bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Scratch to Improve Learning Programming in College Students: A Positive Experience from a Non-WEIRD Country
Authors: Cárdenas-Cobo Jesennia , Puris Amilkar , Novoa-Hernández Pavel , Parra-Jiménez Águeda , Moreno-León Jesús , Benavides David
Published: May 2021

Teaching computer programming is a real challenge in the State University of Milagro (UNEMI), located in one of the least-developed zones in Ecuador, a non-WEIRD country (WEIRD stands for Western, Educated, Industrialized, Rich and Democratic). Despite the application of various learning strategies, the historical pass rate does not exceed 43%. To solve this problem, we have relied on visual programming languages, specifically Scratch. Scratch is an open source software to learn programming that has a strong assumption of the benefits of community work. A quasi-experiment conducted with 74 undergraduate students during the first semester of CS showed that: (1) Both groups (control and experimental) are homogeneous in terms of their demographic characteristics, previous academic performance and motivation (expectations) concerning the course; (2) Scratch is strongly accepted by students in the experimental group and concerning the learning process, both groups showed similar levels of satisfaction; (3) the experimental group showed a pass rate four times higher than the control group; (4) in general, student success is associated with having learned programming with Scratch. While limited, our results are an important step in our road to improve the learning of programming in a low social status area of Ecuador.
Digital Image Watermarking Processor Based on Deep Learning
Authors: Lee Jae-Eun , Kang Ji-Won , Kim Woo-Suk , Kim Jin-Kyum , Seo Young-Ho , Kim Dong-Wook
Published: May 2021

Much research and development have been made to implement deep neural networks for various purposes with hardware. We implement the deep learning algorithm with a dedicated processor. Watermarking technology for ultra-high resolution digital images and videos needs to be implemented in hardware for real-time or high-speed operation. We propose an optimization methodology to implement a deep learning-based watermarking algorithm in hardware. The proposed optimization methodology includes algorithm and memory optimization. Next, we analyze a fixed-point number system suitable for implementing neural networks as hardware for watermarking. Using these, a hardware structure of a dedicated processor for watermarking based on deep learning technology is proposed and implemented as an application-specific integrated circuit (ASIC).
Identification of the Factors That Influence University Learning with Low-Code/No-Code Artificial Intelligence Techniques
Authors: Villegas-Ch. William , García-Ortiz Joselin , Sánchez-Viteri Santiago
Published: May 2021

Education is one of the sectors that improves the future of societies; unfortunately, the pandemic generated by coronavirus disease 2019 has caused a variety of problems that directly affect learning. Universities have found it necessary to begin a transition towards remote or online educational models. To do so, the only method that guarantees the continuity of classes is using information and communication technologies. The transition in the foreground points to the use of technological platforms that allow interaction and the development of classes through synchronous sessions. In this way, it has been possible to continue developing both administrative and academic activities. However, in effective education, there are factors that create an ideal environment where the generation of knowledge is possible. By moving from traditional educational models to remote models, this environment has been disrupted, significantly affecting student learning. Identifying the factors that influence academic performance has become the priority of universities. This work proposes the use of intelligent techniques that allow the identification of the factors that affect learning and allow effective decision-making that allows improving the educational model.
Phase-Based Accurate Power Modeling for Mobile Application Processors
Authors: Lee Kitak , Ohk Seung-Ryeol , Lim Seong-Geun , Kim Young-Jin
Published: May 2021

Modern mobile application processors are required to execute heavier workloads while the battery capacity is rarely increased. This trend leads to the need for a power model that can analyze the power consumed by CPU and GPU at run-time, which are the key components of the application processor in terms of power savings. We propose novel CPU and GPU power models based on the phases using performance monitoring counters for smartphones. Our phase-based power models employ combined per-phase power modeling methods to achieve more accurate power consumption estimations, unlike existing power models. The proposed CPU power model shows estimation errors of 2.51% for ARM Cortex A-53 and 1.97% for Samsung M1 on average, and the proposed GPU power model shows an average error of 8.92% for the Mali-T880. In addition, we integrate proposed CPU and GPU models with the latest display power model into a holistic power model. Our holistic power model can estimate the smartphone′s total power consumption with an error of 6.36% on average while running nine 3D game benchmarks, improving the error rate by about 56% compared with the latest prior model.
Analysis of the Effects of the Location of Passive Control Devices on the Platform of a Floating Wind Turbine
Authors: Galán-Lavado Antonio , Santos Matilde
Published: May 2021

Floating offshore wind turbines (FOWT) are subjected to strong loads, mainly due to wind and waves. These disturbances cause undesirable vibrations that affect the structure of these devices, increasing the fatigue and reducing its energy efficiency. Among others, a possible way to enhance the performance of these wind energy devices installed in deep waters is to combine them with other marine energy systems, which may, in addition, improve its stability. The purpose of this work is to analyze the effects that installing some devices on the platform of a barge-type wind turbine have on the vibrations of the structure. To do so, two passive control devices, TMD (Tuned Mass Damper), have been installed on the platform of the floating device, with different positions and orientations. TMDs are usually installed in the nacelle or in the tower, which imposes space, weight, and size hard constraints. An analysis has been carried out, using the FAST software model of the NREL-5MW FOWT. The results of the suppression rate of the tower top displacement and the platform pitch have been obtained for different locations of the structural control devices. They have been compared with the system without TMD. As a conclusion, it is possible to say that these passive devices can improve the stability of the FOWT and reduce the vibrations of the marine turbine. However, it is indispensable to carry out a previous analysis to find the optimal orientation and position of the TMDs on the platform.
Machine Learning-Based Classification of Electrical Low Voltage Cable Degradation
Authors: Codjo Egnonnumi Lorraine , Bakhshideh Zad Bashir , Toubeau Jean-François , François Bruno , Vallée François
Published: May 2021

Low voltage distribution networks have not been traditionally designed to accommodate the large-scale integration of decentralized photovoltaic (PV) generations. The bidirectional power flows in existing networks resulting from the load demand and PV generation changes as well as the influence of ambient temperature led to voltage variations and increased the leakage current through the cable insulation. In this paper, a machine learning-based framework is implemented for the identification of cable degradation by using data from deployed smart meter (SM) measurements. Nodal voltage variations are supposed to be related to cable conditions (reduction of cable insulation thickness due to insulation wear) and to client net demand changes. Various machine learning techniques are applied for classification of nodal voltages according to the cable insulation conditions. Once trained according to the comprehensive generated datasets, the implemented techniques can classify new network operating points into a healthy or degraded cable condition with high accuracy in their predictions. The simulation results reveal that logistic regression and decision tree algorithms lead to a better prediction (with a 97.9% and 99.9% accuracy, respectively) result than the k-nearest neighbors (which reach only 76.7%). The proposed framework offers promising perspectives for the early identification of LV cable conditions by using SM measurements.
PV Modules Interfacing Isolated Triple Active Bridge for Nanogrid Applications
Authors: Santoro Danilo , Kortabarria Iñigo , Toscani Andrea , Concari Carlo , Cova Paolo , Delmonte Nicola
Published: May 2021

DC nanogrid architectures with Photovoltaic (PV) modules are expected to grow significantly in the next decades. Therefore, the integration of multi-port power converters and high-frequency isolation links are of increasing interest. The Triple Active Bridge (TAB) topology shows interesting advantages in terms of isolation, Zero Voltage Switching (ZVS) over wide load and input voltage ranges and high frequency operation capability. Thus, controlling PV modules is not an easy task due to the complexity and control stability of the system. In fact, the TAB power transfer function has many degrees of freedom, and the relationship between any of two ports is always dependent on the third one. In this paper we analyze the interfacing of photovoltaic arrays to the TAB with different solar conditions. A simple but effective control solution is proposed, which can be implemented through general purpose microcontrollers. The TAB is applied to an islanded DC nanogrid, which can be useful and readily implemented in locations where the utility grid is not available or reliable, and applications where isolation is required as for example More Electric Aircraft (MEA). Different conditions have been simulated and the control loops are proved for a reliable bus voltage control on the load side and a good maximum power point tracking (MPPT).
Risk Assessment of the Large-Scale Hydrogen Storage in Salt Caverns
Authors: Portarapillo Maria , Di Benedetto Almerinda
Published: May 2021

Salt caverns are accepted as an ideal solution for high-pressure hydrogen storage. As well as considering the numerous benefits of the realization of underground hydrogen storage (UHS), such as high energy densities, low leakage rates and big storage volumes, risk analysis of UHS is a required step for assessing the suitability of this technology. In this work, a preliminary quantitative risk assessment (QRA) was performed by starting from the worst-case scenario: rupture at the ground of the riser pipe from the salt cavern to the ground. The influence of hydrogen contamination by bacterial metabolism was studied, considering the composition of the gas contained in the salt caverns as time variable. A bow-tie analysis was used to highlight all the possible causes (basic events) as well as the outcomes (jet fire, unconfined vapor cloud explosion (UVCE), toxic chemical release), and then, consequence and risk analyses were performed. The results showed that a UVCE is the most frequent outcome, but its effect zone decreases with time due to the hydrogen contamination and the higher contents of methane and hydrogen sulfide.
Heat Transfer by Natural Convection in a Square Enclosure Containing PCM Suspensions
Authors: Ho Ching-Jenq , Huang Chau-Yang , Lai Chi-Ming
Published: May 2021

Research on using phase change material (PCM) suspension to improve the heat transfer and energy storage capabilities of thermal systems is booming; however, there are limited studies on the application of PCM suspension in transient natural convection. In this paper, the implicit finite difference method was used to numerically investigate the transient and steady-state natural convection heat transfer in a square enclosure containing a PCM suspension. The following parameters were included in the simulation: aspect ratio of the physical model = 1, ratio of the buoyancies caused by temperature and concentration gradients = 1, Raleigh number (RaT) = 103–105, Stefan number (Ste) = 0.005–0.1, subcooling factor (Sb) = 0–1.0, and initial mass fraction (or concentration) of PCM particles (ci) = 0–0.1. The results showed that the use of a PCM suspension can effectively enhance heat transfer by natural convection. For example, when RaT = 103, Ste = 0.01, ci = 0.1, and Sb = 1, the steady-state natural convection heat transfer rate inside the square enclosure can be improved by 70% compared with that of pure water. With increasing Sb, the Nusselt number can change nonlinearly, resulting in a local optimal value.
Numerical Investigation on Shape Optimization of Small-Spacing Twin-Well for Salt Cavern Gas Storage in Ultra-Deep Formation
Authors: Li Haitao , Deng Jingen , Wanyan Qiqi , Feng Yongcun , Kamgue Lenwoue Arnaud Regis , Luo Chao , Hui Cheng
Published: May 2021

Small-spacing twin-well (SSTW) salt caverns have an extensive application prospect in thin or bedded rock salt formations due to their good performance, while they are rarely used in ultra-deep formations. The target strata depth of Pingdingshan salt mine is over 1700 m, and it is planned to apply an SSTW cavern to construct the underground gas storage (UGS). A 3D geomechanical model considering the viscoelastic plasticity of the rock mass is introduced into Flac3D to numerically study the influence of internal gas pressure, cavern upper shape and well spacing on the stability of an SSTW salt cavern for Pingdingshan UGS. A set of assessment indices is summarized for the stability of gas storage. The results show that the minimum internal gas pressure is no less than 14 MPa, and the cavern should not be operated under constant low gas pressure for a long time. The cavern with an upper height of 70 m is recommended for Pingdingshan gas storage based on the safety evaluation and maximum volume. The well spacing has a limited influence on the stability of the salt cavern in view of the volume shrinkage and safety factor. Among the values of 10 m, 20 m and 30 m, the well spacing of 20 m is recommended for Pingdingshan gas storage. In addition, when the cavern groups are constructed, the pillar width on the short axis should be larger than that on the long axis due to its greater deformation in this direction. This study provides a design reference for the construction of salt cavern gas storage in ultra-deep formations with the technology of SSTW.
Towards 100% Renewables by 2030: Transition Alternatives for a Sustainable Electricity Sector in Isla de la Juventud, Cuba
Authors: Korkeakoski Mika
Published: May 2021

Renewable Energy Sources (RES) have become increasingly desirable worldwide in the fight against global climate change. The sharp decrease in costs of especially wind and solar photovoltaics (PV) have created opportunities to move from dependency on conventional fossil fuel-based electricity production towards renewable energy sources. Renewables experience around 7% (in 2018) annual growth rate in the electricity production globally and the pace is expected to further increase in the near future. Cuba is no exception in this regard, the government has set an ambitious renewable energy target of 24% RES of electricity production by the year 2030. The article analyses renewable energy trajectories in Isla de la Juventud, Cuba, through different future energy scenarios utilizing EnergyPLAN tool. The goal is to identify the best fit and least cost options in transitioning towards 100% electric power systemin Isla de la Juventud, Cuba. The work is divided into analysis of (1) technical possibilities for five scenarios in the electricity production with a 40% increase of electricity consumption by 2030: Business As Usual (BAU 2030, with the current electric power system (EPS) setup), VISION 2030 (according to the Cuban government plan with 24% RES), Advanced Renewables (ARES, with 50% RES), High Renewables (HiRES, with 70% RES), and Fully Renewables (FullRES, with 100% RES based electricity system) scenarios and (2) defining least cost options for the five scenarios in Isla de la Juventud, Cuba. The results show that high penetration of renewables is technically possible even up to 100% RES although the best technological fit versus least cost options may not favor the 100% RES based systems with the current electric power system (EPS) setup. This is due to realities in access to resources, especially importation of state of the art technological equipment and biofuels, financial and investment resources, as well as the high costs of storage systems. The analysis shows the Cuban government vision of reaching 24% of RES in the electricity production by 2030 can be exceeded even up to 70% RES based systems with similar or even lower costs in the near future in Isla de la Juventud. However, overcoming critical challenges in the economic, political, and legal conditions are crucially important; how will the implementation of huge national capital investments and significant involvement of Foreign Direct Investments (FDI) actualize to support achievement of the Cuban government’s 2030 vision?
Implications on Feedstock Processing and Safety Issues for Semi-Batch Operations in Supercritical Water Gasification of Biomass
Authors: De Blasio Cataldo , Salierno Gabriel , Magnano Andrea
Published: May 2021

Biomass with a large amount of moisture is well-suited to be processed by supercritical water gasification, SCWG. The precipitation of inorganics, together with char formation and re-polymerization, can cause reactor plugging and stop the process operations. When plugging occurs, sudden injections of relatively large mass quantities take place, influencing the mass flow dynamics significantly in the process. Reactor plugging is a phenomenon very well observed during SCWG of industrial feedstock, which hinders scale-up initiatives, and it is seldom studied with precision in the literature. The present study provides an accurate evaluation of continuous tubular reactor dynamics in the event of sudden injections of water. An interpretation of the results regarding water properties at supercritical conditions contributes to comprehending mass and heat transfer when plugging occurs. Experiments are then compared to SCWG of a biomass sample aiming to give key insights into heat transfer and fluid dynamics mechanisms that could help develop operational and control strategies to increase the reliability of SCWG. In addition, a simplified model is presented to assess the effect of material integrity on burst-event likelihood, which states that SCWG is safe to operate, at 250 bar and 610 °C, in tubular reactors made of 0.22 wall thickness-to-diameter ratio Inconel-625 with superficial microfractures smaller than 30 µm. We also suggest improvement opportunities for the safety of SCWG in continuous operation mode.
Energy Policy of European Union Member States in the Context of Renewable Energy Sources Development
Authors: Musiał Wiesław , Zioło Monika , Luty Lidia , Musiał Kamila
Published: May 2021

As a consequence of increasing air pollution, the European Commission has decided to introduce special directives laying down the measures to achieve climate and energy neutrality. Renewable energy (RE) sources play an important role in the pursuit of these goals, which has been taken into account in the 2030 Agenda for Sustainable Development. The aim of this article is to describe patterns and trends in the achievements of the energy policy of European Union (EU) countries in the field of renewable energy in sustainable development. The identification of leaders in this field gives the possibility to analyse actions taken by the governments of these countries and the possible implementation of the introduced solutions on the ground of individual Member States at the regional and national levels. At the beginning Main goal of energy policy on the field of renewable energy sources (RES) is to increase production from environmentally friendly sources that is why trends were determined in order to assess the rate of achievement of the national target for changes the share of energy from renewable sources in total gross energy consumption. Groups of similar countries were then identified on the basis of three indicators corresponding to the targets set in the climate and energy package. In the group of analysed countries, 14 have achieved the 2020 targets and 4 have exceeded the 2030 targets. The main renewable energy sources (RES) are biofuels, wind, and hydropower. In the assessment of the achievement of energy policy targets, the best situation was observed in the case of Denmark, Ireland, and the United Kingdom. These countries have significantly increased the share of renewable energy in total energy consumption. Compared to other EU countries, they have reduced the economy’s energy consumption and greenhouse gas emissions the most.
Feasibility of Quasi-Square-Wave Zero-Voltage-Switching Bi-Directional DC/DC Converters with GaN HEMTs
Authors: Karakaya Furkan , Gülsuna Özgür , Keysan Ozan
Published: May 2021

There are trade-offs for each power converter design which are mainly dictated by the switching component and passive component ratings. Recent power electronic devices such as Gallium Nitride (GaN) transistors can improve the application range of power converter topologies with lower conduction and switching losses. These new capabilities brought by the GaN High Electron Mobility Transistors (HEMTs) inevitably changes the feasible operation ranges of power converters. This paper investigates the feasibility of Buck and Boost based bi-directional DC/DC converter which utilizes Quasi-Square-Wave (QSW) Zero Voltage Switching (ZVS) on GaN HEMTs. The proposed converter applies a high-switching frequency at high output power to maximize the power density at the cost of high current ripple with high frequency of operation which requires a design strategy for the passive components. An inductor design methodology is performed to operate at 28 APP with a switching frequency of 450 kHz. In order to minimize the high ripple current stress on the output capacitors an interleaving is performed. Finally, the proposed bi-directional converter is operated at 5.4 kW with 5.24 kW/L or 85.9 W/in3 volumetric power density with air-forced cooling. The converter performance is verified for buck and boost modes and full load efficiencies are recorded as 97.7% and 98.7%, respectively.
Electricity Market in Brazil: A Critical Review on the Ongoing Reform
Authors: Santos André Quites Ordovás , da Silva Adriel Rodrigues , Ledesma Jorge Javier Gimenez , de Almeida Adriano Batista , Cavallari Marco Roberto , Junior Oswaldo Hideo Ando
Published: May 2021

With the current worsening of climate change-associated risks, the transition to low-carbon energy sources has become a global priority. In this context, the advances in the implementation of smart grids, which, in addition to greater efficiency and resilience, also allow greater penetration of renewable distributed energy resources, are becoming increasingly important. However, the necessary investments will be colossal. Many specialists see the process of opening up the electric energy markets as essential to boosting these new technologies. Greater decentralization of the decision-making process can potentially promote greater scalability. However, not all liberalization reforms have led to good results. Several researchers have been evaluating experiences in different countries. Brazil, a country with continental dimensions and peculiar characteristics, already counts with a mostly renewable electric energy generation mix. In recent decades, however, it has become increasingly dependent on fossil fuel sources. Brazil has been conducting a process of opening the electric energy market since the 1990s. This process has faced a series of barriers. This article presents a critical bibliographic review of the Brazilian Power System history and its ongoing opening process, its possible successes and errors, as well as its perspectives and challenges.
Cost of Industrial Process Shutdowns Due to Voltage Sag and Short Interruption
Authors: Motoki Édison Massao , Filho José Maria de Carvalho , da Silveira Paulo Márcio , Pereira Natanael Barbosa , de Souza Paulo Vitor Grillo
Published: May 2021

The objective of this work is to propose and apply a methodology to obtain the cost of industrial process shutdowns due to voltage sag and short interruption. A field survey, aided by a specific questionnaire, was carried out in several industries connected to medium voltage networks, in the states of Espírito Santo and São Paulo in Brazil. The results obtained were the costs per event and the costs per demand in a total of 33 companies in 12 different types of activities. It is noteworthy that this survey brings a relevant technical contribution to the electricity sector, helping to fill, even partially, an existing gap in both national and international literature.
Optimal SoC Balancing Control for Lithium-Ion Battery Cells Connected in Series
Authors: Van Chi Nguyen , Vinh Thuy Nguyen , Ngo Minh-Duc , Ahn Seon-Ju
Published: May 2021

The optimal state of charge (SoC) balancing control for series-connected lithium-ion battery cells is presented in this paper. A modified SoC balancing circuit for two adjacent cells, based on the principle of a bidirectional Cuk converter, is proposed. The optimal SoC balancing problem is established to minimize the SoC differences of cells and the energy loss subject to constraints of the normal SoC operating range, the balancing current, and current of cells. This optimization problem is solved using the sequential quadratic programming algorithm to determine the optimal duties of PWM signals applied to the SoC balancing circuits. An algorithm for the selection of the initial points for the optimal problem-solving process is proposed. It is applied in cases where the cost function has no decreasing part. Experimental tests are conducted for seven series-connected Samsung cells. The optimal SoC balancing control and SoC estimation algorithms are coded in MATLAB and embedded in LabVIEW to control the SoC balancing in real time. The test results show that the differences between the SoCs of cells converges to the desired range using the proposed optimal SoC balancing control strategy.
Determinants of Improving the Strategy of Sustainable Energy Management of Building Sustainable Value for Stakeholders—Experience of Organizations in Poland
Authors: Wysokińska-Senkus Aneta
Published: May 2021

The purpose of the research was to identify the factors determining the improvement of the sustainable energy management strategy in the process of building lasting value for stakeholders, identifying key activities supporting the process of improving the sustainable energy management strategy, and analyzing the degree of use of environmental indicators by organizations in Poland. In the research process, to achieve the assumed research goals, it was decided to use the following research methods: The “Delphic Method” and the CAWI method (Computer-Assisted Web Interview). The research was carried out on a sample of 102 organizations in Poland. The study identifies goals for the sustainable development of the organization, activities supporting the process of sustainable energy management, and indicators in the field of energy management. The key factors for the improvement of energy management strategies have been identified, including implementation of modern technologies, reduction of energy consumption, development of procedures, increase of employee awareness, and clearly defined goals in the field of energy management. The strategy of the organization’s future actions towards achieving sustainable development determines the process of creating value for stakeholders. Dialogue with stakeholders is one of the basic conditions for proper planning and implementation of the organization’s strategy and taking actions in the field of sustainable energy management. Effective energy management becomes a necessity. Organizations must take a number of steps to achieve maximum resource efficiency. This can only be achieved through a holistic approach to the process of formulating the goals of the organization, which is necessary in decision-making processes and in the approach to energy management. The Polish economy has been built on coal and other fossil fuels. So far, the majority of polish organizations have not cared about the natural environment and energy management, which is why the research on redefining their strategies is a novelty.
Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car
Authors: Cuturi Nicolò , Sciubba Enrico
Published: May 2021

Within a broader national project aimed at the hybridization of a standard city car (the 998 cc Mitsubishi-derived gasoline engine of the Smart W451), our team tackled the problem of improving the supercharger performance and response. The originally conceived design innovation was that of eliminating the mechanical connection between the compressor and the turbine. In the course of the study, it turned out that it is also possible to modify both components to extract extra power from the engine and to use it to recharge the battery pack. This required a redesign of both compressor and turbine. First, the initial configuration was analyzed on the basis of the design data provided by the manufacturer. Then, a preliminary performance assessment of the turbocharged engine allowed us to identify three “typical” operating points that could be used to properly redesign the turbomachinery. It was decided to maintain the radial configuration for both turbine and compressor, but to redesign the latter by adding an inducer. For the turbine, only minor modifications to the nozzle guide vanes (NGV) and rotor blades shape were deemed necessary, while a more substantial modification was in order for the compressor. Fully 3-D computational fluid dynamics simulations of the rotating machines were performed to assess their performance at three operating points: the kick-in point of the original turbo (2000 rpm), the maximum power regime (5500 rpm), and an intermediate point (3500 rpm) close to the minimum specific fuel consumption for the original engine. The results presented in this paper demonstrate that the efficiency of the compressor is noticeably improved for steady operation at all three operating points, and that its choking characteristics have been improved, while its surge line has not been appreciably affected. The net energy recovery was also calculated and demonstrated interesting returns in terms of storable energy in the battery pack.
Impact of Employing Hybrid Nanofluids as Heat Carrier Fluid on the Thermal Performance of a Borehole Heat Exchanger
Authors: Javadi Hossein , Urchueguia Javier F. , Mousavi Ajarostaghi Seyed Soheil , Badenes Borja
Published: May 2021

In this numerical study, 4 types of hybrid nanofluid, including Ag-MgO/water, TiO2-Cu/water, Al2O3-CuO/water, and Fe3O4-multi-wall carbon nanotube/water, have been considered potential working fluid in a single U-tube borehole heat exchanger. The selected hybrid nanofluid is then analyzed by changing the volume fraction and the Reynolds number. Based on the numerical results, Ag-MgO/water hybrid nanofluid is chosen as the most favorable heat carrier fluid, among others, considering its superior effectiveness, minor pressure drop, and appropriate thermal resistance compared to the pure water. Moreover, it was indicated that all cases of Ag-MgO/water hybrid nanofluid at various volume fractions (from 0.05 to 0.20) and Reynolds numbers (from 3200 to 6200) could achieve better effectiveness and lower thermal resistances, but higher pressure drops compared to the corresponding cases of pure water. Nevertheless, all the evaluated hybrid nanofluids present lower coefficient of performance (COP)-improvement than unity which means that applying them as working fluid is not economically viable because of having higher pressure drop than the heat transfer enhancement.
A Study of Fast Front Transients of an HVDC Mixed Transmission Line Exposed to Bipolar Lightning Strokes
Authors: Shakeel Ayesha , Park Kyu-Hoon , Shin Koo-Yong , Lee Bang-wook
Published: May 2021

Bipolar lightning strokes are associated with multiple polarity electrical discharge with no current intervals in between, making their behavior quite peculiar. This work presents a fast front analysis of a mixed high voltage direct current (HVDC) transmission link, evaluating the factors that influence the line transients due to shielding failures and backflashovers (BFOs), considering both overvoltage and repeated polarity reversal at the cable sending terminal. The research process includes a detailed modeling of a bipolar lightning stroke, frequency-dependent HVDC overhead, and underground transmission line sections. Noticeable findings include the occurrence of only a positive polarity insulator BFO for the adjacent and subsequent tower, despite the dual polarity of the lightning stroke with relatively small values for the lightning parameters. The influence of traveling waves on the insulator flashover performance of the line with varying parameters (such as the riser section length, the tower grounding impedance, and the location of the lightning stroke) is recorded and explained.
Households’ Electricity Consumption in Hungarian Urban Areas
Authors: Bakó Ferenc , Berkes Judit , Szigeti Cecília
Published: May 2021

The aim of this study is to examine the factors influencing the electricity consumption of urban households and to prove these with statistically significant results. The study includes 46 small and medium-sized towns in Hungary. The methodology of the study is mainly provided by a model that can be used for this purpose; however, the results obtained with the traditional regression method are compared with the results of another, more complex estimation method, the artificial neural network, which has the advantage of being able to use different types of models. The focus of our article is on methodological alignment, not necessarily the discovery of new results. Certain demographic characteristics significantly determine the energy demand of a household sector in a municipality. In this case, as the ratio of people aged 60 or over within a city rises by 1%, the urban household average energy consumption decreases by 61 kilowatt hours, and when it rises by 1%, the amount of pollutants expelled from urban households’ average energy consumption may decrease by 22.8745 kg. The research area of our paper was greatly influenced by the availability of the statistical data. The results can be used in the planning of urban developments.
Diesel Migration and Distribution in Capillary Fringe Using Different Spill Volumes via Image Analysis
Authors: Alazaiza Motasem Y. D. , Al Maskari Tahra , Albahansawi Ahmed , Amr Salem S. Abu , Abushammala Mohammed F. M. , Aburas Maher
Published: May 2021

Laboratory-scale column experiments were conducted to assess the impact of different LNAPL volumes on LANPL migration behavior in capillary zone in porous media. Three different volumes of diesel (50 mL, 100 mL, and 150 mL) were released in different experiments using a 1D rectangular column filled with natural sand. The water table was set at 29 cm from the bottom of the column. The image analysis results provided quantitative time-dependent data on the LNAPL distribution through the duration for the experiments. Results demonstrated that the higher diesel volume (150 mL) exhibited the faster LNAPL migration through all experiments. This observation was due to the high volume of diesel as compared to other cases which provides high pressure to migrate deeper in a short time. In all experiments, the diesel migration was fast during the first few minutes of observation and then, the velocity was decreased gradually. This is due to pressure exerted by diesel in order to allow the diesel to percolate through the sand voids. Overall, this study proved that the image analysis can be a good and reliable tool to monitor the LNAPL migration in porous media.
Assessment of Sensory and Texture Profiles of Grape Seeds at Real Maturity Stages Using Image Analysis
Authors: Cejudo-Bastante María Jesús , Rodríguez-Pulido Francisco J. , Heredia Francisco J. , González-Miret M. Lourdes
Published: May 2021

The usefulness of digital image analysis in estimating sensory attributes of grape seeds in relation to maturation level was evaluated for the first time. Seeds from Syrah grapes harvested throughout the ripening period were grouped according to maturity using the DigiEye® system. The discriminant ability, homogeneity, repeatability, and uniformity of a sensory panel were assessed after training on grape seeds. The aim was to evaluate the use of digital image techniques in order to accurately establish the maturity level of grape seeds, based on sensory and textural features. All sensory attributes (color, hardness, cracking, vegetal, bitterness and astringency) showed significant (p < 0.05) correlations with the chemical maturity stage. Color and vegetal (sensory attributes), together with deformation energy (instrumental texture parameter) (De), allowed for the classification of the seeds into four real maturity stages, hence their usefulness as grape seed ripening indicators. Significant (p < 0.05) and high-correlation factors were also found between instrumental and sensory attributes. Therefore, digital analysis can be a useful tool to better define the maturity stage in the vineyard, and to dispose of grape seeds with well-defined sensory profiles for specific oenological applications. This could help to determine the optimal harvest date to manage winemaking, in order to produce high quality wines in warm climates.
Food Puree for Seniors: The Effects of XanFlax as a New Thickener on Physicochemical and Antioxidant Properties
Authors: Lee Chang Geun , Shim Youn Young , Reaney Martin J. T. , Chang Hye-Ja
Published: May 2021

With the increasing number of older adults, the elderly-friendly food market has been rapidly growing. The physicochemical and antioxidant properties of soymilk-based banana-blueberry-puree with and without flaxseed-based (XanFlax) and xanthan-gum-based (brand G) thickeners were compared as a potential senior food. Samples included a control, three treatments with XanFlax (1%, 3%, and 5%), and three treatments with brand G (1.35%, 2.7%, and 5.4%). The physicochemical (color, sugar, salinity, pH, viscosity, and hardness) and antioxidant properties [DPPH, ABTS, reducing power (RP), and total polyphenol content (TPC)] were compared. The chromaticity values (L*, a*, and b*) and pHs were similar among all treatments and the control, but the salinity of brand G showed statistical differences (p < 0.05). All samples met the Korean Industrial Standards for senior foods in terms of viscosity and hardness, while samples with brand G were harder and more viscous than those with XanFlax and the control (p < 0.001). XanFlax samples had greater ABTS radical scavenging activities than the control and brand G samples (p < 0.001). Although, the developed puree can be a possible senior food product without the addition of thickeners, XanFlax might be applied as a non-xanthan gum-based viscosity thickener with antioxidant functions for senior-friendly foods.
Physicochemical and Structural Characterization of Potato Starch with Different Degrees of Gelatinization
Authors: Xu Fen , Zhang Liang , Liu Wei , Liu Qiannan , Wang Feng , Zhang Hong , Hu Honghai , Blecker Christophe
Published: May 2021

Starch gelatinization has been widely studied previously, but there is still a lack of systematical research on the relationship between the degree of starch gelatinization (DSG) and its physicochemical and structural properties. In this study, potato starch samples with DSG ranging from 39.41% to 90.56% were obtained by hydrothermal treatment. The thermal, rheological, and structural properties, as well as the water-binding capacity of samples were investigated. A starch solution with a DSG of 39.41% was partially sedimented at room temperature, while starch with a DSG of 56.11% can form a stable paste with a fine shear-thinning property, as well as samples with a DSG larger than 56.11%. The endothermic enthalpy, gelatinization range, and short-range ordered structure of starch were negatively correlated with DSG, whereas onset gelatinization temperature, apparent viscosity, and water-binding capacity were positively correlated. The viscoelasticity of starch gels was negatively correlated with the DSG after full gelatinization (DSG > 39.41%). Starch granules gradually lose their typical shape and less birefringence can be observed with increasing DSG. Hydrothermal treatment has a more significant effect on the amount of exposed hydroxyl groups than the ordered and amorphous structures of partially gelatinized starch. This study built linear correlations between starch physicochemical properties and the DSG and provided comprehensive insight into the characteristics of partially gelatinized potato starch.
Microbial Metabolic Pathways and the “Fermented Plant Foods—Human Health” Axis
Authors: Di Cagno Raffaella , Filannino Pasquale , Gobbetti Marco
Published: May 2021

Plant matrices are widely recognized as valuable sources of several health promoting compounds [...]
A Novel Quantitative Prediction Approach for Pungency Level of Chinese Liquor (Baijiu) Based on Infrared Thermal Imager
Authors: He Yingxia , Chen Shuang , Tang Ke , Xu Yan , Yu Xiaowei
Published: May 2021

Pungency is a crucial sensory feature that influences consumers’ appreciation and preferences toward alcoholic beverages. However, the quantitation of pungency is challenging to achieve using sensory analysis because of persistence, accumulation, and desensitization to the pungency perception. This study aimed to design a novel pungency evaluation method based on the measurement of tongue surface temperature. An infrared thermal (IRT) imager technique for measuring tongue surface temperature was established. To validate its feasibility, the IRT technique was used to measure tongue surface temperatures after the tongue was stimulated by (1) water and Baijiu, (2) different concentrations of ethanol aqueous solution (10, 20, 30, 40, and 50%, v/v), (3) ethanol aqueous solution and Baijiu samples with the same ethanol content, and (4) 26 Baijiu samples with different pungency level. For all cases, tongue surface temperatures showed large differences as a result of the different stimulation. The results showed that the tongue surface temperature correlated with the pungency intensity obtained by the sensory analysis. The relationship between tongue surface temperature and pungency intensity was established by multiple linear regression analysis. The IRT technique was able to be a useful support tool to quantitatively predict the pungency of alcoholic beverages, based on the measurement of tongue surface temperature.
Use of a Highly Antioxidant Diet in the Regulation of Adipose Tissue Secretion in Patients after the BIB Procedure
Authors: Balejko Edyta , Balejko Jerzy
Published: May 2021

Obesity is a global problem. The secretory activity of adipose tissue causes inflammation and disturbs metabolic parameters. Low-invasive bariatric procedures are an alternative to surgical treatment, especially in individuals who do not qualify for surgery or in whom conservative treatment does not bring the expected results. The diets designed for bariatric patients contained an increased proportion of bioflavonoids. The dietary components were carefully selected to provide anti-inflammatory effects. The experimental diets showed an antioxidant capacity (TEAC) of 433–969 µM TE/100 g or 100 mL, reducing ability (FRAP) of 13–58 µM TE/100 g or 100 mL, and total polyphenol content of 80–250 mg catechins/100 g or 100 mL. Lower levels of adipocytokines were obtained in the blood of patients following the diet. The results of the present study showed the participation of some adipocytokines in the regulation of energy homeostasis, lipid metabolism, glucose level, blood pressure and inflammation. Diet therapy should yield positive results in the long term, with the possibility of using immune modulation in personalized therapy for metabolic syndrome.
Design of Fractional-Order Lead Compensator for a Car Suspension System Based on Curve-Fitting Approximation
Authors: Memlikai Evisa , Kapoulea Stavroula , Psychalinos Costas , Baranowski Jerzy , Bauer Waldemar , Tutaj Andrzej , Piątek Paweł
Published: May 2021

An alternative procedure for the implementation of fractional-order compensators is presented in this work. The employment of a curve-fitting-based approximation technique for the approximation of the compensator transfer function offers improved accuracy compared to the Oustaloup and Padé methods. As a design example, a lead compensator intended for usage in car suspension systems is realized. The open-loop and closed-loop behavior of the system is evaluated by post-layout simulation results obtained using the Cadence IC design suite and the Metal Oxide Semiconductor (MOS) transistor models provided by the Austria Mikro Systeme 0.35 μm Complementary Metal Oxide Semiconductor (CMOS) process. The derived results verify the efficient performance of the introduced implementation.
Exploiting the IRT-THESEUS Capability to Observe Lensed Quasars
Authors: Hamolli Lindita , Hafizi Mimoza , De Paolis Francesco , Nucita Achille A.
Published: May 2021

THESEUS is an ESA space based project, which aims to explore the early universe by unveiling a complete census of Gamma-ray Burst (GRB) population in the first billion years. This goal is expected to be realized by the combined observations of its three instruments on board: the Soft X-ray Imager (SXI), the X and Gamma Imaging Spectrometer (XGIS), and the InfraRed Telescope (IRT). This last one will identify, localise, and study the afterglow of the GRBs detected by SXI and XGIS, and about 40% of its time will be devoted to an all-sky photometric survey, which will certainly detect a relevant number of extragalactic sources, including Quasars. In this paper, we focus on the capability of IRT-THESEUS Telescope to observe Quasars and, in particular, Quasars lensed by foreground galaxies. In our analysis we consider the recent results for the Quasar Luminosity Function (QLF) in the infrared band based on the Spitzer Space Telescope imaging survey. In order to estimate the number of lensed Quasars, we develop Monte Carlo simulations using the mass-luminosity distribution function of galaxies and the galaxy and Quasar redshift distributions. We predict about 2.14 × 105 Quasars to be observed during IRT-Theseus sky survey, and approximately 140 of them lensed by foreground galaxies. Detailed studies of these events would provide a powerful probe of the physical properties of Quasars and the mass distribution models of the galaxies.
Gamma-ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei
Authors: Inoue Yoshiyuki , Khangulyan Dmitry , Doi Akihiro
Published: May 2021

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 year survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.