Q-criterion is used to identify turbulent structures for an instantaneous flow field. Then we analyse the spatial distribution of the conductive heat flux at the walls to locate the regions with intense convection. We show that the conductive flux smaller than the wall-to-wall radiative flux in the major part of the cavity, and close to its value at some spots.
Jet impingement cooling using fluidic oscillators: an experimental study
Authors: Saliba Georges , Raimbault Vincent , Colin Stéphane , Batikh Ahmad , Orieux Stéphane , Gilblas Rémi , Baldas Lucien
Published: December 2021

A growing portion of the thermal load on board airplanes is due to densely packed electronic systems. This increased thermal load along with constraints on weight and volume have made simple and reliable cooling solutions an urgent need in the aerospace industry. There is a wealth of cooling solutions available in order to meet these demands, the simplest and most adaptable of which is probably jet impingement cooling. In this study, fluidic oscillators capable of producing pulsating jets were used to cool a heated surface and were then compared to equivalent steady jets. Although pulsating jets can be produced using a number of devices, fluidic oscillators offer the advantage of not having any moving parts. These oscillators are sustained by a self-induced internal flow instability and can function at different scales. Although the major part of this work is based on prototypes that produce jets with sub-millimetric widths, designs at one tenth that scale, i.e. with an exit slot width of 50 µm, are also presented. Reynolds numbers ranging from ReD = 3500 to 5250 and jet-to-plate spacing from 1D to 10D were studied (where D is the initial width of the jet). The Nusselt number distribution is found for each case and a comparison is made between the performance of equivalent steady and pulsating jets based on the average Nusselt number.
Dynamic LES of the magnetohydrodynamic flow in a square duct with the varied wall conductance parameters
Authors: Blishchik A , Kenjereš S
Published: December 2021

The current study is focused on the magnetohydrodynamics and demonstrates how electrical conductivity of the wall can affect the turbulent flow in the square duct. Different variations of the boundary walls have been considered including arbitrary conductive walls. The Large Eddy Simulations method with the dynamic Smagorinsky sub-grid scale model have been used for the turbulent structures resolving. Results show the significant impact of the wall conductance parameters for both Hartmann and side walls.
Hydrogen diffusion under the effect of stress and temperature gradients
Authors: Zhang Zhichao , Ayas Can , Popovich Vera , Peeters Jurriaan
Published: December 2021

In this paper, a finite element (FE) model is developed to investigate lattice hydrogen diffusion in a solid metal under the influence of stress and temperature gradients. This model is applied to a plate with a circular hole which is subjected to temperature and hydrogen concentration gradients. It is demonstrated that temperature gradients significantly influence hydrogen diffusion and hence susceptibility to hydrogen embrittlement when utilizing hydrogen for gas turbines.
Algorithms for thermal diffusivity measurement of heterogeneous 1D materials based on Infrared Microscopy Enhanced Angstrom Method
Authors: Guo Wei , Chen Anqi , Wu Yanyan , Zhu Yuan , Zeng Shaobo
Published: December 2021

An infrared microscopy enhanced Angstrom method has been develpoed to measure the thermal diffusivity. Infrared microscopy technique can acquire temperatures of multiple points at one shot. Two algorithms for calculating thermal diffusivity were proposed and compared in practice. One is based on global temperature data and the other is based on local temperature data. The according calculated thermal diffusivities are denoted as

α

n

G

and

α

n

L

. Three 1D materials of different heterogeneity (Cu wire, Ni-Cu wire and PVA-CNT fiber) were measured on the experimental platform. The calculated

α

n

G

and

α

n

L

values show that for homogeneous material such as Cu, these two algorithms give similar results, while for heterogeneous ones (Ni-Cu and PVA-CNT), they come to be discrepant. The data fluctuation analysis of

f

n

L

zooms in the discrepancy and verifies that

α

n

L

is more sensitive to local property change and more competent in revealing heterogeneous properties.
A 2D Numerical Simulation of Binary Alloy Solidification: Effect of Mesh Resolution on Formation of Channel Segregates
Authors: Kumar Alok , Singh Anup , Kumar Arvind
Published: December 2021

Mesh refinement is crucial for capturing the complex phenomena that governs the formation of channel segregates during binary alloy solidification. In this article, the influence of mesh size on the formation of channel segregates during the solidification of Sn-5wt%Pb alloy is numerically investigated. A solver is developed in OpenFOAM for solving the coupled transport equations of mass, momentum, energy and species. Subsequently, the simulations are performed for different mesh sizes to predict the flow field, temperature, species and solid fraction distribution including the morphology of channel segregates. From this study, it is observed that the mesh size significantly affects the morphology and the strength of channel segregates. For very fine mesh size, having sufficient number of grid point along their width, the formed channels are more continuous and the flow inside channels is resolved.
Optimal design of subcooled triangular microchannel heat sink exchangers with variable heat loads for high performance cooling
Authors: Ariyo David Olugbenga , Bello-Ochende Tunde
Published: December 2021

Deionized water at a temperature of 25 °C was used as the cooling fluid and aluminium as the heat sink material in the geometric optimization and parameter modelling of subcooled flow boiling in horizontal equilateral triangular microchannel heat sinks. The thermal resistances of the microchannels were minimized subject to fixed volume constraints of the heat sinks and microchannels. A computational fluid dynamics (CFD) ANSYS code used for both the simulations and the optimizations was validated by the available experimental data in the literature and the agreement was good. Fixed heat fluxes between 100 and 500 W/cm2 and velocities between 0.1 and 7.0 m/s were used in the study. Despite the relatively high heat fluxes in this study, the base temperatures of the optimal microchannel heat sinks were within the acceptable operating range for modern electronics. The pumping power requirements for the optimal microchannels are low, indicating that they can be used in the cooling of electronic devices.
Forced convection heat transfer characteristics of Al2O3 nanofluids in a minichannel - an experimental study
Authors: Roque D , Ajeeb W , Murshed S M S , Pereira J M C
Published: December 2021

In this study, an experimental investigation on the convective heat transfer characteristics of Al2O3 nanofluids flowing through an horizontal minichannel under the laminar and turbulent flow and constant heat flux conditions is performed. Several sample nanofluids were prepared using two base fluids (water and the mixture 80/20 DW/EG vol.%) and several low concentrations of Al2O3 nanoparticles ranging from 0.01 to 0.1 vol%. An existing experimental setup was modified for this study. The measurements were taken for the base fluid and nanofluids at each flow and heating conditions. The results are analyzed in terms of Nu and friction factor (f) in comparison with those of the base fluid. The results demonstrate that the used low concentrations of Al2O3 nanoparticles are not enough to yield any noticeable enhancement in heat transfer of the nanofluid samples. The deviations between the results of the nanofluids and the base fluid are small and within the uncertainty range of the experimental setup.
Velocity measurements of individual droplets in liquid-liquid Taylor flows in circular capillaries
Authors: Shojaee Zadeh Seyyed Saeed , Walsh Patrick , Egan Vanessa
Published: December 2021

This study is focused on the effect of droplet length on droplet velocity in liquid-liquid Taylor flows for microfluidic applications. An experimental set up was designed to measure droplet velocity over a wide range of droplet lengths and flow velocities while also varying viscosity ratio. Five different fluid combinations were examined by employing AR20, FC40, HFE7500 and water. Results indicate the complexity of predicting droplet velocity in such flow regimes and also show a strong influence of viscosity ratio and Bond number.
Modelling plant transpiration and leaf climate using CFD
Authors: Plas Wito , De Paepe Michel
Published: December 2021

Research into vertical farms or plant factories is steadily increasing over the years, as the demand for sustainable food production and a shift to more environmental friendly food production is occurring. Modelling plant climate in these confined spaces is therefore essential to guarantee optimal growing conditions. Modelling of plant climate has already been done in greenhouses, but at length scales much bigger than individual leaves. In this study, one single plant will be modelled, using computational fluid dynamics and by incorporating additional source terms in the relevant transport equations. Plants are modelled using the big leaf approach, where a plant is modelled as one artificial leaf. Water vapour flux in plants is controlled by two resistances in series, the aerodynamic resistance, which is a function of the boundary layer around the leaves and the stomatal resistance, which is the resistance against water vapour transport in leaves. Two different plants are studied, impatiens pot plant and basil plants. Values of stomatal resistance for these crops are obtained from literature or were measured. Evapotranspiration was compared with the Penman-Monteith equation.
A parametric analysis of thermodynamic losses in an anode of a solid oxide fuel cell
Authors: Prokop Tomasz , Brus Grzegorz , Kimijima Shinji , Szmyd Janusz
Published: December 2021

In this paper, generation of thermodynamic losses in the micro-channels of a Solid Oxide Fuel Cell electrode is discussed. Diffusive-convective equation is implemented to compute local concentrations of reagents. The model accounts for both the Fick’s, and the Knudsen’s diffusion. For a number of cases the total losses are decomposed to isolate the contributions of the diffusion, the current conduction, and the chemical reaction irreversibilities.
Thermodynamic modeling and controlling of a combined Free Piston Stirling Engine System (FPSE) with a Permanent Magnet Linear Synchronous Machine (PMLSM)
Authors: Majidniya M , Boileau T , Remy B , Zandi M
Published: December 2021

Converting thermal energy to electricity is one of the most common energy conversions in the field of electricity production. This transformation of energy is essential for both renewable and non-renewable heat sources. One of the main parameters of such a system that is responsible for this conversion is its efficiency. To have an efficient transformation, many improvements have been made to the old methods, and also new techniques were developed. One of these new methods that will be discussed here is a combined system of a Free Piston Stirling Engine (FPSE) with a Permanent Magnet Linear Synchronous Machine (PMLSM). The two purposes of presenting such a system are that firstly, the theoretical efficiency of a Stirling engine is high. Secondly, by eliminating crank-shaft from this system compared to the standard Stirling engine system, some of the losses will be removed. To study this system, a thermodynamic model of a RE-1000 FPSE was presented and validated. Then it was coupled with a PMLSM, and the combined system was controlled. The total efficiency of this system in steady-state is 14.4%.
Performance evaluation of thermoelectric generators under cyclic heating
Authors: Williams N P , Roumen L , McCauley G , O’Shaughnessy S M
Published: December 2021

The effect of thermal cycling on thermoelectric generator (TEG) performance is investigated for six nominally identical samples subjected to the same heating cycle profile. All TEGs experienced performance degradation, with maximum power outputs between 28 % and 49 % of pre-cycling values and a post-cycling decrease in the dimensionless figure of merit ZT of 21 % to 49 %. Sudden significant power reductions and subsequent internal resistance increases were observed for all samples, indicative of internal damage to the structure of the TEGs arising from material interface separation and micro-crack formation.
Lumped parameter modelling of two-phase ejectors: numerical implications of the equilibrium assumptions
Authors: Besagni Giorgio
Published: December 2021

The use of carbon dioxide as refrigerant is attracting a growing attention and is a cutting-edge research topic. In spite of its many advantages, carbon dioxide has a major shortcoming, viz., low critical temperature. Owing to the low critical temperature, carbon dioxide cycles encompass both the sub-critical and the trans-critical operation conditions; the trans-critical operating conditions are characterized by high thermodynamic losses, requiring particular attention in the integrated component/system design criteria. In this perspective, in recent years, ejector technology has been widely recognized as a promising technical solution to support the deployment of carbon dioxide cycles, by reducing throttling losses. Unfortunately, the large variation in system operations as well as the changes in sub-critical and trans-critical operating conditions makes the numerical simulation of carbon dioxide ejector-based system a cutting-edge challenge. This paper contributes to the present day discussion on the validation of lumped parameter models for carbon dioxide ejectors. A model taken from the literature has been tested against literature data and the equilibrium assumptions, underlying the modelling approach have been tested.
Computational fluid dynamic modelling of supersonic ejectors: comparison between 2D and 3D modelling
Authors: Besagni Giorgio , Croci Lorenzo , Cristiani Nicolò , Inzoli Fabio , Guédon Gaël Raymond
Published: December 2021

It is known that the global performances of ejector-based systems (viz., at the “global-scale”) depend on the local flow properties within the ejector (viz., at the “local-scale”). For this reason, reliable computational fluid-dynamics (CFD) approaches, to obtain a precise and an a-priori knowledge of the local flow phenomena, are of fundamental importance to support the deployment of innovative ejector-based systems. This communication contributes to the existing discussion by presenting a numerical study of the turbulent compressible flow in a supersonic ejector. In particular, this communication focuses on a precise knowledge gap: the comparison between 2D and 3D modelling approaches as well as density-based and pressure-based solvers. The different approaches have been compared and validated against literature data consisting in entrainment ratio and wall static pressure measurements. In conclusion, this paper is intended to provide guidelines for researchers dealing with the numerical simulation of ejectors.
Nanofluid suspensions as heat carrier fluids in single U-tube borehole heat exchangers
Authors: Jahanbin A , Semprini G , Pulvirenti B
Published: December 2021

The borehole heat exchanger (BHE) is a critical component to improve energy efficiency and decreasing environmental impact of ground-source heat pump systems. The lower thermal resistance of the BHE results in the better thermal performance and/or in the lower required borehole length. In the present study, effects of employing a nanofluid suspension as a heat carrier fluid on the borehole thermal resistance are examined. A 3D transient finite element code is adopted to evaluate thermal comportment of nanofluids with various concentrations in single U-tube borehole heat exchangers and to compare their performance with the conventional circuit fluid. The results show, in presence of nanoparticles, the borehole thermal resistance is reduced to some extent and the BHE renders a better thermal performance. It is also revealed that employing nanoparticle fractions between 0.5% and 2 % are advantageous in order to have an optimal decrement percentage of the thermal resistance.
Experimental analysis of the thermal comfort provided by an electrical heater and a heat pump
Authors: García-Cascales J R , Illán-Gómez F , Velasco F J S , Vera-García F , Dengra Vera A , García F
Published: December 2021

After considering heating sector, one realises that there is no clear and consensual way to quantify or qualify the thermal comfort of the different technologies available to satisfy the heating demand of a home. This contribution tries to call attention to this by means of an experimental study of the thermal comfort provided by two very different technologies, an electrical heater and a heat pump. To do so, a test matrix is developed by considering [2]. Some experiments are carried out in a climate chamber constructed following [1]. The variables registered are used to determine the comfort variables defined in [3] for each technology. After both technologies are compared and some conclusions are drawn.
Application of RC delay time for estimation of thermal properties
Authors: Jena Priyanka , Gupta Rajesh
Published: December 2021

The analogy between the electrical and thermal system has been extensively used to solve different kinds of direct heat transfer problems. However, this analogy has not been explored much to obtain solutions of inverse heat transfer problems like estimation of thermal properties. This paper presents an approach of estimation of thermal properties using the correspondence between the thermal and electrical domains by exploiting the concept of RC delay time in the resistance-capacitance (RC) circuit. Simulations and experiments have been performed on stainless steel and glass samples to show the applicability of the proposed approach for materials belonging to different conductivity range.
The influence of solar heating upon ground temperature
Authors: Sousa A M , Azevedo L , Pereira M J , Matos H A
Published: December 2021

To predict the superficial ground temperature due to solar radiation as a function of the depth and rock physical properties, the Finite Volume Method was employed upon an energy conservation model. ANSYS Transient Thermal was selected to simulate a 3D geological volume, 1625 m wide, 2000 m long and with variable height as a function of topographical data. As a result, the variability of ground temperature during a 24h day was assessed. A set of climatological data was used to evaluate the ground temperature for the colder periods. The numerical results were compared against the Kusuda and Achenbach’s analytical solution to evaluate the possibility of extending the validity of a widely used method, from daily to intraday data.
Vibration transmission simulation model of a seated vehicle passenger
Authors: Ho I , Abu Bakar N Z
Published: December 2021

The paper presents development of vertical vibration simulation for a seated passenger in a moving vehicle is resulting from the bounce effect of the vehicle under various conditions. Although extensive research has been conducted in this field of study, the existing analysis were conducted on either the suspension of vehicle or the human body and not both. In this paper, the simulation model consists of three sub-systems, namely, vehicle suspension, seat suspension and human body model in which the vertical vibration is transmitted. By incorporating these sub-systems into the simulation, a correlation between mechanical and biological aspects can be formed between the three sub-systems. The transmission of vertical vibration in the validated simulation model provides a more realistic approach which can result to a better comparison to the real-life scenario. Parametric analysis of passive suspension system shows that lower mass ratio, higher stiffness ratio and lower damping coefficient results in better ride comfort. The incorporation of variable damper into the suspension system shows significant improvement in settling time, peak displacement and velocity, lesser discomfort rating and higher safety in passenger body.
Geometry design and optimization of piston by using finite element method
Authors: Lee Z R , Ku P X
Published: December 2021

The piston performance may be impacted by piston geometry, stress, temperature and deformation applied. Thus, the purpose of this study is to investigate the changes of piston performance with different piston head designs. Besides, the piston is optimized by using topology optimization to remove excessive material. The study was carried out by using the dimension of a piston based on the cylinder of a spark ignition engine. The four piston head designs are flat-top piston, bowl piston, square bowl piston and dome piston. All four piston designs were modelled by using Solidworks. Static Structural and Steady State Thermal Analysis in ANSYS Workbench were used to analyze the piston performance. The measured parameters are stress, deformation and temperature distribution. Next, optimization of piston was done by using topology optimization to identify non-essential parts that can be removed. The optimized piston design was analyzed. The findings for the original and optimized piston geometries were tabulated to make comparison. It is found that bowl piston has lower stress, deformation and temperature. The stress, deformation and temperature of optimized piston is lower than original piston. The mass of optimized piston is about 5 percent lesser than the original piston.
Effect of Infill Pattern and Lattice Structure on the Mechanical Properties of 3D Printed Metal Polylactide Filament
Authors: Umapathi Rishitena , Lim Joon Hoong
Published: December 2021

The purpose of this given research is to study the mechanical properties of the printed metal polylactide filament due to the recent growth of 3D printing technology. It had been widely used in many industries, but some consequences influence the material properties of printed parts and cause anisotropy. The consequences mentioned are based on parameters that have been involved in causing changes in the mechanical properties of the printed specimen such as the infill pattern, infill density, printing temperature, surrounding temperature, printing orientation, and printing speed. This paper will emphasize more on the infill patterns and choosing the better infill pattern for a printed material using copper metal polylactide (PLA) filament in terms of better strength. The strength of the printed material can be analysed using the tensile test method according to ASTM D68-10 standards. so that Young’s Modulus can be evaluated based on stress and strain data collected from each specimen that has been tested. This experiment is conducted twice using PLA and copper metal PLA whereby the PLA is used as a comparison towards copper metal PLA. Based on previous studies shows honeycomb has the strongest infill pattern but after running through the certain test it is found out that grid pattern has the qualities for FDM processes which will be discussed further.
Modelling and analysis of vienna rectifier for more electric aircraft applications using wide band-gap materials
Authors: Loong Ling Jin , Vaithilingam Chockalingam Aravind , Rajendran Gowthamraj , Muneeswaran Venkatkumar
Published: December 2021

This paper presents a comprehensive study on the switching effects of wide bandgap devices and the importance of power electronics in an aircraft application. Silicon (Si), silicon carbide (SiC), and gallium nitride (GaN) are wide bandgap devices that act as a power electronic switch in the AC-DC converter for More Electric Aircraft (MEA) applications. Therefore, it is important to observe their converting efficiency to identify the most suitable wide bandgap device among three devices for AC-DC converters in aircraft applications to provide high efficiency and high-power density. In this study, the characteristics of Si, SIC, and GaN devices are simulated using PSIM software. Also, this paper presents the performance of the Vienna rectifier for aircraft application. The Vienna rectifier using Si, SiC, and GaN devices are simulated using PSIM software for aircraft application. GaN with Vienna rectifier provides better performance than Si and SiC devices for aircraft applications among the three devices. It gives high efficiency, high power density, low input current THD to meet IEEE-519 standard, and high-power factor at mains.
Evaluating Quality Characteristics of Ubiquitous Application Through Means of Quality Models using Meta-metrics Approach
Authors: Hamzah N , Chuprat S , Dwi Handayani D O , Xiaoxi K , Nagappan S D
Published: December 2021

Ubiquitous computing shifted the way how users interact with applications. The demand of information anytime and anywhere impacts the daily life of its users, be it work related or personal. Difficulty arises when determining the quality of ubiquitous application due to lack in appropriate metrics of quality models, which serves as the motivation behind this paper. The aim of this paper is to assess the quality of ubiquitous application using comparative analysis of quality model metrics via meta-metrics approach. Preliminary review mapping was conducted where distinctive quality characteristics of ubiquitous applications from AQUARIUM model are identified. Metrics mapping was then conducted to compare metrics characteristics with quality characteristics via value assignment using meta-metrics technique. Results shows that most of the metrics mapped are not of definitive derivation, providing opportunity to have a more structured and defined measurement function.
Effect of Perforation Volume on Acoustic Absorption of the 3D Printed Micro-Perforated Panels made of Polylactic Acid reinforced with Wood Fibers
Authors: Sekar V , Eh Noum S Y , Sivanesan S , Putra A , Kassim Dg H , Wong Y S , Chin K C
Published: December 2021

In recent times, Additive Manufacturing (AM) has been applied rapidly in almost all fields. This study was conducted to apply the additive manufacturing into an acoustic application by 3D printing the Micro-Perforated Panels (MPP) through Fused Deposition Modelling (FDM) made of Polylactic Acid (PLA) reinforced with wood fibers. MPP were fabricated by altering its perforation volume. Later, the effect of perforation volume on acoustic absorption of the fabricated MPP was measured using the two-microphone impedance tube method as per ISO 10534-2 standard. The result shows altering the perforation volume affects the acoustic absorption of the MPP. MPP with a thickness of 2 mm and a perforation diameter of 0.2 mm shows the maximum sound absorption coefficient of 0.93 at 2173 Hz. It is made possible to absorb the 3D printed MPP made of natural fiber reinforced composite at different spectrums by altering the perforation volume.
Liquefaction alarm prototype using arduino uno microcontroller
Authors: Saehana S , Lala A
Published: December 2021

This study aims to create an alarm tool that can detect disasters such as earthquakes and liquefaction in Palu City. It was laboratory research conducted in Sub department of Physics Education, Tadulako University. Research and experiments with modelling tools were conducted to simulate soil conditions during the earthquake and liquefaction. The research sample was focused on soil samples that have been affected by liquefaction disasters. The method used was the waterfall with the procedures of requirements analysis, system design, implementation, and testing of Arduino programs and software as ground movement monitoring. This study indicated that a liquefaction alarm prototype using a microcontroller component in the form of Arduino Uno, soil moisture sensor, and MPU6050 sensor could detect a natural liquefaction disaster was signed by a siren sound.
DSSC with PEDOT-Carrageenan Electrolyte as Learning Media for Photovoltaic Concept Physics
Authors: Sari N , Palamba A J , Saehana S , Diah A W M
Published: December 2021

This study aims to create a DSSC using PEDOT-Carrageenan-based electrolyte as a learning media for photovoltaic physics concepts. This research was experimental research conducted in the laboratory of subdepartment of physics education, Tadulako University. In this study, DSSC making process used a substrate made from TCO-FTO polymer. The TiO2 photoelectrode layer was deposited using the doctor blade technique and Ruthenizer as a dye-sensitizer and the platinum layer was deposited on the counter electrode using the sputtering technique. Process parameters that affect the characteristics of solar cells were analyzed and measured using the I-V characteristic curve. The samples measured consisted of several types of PEDOT-Carrageenan electrolytes, including Kappa, Lambda and Iota. The results of voltage measurements of each sample of the DSSC prototype were obtained quite well at a voltage of 91.8 mV using PEDOT-Carrageenan Kappa 1:2 electrolyte and the short circuit current obtained reached 57.6 uA. The best solar cell prototype produces an efficiency of 0.0003333728 %. It indicates that DSSC can be made by PEDOT-Carragenan electrolyte and can be used as a learning tool for photovoltaic physics concepts.
The analysis of student kinesthetic learning activity on the materials of Compton and photoelectric effects
Authors: Saehana S , Werdhiana I K , Safitri N S , Saputra O , Safira N
Published: December 2021

This study aims to analyze the kinesthetic learning activities of students on Compton and photoelectric effects. This further involved a qualitative descriptive study, where students of class XII Mathematical and Natural Science 2, State of Madrasah Aliyah in Palu Region (Central of Sulawesi, Indonesia), were the sample population examined, in the odd semester of 2018/2019 academic session. Data was obtained through observation of learning activities, concept understanding tests, interviews and learning style identification questionnaires. The selection of respondents was based on the level of understanding of students’ concept categories. The results of the study showed that students perform kinesthetic learning activities very well, as seen from their endeavors in following the lessons and the results of theoretical understanding assessments, which were observed to be in the high category. Furthermore, the interview evaluated that the students are happy with the kinesthetic learning method carried out as it promoted their understanding and recollection of the content of the material and questionnaires indicate that students have visual, auditory and kinesthetic learning styles. From the performance of Compton and the photoelectric effect, it was shown that students playing as electrodes and electrons (kinesthetic learning style) possess high understanding of the concept in the kinesthetic learning model.
A Qualitative Study: Physics Concepts Used by Survivors in the 2018 Tsunami in Palu City
Authors: Suleman W A , Wahyono U
Published: December 2021

This study aimed to identify and examine the Physics concepts used by victims of the tsunami disaster in Palu City based on the earthquake, tsunami and liquefaction events that occurred on September 28, 2018 in Palu City. This research was descriptive qualitative. Data were collected by observation, interviews and documentation. Based on the results of the study, the researchers found several Physics concepts that were applied when the victims made efforts to save themselves from the tsunami. These findings were discussed and grouped according to the theme of the Physics concept, including: the concept of speed and velocity, Newton’s Second Law Concept, the concept of floating objects, and the concept of waves. The results can be used as a contextual example in learning physics. By doing so, the students will not only learn about Physics concepts, but also improve their understanding and awareness of local disasters.
The Development of Local Disasters-based Mitigation Module Integrated to Physics Learning
Authors: Yuliani  , Wahyono U
Published: December 2021

This study aimed to develop a local disaster potential-based mitigation module that is integrated into physics learning. The compilation of these teaching materials can be utilized as one of the learning media for students to learn about disaster mitigation materials independently. This study was research and development using 4D model that consisted of 4 phases namely, Define, Design, Development, and Disseminate. The participants in this study were 12 students from SMPN 1 Palu. The feasibility test phase of the product was conducted to determine the feasibility of the instructional materials. The trial phase was conducted on trials of material experts, media experts, teachers, and students. Based on the results of trials and questionnaire analysis, the average score of the material experts assessment was 3.24 categorized as “Good”, the average score of media expert assessment was 3.00 categorized as “Good”, the average score of teacher assessment was 4 0.0 categorized as “Very Good”, and the average score of the assessment based on student responses was 3.52 categorized as “Very Good”. The result of the study shows that the teaching materials generated, particularly those on disaster mitigation, are very suited for use in the learning process.
Characterization of patchouli oil (Pogostemon cablin Benth) production of Tinombala Village, Ongka Malino District, Parigi Moutong Regency
Authors: Abram P H , Putri W , Nuryanti S , Sabang S M
Published: December 2021

Patchouli oil comes from Tinombala village which has never been tested for the Indonesian National Standard (SNI). The purpose of this study was to determine the quality of patchouli oil by characterizing parameters of physical and chemical properties including color, refractive index, specific gravity, solubility in alcohol, acid number, ester number, iron content (Fe), and patchouli alcohol and alpha copaene content.. Sampling was done by random sampling. The results show a specific gravity of 25/25oC sample A = 0.9564, B = 0.9658, and C = 0.9590, refractive index (nD20) sample A = 1.5111, B = 1.5085 and C = 1.5086, the solubility in alcohol using ethanol of the three samples is >1:10 while using methanol 1:10, the acid number of the sample A=21.0375, B=9.1162 and C=19.6350, the ester number of the sample A=28,05, B=21.04 and C=21.04, iron (Fe) content of sample A=1.84210 mg/L, B=0.186842 mg/L and C=6.78950 mg/L, patchouli content alcohol sample A=,16,96%, B=15,52% and C=14,55% and for alpha copaene not detected. The results showed that the quality of patchouli oil in Tinombala village did not meet the Indonesian National Standard (SNI). Only the specific gravity, refractive index, and iron content are by the quality requirements, while the acid number and ester number and the main component determining the quality of patchouli oil, namely the patchouli alcohol content are still below the Indonesian National Standard, which is below 30%.
Electromagnetic Reflection Field Detection Based on TEO
Authors: Wang Xinyi , Zhuang Rui
Published: December 2021

Active electromagnetic detection explores targets using electromagnetic reflection field of metal objects. In view of the detection of active electromagnetic by detecting target reflection field, a Teager energy operator(TEO) is adopted to improve the electromagnetic reflection amplitude and instantaneous frequency detection method, the method of theoretical description and simulation verification has also carried out in this paper. Results show that this method is able to track the change of the single frequency signal of electromagnetic reflection field with good effect. It is also able to provide full details of the judgment to confirm the target. This method is simple and convenient for real-time processing, and has good application value.
Power Transformer Voiceprint Operation State Monitoring Considering Sample Unbalance
Authors: Chen shoulong , He Ping , Xu HongHua , Yin LaiBin , Wang LingYan , Zhu Lei
Published: December 2021

The voiceprint characteristics of transformers are closely related to the operating conditions, but there is currently a lack of effective research on the voiceprint characteristics of transformers during operation. First of all, this article collects three operating conditions of load, light load, and no load on the basis of the transformer voiceprint signal acquisition platform. Secondly, in view of the characteristics of the transformer’s voiceprint, the 50Hz frequency multiplier component amplitude is extracted to form a feature vector, which solves the problem of low utilization rate of common feature extraction information. Finally, in view of the problem of transformer voiceprint failure and sample imbalance caused by fewer abnormal samples, a pattern recognition based on the RUSBoost algorithm is proposed. The algorithm has good recognition accuracy and applicability for transformer voiceprint samples with imbalance problems. The research results provide effective support for the monitoring and identification of the mechanical condition of transformers with sample unbalanced voiceprints, and the analysis of the operating conditions can effectively eliminate the errors that may be caused by their own different operating conditions.
Performance test of small-current grounding line selection device based on the real-time digital simulation system
Authors: Xu Biao , Xu Yuxin , Ouyang Fan , LI Hui , Liang Wenwu , Gong Yusheng
Published: December 2021

Single phase grounding fault is the most common fault type in small-current grounding distribution network, but the small-current grounding line selection device put into operation on site is often difficult to meet the application requirements, affecting the rapid and accurate treatment of grounding fault. Considering that there are many small-current grounding line selection manufacturers and various device forms, it is difficult to intuitively evaluate the line selection performance of different devices and make horizontal comparison, and there is no supporting basis for the selection and application of on-site line selection devices. Therefore, based on the real-time digital simulation system (RTDS), this paper establishes a test platform for small-current grounding line selection device. Based on the constructed test platform, four line selection devices form different manufacturers are tested in parallel, the performance of the devices is compared, and the influencing factors affecting the accuracy of line selection results are analyzed. The conclusions of this paper can provide strong support for the pilot application of small-current line selection devices.
Application of two-phase hybrid stepping motor based on three-phase inverter chopping control strategy in aircraft electric drive servo valve
Authors: Hu Mingliang , Han Wei , Gao Wei , Liu Yang
Published: December 2021

With the development of multi-/all-electric technology, more and more aircraft platforms use electrically driven servo valves as the driving source to realize real-time adjustments of flow, pressure and temperature in the area network. The new generation of aircraft applies a stepper motor to drive the servo valve as the drive source, and utilizes the holding torque and open-loop control characteristics of the stepper motor when the stepper motor could not meet aircraft’s requirements of the reliability of the servo valve, the controllability of the opening and closing angle, and the environmental resistance. This paper develops a set of stepper motor drive servo valve control system. The system is mainly composed of flight tube bus, electromechanical management computer, remote actuation unit, remote interface unit and motor-driven servo valve. The stepper motor driver is integrated in the remote execution unit and is used to control the two-phase hybrid stepper motor to drive the servo valve. The topology of a three-phase inverter bridge drive is used to achieve the two-phase double four-shot drive, which saves about 25% power drive hardware. By controlling the two-phases motor, the direction and amplitude of the current one can realize micro-step control. The test and simulation result show that the system has higher control accuracy and better acceleration. The deceleration characteristics in two-phase full step and micro step working modes can expand the application of electric servo valve and improve aircraft performance.
The invention relates to an intermediate frequency power supply fast start and digital phase locked loop control technology
Authors: Li Demin , Qin Qingliang
Published: December 2021

Intermediate frequency induction heating is widely used because of its low energy consumption and high thermal efficiency, but the speed of traditional intermediate frequency power supply is slow and its frequency tracking accuracy is limited. In order to maintain the resonant state of the load during the working process of the induction heating power supply and realize the automatic frequency tracking control during the working process. The frequency tracking of the 40kW intermediate frequency power supply is researched, and a method of combining the resonant frequency automatic identification algorithm and the digital phase locked loop frequency tracking control method is proposed. MATLAB simulation and experiment show that the system based on this control method can save the time of searching the load resonance frequency in the initial stage of the power supply, improve the frequency tracking speed, accelerate the dynamic response speed of the system, avoid the failure of frequency lock, and play the role of fast and stable startup.
Hardware in the Loop Real-time Simulation of Doubly Fed Off-grid Wind Power System
Authors: Xinyuan Gao , Kanru Gu , Qianru Zhou
Published: December 2021

Hardware in the Loop (HIL) semi-physical real-time simulation can shorten the research period and complete the harsh working condition test, which is difficult to be carried out on the physical platform. Taking the off-grid Doubly Fed Induction Generator (DFIG) wind power system as the research object, this paper proposes the bottom modelling method of HIL real-time simulation. Using the Hardware Description Language VERILOG, the bottom real-time models of DFIG, converter and load are designed on Field Programmable Gate Array (FPGA), connected with the real controller, and the HIL real-time simulation platform is constructed. The experiments of conventional working conditions and unbalance load are carried out on the HIL platform and the physical platform. The operation speed of the HIL platform reaches 0.48μs. Compared with the physical platform, the error of HIL platform is between 1.17 ~ 3.29% under various working conditions.